Four-chamber pacing system for optimizing cardiac output and determining heart condition

Abstract

A pacing system and method for providing multiple chamber pacing of a patient's heart, and in particular, pacing programmed for treatment of various forms of heart failure. The system utilizes impedance sensing for determining optimum pacing parameters, e.g., for pacing the left ventricle so that left heart output is maximized. The impedance sensing also is used for determination of arrhythmias or progression of heart failure. Impedance sensing is provided for between selected pairs of the four chambers, to enable optimizing of information for control and diagnosis. In a preferred embodiment/of the invention, impedance measurements are obtained for determining the timing of right heart valve closure or right ventricular contractions, and the timing of delivery of left ventricular pace pulses is adjusted so as to optimally synchronize left ventricular pacing with the right ventricular contractions. Impedance sensing in the left heart also provides timing of mechanical contraction, and the pacemaker controls pacing to maintain bi-ventricular mechanical synchronization adjusted for maximum cardiac output.

1 . A pacing system for providing pacing of a patient's left heart, comprising: 
 first means for obtaining indications of mechanical contractions of the right ventricle;    left ventricular pacing means for pacing the left ventricle; and    LV control means for controlling the timing of said left ventricular pacing relative to indicated right ventricular mechanical contractions:    
     
     
         2 . The pacing system as described in    claim 1   , comprising 
 second means for obtaining indications of mechanical contractions of the left ventricle, and wherein said LV control means has means for controlling the timing of said left ventricular pacing so as to provide substantially synchronous left and right ventricular mechanical contractions.    
     
     
         3 . The pacing system as described in    claim 1   , wherein said LV control means has means for delivering a left ventricular pacing pulse just before the expected time of the next right ventricular mechanical contraction.  
     
     
         4 . The pacing system as described in    claim 2   , comprising left atrial pacing means for pacing the patient's left atrium; left AV control means for controlling the left AV delay between pacing the left atrium and the left ventricle, cardiac output means for measuring left heart output as a function of said left AV delay, and wherein said left AV control means further comprises maximizing means for adjusting said left AV delay to maximize left cardiac output.  
     
     
         5 . The pacing system as described in    claim 4   , comprising means for sensing sinus signals, and left atrial timing means for timing delivery of left atrial pacing pulses relative to said sinus signals.  
     
     
         6 . The system as described in    claim 1   , wherein said first means comprises an impedance measuring circuit for obtaining an impedance signal representative of impedance between the patient's right atrium and right ventricle, and processing means for processing said impedance signal to determine the timing of right heart valve closures.  
     
     
         7 . The system as described in    claim 1   , comprising second impedance means for obtaining a left impedance signal representative of impedance change over the patient's left heart, and second processing means for processing said left impedance signal to obtain a measure of left heart output.  
     
     
         8 . The system as described in    claim 7   , comprising third processing means for processing said left impedance signal to obtain filling signals indicative of the filling of the left ventricle, and wherein said LV control means comprises means for controlling timing of said left ventricular pacing signals as a function of said filling signals.  
     
     
         9 . The system as described in    claim 1   , further comprising means for obtaining indications of left ventricular mechanical contractions, and wherein said LV control means comprises mechanical sync means for controlling said left ventricular pacing to achieve mechanical synchrony of said left and right mechanical contractions.  
     
     
         10 . The system as described in    claim 9   , wherein said mechanical sync means comprises adjusting means for adjusting the timing of aid left ventricular pacing so as to maximize left heart output.  
     
     
         11 . A four-chamber pacing system for providing pacing of a patient's left heart to improve cardiac output, comprising: 
 RV means for determining the timing of right ventricular mechanical contractions;    LV means for determining the timing of left ventricular mechanical contractions; and    pacing sync means for pacing the patient's left ventricle; and    control means for controlling said pacing means so as to substantially synchronize said left and right mechanical contractions;    
     
     
         12 . The four-chamber pacing system as described in    claim 13   , comprising: 
 LA means for determining the timing of left atrial depolarization;    CO means for measuring cardiac output from the patient's left heart; and    wherein said control sync means comprises LAVD means for controlling said pacing means to deliver pacing pulses to said patient's left ventricle at a left atrio-ventricular delay following left atrial depolarizations, and adjusting means for adjusting said left atrio-ventricular delay to correspond to maximum measured cardiac output.    
     
