Method and apparatus for treating hemodynamic disfunction

Abstract

A method of treating hemodynamic disfunction by simultaneously pacing both ventricles of a heart. At least one ECG amplifier is arranged to separately detect contraction of each ventricle and a stimulator is then activated for issuing stimulating pulses to both ventricles in a manner to assure simultaneous contraction of both ventricles, thereby to assure hemodynamic efficiency. A first ventricle is stimulated simultaneously with contraction of a second ventricle when the first fails to properly contract. Further, both ventricles are stimulated after lapse of a predetermined A-V escape interval. One of a pair of electrodes, connected in series, in placed through the superior vena cava into the right ventricle and a second is placed in the coronary sinus about the left ventricle. Each electrode performs both pacing and sensing functions. The pacer is particularly suitable for treating bundle branch blocks or slow conduction in a portion of the ventricles.

1. A method for improving the hemodynamic efficiency of a sick heart comprising the steps of:
 (a) detecting respective cardiac signals originating in the left and right ventricles of the heart;    (b) analyzing said cardiac signals and the absence thereof in an electronic control circuit; and    (c) providing electrical pulses from a stimulating circuit controlled by said control circuit to one, the other or both ventricles as required for effecting substantially simultaneous contraction of both ventricles, said step of analyzing including providing a control signal from said control circuit to said stimulating circuit for producing an electrical stimulating pulse to one or both ventricles in response to the absence of a detected cardiac signal from one or both ventricles within a time interval which is a small fraction of the pulse width of a detected cardiac signal.    
     
     
       2. The method of  claim 1  wherein said step of detecting respective cardiac signals comprises deposing electrodes in or on the left and right ventricles for separately detecting the respective cardiac signals of the left and right ventricles, and applying said cardiac signals to separate ECG amplifier means connected to each of said electrodes to amplify the cardiac signal for analysis. 
     
     
       3. The method of  claim 2  wherein said step of providing electrical pulses includes delivering an electrical pulse from said stimulating circuit to said electrodes in or on both the left and right ventricles. 
     
     
       4. The method of  claim 1  wherein said step of analyzing further includes providing a control signal from said control circuit to the stimulating circuit to produce an electrical stimulating pulse to the left ventricle in the absence of a detected cardiac signal from the left ventricle, or to the right ventricle in the absence of a detected cardiac signal from the right ventricle, or to both ventricles in the absence of detected cardiac signals from both ventricles. 
     
     
       5. A method for effecting simultaneous contraction of both left and right ventricles of a heart for improving hemodynamic efficiency comprising the steps of:
 separately sensing for the presence of cardiac depolarization signals from both left and right ventricles;    determining whether said cardiac depolarization signals are simultaneously present in both the left and right ventricles; and    stimulating at least one ventricle substantially simultaneously with the contraction of at least one other ventricle in the event that said cardiac depolarization signals are determined not to be simultaneously present in both ventricles.    
     
     
       6. A method of effecting simultaneous contraction of both left and right ventricles of a heart for improving hemodynamic efficiency comprising the steps of:
 sensing the cardiac signals of the atria and separately sensing the cardiac depolarization signals of both the left and right ventricles;    determining whether said cardiac depolarization signals are simultaneously present in both the left and right ventricles;    stimulating at least one ventricle simultaneously with the contraction of at least one other ventricle after a predetermined A-V period in the event that said cardiac depolarization signals are determined not to be simultaneously present in both ventricles.    
     
     
       7. A method of increasing the cardiac output of a sick heart comprising the steps of:
 (a) implanting a pacing lead having at least two sensing/pacing electrodes in the body such that one of said sensing/pacing electrodes is in or on the right ventricle and the other of said sensing/ pacing electrodes is in or on the left ventricle;    (b) sensing depolarization signals picked up by said sensing/pacing electrodes upon their occurrence;    (c) determining whether the depolarization signals sensed in step (b) fail to occur within a predetermined time interval of one another and, if so;    (d) applying an electrical stimulating pulse to the sensing/pacing electrode associated with the ventricle not producing a depolarization signal within said time interval at the conclusion of said time interval.    
     
     
       8. The method as in  claim 7  wherein said predetermined time interval is in the range of from about  5  ms. to  10  ms. 
     
     
       9. A bi-ventricular pacemaker, comprising:
 (a) sense means for sensing ventricular depolarization signals originating in or on the right and left ventricles;    (b) means coupled to said sense means for initiating a time delay of a predetermined length which is short compared to the period of a QRS complex upon detection of a ventricular depolarization signal in one of said right or left ventricles; and    (c) pulse generator means operative upon the termination of said time delay for producing a ventricular simulating pulse and applying same to the other of said right or left ventricles unless a ventricular depolarization signal occurs in said other of said right of left ventricle prior to the expiration of said time delay.    
     
     
       10. The bi-ventricular pacemaker as in  claim 9  wherein said sense means comprises a bi-ventricular lead having a first electrode for contacting the right ventricle and a second electrode for contacting the left ventricle and sense amplifier means electrically coupled to said first and second electrodes. 
     
     
       11. The bi-ventricular pacemaker as in  claim 10  wherein said means coupled to said sense means includes:
 (a) first and second set-reset flip-flop connected to be set by an output from said sense amplifier means;    (b) presetable counter means for initially containing a digital value representative of said time delay;    (c) means for incrementing or decrementing said digital value in said presettable counter means at regular intervals until a predetermined count is reached;    (d) means responsive to the value in said counter means reaching said predetermined count for producing a control signal;    (e) logic means coupled to said first and second flip-flops and to said presettable counter means for receiving said control signals; and wherein    (f) said pulse generator means is enabled by said logic means.    
     
     
       12. The bi-ventricular pacemaker as in  claim 11  wherein said pulse generator means is coupled to said first and second electrodes. 
     
     
       13. An atrial-coupled, bi-ventricular pacemaker for implantation or external use comprising atrial and ventricular sensing means for detecting cardiac signals, said sensing means including first and second ventricular electrodes connected in series for sensing and stimulating the right and the left ventricles, respectively, and an atrial electrode adapted to be disposed in an atrial chamber for detecting cardiac signals of the atria, all of said electrodes being connected to separate ECG amplifier means for amplifying the sensed signals; a control circuit coupled to said ECG amplifier means for analyzing the cardiac signals picked up by said sensing means and providing a control signal; and a stimulating circuit means for producing an electrical stimulating pulse to the left ventricle in the absence of a detected cardiac signal from the left ventricle, and to the right ventricle in the absence of a detected cardiac signal from the right ventricle, and to both ventricles in the absence of detected cardiac signals from both ventricles to effect substantially simultaneous contraction of both ventricles after a predetermined A-V delay period. 
     
     
       14. The pacemaker of  claim 13  wherein said first electrode is adapted to be placed in the right ventricle and the second electrode is adapted to be placed in the coronary sinus extending about the left ventricle. 
     
     
       15. A heart stimulating device for treating heart failure, comprising:
 a sense amplifier to receive ventricular depolarization signals originating from a first ventricle;    a pulse generator, connected to the sense amplifier, to generate a stimulating pulse in the event the sense amplifier receives a ventricular depolarization signal; and    an electrode, connected to the pulse generator, to apply the stimulating pulse to a second ventricle in the event the sense amplifier receives a ventricular depolarization signal.   
     
     
       16. The heart stimulating device of  claim 15 , the electrode further comprising:
 an electrode adapted to be disposed in or about the right ventricle to sense ventricular depolarization signals originating from the right ventricle.   
     
