Systems and methods for determining cardiac output

Abstract

The systems and methods described herein determine metrics of cardiac or vascular performance, such as cardiac output, and can use the metrics to determine appropriate levels of mechanical circulatory support to be provided to the patient. The systems and methods described determine cardiac performance by determining aortic pressure measurements (or other physiologic measurements) within a single heartbeat or across multiple heartbeats and using such measurements in conjunction with flow estimations or flow measurements made during the single heartbeat or multiple heartbeats to determine the cardiac performance, including determining the cardiac output. By utilizing a mechanical circulatory support system placed within the vasculature, the need to place a separate measurement device within a patient is reduced or eliminated. The system and methods described herein may characterize cardiac performance without altering the operation of the heart pump (e.g., without increasing or decreasing pump speed).

1 - 23 . (canceled) 
     
     
         24 . A method for determining cardiac performance of a heart, the method comprising:
 monitoring a hemodynamic parameter during operation of a mechanical circulatory support device at a first device operational parameter;   identifying a diastolic period of a heartbeat cycle, based on a shape of the hemodynamic parameter over time;   establishing a time-variant relationship between aortic pressure and blood flow during the diastolic period; and   calculating, based on the time-variant relationship between aortic pressure and blood flow during the diastolic period, total volume of blood induced by the mechanical circulatory support device per heartbeat, to indicate cardiac performance.   
     
     
         25 . The method of  claim 24 , wherein the mechanical circulatory support device is an intravascular blood pump, and wherein monitoring occurs when operating the pump at a first pump speed. 
     
     
         26 . The method of  claim 24 , wherein the hemodynamic parameter is aortic pressure. 
     
     
         27 . The method of  claim 24 , wherein calculating total volume of blood pumped per heartbeat comprises:
 determining, based on the mathematical representative of the hemodynamic parameter over time, vascular compliance and vascular resistance of the systemic vasculature; and   calculating, using the determined vascular compliance and vascular resistance, stroke volume of the systemic vasculature.   
     
     
         28 . A blood vessel sensor comprising:
 a system for inducing blood flow within a patient's blood vessel, the system comprising a motor and an impeller; and   a controller configured to:
 detect changes in resistance of impeller rotation within the blood vessel; 
 maintain a constant impeller rotational speed, based on the detected resistance of impeller rotation; 
 calculate, based on the change in resistance of impeller rotation, vascular compliance and vascular resistance using a transfer function. 
   
     
     
         29 . The blood vessel sensor of  claim 28 , wherein the transfer function is a Windkessel model. 
     
     
         30 . The blood vessel sensor of  claim 28 , wherein the controller is configured to determine a metric indicative of cardiac performance based on the vascular compliance and the vascular resistance. 
     
     
         31 . The blood vessel sensor of  claim 30 , wherein the metric indicative of cardiac performance is at least one of: cardiac output, cardiac power output, stroke volume, stroke work, ejection fraction, cardiac contractility, ventricular elastance, cardiac index, or a prediction of patient survival. 
     
     
         32 . The blood vessel sensor of  claim 28 , wherein the controller is configured to adjust the impeller rotational speed based on at least one of: the vascular resistance, the vascular compliance, or the cardiac output. 
     
     
         33 . The blood vessel sensor of  claim 28 , wherein the controller is configured to:
 receive measurements indicative of aortic pressure for a time period;   detect current delivered to the pump; and   determine, based on the current delivered to the pump, rates of blood flow pumped by the system for the time period,   wherein the calculation of the vascular compliance and the vascular resistance is further based on the measurements indicative of aortic pressure and the rates of blood flow.   
     
     
         34 . The blood vessel sensor of  claim 28 , wherein the system for inducing blood flow within the patient's blood vessel comprises a cannula that is configured to extend within the left ventricle of a heart and a pressure sensor configured to detect at least one of: aortic pressure, left ventricular pressure, or differential pressure. 
     
     
         35 . The blood vessel sensor of  claim 28 , wherein the system for inducing blood flow within the patient's blood vessel is an intracardiac blood pump incorporating the impeller within a shroud. 
     
     
         36 . A blood vessel sensor comprising:
 a system for inducing blood flow within a patient's blood vessel;   a hemodynamic sensor configured to detect a change in a hemodynamic parameter resulting from the induced blood flow; and   a controller configured to receive a sensor signal and calculate resistance of the blood vessel as a function of blood flow within the blood vessel and aortic pressure.   
     
     
         37 . The blood vessel sensor of  claim 36 , wherein the system comprises a motor and an impeller, and wherein the controller is configured to:
 detect change in resistance of impeller rotation within the blood vessel;   maintain a constant impeller rotational speed, based on the detected resistance of impeller rotation; and   transmit pump operation data to a computing device.   
     
     
         38 . The blood vessel sensor of  claim 37 , wherein the pump operation data includes at least one of: pressure measurement, current measurement, change in resistance of impeller rotation, and flow estimation. 
     
     
         39 . The blood vessel sensor of  claim 36 , wherein the controller is configured to:
 receive a first aortic pressure measurement corresponding to a first time and a second aortic pressure measurement corresponding to a second time, wherein the first time and the second time occur during a diastolic fall of a heartbeat;   determine a first rate of blood flow pumped by the blood pump at the first time and a second rate of blood flow pumped by the blood pump at the second time; and   calculate, using (i) the first aortic pressure measurement, (ii) the second aortic pressure measurement, (iii) the first rate of blood flow, and (iv) the second rate of blood flow, a time dependent non-linear model of a vascular system to determine systemic vascular resistance and compliance.   
     
     
         40 . The blood vessel sensor of  claim 39 , wherein the time dependent non-linear model is a Windkessel model. 
     
     
         41 . The blood vessel sensor of  claim 39 , wherein the controller is further configured to determine cardiac output based on the first aortic pressure measurement, the second aortic pressure measurement, the first rate of blood flow, and the second rate of blood flow. 
     
     
         42 . The blood vessel sensor of  claim 39 , wherein the controller is configured to receive pump operation commands from the computing device, wherein the pump operation commands are based on the pump operation data. 
     
     
         43 - 45 . (canceled)