Method and system for remote hemodynamic monitoring

Abstract

A cardiac sensor system includes implanted cardiac sensor assemblies and an external controller which receives information from the implanted sensors. The sensors permit direct measurement of a number of physiologic parameters. The external controller permits calculation of a variety of performance values based on the measured physiological parameters. Optionally, patient oxygen consumption can be measured externally and combined with the internally measured physiologic parameters in order to calculate a variety of unique performance values.

1 . A cardiac sensor system implantable in a heart, said system comprising: 
 means for measuring a cardiac characteristic at least one point in the cardiac cycle;    means for measuring a myocardial characteristic at least one point in the cardiac cycle; and    means for transmission of the data from an implanted location in the heart to an external location.    
     
     
         2 . A cardiac sensor system as in  claim 1 , wherein the means for measuring a cardiac characteristic comprises a sensor adapted to measure pressure, differential pressure, volume, temperature, pH hemocrit, oxygen concentration, regurgitant flow, and cardiac valve area.  
     
     
         3 . A cardiac sensor system as in  claim 1 , wherein the means for measuring a myocardial characteristic comprises a sensor adapted to measure myocardial displacement, myocardial compliance, myocardial dimensions such as thickness, myocardial strain, myocardial expansibility, myocardial contractility, myocardial density, myocardial temperature, myocardial thermal conductivity, myocardial electrical conductivity, myocardial acoustic velocity, myocardial force, and myocardial stress.  
     
     
         4 . A cardiac sensor system as in  claim 1 , further comprising a flame, wherein the cardiac characteristic measuring means and the myocardial characteristic measuring means are locked on the frame.  
     
     
         5 . A cardiac sensor system as in  claim 4 , wherein the frame is implantable in tissue.  
     
     
         6 . A cardiac sensor system as in  claim 5 , wherein the frame is implantable across a cardiac wall.  
     
     
         7 . A cardiac sensor system as in  claim 1 , further comprising a power source control circuitry, and a transmitter, wherein the transmitter is adapted to transmit signals from the sensors to an external receiver.  
     
     
         8 . A cardiac sensor system as in  claim 7 , wherein the power source includes a coil for receiving externally generated power.  
     
     
         9 . A cardiac sensor system ad in  claim 7 , wherein the power source includes a battery.  
     
     
         10 . A cardiac sensor system as in  claim 7 , further comprising a receiver adapted to receive signals generated externally and communicate with the control circuitry to modify or initiate function of at least one of the sensors.  
     
     
         11 . A cardiac sensor assembly implantable across a cardiac wall, said assembly comprising: 
 means for spanning the cardiac wall to provide surfaces on each side of the wall; and 
 at least one sensor on each surface.  
   
     
     
         12 . A cardiac sensor as in  claim 11 , wherein the spanning means comprises a pair of anchors joined by a tether.  
     
     
         13 . A cardiac sensor as in  claim 12 , wherein the anchors contact the cardiac wall over a surface area in the range from 1 mm 2  to 100 mm 2 .  
     
     
         14 . A cardiac sensor as in  claim 12 , wherein the tether comprises electrical conductors coupling the anchors together, wherein at least some of the sensors are coupled to some of the wires.  
     
     
         15 . A cardiac sensor as in  claim 11 , wherein at least one of the sensors measures a cardiac characteristic selected from the group consisting of pressure, differential pressure, volume, temperature, pH, hemocrit, oxygen concentration, regurgitant flow, cardiac output, and cardiac valve area.  
     
     
         16 . A cardiac sensor as in  claim 15 , wherein at least another of the sensors measures a myocardial characteristic selected from the group consisting of myocardial displacement, myocardial dimensions such as thickness, myocardial strain, myocardial compliance, myocardial expansibility, myocardial contractility, myocardial density, 
 myocardial temperature, myocardial thermal conductivity, myocardial electrical conductivity, myocardial acoustic velocity, myocardial force, and myocardial stress.    
     
     
         17 . A cardiac sensor as in  claim 11 , further comprising a power source control circuitry, and a transmitter, wherein the transmitter is adapted to transmit signals from the sensors to an external receiver.  
     