     
       17. The heart stimulating device of  claim 15 , wherein the sense amplifier receives ventricular depolarization signals originating from the right ventricle. 
     
     
       18. The heart stimulating device of  claim 17 , wherein the electrode connected to the pulse generator applies the stimulating pulse to the left ventricle. 
     
     
       19. The heart stimulating device of  claim 15 , the electrode further comprising:
 an electrode adapted to be disposed in or about the left ventricle to sense ventricular depolarization signals originating from the left ventricle.   
     
     
       20. The heart stimulating device of  claim 15 , wherein the sense amplifier receives ventricular depolarization signals originating from the left ventricle. 
     
     
       21. The heart stimulating device of  claim 20 , wherein the electrode connected to the pulse generator applies the stimulating pulse to the right ventricle. 
     
     
       22. The heart stimulating device of  claim 15 , wherein the pulse generator generates the stimulating pulses immediately after the sense amplifier receives a ventricular depolarization signal. 
     
     
       23. The heart stimulating device of  claim 15 , further comprising:
 a timer to initiate a delay period after the sense amplifier receives a ventricular depolarization signal.   
     
     
       24. The heart stimulating device of  claim 23 , wherein the pulse generator generates the stimulating pulse after the delay period. 
     
     
       25. The heart stimulating device of  claim 15 , wherein the sense amplifier receives ventricular depolarization signals from both the right ventricle and the left ventricle. 
     
     
       26. The heart stimulating device of  claim 15 , wherein the pulse generator generates stimulating pulses for both the right ventricle and the left ventricle. 
     
     
       27. A heart stimulating device for treating heart failure, comprising:
 means for receiving ventricular depolarization signals originating from a first ventricle;    means for generating a stimulating pulse in the event the receiving means receives a ventricular depolarization signal; and    means for applying the stimulating pulse to a second ventricle in the event the receiving means receives a ventricular depolarization signal.   
     
     
       28. The heart stimulating device of  claim 27 , the receiving means further comprising:
 an electrode means adapted to be disposed in or about the right ventricle for sensing ventricular depolarization signals originating from the right ventricle.   
     
     
       29. The heart stimulating device of  claim 28 , wherein the applying means applies the stimulating pulse to the left ventricle. 
     
     
       30. The heart stimulating device of  claim 28 , wherein the applying means applies stimulating pulses to both the left ventricle and the right ventricle. 
     
     
       31. The heart stimulating device of  claim 27 , the receiving means further comprising:
 an electrode means adapted to be disposed in or about the left ventricle for sensing ventricular depolarization signals originating from the left ventricle.   
     
     
       32. The heart stimulating device of  claim 31 , wherein the applying means applies the stimulating pulse to the right ventricle. 
     
     
       33. The heart stimulating device of  claim 31 , wherein the applying means applies stimulating pulses to both the left ventricle and the right ventricle. 
     
     
       34. The heart stimulating device of  claim 27 , wherein the getor means generates the stimulating pulses immediately after the receiving means receives a ventricular depolarization signal. 
     
     
       35. The heart stimulating device of  claim 27 , further comprising:
 means for initiating a delay period after the receiving means receives a ventricular depolarization signal.   
     
     
       36. The heart stimulating device of  claim 35 , wherein the generator means generates the stimulating pulse after the delay period. 
     
     
       37. The heart stimulating device of  claim 27 , wherein the receiving means receives ventricular depolarization signals from both the right ventricle and the left ventricle. 
     
     
       38. The heart stimulating device of  claim 27 , wherein the generator means generates stimulating pulses for both the right ventricle and the left ventricle. 
     
     
       39. A method for improving the hemodynamic efficiency of a heart, comprising:
 receiving ventricular depolarization signals originating from a first ventricle;    generating a stimulating pulse in response to the receiving of a ventricular depolarization signal; and    applying the stimulating pulse to a second ventricle in response to the receiving of a ventricular depolarization signal.   
     
     
       40. The method of  claim 39 , the receiving further comprising:
 receiving ventricular depolarization signals originating from the right ventricle.   
     
     
       41. The method of  claim 40 , the applying further comprising:
 applying the stimulating pulse to the left ventricle.   
     
     
       42. The method of  claim 40 , the applying further comprising:
 applying stimulating pulses to both the left ventricle and the right ventricle.   
     
     
       43. The method of  claim 39 , the receiving further comprising:
 sensing ventricular depolarization signals originating from the left ventricle.   
     
     
       44. The method of  claim 43 , the applying further comprising:
 applying the stimulating pulse to the right ventricle.   
     
     
       45. The method of  claim 43 , the applying further comprising:
 applying stimulating pulses to both the left ventricle and the right ventricle.   
     
     
       46. The method of  claim 39 , the generating further comprising:
 generating the stimulating pulses immediately after receiving a ventricular depolarization signal.   
     
     
       47. The method of  claim 39 , further comprising:
 initiating a delay period after receiving a ventricular depolarization signal.   
     
     
       48. The method of  claim 47 , the generating further comprising:
 generating the stimulating pulse after the delay period.   
     
     
       49. The method of  claim 39 , the receiving further comprising:
 receiving ventricular depolarization signals from both the right ventricle and the left ventricle.   
     
     
       50. The heart stimulating device of  claim 39 , the generating further comprising:
 generating stimulating pulses for both the right ventricle and the left ventricle.   
     
     
       51. A heart stimulating device for treating heart failure comprising:
 an electrode to sense a cardiac depolarization signal from a first ventricle;    a sense amplifier, connected to the electrode, to process the cardiac depolarization signal; and    a stimulator, connected to the sense amplifier, to issue a stimulating pulse to a second ventricle in response to the ventricular cardiac depolarization signal.   
     
     
       52. The heart stimulating device of  claim 51 , wherein the electrode senses a cardiac depolarization signal from the right ventricle. 
     
     
       53. The heart stimulating device of  claim 52 , wherein the stimulator issues a stimulating pulse to the left ventricle in response to sensing a cardiac depolarization signal from the right ventricle. 
     
     
       54. The heart stimulating device of  claim 52 , wherein the stimulator issues stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the right ventricle. 
     
     
       55. The heart stimulating device of  claim 51 , wherein the electrode senses a cardiac depolarization signal from the left ventricle. 
     
     
       56. The heart stimulating device of  claim 55 , wherein the stimulator issues a stimulating pulse to the right ventricle in response to sensing a cardiac depolarization signal from the left ventricle. 
     
     
       57. The heart stimulating device of  claim 55 , wherein the stimulator issues stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the left ventricle. 
     
     
       58. The heart stimulating device of  claim 51 , wherein the stimulator issues the stimulating pulse immediately after the electrode senses a ventricle depolarization signal. 
     
     
       59. The heart stimulating device of  claim 51 , further comprising:
 a timer to initiate a delay period after the electrode senses a ventricular depolarization signal.   
     
     
       60. The heart stimulating device of  claim 59 , wherein the stimulator issues the stimulating pulse after the delay period. 
     
     
       61. The heart stimulating device of  claim 51 , wherein the sense amplifier processes cardiac depolarization signals received from both the right ventricle and the left ventricle. 
     
     
       62. A heart stimulating device for treating heart failure comprising:
 means for sensing a cardiac depolarization signal from a first ventricle;    means, connected to the sensing means, for receiving the cardiac depolarization signal; and    means, connected to the receiving means, for issuing a stimulating pulse to a second ventricle in response to the ventricular cardiac depolarization signal.   
     
     
       63. The heart stimulating device of  claim 62 , wherein the sensing means senses a cardiac depolarization signal from the right ventricle. 
     
