Cardiovascular assist system that quantifies heart function and facilitates heart recovery
The systems, devices, and methods presented herein use a heart pump to obtain measurements of cardiovascular function. The heart pumps described herein can operate in parallel with and unload the heart. The system can quantify the functioning of the native heart by measuring certain parameters/signals such as pressure or motor current, then calculate and display one or more metrics of cardiovascular function. These metrics, such as left ventricular end diastolic pressure (LVEDP), left ventricular pressure, and contractility, provide valuable information to a user regarding a patient's state of heart function and recovery.
1. A heart pump system comprising:
a catheter;
a motor;
a rotor operatively coupled to the motor; and
a pump housing at least partially surrounding the rotor so that actuating the motor drives the rotor and pumps blood through the pump housing;
a sensor configured to detect a hemodynamic parameter over time; and
a controller configured to:
detect over time a motor parameter associated with the motor,
receive an input from the sensor of the detected hemodynamic parameter over time,
determine a relationship between the detected hemodynamic parameter and the detected motor parameter,
characterize the relationship between the hemodynamic parameter and the motor parameter using a polynomial best fit algorithm,
store the determined relationship in a memory,
determine a cardiac cycle phase from the relationship between the hemodynamic parameter and the motor parameter,
obtain a hysteresis curve based on the relationship between the hemodynamic parameter and the motor parameter, and
select a sample time on the hysteresis curve corresponding to the cardiac cycle phase.
2. The heart pump system of claim 1 , wherein the motor parameter is current delivered to the motor, power delivered to the motor, or motor speed.
3. The heart pump system of claim 1 , wherein the controller is further configured to determine at least one cardiovascular metric by extracting an inflection point, a local slope change, or a curvature change from the characterized relationship between the detected hemodynamic parameter and the motor parameter.
4. The heart pump system of claim 3 , wherein the at least one cardiovascular metric is at least one of contractility, stroke volume, ejection fraction, chamber pressure, stroke work, cardiac output, cardiac power output, left ventricular pressure, preload state, afterload state, heart rate, heart recovery, flow load state, variable volume load state, cardiac cycle volume load state, or cardiac cycle flow state.
5. The heart pump system of claim 4 , wherein the at least one cardiovascular metric is the left ventricular end diastolic pressure (LVEDP).
6. The heart pump system of claim 5 , wherein the hemodynamic parameter is aortic pressure, the motor parameter is current, and wherein characterizing the relationship includes fitting an equation to at least a portion of data representing the measured current and a pressure head calculated from the measured current and the aortic pressure.
7. The heart pump system of claim 6 , the controller further configured to:
determine, from the equation fit to at least a portion of the data representing the measured current and pressure head, an LVEDP point; and
access a look-up table to determine an actual LVEDP value from the LVEDP point in the pressure head data.
8. The heart pump system of claim 7 , wherein determining an LVEDP point includes identifying the change in slope, the change in curvature or the inflection point in the equation fit to at least a portion of the current and the pressure head.
9. The heart pump system of claim 1 , wherein determining the cardiac cycle phase further comprises:
detecting that the cardiac cycle phase is in diastolic relaxation when the sample time corresponds to a segment of the hysteresis curve corresponding to an increasing pressure head; or
detecting that the cardiac cycle phase is in diastolic filling when the sample time corresponds to a segment of the hysteresis curve corresponding to a decreasing pressure head following diastolic relaxation to a point distinguished by a rapid change in slope or curvature, or identification of the inflection point; or
detecting that the cardiac cycle phase is in systole when the sample time corresponds to a segment of the hysteresis curve having a decreasing pressure head from the inflection point to a minimum pressure head.
10. The heart pump system of claim 1 , wherein the motor parameter and hemodynamic parameter are detected over a portion of a cardiac cycle.
11. The heart pump system of claim 1 , wherein the motor parameter and hemodynamic parameter are detected over one or more cardiac cycles.
12. The heart pump system of claim 1 , wherein the motor is configured to maintain a substantially constant speed of the rotor during actuation of the rotor.
13. The heart pump system of claim 1 , wherein the controller is further configured to store the at least one cardiovascular metric in a memory with a previously determined at least one cardiovascular metric.
14. The heart pump system of claim 1 , comprising an integrated motor positioned near the distal end of the catheter proximate the heart pump.
15. A heart pump system comprising:
a catheter; a motor;
a rotor operatively coupled to the motor;
a pump housing at least partially surrounding the rotor so that actuating the motor drives the rotor and pumps blood through the pump housing, and
a pressure sensor configured to detect an aortic pressure over time; and a
controller configured to:
detect a motor parameter over time,
receive the aortic pressure over time from the sensor,
store a relationship between the motor parameter and the aortic pressure in the memory;
determine a time period in which an inflection point of a curve based on the relationship is found, wherein the inflection point is indicative of LVEDP, and
identify the inflection point of the curve based on the determined time period.
16. The heart pump system of claim 1 , wherein the controller is configured to adjust, based on the relationship, operation of the heart pump system to change the driving of the rotor.
17. The heart pump system of claim 1 , wherein the controller is further configured to:
display an indicator of the determined relationship;
receive a request for adjustment of operation of the heart pump system, and
adjust, based on the request, operation of the motor to drive the heart pump system.
18. The heart pump system of claim 15 , wherein determining a time period in which the inflection point indicative of LVEDP is found includes identifying a time period in which the received motor parameter changes.
19. The heart pump system of claim 18 , the controller further configured to determine LVEDP based on the inflection point from a dynamic curve look-up table in the memory.
20. The heart pump system of claim 18 , wherein the controller is further configured to receive an ECG signal, and wherein determining a time period in which an inflection point indicative of LVEDP is found includes identifying a time period in which the ECG signal indicates an end cycle of diastole.
21. The heart pump system of claim 15 , wherein the controller is further configured to determine from the stored relationship at least one heart metric, and wherein the heart metric is at least one of contractility, stroke volume, ejection fraction, chamber pressure, stroke work, cardiac output, cardiac power output, left ventricular pressure, preload state, afterload state, heart rate, heart recovery, flow load state, variable volume load state, cardiac cycle volume load state, or cardiac cycle flow state.
22. The heart pump system of claim 15 , wherein the motor parameter is one of motor current, change in motor current, variability of motor current, and a net integrated area of motor current and pressure.
23. The heart pump system of claim 15 , the controller further configured to determine a cardiac cycle phase from the relationship between the motor parameter and the aortic pressure, wherein the cardiac cycle phase is determined using one or more of ECG data, a hemodynamic parameter, the motor parameter and the motor speed, and/or a slope of the aortic pressure.
24. The heart pump system of claim 15 , wherein the motor is configured to maintain a substantially constant rotor speed during actuation of the rotor.
25. The heart pump system of claim 15 , wherein the heart pump further comprises an integrated motor sized and configured for insertion into a patient's vasculature.