System and method for system identification

Abstract

The systems and methods described herein determine a measure of cardiac or vascular performance, such as cardiac output, and may be used to determine an appropriate level of mechanical circulation support to be provided to a patient. The described systems and methods determine heart performance by determining aortic pressure measurements (or other physiological measurements) within a single cardiac beat or across multiple cardiac beats, and using such measurements in combination with flow estimates or flow measurements derived during a single or multiple cardiac pulsations to determine cardiac performance, including determining cardiac output. By utilizing a mechanical circulation support system placed within the vasculature, the need to place a separate measurement device within a patient is reduced or eliminated. The systems and methods described herein can characterize heart performance without altering the operation of the heart pump (e.g., without increasing or decreasing the pump speed).

Description

[0001] This application is a divisional application of the invention patent application with application number 201980054311.7, application date June 19, 2019, and titled “System and method for system identification”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 687,133, filed on June 19, 2018, entitled “METHODS AND SYSTEMS FOR IMPROVED ASSESSMENT OF VASCULAR AND CARDIAC STATE”; U.S. Provisional Patent Application No. 62 / 863,136, filed on June 18, 2019, entitled “SYSTEMS AND METHODS FOR SYSTEM IDENTIFICATION”; and U.S. Provisional Patent Application No. 62 / 863,146, filed on June 18, 2019, entitled “SYSTEMS AND METHODS FOR DETERMINING CARDIAC PERFORMANCE”. The entire contents of the above-referenced applications are incorporated herein by reference. Technical Field

[0004] none. Background Art

[0005] Cardiovascular disease is a leading cause of morbidity, mortality, and healthcare burden worldwide. Various treatment modalities have been developed for cardiac health, ranging from medications to mechanical devices and transplantation. Temporary cardiac support devices, such as heart pump systems, provide hemodynamic support and promote cardiac recovery. Some heart pump systems are inserted percutaneously into the heart and can operate in parallel with the native heart to supplement cardiac output, such as The invention relates to a heart pump system that can measure and / or calculate heart pump parameters useful for determining patient health and judging the operation of the heart pump system. The pump can be positioned across the aortic valve of the heart so that the blood inlet of the pump is in the left ventricle and the outlet of the pump is in the aorta. In some embodiments, the pump is positioned in the right ventricle of the heart. If the pump is positioned across the aortic valve so that the blood inlet of the pump is in the left ventricle and the outlet of the pump is in the aorta, the pump promotes native heart operation by unloading the left ventricle.

[0006] The duration of cardiac support (as measured by the volume flow of blood delivered by the pumping device) or required by each patient can vary. It is difficult for clinicians to directly and quantitatively determine how much support the device should deliver or when to terminate the use of the heart pump system, especially for patients recovering from interventions or other cardiac care. Therefore, clinicians tend to rely on judgment and indirect estimates of cardiac function, such as using fluid-filled catheters to measure intracardiac or intravascular pressures. Cardiac output (CO) is particularly difficult to quantify. The pulmonary artery catheter (PAC) can provide real-time measurements of central venous pressure and pulmonary artery pressure, and CO can be estimated using Fick's law by systemic oxygen consumption or bolus thermodilution. Since assumptions must be made to derive CO measurements and corresponding lack of fidelity and more invasive measurements, PAC cannot establish a reliable association with clinical outcomes. Measurements made by PAC ignore the dynamic changes in cardiac function and are therefore discontinuous, and the nonlinear aspects of systemic ventricular vascular connections cannot be fully captured. Summary of the invention

[0007] The systems and methods described herein determine a measure of cardiac performance (such as CO) for a single heart beat of a patient, and the measure can be used to determine the appropriate level of mechanical circulatory support to be provided to the patient. The cardiac performance measure can be measured over multiple beats and mathematically processed to derive a model of the performance of the patient's heart as a whole. These determinations can be made using a mechanical circulatory support system (such as an intravascular blood pump system). The systems and methods characterize cardiac performance based on pressure and flow measurements or pressure and flow estimates during use of the mechanical circulatory support system, as determined within a single heart beat cycle in one or more heart beats. The systems and methods described herein can be easily validated and utilized in clinical applications because they utilize existing measurements obtained by a mechanical circulatory support system. The systems and methods described herein utilize the operation of an indwelling mechanical circulatory support device without the need for additional measurements or catheters to determine CO. The potential to continuously and accurately track changes in systemic vascular resistance and compliance and estimate cardiac output marks a significant advance compared to traditional measures obtained from PACs or other diagnostics that are easily deployed in clinical practice.

[0008] The described systems and methods determine cardiac performance by determining aortic pressure measurements (or other physiological measurements) within a single heart beat or across multiple heart beats, and using such measurements in conjunction with flow estimates or flow measurements derived during a single heart beat or multiple heart beats to determine cardiac performance, including determining cardiac output. By utilizing a mechanical circulatory support system placed within the vascular system, the need to place a separate measurement device within the patient is reduced or eliminated. Since measurements can be made within a single heart beat, cardiac performance within one or more heart beats can be characterized in a continuous manner from one beat to another—for example, cardiac performance can be measured for each heart beat in a series of heart beats. Additionally, the acquisition of these measurements does not impair the operation of the heart pump. The systems and methods described herein can characterize cardiac performance without changing the operation of the heart pump (e.g., without increasing or decreasing the pump speed). This can be particularly beneficial if the patient is completely dependent on the heart pump's blood flow contribution such that the heart pump's speed cannot be reduced without potentially harming the patient, or if other equipment (e.g., an extracorporeal membrane oxygenation (ECMO) system) prevents an increase in the heart pump's speed. In some applications, the systems and methods described herein are used in conjunction with such other equipment. Thus, the systems and methods described herein can provide continuous measurement of cardiac performance while also providing appropriate cardiac support.