     
       64. The heart stimulating device of  claim 63 , wherein the issuing means issues a stimulating pulse to the left ventricle in response to sensing a cardiac depolarization signal from the right ventricle. 
     
     
       65. The heart stimulating device of  claim 63 , wherein the issuing means issues stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the right ventricle. 
     
     
       66. The heart stimulating device of  claim 62 , wherein the sensing means senses a cardiac depolarization signal from the left ventricle. 
     
     
       67. The heart stimulating device of  claim 66 , wherein the issuing means issues a stimulating pulse to the right ventricle in response to sensing a cardiac depolarization signal from the left ventricle. 
     
     
       68. The heart stimulating device of  claim 66 , wherein the issuing means issues stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the left ventricle. 
     
     
       69. The heart stimulating device of  claim 62 , wherein the issuing means issues the stimulating pulse immediately after the electrode senses a ventricular depolarization signal. 
     
     
       70. The heart stimulating device of  claim 62 , further comprising:
 means for initiating a delay period after the electrode senses a ventricular depolarization signal.   
     
     
       71. The heart stimulating device of  claim 70 , wherein the issuing means issues the stimulating pulse after the delay period. 
     
     
       72. The heart stimulating device of  claim 62 , wherein the receiving means receives cardiac depolarization signals from both the right ventricle and the left ventricle. 
     
     
       73. A method for improving the hemodynamic efficiency of a heart, comprising:
 sensing a cardiac depolarization signal from a first ventricle;    receiving the ventricular cardiac depolarization signal; and    issuing a stimulating pulse to a second ventricle in response to the ventricular cardiac depolarization signal.   
     
     
       74. The method of  claim 73 , the sensing further comprising:
 sensing a cardiac depolarization signal from the right ventricle.   
     
     
       75. The method of  claim 74 , the issuing further comprising:
 issuing a stimulating pulse to the left ventricle in response to sensing a cardiac depolarization signal from the right ventricle.   
     
     
       76. The method of  claim 74 , the issuing further comprising:
 issuing stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the right ventricle.   
     
     
       77. The method of  claim 73 , the sensing further comprising:
 sensing a cardiac depolarization signal from the left ventricle.   
     
     
       78. The method of  claim 77 , the issuing further comprising:
 issuing a stimulating pulse to the right ventricle in response to sensing a cardiac depolarization signal from the left ventricle.   
     
     
       79. The method of  claim 77 , the issuing further comprising:
 issuing stimulating pulses to both ventricles in response to sensing a cardiac depolarization signal from the left ventricle.   
     
     
       80. The method of  claim 73 , the issuing further comprising:
 issuing the stimulating pulse immediately after the sensing of the ventricular depolarization signal.   
     
     
       81. The method of  claim 73 , further comprising:
 initiating a delay period after the sensing of the ventricular depolarization signal.   
     
     
       82. The method of  claim 81 , the issuing further comprising:
 issuing the stimulating pulse after the delay period.   
     
     
       83. The method of  claim 73 , the receiving further comprising:
 receiving ventricular cardiac depolarization signals from both the left and the right ventricles.   
     
     
       84. A heart stimulating device for treating heart failure, comprising:
 an electrode to sense ventricular depolarization signals originating from the right ventricle; and    a pulse generator, connected to the electrode, operative upon sensing of a ventricular depolarization signal from the right ventricle to apply a stimulating pulse to another ventricle.   
     
     
       85. The heart stimulating device of  claim 84 , wherein the pulse generator applies the stimulating pulse to the left ventricle. 
     
     
       86. The heart stimulating device of  claim 84 , wherein the pulse generator applies stimulating pulses to both the left ventricle and the right ventricle. 
     
     
       87. The heart stimulating device of  claim 84 , wherein the pulse generator applies the stimulating pulse immediately upon the sensing the ventricular depolarization signal. 
     
     
       88. The heart stimulating device of  claim 84 , further comprising:
 a timer to initiate a delay period after the sensing of the ventricular depolarization signal.   
     
     
       89. The heart stimulating device of  claim 88 , wherein the pulse generator applies the stimulating pulse after the delay period. 
     
     
       90. A heart stimulating device for treating heart failure, comprising:
 means for sensing ventricular depolarization signals originating from the right ventricle; and    means for applying a stimulating pulse to another ventricle in response to the sensing means sensing a ventricular depolarization signal originating from the right ventricle.   
     
     
       91. The heart stimulating device of  claim 90 , wherein the applying means applies the stimulating pulse to the left ventricle. 
     
     
       92. The heart stimulating device of  claim 90 , wherein the applying means applies stimulating pulses to both the left ventricle and the right ventricle. 
     
     
       93. The heart stimulating device of  claim 90 , wherein the applying means applies the stimulating pulse immediately upon the sensing of the ventricular depolarization signal. 
     
     
       94. The heart stimulating device of  claim 90 , further comprising:
 means to initiate a delay period after the sensing of the ventricular depolarization signal.   
     
     
       95. The heart stimulating device of  claim 94 , wherein the applying means applies the stimulating pulse after the delay period. 
     
     
       96. A method for improving the hemodynamic efficiency of a heart, comprising:
 sensing ventricular depolarization signals originating from the right ventricle; and    applying a stimulating pulse to another ventricle in response to the sensing of a ventricular depolarization signal originating from the right ventricle.   
     
     
       97. The method of  claim 96 , the applying further comprising:
 applying the stimulating pulse to the left ventricle.   
     
     
       98. The method of  claim 96 , the applying further comprising:
 applying stimulating pulses to both the left ventricle and the right ventricle.   
     
     
       99. The method of  claim 96 , the applying further comprising:
 applying the stimulating pulse immediately upon the sensing of the ventricular depolarization signal.   
     
     
       100. The method of  claim 96 , further comprising:
 initiating a delay period after the sensing of the ventricular depolarization signal.   
     
     
       101. The method of  claim 100 , the applying further comprising:
 applying the stimulating pulse after the delay period.   
     
     
       102. A heart stimulating device for treating heart failure, comprising:
 an electrode to sense ventricular depolarization signals originating from the right ventricle; and    a pulse generator operative upon sensing of a ventricular depolarization signal to apply a stimulating pulse to another ventricle.   
     
     
       103. The heart stimulating device of  claim 102 , wherein the pulse generator applies the stimulating pulse to the right ventricle. 
     
     
       104. The heart stimulating device of  claim 102 , wherein the pulse generator applies a stimulating pulse to both the right ventricle and the left ventricle. 
     
     
       105. The heart stimulating device of  claim 102 , wherein the pulse generator applies the stimulating pulse immediately upon the sensing of the ventricular depolarization signal. 
     
     
       106. The heart stimulating device of  claim 102 , further comprising:
 a timer to initiate a delay period after the sensing of the ventricular depolarization signal.   
     
     
       107. The heart stimulating device of  claim 106 , wherein the pulse generator applies the stimulating pulse after the delay period. 
     
     
       108. A heart stimulating device for treating heart failure, comprising:
 means for sensing ventricular depolarization signals originating from the left ventricle; and    means for applying a stimulating pulse to another ventricle in response to the sensing means sensing ventricular depolarization signals originating from the left ventricle.   
     
     
       109. The heart stimulating device of  claim 108 , wherein the applying means applies the stimulating pulse to the right ventricle. 
     
     
       110. The heart stimulating device of  claim 108 , wherein the applying means applies a stimulating pulse to both the right ventricle and the left ventricle. 
     