     
         18 . A cardiac sensor as in  claim 17 , wherein the power source includes a coil for receiving externally generated power.  
     
     
         19 . A cardiac sensor as in  claim 17 , wherein the power source includes a battery.  
     
     
         20 . A cardiac sensor as in  claim 17 , further comprising a receiver adapted to receive signals generated externally and communicate with the control circuitry to modify or initiate function of at least one of the sensors.  
     
     
         21 . A cardiac sensor system implantable across a cardiac wall, said system comprising means for measuring displacement of opposite surfaces of the cardiac wall over time.  
     
     
         22 . A cardiac sensor system as in  claim 21 , wherein the displacement measuring means comprises a first position locator positionable on one surface of the cardiac wall and a second position locator positionable on the other surface of the cardiac wall and means for measuring the displacement between the two locations.  
     
     
         23 . A cardiac sensor system as in  claim 22 , further comprising means for spanning the cardiac wall, wherein the position locators on opposite surfaces of the cardiac wall are connected by the spanning means.  
     
     
         24 . A cardiac sensor system as in  claim 22 , wherein the position locators are independently implantable in the opposite surfaces of the cardiac wall.  
     
     
         25 . A cardiac sensor system implantable across a cardiac wall, said system comprising means for measuring expansibility across the wall over time.  
     
     
         26 . A cardiac sensor system as in  claim 25 , further comprising means for spanning the cardiac wall, wherein the expansibility measuring means is disposed on or in the spanning means.  
     
     
         27 . A cardiac sensor system as in  claim 26 , wherein the expansibility measuring means comprises a strain gauge mounted on the wall spanning means, wherein the opposite ends of the wall spanning means are anchored on opposite surfaces of the cardiac wall so that an expansive force exerted by the wall applies a tensile force on the wall spanning means which is measured by the strain gauge.  
     
     
         28 . A cardiac sensor system implantable on a cardiac wall, said system comprising means for measuring muscular contractility over a surface of the wall over time.  
     
     
         29 . A cardiac sensor system as in  claim 28 , wherein the muscular contractility measuring means comprises a planar strain gauge.  
     
     
         30 . A cardiac sensor system as in  claim 29 , wherein the planar strain gauge has a circular configuration.  
     
     
         31 . A cardiac sensor system as in  claim 29 , wherein the planar strain gauge has an orthogonal configuration.  
     
     
         32 . A cardiac sensor system implantable on or across a cardiac wall, said system comprising means for measuring myocardial compliance.  
     
     
         33 . A cardiac sensor system as in  claim 32 , wherein the compliance measuring means comprises a probe which pushes against the myocardium to measure stiffness as a ratio offeree and displacement of the probe.  
     
     
         34 . A system for assessing cardiac status of a patient, said system comprising: 
 a first interface adapted to receive data from cardiac sensors implanted in a patient and produce a plurality of outputs corresponding to said data;    a second interface adapted to receive external data selected from the group consisting of ambient pressure, patient oxygen consumption data, and patient carbon dioxide production data from a breath analyzer; and    a processor adapted to receive data from both interfaces and to calculate one or more cardiac performance values from the received data.    
     
     
         35 . A system as in  claim 34 , wherein the first interface is adapted to receive cardiac characteristic data transmitted from an implanted cardiac sensor and selected from the group consisting of pressure, differential pressure, volume, temperature, pH, hemocrit, oxygen concentration, regurgitant flow, cardiac output, and cardiac valve area.  
     
     
         36 . A system as in  claim 34 , wherein the first interface is adapted to receive myocardial characteristic data transmitted from an implanted cardiac sensor and selected from the group consisting of myocardial displacement, myocardial dimensions such as thickness, myocardial strain, myocardial compliance, myocardial expansibility, myocardial contractility, myocardial density, myocardial temperature, myocardial thermal conductivity, myocardial electrical conductivity, myocardial acoustic velocity, myocardial force, and myocardial stress.  
     
