Devices, systems, and methods to evaluate cardiovascular function

Abstract

Methods of determining an index of vessel and heart function are disclosed. The methods determine the maximum volume and rate of change of volume so that an efficiency of the heart can be determined. Conductance readings indicative of the heart can be taken from a variety of locations such as the lumen of a vessel, the lumen of a heart, the pericardial space, and the epicardial surface. Said conductance readings are then used to determine the efficiency of the heart.

1 . A method of determining an index of heart function, the method comprising the steps of:
 positioning an impedance device at a heart location selected from the group consisting of: a pericardial space on a surface of the heart, a lumen of the heart, or an epicardial surface of the heart;   measuring a conductance at the heart location during a cardiac cycle using the impedance device; and   generating an efficiency model of the heart from the conductance, wherein the conductance comprises parallel conductance.   
     
     
         2 . The method of  claim 1 , wherein the step of measuring the conductance during the cardiac cycle further comprises the step of obtaining a parallel conductance measurement. 
     
     
         3 . The method of  claim 1 , wherein the step of measuring a conductance during a cardiac cycle further comprises the step of measuring a change in conductance; and
 the step of generating an efficiency model of the heart further comprises the step of generating an efficiency model of the heart from the measurement of the change in conductance.   
     
     
         4 . The method of  claim 3 , further comprising the step of calculating a max rate of change of a cross sectional area of the heart based on the change in conductance; and
 wherein the step of generating an efficiency model of the heart further comprises generating an efficiency model of the heart from the calculated max rate of change of the cross sectional area.   
     
     
         5 . The method of  claim 1 , wherein the step of generating an efficiency model further comprises the step of comparing the conductance to a rate of volumetric change of the heart. 
     
     
         6 . The method of  claim 1 , wherein the step of measuring a conductance comprises multiple conductance measurements to determine the volume of the heart. 
     
     
         7 . The method of  claim 1 , wherein the step of generating an efficiency model further comprises the step of evaluating the maximum rate of volumetric change of the heart. 
     
     
         8 . A method of determining an index of heart function, the method comprising the steps of:
 positioning an impedance device directly onto an epicardial surface of the heart, the impedance device comprising a first excitation electrode, a second excitation electrode, a first detection electrode, and a second detection electrode;   measuring a conductance during a cardiac cycle from the epicardial surface of the heart using the impedance device; and   generating an efficiency model of the heart from the conductance, wherein the conductance comprises parallel conductance.   
     
     
         9 . The method of  claim 8 , wherein the step of measuring the conductance during the cardiac cycle further comprises the step of obtaining a parallel conductance measurement. 
     
     
         10 . The method of  claim 8 , wherein the step of measuring a conductance during a cardiac cycle further comprises the step of measuring a change in conductance; and
 the step of generating an efficiency model of the heart further comprises the step of generating an efficiency model of the heart from the measurement of the change in conductance.   
     
     
         11 . The method of  claim 10 , further comprising the step of calculating a max rate of change of a cross sectional area of the heart based on the change in conductance; and
 wherein the step of generating an efficiency model of the heart further comprises generating an efficiency model of the heart from the calculated max rate of change of the cross sectional area.   
     
     
         12 . The method of  claim 8 , wherein the step of generating an efficiency model further comprises the step of comparing the conductance to a rate of volumetric change of the heart. 
     
     
         13 . The method of  claim 8 , wherein the step of measuring a conductance comprises multiple conductance measurements to determine the volume of the heart. 
     
     
         14 . The method of  claim 8 , wherein the step of generating an efficiency model further comprises the step of evaluating the maximum rate of volumetric change of the heart. 
     
     
         15 . A method of determining an index of vessel function, the method comprising the steps of:
 introducing an impedance device into a lumen of a vessel;   measuring a conductance from the lumen of the vessel during a cardiac cycle using the impedance device; and   generating an efficiency model of the heart from the conductance, wherein the conductance measurement comprises a parallel conductance.   
     
     
         16 . The method of  claim 15  wherein the step of measuring the conductance during the cardiac cycle further comprises the step of obtaining a parallel conductance measurement. 
     
     
         17 . The method of  claim 1 , wherein the step of measuring a conductance during a cardiac cycle further comprises the step of measuring a change in conductance; and
 the step of generating an efficiency model of the heart further comprises the step of generating an efficiency model of the heart from the measurement of the change in conductance.   
     
     
         18 . The method of  claim 17 , further comprising the step of calculating a max rate of change of a cross sectional area of the heart based on the change in conductance; and
 wherein the step of generating an efficiency model of the heart further comprises generating an efficiency model of the heart from the calculated max rate of change of the cross sectional area.   
     
     
         19 . The method of  claim 15 , wherein the step of generating an efficiency model further comprises the step of comparing the conductance to a rate of volumetric change of the heart. 
     
     
         20 . The method of  claim 15 , wherein the step of generating an efficiency model further comprises the step of evaluating the maximum rate of volumetric change of the heart.