     
       111. The heart stimulating device of  claim 108 , wherein the applying means applies the stimulating pulse immediately upon the sensing of the ventricular depolarization signal. 
     
     
       112. The heart stimulating device of  claim 108 , further comprising:
 means for initiating a delay period after the sensing of the ventricular depolarization signal.   
     
     
       113. The heart stimulating device of  claim 112 , wherein the applying means applies the stimulating pulse after the delay period. 
     
     
       114. A method for improving the hemodynamic efficiency of a heart, comprising:
 sensing ventricular depolarization signals originating from the left ventricle; and    applying a stimulating pulse to another ventricle in response to the sensing of the ventricular depolarization signals originating from the left ventricle.   
     
     
       115. The method of  claim 114 , the applying further comprising:
 applying the stimulating pulse to the right ventricle.   
     
     
       116. The method of  claim 114 , the applying further comprising:
 applying a stimulating pulse to both the right ventricle and the left ventricle.   
     
     
       117. The method of  claim 114 , the applying further comprising:
 applying the stimulating pulse immediately upon the sensing of the ventricular depolarization signal.   
     
     
       118. The method of  claim 114 , further comprising:
 initiating a delay period after the sensing of the ventricular depolarization signal.   
     
     
       119. The method of  claim 118 , the applying further comprising:
 applying the stimulating pulse after the delay period.   
     
     
       120. A heart stimulating device for treating heart failure, comprising:
 a first electrode to sense atrial cardiac depolarization signals originating from an atrial chamber;    a second electrode to sense ventricular cardiac depolarization signals originating from a ventricular chamber;    a pulse generator operative to apply stimulating pulses to both ventricles in the event that no ventricular cardiac depolarization signals are sensed within a predetermined atrial-ventricular delay period.   
     
     
       121. The heart stimulating device of  claim 120 , further comprising:
 a control circuit, connected to the first and second electrodes, to determine whether ventricular cardiac depolarization signals are sensed by the second electrode within the predetermined atrial-ventricular delay period.   
     
     
       122. The heart stimulating device of  claim 120 , wherein the pulse generator applies the stimulating pulses to both ventricles simultaneously. 
     
     
       123. The heart stimulating device of  claim 120 , wherein the pulse generator applies the stimulating pulses to each of the ventricles sequentially. 
     
     
       124. A heart stimulating device for treating heart failure, comprising:
 means for sensing atrial cardiac depolarization signals originating from an atrial chamber;    means for sensing ventricular cardiac depolarization signals originating from a ventricular chamber;    means for applying stimulating pulses to both ventricles in the event that no ventricular cardiac depolarization signals are sensed within a predetermined atrial-ventricular delay period.   
     
     
       125. The heart stimulating device of  claim 124 , further comprising:
 a control means, connected to the atrial sensing means and the ventricular sensing means, for determining whether ventricular cardiac depolarization signals are sensed by the ventricular sensing means within the predetermined atrial-ventricular delay period.   
     
     
       126. The heart stimulating device of  claim 124 , wherein the applying means applies the stimulating pulses to both ventricles simultaneously. 
     
     
       127. The heart stimulating device of  claim 124 , wherein the applying means applies the stimulating pulses to each of the ventricles sequentially. 
     
     
       128. A method for improving the hemodynamic efficiency of a heart, comprising:
 sensing for the presence of cardiac depolarization signals from a ventricle; and    stimulating both ventricles in the event that no cardiac depolarization signals are sensed from either ventricle within a predetermined atrial-ventricular delay period.   
     
     
       129. The method of  claim 128 , wherein stimulating both ventricles further comprises generating a stimulating pulse and immediately and unconditionally applying the stimulating pulse to both ventricles. 
     
     
       130. The method of  claim 128 , wherein stimulating both ventricles further comprises generating a stimulating pulse and applying the stimulating pulse to both ventricles simultaneously. 
     
     
       131. The method of  claim 128 , wherein stimulating both ventricles further comprises generating a stimulating pulse and sequentially applying the stimulating pulse to the ventricles. 
     
     
       132. An atrial-coupled bi-ventricular stimulating device for treatment of congestive heart failure comprising:
 atrial and ventricular sensing means for detecting cardiac signals originating in an atrium and in a ventricle;    a control circuit connected to said sensing means to receive the cardiac signals and provide a control signal; and    a stimulating circuit for effecting simultaneous contraction of both ventricles in response to the control signal of the control circuit after a predetermined A-V delay period.   
     
     
       133. An atrial-coupled bi-ventricular stimulating device for implantation or external use for treating heart failure comprising:
 a sensing electrode adapted to be located in an atrium;    a pacing electrode adapted to be located through the coronary sinus in the left ventricle;    a sensing electrode adapted to be located in the right ventricle;    ventricular sensing means for detecting cardiac signals from the sensing electrode adapted to be in the right ventricle;    a control circuit connected to said sensing means to provide a control signal in response to detecting a cardiac signal; and    a stimulating circuit for effecting simultaneous contraction of both ventricles in response to the control signal of the control circuit after a predetermined A-V delay period.   
     
     
       134. The stimulating device of  claim 133 , wherein the sensing electrode adapted to be in the right ventricle also functions to deliver an electrical pulse from said stimulating circuit in response to the control signal of the control circuit. 
     
     
       135. The stimulating device of  claim 133 , wherein the pacing electrode delivers an electrical pulse from said stimulating circuit in response to the control signal of the control circuit. 
     
     
       136. A method for treating congestive heart failure comprising:
 locating a sensing electrode in an atrium;    locating a pacing electrode through the coronary sinus in the left ventricle;    locating a sensing electrode in the right ventricle;    sensing for cardiac signals from the sensing electrode in the right ventricle;    detecting the cardiac signals; and    effecting simultaneous contraction of both ventricles after a predetermined A-V delay period.   
     
     
       137. The method of  claim 136 , wherein locating a sensing electrode in the right ventricle includes locating a sensing and pacing electrode in the right ventricle. 
     
     
       138. The method of  claim 137 , wherein effecting simultaneous contraction of both ventricles after a predetermined A-V delay period includes delivering an electrical pulse to the right ventricle via the sensing and pacing electrode. 
     
     
       139. The method of  claim 136 , wherein effecting simultaneous contraction of both ventricles after a predetermined A-V delay period includes delivering an electrical pulse to the left ventricle via the pacing electrode. 
     
     
       140. A method of effecting simultaneous contraction of both left and right ventricles of a heart for improving hemodynamic efficiency comprising:
 locating a pacing electrode through the coronary sinus to the left ventricle;    sensing the cardiac signals of the atria and separately sensing the cardiac depolarization signals of the right ventricle;    detecting the cardiac signals of the atria and the cardiac depolarization signals of the right ventricle; and    stimulating the left ventricle simultaneously with the contraction of the right ventricle after a predetermined A-V delay period.   
     
     
       141. The method of  claim 140 , wherein stimulating the left ventricle simultaneously with the contraction of the right ventricle after a predetermined A-V delay period includes delivering an electrical pulse to the left ventricle via the pacing electrode. 
     
     
       142. The method of  claim 140 , wherein stimulating the left ventricle simultaneously with the contraction of the right ventricle after a predetermined A-V delay period includes stimulating both the left ventricle and the right ventricle after a predetermined A-V delay period. 
     