     
         37 . A system as in  claim 34 , wherein the first interface comprises a radiofrequency receiver adapted to receive plurality of different signals from different implanted sensors and input corresponding data to the processor.  
     
     
         38 . A system as in  claim 34 , wherein the second interface is adapted to receive at least inhalation and exhalation volumes, oxygen concentrations, and ambient pressure.  
     
     
         39 . A system as in  claim 38 , wherein the second interface comprises a mouthpiece, a pressure transducer, and analysis and measurement circuitry adapted to input corresponding data to the processor.  
     
     
         40 . A system as in  claim 34 , wherein the processor is adapted to calculate a cardiac hypertrophy value by performing the following steps: 
 determining a cardiac output value based on oxygen consumption data received from the second interface and blood oxygen concentration data received from the first interface;    determining a myocardial thickness change at two points in the cardiac cycle based on data received from a muscle displacement sensor implanted in the patient's heart through the first interface; and    determining the hypertrophy value based at least in part on the ratio of the cardiac output value and the myocardial thickness change.    
     
     
         41 . A system as in  claim 34 , wherein the processor is adapted to calculate a ventricular performance value by performing the following steps: 
 determining a cardiac output value based on oxygen consumption data received from the second interface and blood oxygen concentration data received from the first interface;    determining a change in ventricular pressure at two points in the cardiac cycle based on data received from a pressure sensor implanted in a patient's heart through the first interface;    determining a change in a myocardial contraction force at corresponding points in the cardiac cycle based on data received from a muscle contraction force sensor implanted in the patient's heart; and    determining the ventricular performance value based at least in part on the ratio of the determined changes in ventricular pressure and myocardial contraction force.    
     
     
         42 . A system as in  claim 34 , wherein the processor is adapted to calculate a cardiac efficiency value by performing the following steps: 
 determining a maximum pressure difference between a right ventricle or atrium and a left ventricle or atrium based on pressure data received from pressure sensors in the right and left ventricle or atrium through the first interface;    determining a myocardial thickness change at two points in the cardiac cycle based on data received from a muscle displacement sensor implanted across the myocardium through the first interface;    determining a myocardial contraction force difference at a location on the myocardium based on data received from a muscle contraction force sensor in the patients heart through the first interface;    determining a cardiac output value based on oxygen consumption data received from the second interface and blood oxygen concentration data received from the first interface; and    determining a cardiac efficiency value based at least in part on the cardiac output value, the determined maximum pressure difference, the determined myocardial thickness change, and the determined myocardial difference contraction force.    
     
     
         43 . A method for measuring a cardiac performance value, said method comprising: 
 measuring a cardiac characteristic at least one point in the cardiac cycle;    measuring a myocardial characteristic at least one point in the cardiac cycle; and    determining the cardiac performance value based on a ratio of the measured cardiac characteristic and the measured myocardial characteristic.    
     
     
         44 . A method as in  claim 43 , wherein the cardiac characteristic is selected from the group consisting of intracardiac pressure, intracardiac differential pressure, intracardiac volume, temperature, pH, hemocrit, oxygen concentration, intracardiac regurgitant flow, cardiac output, and cardiac valve area.  
     
     
         45 . A method as in  claim 43 , displacement, myocardial dimensions such as thickness, myocardial strain, myocardial compliance, myocardial wherein the myocardial characteristic is selected from the group consisting of myocardial contractility, myocardial density, myocardial temperature, myocardial thermal conductivity, myocardial electrical conductivity, myocardial acoustic velocity, myocardial force, and myocardial stress.  
     
     
         46 . A method as in  claim 43 , wherein the cardiac characteristic and the myocardial characteristic are measured at the same point on the cardiac cycle.  
     
     
         47 . A method as in  claim 43 , wherein at least one of the cardiac characteristic and the myocardial characteristic is a difference in values measured at two points on the cardiac cycle.  
     
     
         48 . A method as in  claim 43 , wherein both the cardiac characteristic and the myocardial characteristic are differences in values measured at the same two points on the cardiac cycle.  
     
     
         49 - 99 . (canceled)