     
         13 . A system for bi-ventricular pacing, comprising: 
 RVP generating means for generating and delivering pacing pulses to the patient's right ventricle;    LVP generating means for generating and delivering pacing pulses to the patient's left ventricle;    atrial sense means for determining the cyclical time of excitation of the patient's right and left atria;    RAVD control means for controlling said RVP generating means to deliver pace pulses at a predetermined RAVD delay following right atrial activation;    LAVD control means for controlling said LVP generating means to generate pace pulses at an LAVD delay following left atrial activation;    output means for determining a measure of cardiac output from the patient's left ventricle;    adjusting means for adjusting said LAVD and RAVD delays and determining the optimum relationship of said LAVD and RAVD delays which results in maximized cardiac output; and    program means for programming said RAVD control means and said LAVD control means to control delivery of pacing pulses to the left and right ventricles with said optimum relation.    
     
     
         14 . The system as described in    claim 13   , comprising second adjusting means for adjusting said LAVD and RAVD equally, and wherein said output means obtains values of LAVD and RAVD corresponding to maximum cardiac output and 
 wherein said program means controls said RAVD control means and said LAVD control means to deliver pacing pulses with said values.    
     
     
         15 . The system as described in    claim 14   , comprising means for obtaining the difference between LMAVD and RMAVD corresponding to optimized cardiac output, and means for maintaining said difference.  
     
     
         16 . A method of cardiac pacing, comprising: 
 cyclically determining mechanical events indicative of left ventricular contraction and right ventricular contraction;    cyclically determining cardiac output from the patient's left ventricle;    pacing said patient's left ventricle with varying timing relative to said right ventricular contractions and determining the relative mechanical synchronization of left ventricular and right ventricular contractions which results in maximum cardiac output; and    maintaining said relative mechanical synchronization.    
     
     
         17 . A method as described in    claim 16   , comprising: 
 determining atrial excitations of the patient;    controlling delivery of each left ventricular pace pulse at an LAVD delay following each said atrial excitation; and    adjusting said LAVD to obtain said relative mechanical synchronization for optimum cardiac output.    
     
     
         18 . The method as described in    claim 16   , comprising pacing the patient's right ventricle at an RAVD delay a following said atrial excitation, and controlling said RAVD and LAVD delays to maintain said relative mechanical synchronization.  
     
     
         19 . The method as described in    claim 17   , comprising.  
     
     
         20 . A method of bi-ventricular pacing, comprising sensing sinus signals from the patient's right atrium; 
 cyclically generating and delivering left and right ventricular pace pulses for pacing the patient's left and right ventricles respectively;    cyclically determining a measure of cardiac output from the patient's left ventricle; and    adjusting the relative timing of said left and right ventricular pace pulses to correspond to maximum cardiac output.    
     
     
         21 . The method as described in    claim 20   , comprising sensing patient-sinus signals, timing out an LAVD delay between a sensed sinus signal and delivery of the left ventricular pace pulse and an RAVD delay between a sensed sinus signal and delivery of a right ventricular pace pulse, varying said LAVD delay relative to said RAVD delay, and determining the relationship between said LAVD delay and said RAVD delay which results in said maximum cardiac output.  
     
     
         22 . The method as described in    claim 21   , having electrodes positioned in each of a patient's four heart chambers, comprising further adjusting both said LAVD and RAVD delays by equal amounts and determining the values of said delays corresponding to maximum cardiac output.  
     
     
         23 . A four chamber pacing system, having electrodes positioned in each of a patient's four heart chambers, comprising: 
 impedance means for obtaining impedance measurements between a selected pair of said four chambers;    processing means for processing said impedance measurements, and determining changes in said measurements over a period of time; and    determining means for determining whether any said change occurs which indicates a physically abnormal heart condition.    
     
     
         24 . The system as described in    claim 22   , wherein said determining means determines whether any such change occurs which is indicative of an arrhythmia.  
     
     
         25 . The system as described in    claim 22   , wherein said determining means comprises means for determining whether said any such change occurs which indicates a heart failure condition.  
     
     
         26 . The system as described in    claim 22   , comprising programmable selection means for selecting impedance measurements between any two of said four heart chambers.