     
       143. A heart stimulating device for treating heart failure, comprising:
 an electrode adapted to be disposed in or about the right ventricle to sense ventricular depolarization signals originating from the right ventricle;    a sense amplifier to receive the ventricular depolarization signals originating from the right ventricle;    a pulse generator, connected to the sense amplifier, to generate a stimulating pulse in the event the sense amplifier receives a ventricular depolarization signal originating from the right ventricle; and    an electrode, adapted to be disposed in or about the left ventricle and connected to the pulse generator, to apply the stimulating pulse to the left ventricle in the event the sense amplifier receives a ventricular depolarization signal originating from the right ventricle.   
     
     
       144. The heart stimulating device of  claim 143 , wherein the electrode adapted to be disposed in or about the left ventricle is positioned through the coronary sinus. 
     
     
       145. The heart stimulating device of  claim 143 , wherein the electrode adapted to be disposed in or about the right ventricle stimulates the right ventricle in the event the sense amplifier receives a ventricular depolarization signal originating from the right ventricle. 
     
     
       146. A method for treating congestive heart failure, comprising:
 receiving ventricular depolarization signals originating from the right ventricle;    generating a stimulating pulse in response to the receiving of a ventricular depolarization signal in the right ventricle; and    applying the stimulating pulse to the left ventricle in response to the receiving of a ventricular depolarization signal in the right ventricle.   
     
     
       147. The method of  claim 146 , the applying further comprising:
 applying stimulating pulses to both the left ventricle and the right ventricle in response to the receiving of a ventricular depolarization signal in the right ventricle.   
     
     
       148. The method of  claim 146 , further comprising:
 locating an electrode through the coronary sinus and in the left ventricle.   
     
     
       149. A heart stimulating device for treating heart failure, comprising:
 an electrode adapted to be disposed in or about the left ventricle to sense ventricular depolarization signals originating from the left ventricle;    a sense amplifier to receive the ventricular depolarization signals originating from the left ventricle;    a pulse generator, connected to the sense amplifier, to generate a stimulating pulse in the event the sense amplifier receives a ventricular depolarization signal originating from the left ventricle; and    an electrode, adapted to be disposed in or about the right ventricle and connected to the pulse generator, to apply the stimulating pulse to the right ventricle in the event the sense amplifier receives a ventricular depolarization signal originating from the left ventricle.   
     
     
       150. The heart stimulating device of  claim 149 , wherein the electrode adapted to be disposed in or about the left ventricle is positioned through the coronary sinus. 
     
     
       151. The heart stimulating device of  claim 149 , wherein the electrode adapted to be disposed in or about the left ventricle stimulates the left ventricle in the event the sense amplifier receives a ventricular depolarization signal originating from the left ventricle. 
     
     
       152. A method for treating a heart suffering from heart failure, comprising:
 receiving ventricular depolarization signals originating from the left ventricle;    generating a stimulating pulse in response to the receiving of a ventricular depolarization signal in the left ventricle; and    applying the stimulating pulse to the right ventricle in response to the receiving of a ventricular depolarization signal in the left ventricle.   
     
     
       153. The method of  claim 152 , the applying further comprising:
 applying stimulating pulses to both the left ventricle and the right ventricle in response to the receiving of a ventricular depolarization signal in the left ventricle.   
     
     
       154. The method of  claim 152 , further comprising:
 locating an electrode through the coronary sinus and in the left ventricle.   
     
     
       155. A method for improving the hemodynamic efficiency of a heart, comprising:
 detecting a cardiac depolarization signal originating from a first ventricle; and    unconditionally stimulating both ventricles for effecting a coordinated contraction of both ventricles when a cardiac depolarization signal originating from the first ventricle is detected.   
     
     
       156. The method of  claim 155 , wherein unconditionally stimulating both ventricles includes providing electrical pulses from a stimulating circuit to both ventricles. 
     
     
       157. The method of  claim 155 , wherein detecting a cardiac depolarization signal further comprises conducting the signal to a sense amplifier to amplify the detected signal, and applying the amplified signal to a control circuit. 
     
     
       158. A heart stimulating device for treating heart failure, comprising:
 an electrode adapted to be disposed in or about a first ventricle for detecting a cardiac depolarization signal originating from the first ventricle;    a sense amplifier to receive the cardiac depolarization signal originating from the first ventricle;    a pulse generator, connected to the sense amplifier, to unconditionally stimulate both ventricles for effecting a coordinated contraction of both ventricles when the cardiac depolarization signal from the first ventricle is detected.   
     
     
       159. The heart stimulating device of  claim 158 , further comprising an electrode adapted to be disposed in or about a second ventricle. 
     
     
       160. The heart stimulating device of  claim 159 , wherein the pulse generator unconditionally stimulates both ventricles by delivering an electronic pulse to the first ventricle via the electrode adapted to be disposed in or about the first ventricle and by delivering an electronic pulse to the second ventricle via the electrode adapted to be disposed in or about the second ventricle. 
     
     
       161. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle; and    stimulating the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected for effecting a coordinate contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       162. The method of  claim 161 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       163. The method of  claim 162 , further comprising locating an electrode in the right ventricle. 
     
     
       164. The method of  claim 161 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle and the right ventricle within a period of time after detecting a depolarization signal from either the left ventricle or the right ventricle, the period of time being sufficient to effect a substantially simultaneous contraction of the ventricles. 
     
     
       165. The method of  claim 164 , wherein the left ventricle and the right ventricle are stimulated within  10  milliseconds after detecting the depolarization signal. 
     
     
       166. The method of  claim 161 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       167. The method of  claim 161 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       168. The method of  claim 161 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       169. The method of  claim 161 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       170. The method of  claim 161 , further comprising stimulating the left ventricle and the right ventricle if a depolarization signal from either the left ventricle or the right ventricle is not detected within a period of time. 
     
     
       171. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals only from one ventricle of the heart;    stimulating the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected for effecting a coordinate contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       172. The method of  claim 171 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       173. The method of  claim 172 , further comprising locating an electrode in the right ventricle. 
     
     
       174. The method of  claim 171 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle and the right ventricle within a period of time after detecting a depolarization signal from the one ventricle, the period of time being sufficient to effect a substantially simultaneous contraction of the ventricles. 
     
     
       175. The method of  claim 174 , wherein the left ventricle and the right ventricle are stimulated within  10  milliseconds after detecting the depolarization signal. 
     
     
       176. The method of  claim 171 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       177. The method of  claim 171 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       178. The method of  claim 171 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       179. The method of  claim 171 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       180. The method of  claim 171 , further comprising stimulating the left ventricle and the right ventricle if a depolarization signal from the one ventricle is not detected within a period of time. 
     
     
       181. The method of  claim 171 , wherein the one ventricle is the right ventricle. 
     
     
       182. The method of  claim 171 , wherein the one ventricle is the left ventricle. 
     
     
       183. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 a sense amplifier for receiving depolarization signals originating from left and right ventricles; and    a pulse generator, connected to the sense amplifier, that generates stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from either the left ventricle or the right ventricle for effecting a coordinated contraction of the ventricles to improve the pumping ability of the heart suffering from heart failure;    a first electrode connected to the pulse generator and adapted to be disposed in or about the left ventricle for sensing depolarization signals originating from the left ventricle and for applying a stimulation pulse to the left ventricle when the sense amplifier receives a ventricular depolarization signal originating from either the left ventricle or the right ventricle; and    a second electrode connected to the pulse generator and adapted to be disposed in or about the right ventricle for sensing depolarization signals originating from the right ventricle and for applying a stimulation pulse to the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from either the left ventricle or the right ventricle.   
     
     
       184. The heart failure treatment device of  claim 183 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       185. The heart failure treatment device of  claim 183 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within a period of time after the sense amplifier receives a depolarization signal originating from the left ventricle or the right ventricle, the period of time being sufficient to effect substantially simultaneous contraction of the left and right ventricles. 
     
     
       186. The heart failure treatment device of  claim 185 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within  10  milliseconds after the sense amplifier receives a depolarization signal originating from the left ventricle or the right ventricle. 
     
     
       187. The heart failure treatment device of  claim 183 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from either the left ventricle or the right ventricle regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       188. The heart failure treatment device of  claim 183 , wherein the stimulation pulses generated by the pulse generator are pacing pulses. 
     
     
       189. The heart failure treatment device of  claim 183 , wherein the stimulation pulse applied to the left ventricle is applied substantially simultaneously with the stimulation pulse applied to the right ventricle. 
     
     
       190. The heart failure treatment device of  claim 183 , wherein the sense amplifier includes a first sense amplifier for receiving depolarization signals originating from the right ventricle and a second sense amplifier for receiving depolarization signals from the left ventricle. 
     
     
       191. The heart failure treatment device of  claim 183 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle if a depolarization signal originating from either the left ventricle or the right ventricle is not detected within a period of time. 
     
     
       192. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 a sense amplifier for receiving depolarization signals originating from a left ventricle or a right ventricle;    a pulse generator, connected to the sense amplifier, that generates stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the left ventricle or the right ventricle for effecting a coordinated contraction of the ventricles to improve the pumping ability of the heart suffering from heart failure;    a first electrode connected to the pulse generator and adapted to be disposed in or about the left ventricle, the first electrode capable of sensing depolarization signals originating from the left ventricle and capable of applying a stimulation pulse to the left ventricle when the sense amplifier receives a ventricular depolarization signal originating from the left ventricle or the right ventricle; and    a second electrode connected to the pulse generator and adapted to be disposed in or about the right ventricle, the second electrode capable of sensing depolarization signals originating from the right ventricle and capable of applying a stimulation pulse to the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the left ventricle or the right ventricle.   
     
     
       193. The heart failure treatment device of  claim 192 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       194. The heart failure treatment device of  claim 192 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within a period of time after the sense amplifier receives a depolarization signal originating from the left ventricle or the right ventricle, the period of time being sufficient to effect substantially simultaneous contraction of the left and right ventricles. 
     
     
       195. The heart failure treatment device of  claim 194 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within  10  milliseconds after the sense amplifier receives a depolarization signal originating from the left ventricle or the right ventricle. 
     
     
       196. The heart failure treatment device of  claim 192 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the left ventricle or the right ventricle regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       197. The heart failure treatment device of  claim 192 , wherein the stimulation pulses generated by the pulse generator are pacing pulses. 
     
     
       198. The heart failure treatment device of  claim 192 , wherein the stimulation pulse applied to the left ventricle is applied substantially simultaneously with the stimulation pulse applied to the right ventricle. 
     
     
       199. The heart failure treatment device of  claim 192 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle if a depolarization signal from the left ventricle or the right ventricle is not detected within a period of time. 
     
     
       200. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 a sense amplifier for receiving depolarization signals originating from only one ventricle of the heart;    a pulse generator, connected to the amplifier for generating stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the one ventricle for effecting a coordinated contraction of the ventricles to improve the pumping ability of the heart suffering from heart failure;    a first electrode connected to the pulse generator and adapted to be disposed in or about the left ventricle for applying a stimulation pulse to the left ventricle when the sense amplifier receives a ventricular depolarization signal originating from the one ventricle; and    a second electrode connected to the pulse generator and adapted to be disposed in or about the right ventricle for applying a stimulation pulse to the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the one ventricle.   
     
     
       201. The heart failure treatment device of  claim 200 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       202. The heart failure treatment device of  claim 200 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within a period of time after the sense amplifier receives a depolarization signal originating from the one ventricle, the period of time being sufficient to effect substantially simultaneous contraction of the left and right ventricles. 
     
     
       203. The heart failure treatment device of  claim 202 , wherein the stimulation pulse is applied to the left ventricle and the stimulation pulse applied to the right ventricle within  10  milliseconds after the sense amplifier receives a depolarization signal originating from the one ventricle. 
     
     
       204. The heart failure treatment device of  claim 200 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle when the sense amplifier receives a ventricular depolarization signal originating from the one ventricle regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       205. The heart failure treatment device of  claim 200 , wherein the stimulation pulses generated by the pulse generator are pacing pulses. 
     
     
       206. The heart failure treatment device of  claim 200 , wherein the stimulation pulse applied to the left ventricle is applied substantially simultaneously with the stimulation pulse applied to the right ventricle. 
     
     
       207. The heart failure treatment device of  claim 200 , wherein the one ventricle is the right ventricle. 
     
     
       208. The heart failure treatment device of  claim 200 , wherein the one ventricle is the left ventricle. 
     
     
       209. The heart failure treatment device of  claim 200 , wherein the pulse generator generates stimulation pulses for application to the left ventricle and the right ventricle if a depolarization signal from the one ventricle is not detected within a period of time. 
     
     
       210. A method for improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle; and    stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability to the heart suffering form heart failure.   
     
     
       211. The method of  claim 210 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       212. The method of  claim 211 , further comprising locating an electrode in the right ventricle. 
     
     
       213. The method of  claim 210 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       214. The method of  claim 210 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       215. The method of  claim 210 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       216. A method for improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from only one ventricle; and    stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability to the heart suffering form heart failure.   
     
     
       217. The method of  claim 216 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       218. The method of  claim 217 , further comprising locating an electrode in the right ventricle. 
     
     
       219. The method of  claim 216 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       220. The method of  claim 216 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       221. The method of  claim 216 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       222. The method of  claim 216 , wherein the one ventricle is the right ventricle. 
     
     
       223. The method of  claim 216 , wherein the one ventricle is the left ventricle. 
     
     
       224. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    a ventricular sense amplifier for detecting depolarization signals originating from a left ventricle and a right ventricle;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal; and    a stimulating circuit capable of stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability to the heart suffering form heart failure.   
     
     
       225. The heart failure treatment device of  claim 224 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       226. The heart failure treatment device of  claim 224 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       227. The heart failure treatment device of  claim 224 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with stimulation of the right ventricle. 
     
     
       228. The heart failure treatment device of  claim 224 , wherein the ventricular sense amplifiers includes a first ventricular sense amplifier connected to the pacing control circuitry for detecting depolarization signals originating from the left ventricle and a second ventricular sense amplifier connected to the pacing control circuitry for detecting depolarization signals originating from the right ventricle. 
     
     
       229. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier capable of detecting depolarization signals originating from an atrium;    a ventricular sense amplifier capable of detecting depolarization signals originating from a left ventricle or a right ventricle;    pacing control circuitry, connected to the atrial sense amplifier, capable of starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal;    a stimulating circuit capable of providing stimulating pulses for application to the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability to the heart suffering form heart failure;    a first electrode responsive to the stimulating circuit and adapted to be disposed in or about the left ventricle, the first electrode capable of sensing depolarization signals originating from the left ventricle and capable of providing stimulating pulses to the left ventricle when the ventricular sense amplifier receives a depolarization signal from the left ventricle or the right ventricle; and    a second electrode responsive to the stimulating circuit and adapted to be disposed in or about the right ventricle, the second electrode capable of sensing depolarization signals originating from the right ventricle and capable of providing stimulating pulses to the right ventricle when the sense amplifier receives a depolarization signal from the left ventricle or the right ventricle.   
     
     
       230. The heart failure treatment device of  claim 229 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       231. The heart failure treatment device of  claim 229 , wherein the left ventricle is stimulated substantially simultaneously with stimulation of the right ventricle. 
     
     
       232. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    a ventricular sense amplifier for detecting depolarization signals originating from only one ventricle;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal; and    a stimulating circuit capable of stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period for effecting coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability to the heart suffering form heart failure.   
     
     
       233. The heart failure treatment device of  claim 232 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       234. The heart failure treatment device of  claim 232 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       235. The heart failure treatment device of  claim 232 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with stimulation of the right ventricle. 
     
     
       236. The heart failure treatment device of  claim 232 , wherein the one ventricle is the right ventricle. 
     
     
       237. The heart failure treatment device of  claim 232 , wherein the one ventricle is the left ventricle. 
     
     
       238. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle; and    stimulating the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected during the atrial-ventricular delay period for effecting a coordinated contraction of the ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure; and    stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of the ventricles.   
     
     
       239. The method of  claim 238 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       240. The method of  claim 239 , further comprising locating an electrode in the right ventricle. 
     
     
       241. The method of  claim 238 , wherein the left ventricle is stimulated and the right ventricle is stimulated within a period of time after a depolarization signal from either the left ventricle or the right ventricle is detected during the atrial-ventricular delay period, the period of time being sufficient for effecting substantially simultaneous contraction of the ventricles. 
     
     
       242. The method of  claim 241 , wherein the left ventricle and the right ventricle are stimulated within  10  milliseconds of the detection of the depolarization signal. 
     
     
       243. The method of  claim 238 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       244. The method of  claim 238 , wherein the left ventricle and the right ventricle are stimulated when a depolarization signal from either the left ventricle or the right ventricle is detected during the atrial-ventricular delay period regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       245. The method of  claim 238 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       246. The method of  claim 238 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       247. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from only one ventricle;    stimulating the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected during the atrial-ventricular delay period for effecting a coordinated contraction of the ventricles; and    stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       248. The method of  claim 247 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       249. The method of  claim 248 , further comprising locating an electrode in the right ventricle. 
     
     
       250. The method of  claim 247 , wherein the left ventricle is stimulated and the right ventricle is stimulated within a period of time after a depolarization signal from the one depolarization is detected during the atrial-ventricular delay period, the period of time being sufficient for effecting substantially simultaneous contraction of the ventricles. 
     
     
       251. The method of  claim 250 , wherein the left ventricle and the right ventricle are stimulated within  10  milliseconds of the detection of the depolarization signal. 
     
     
       252. The method of  claim 247 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       253. The method of  claim 247 , wherein the left ventricle and the right ventricle are stimulated when a depolarization signal from the one ventricle is detected during the atrial-ventricular delay period regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       254. The method of  claim 247 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       255. The method of  claim 247 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       256. The method of  claim 247 , wherein the one ventricle is the right ventricle. 
     
     
       257. The method of  claim 247 , wherein the one ventricle is the left ventricle. 
     
     
       258. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal;    a ventricular sense amplifier for detecting depolarization signals originating from a left ventricle and a right ventricle; and    a stimulating circuit for stimulating the left ventricle and the right ventricle when a depolarization signal from either the left or the right ventricle is detected by the ventricular sense amplifier during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure; and for stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left or right ventricles during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       259. The heart failure treatment device of  claim 259 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       260. The heart failure treatment device of  claim 258 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within a time period after a depolarization signal from either the left or the right ventricle is detected by the ventricular sense amplifier, the time period being sufficient for effecting substantially simultaneous contraction of the left ventricle and the right ventricle. 
     
     
       261. The heart failure treatment device of  claim 260 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within  10  milliseconds of the ventricular sense amplifier detecting a depolarization signal from either the left ventricle or the right ventricle. 
     
     
       262. The heart failure treatment device of  claim 258 , wherein the stimulating circuit stimulates the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected by the ventricular sense amplifier during the atrial-ventricular delay period regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       263. The heart failure treatment device of  claim 258 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       264. The heart failure treatment device of  claim 258 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with stimulation of the right ventricle. 
     
     
       265. The heart failure treatment device of  claim 258 , wherein the ventricular sense amplifiers includes a first ventricular sense amplifier for detecting depolarization signals originating from the left ventricle and second ventricular sense amplifier for detecting depolarization signals originating from the right ventricle. 
     
     
       266. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 a atrial sense amplifier for detecting depolarization signals originating from an atrium;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal;    a ventricular sense amplifier for detecting depolarization signals originating from the left ventricle or the right ventricle;    a stimulating circuit for stimulating the left ventricle and the right ventricle when a depolarization signal from the left ventricle or the right ventricle is detected by the ventricular sense amplifier during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure; and for stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure;    a first electrode adapted to be disposed in or about the left ventricle, the first electrode capable of sensing depolarization signals originating from the left ventricle and capable of providing a stimulating pulse to the left ventricle in response to the stimulating circuit; and    a second electrode adapted to be disposed in or about the right ventricle, the second electrode capable of sensing depolarization signals originating from the right ventricle and capable of providing a stimulating pulse to the right ventricle in response to the stimulating circuit.   
     
     
       267. The heart failure treatment device of  claim 266 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       268. The heart failure treatment device of  claim 266 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       269. The heart failure treatment device of  claim 266 , wherein the left ventricle is stimulated substantially simultaneously with stimulation of the right ventricle. 
     
     
       270. The heart failure treatment device of  claim 266 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within a time period after a depolarization signal from the left ventricle or the right ventricle is detected by the ventricular sense amplifier, the time period being sufficient for effecting substantially simultaneous contraction of the left ventricle and the right ventricle. 
     
     
       271. The heart failure treatment device of  claim 270 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within  10  milliseconds of the ventricular sense amplifier detecting a depolarization signal from the left ventricle or the right ventricle. 
     
     
       272. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal;    a ventricular sense amplifier for detecting depolarization signals originating from only one ventricle; and    a stimulating circuit for stimulating the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected by the ventricular sense amplifier during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure; and for stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       273. The heart failure treatment device of  claim 272 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       274. The heart failure treatment device of  claim 272 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within a time period after a depolarization signal from the one ventricle is detected by the ventricular sense amplifier, the time period being sufficient for effecting substantially simultaneous contraction of the left ventricle and the right ventricle. 
     
     
       275. The heart failure treatment device of  claim 274 , wherein the stimulation circuit stimulates the left ventricle and the right ventricle within  10  milliseconds of the ventricular sense amplifier detecting a depolarization signal from the one ventricle. 
     
     
       276. The heart failure treatment device of  claim 272 , wherein the stimulating circuit stimulates the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected by the ventricular sense amplifier during the atrial-ventricular delay period regardless of whether both ventricles would otherwise contract substantially simultaneously. 
     
     
       277. The heart failure treatment device of  claim 272 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       278. The heart failure treatment device of  claim 272 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with the stimulation of the right ventricle. 
     
     
       279. The heart failure treatment device of  claim 272 , wherein the one ventricle is the right ventricle. 
     
     
       280. The heart failure treatment device of  claim 272 , wherein the one ventricle is the left ventricle. 
     
     
       281. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle;    inhibiting stimulation of the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected during the atrial- ventricular delay period; and      stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the atrial- ventricular delay period.     
     
     
       282. The method of  claim 281 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       283. The method of  claim 282 , further comprising locating an electrode in the right ventricle. 
     
     
       284. The method of  claim 281 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       285. The method of  claim 281 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       286. The method of  claim 281 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       287. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from an atrium;    beginning an atrial-ventricular delay period upon sensing a depolarization signal of the atrium;    sensing for depolarization signals originating from only one ventricle;    inhibiting stimulation of the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected during the atrial-ventricular delay period; and    stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period.   
     
     
       288. The method of  claim 287 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       289. The method of  claim 288 , further comprising locating an electrode in the right ventricle. 
     
     
       290. The method of  claim 287 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       291. The method of  claim 287 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       292. The method of  claim 287 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       293. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    a ventricular sense amplifier for detecting depolarization signals originating from a left ventricle and a right ventricle;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal, and for inhibiting stimulation of the left ventricle and the right ventricle when a depolarization signal from either the left or the right ventricle is detected during the atrial-ventricular delay period; and    a stimulating circuit for stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       294. The heart failure treatment device of  claim 293 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       295. The heart failure treatment device of  claim 293 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       296. The heart failure treatment device of  claim 293 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with the stimulation of the right ventricle. 
     
     
       297. The heart failure treatment device of  claim 293 , wherein the ventricular sense amplifier includes a first ventricular sense amplifier for receiving depolarization signals originating from the right ventricle and a second ventricular sense amplifier for receiving depolarization signals from the left ventricle. 
     
     
       298. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    a ventricular sense amplifier for detecting depolarization signals originating from a left ventricle or a right ventricle;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal, and for inhibiting stimulation of the left ventricle and the right ventricle when a depolarization signal from either the left or the right ventricle is detected during the atrial-ventricular delay period;    a stimulating circuit for providing stimulating pulses for application to the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the left ventricle or the right ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure;    a first electrode adapted to be disposed in or about the left ventricle, the first electrode capable of sensing depolarization signals originating from the left ventricle and capable of providing a stimulating pulse to the left ventricle in response to the stimulating circuit; and    a second electrode adapted to be disposed in or about the right ventricle, the second electrode capable of sensing depolarization signals originating from the right ventricle and capable of providing a stimulating pulse to the right ventricle in response to the stimulating circuit.   
     
     
       299. The heart failure treatment device of  claim 298 , wherein the first electrode is adapted to be positioned through the coronary sinus to the left ventricle. 
     
     
       300. The heart failure treatment device of  claim 298 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       301. The heart failure treatment device of  claim 298 , wherein the left ventricle is stimulated substantially simultaneously with the stimulation of the right ventricle. 
     
     
       302. A heart failure treatment device for improving the pumping ability of a heart suffering from heart failure comprising:
 an atrial sense amplifier for detecting depolarization signals originating from an atrium;    a ventricular sense amplifier for detecting depolarization signals originating from only one ventricle;    pacing control circuitry, connected to the atrial sense amplifier, for starting an atrial-ventricular delay period when the atrial sense amplifier detects an atrial depolarization signal, and for inhibiting stimulation of the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected during the atrial-ventricular delay period; and    a stimulating circuit for stimulating the left ventricle and the right ventricle at the end of the atrial-ventricular delay period if a depolarization signal is not detected from the one ventricle during the atrial-ventricular delay period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       303. The heart failure treatment device of  claim 302 , further comprising an electrode adapted to be positioned through the coronary sinus to the left ventricle for stimulating the left ventricle. 
     
     
       304. The heart failure treatment device of  claim 302 , wherein the stimulating circuit generates pacing pulses for stimulating the left ventricle and the right ventricle. 
     
     
       305. The heart failure treatment device of  claim 302 , wherein the stimulation circuit stimulates the left ventricle substantially simultaneously with the stimulation of the right ventricle. 
     
     
       306. The heart failure treatment device of  claim 302 , wherein the one ventricle is the right ventricle. 
     
     
       307. The heart failure treatment device of  claim 302 , wherein the one ventricle is the left ventricle. 
     
     
       308. A method for improving the pumping ability of a heart suffering from heart failure comprising:
 positioning a first electrode through the coronary sinus to the left ventricle;    positioning a second electrode in the right ventricle;    applying a pacing pulse to the left ventricle through the first electrode;    applying a pacing pulse to the right ventricle through the second electrode substantially simultaneously with application of the pacing pulse to the left ventricle, wherein the pacing pulses are applied to the left ventricle and the right ventricle at a programmed rate.   
     
     
       309. The method of  claim 308 , wherein the pacing pulses are applied at the programmed rate without regard to any sensing. 
     
     
       310. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from a first ventricle; and    stimulating a second ventricle when a depolarization signal from the first ventricle is detected for effecting a coordinate contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of the heart suffering from heart failure.   
     
     
       311. The method of  310 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       312. The method of  claim 310 , wherein the second ventricle is stimulated within a period of time after detecting a depolarization signal from the first ventricle, the period of time being sufficient to effect a substantially simultaneous contraction of both ventricles. 
     
     
       313. The method of  claim 312 , wherein the second ventricle is stimulated within  10  milliseconds after detecting the depolarization signal of the first ventricle. 
     
     
       314. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle; and    stimulating the left ventricle and the right ventricle after a time period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the time period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of a heart suffering from heart failure.   
     
     
       315. A method of improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals originating from only one ventricle; and    stimulating a right ventricle and a left ventricle if a depolarization signal is not detected from the one ventricle during a time period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of a heart suffering from heart failure.   
     
     
       316. A method for improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals origination in an atrium;    sensing for depolarization signals originating from a left ventricle;    sensing for depolarization signals originating from a right ventricle; and    stimulating the left ventricle and the right ventricle after a time period if a depolarization signal is not detected from either the left ventricle or the right ventricle during the time period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of a heart suffering from heart failure.   
     
     
       317. The method of  claim 316 , further comprising stimulating the left ventricle and the right ventricle when a depolarization signal from either the left ventricle or the right ventricle is detected during the time period for effecting a coordinate contraction of the ventricles. 
     
     
       318. The method of  claim 316 , wherein the time period is an atrial-ventricular delay. 
     
     
       319. The method of  claim 316 , wherein the time period is a cardiac cycle interval. 
     
     
       320. The method of  claim 316 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       321. The method of  claim 316 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       322. The method of  claim 316 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       323. The method of  claim 316 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle. 
     
     
       324. A method for improving the pumping ability of a heart suffering from heart failure comprising:
 sensing for depolarization signals origination in an atrium;    sensing for depolarization signals originating from only one ventricle; and    stimulating the left ventricle and the right ventricle after a time period if a depolarization signal is not detected from the one ventricle during the time period for effecting a coordinated contraction of ventricles contracting in an incoordinate manner to improve the pumping ability of a heart suffering from heart failure.   
     
     
       325. The method of  claim 324 , further comprising stimulating the left ventricle and the right ventricle when a depolarization signal from the one ventricle is detected during the time period for effecting a coordinated contraction of the ventricles. 
     
     
       326. The method of  claim 324 , wherein the time period is an atrial-ventricular delay. 
     
     
       327. The method of  claim 324 , wherein the time period is a cardiac cycle interval. 
     
     
       328. The method of  claim 324 , further comprising locating an electrode through the coronary sinus to the left ventricle. 
     
     
       329. The method of  claim 324 , wherein stimulating the left ventricle and the right ventricle includes stimulating only one site in the left ventricle and only one site in the right ventricle. 
     
     
       330. The method of  claim 324 , wherein stimulating the left ventricle and the right ventricle includes applying a pacing pulse to the left ventricle and applying a pacing pulse to the right ventricle. 
     
     
       331. The method of  claim 324 , wherein stimulating the left ventricle and the right ventricle includes stimulating the left ventricle substantially simultaneously with stimulating the right ventricle.