[0009] Hemodynamic support may be provided to the patient's heart via a mechanical circulatory support system, which may include a blood pump, and hemodynamic parameters may be measured during operation of the blood pump. The blood pump may be an intravascular blood pump, an intra-aortic balloon pump, an ECMO device, or other blood pump (e.g., available from Abiomed Inc. of Danvers, Massachusetts). family of devices, or CardiacAssist Inc. of Pittsburgh, Pennsylvania. A family of devices). Multiple measurements of hemodynamic parameters may be obtained during a single cardiac beat. For example, multiple measurements (e.g., three, four, five, six, seven, ten, twenty, thirty, one hundred, or any suitable number of measurements) may be obtained at different times during the diastolic decline of a cardiac beat. If cardiac performance is modeled as a mathematical system (e.g., via a Windkessel model), the pressures and blood flow rates at these different times allow for the configuration of a system of equations that can then be solved to determine functional values ​​indicative of cardiac performance, such as systemic vascular resistance and compliance. Cardiac output (and other metrics indicative of cardiac and / or vascular performance) may then be calculated from the resistance or compliance values. These calculations are not limited to calculating resistance and compliance only once for a single heart beat - for example, the calculations described herein may include calculating resistance and compliance for multiple pressure measurements (or sets of pressure measurements) within a single heart beat, determining resistance and compliance from those measurements, and then averaging or otherwise processing those resistance and compliance values ​​to determine a representative resistance, compliance, or other metric for overall vasculature or heart health for a single heart beat. Similar measurements may be made for multiple heart beats and used to determine an average or other combined measurement that models cardiac performance of the patient's heart.

[0010] In some aspects, hemodynamic support can be applied or adjusted based on the determined cardiac performance measurements. Hemodynamic support is applied to the patient's heart via a mechanical circulatory support device (MCS). In some embodiments, the device is an intravascular blood pump placed in the patient's heart via percutaneous insertion. The MCS can be a surgically implanted device, a left ventricular assist device, a counterpulsation device, an expandable heart pump, an extracorporeal membrane oxygenation device, an intra-aortic balloon pump, or any other suitable device. A pump can be introduced to a patient because the patient is in cardiogenic shock, is receiving a coronary intervention, has heart disease, or is otherwise experiencing a decline in heart health. The pump facilitates native heart operation so that the CO from the heart is equal to the native CO plus the pump output.

[0011] Providing hemodynamic support can include operating the intravascular blood pump at a first pumping rate or pump speed. The pumping rate is the operating speed of the pump and corresponds to the amount of blood flow provided by the operation of the pump. In some embodiments, the pumping rate may correspond to the rotational speed of the rotor. For example, the pump speed can be 10,000RPM, 20,000RPM, 30,000RPM, 40,000RPM, 50,000RPM, 60,000RPM, 70,000RPM, 80,000RPM, 90,000RPM, 100,000RPM, or any suitable speed. The pump speed may correspond to a power level or P level, as described below with respect to Figure 1For example, the pump speed may be P-1, P-2, P-3, P-4, P-5, P-6, P-7, P-8, or P-9. In some embodiments, the pumping rate may be modified to correspond to the rate at which the chamber of the pump fills and releases blood.

[0012] In some embodiments, hemodynamic support is provided at a first pumping rate during multiple beats of the heart. Each beat includes a systolic rise, a dicrotic notch, and a diastolic decline that occurs after the dicrotic notch. For example, a hemodynamic pumping rate can be provided within a range of two, three, four, ten, twenty, thirty, one hundred, two hundred, or any other suitable number of heart beats. The dicrotic notch marks the beginning of diastole, which is the stage of heart beat when the heart muscles relax and allow the chambers to fill with blood. If the intravascular blood pump is a left heart system, then while the blood pump is operating, the only major flow that comes out of the patient's left ventricle into the aorta during diastole is the flow facilitated by the blood pump. Diastole is the time when the heart completes diastole-diastole is the stage of heart beat when the heart muscles relax and allow the chambers to fill with blood. For example, the diastole period may be 0.05 seconds, 0.1 seconds, 0.2 seconds, 0.3 seconds, 0.4 seconds, 0.5 seconds, 0.6 seconds, 0.7 seconds, 0.8 seconds, 0.9 seconds, 1 second, or any suitable length of time.

[0013] In some embodiments, hemodynamic parameters are measured to monitor the positioning and performance of the device and the well-being of the patient while on the device. For example, the hemodynamic parameters can be measured using sensors included in an intravascular blood pump, or can be measured by a separate device. The hemodynamic parameters can be any parameters related to blood flow within organs and tissues of the body. For example, the hemodynamic parameters can include at least one or more of the following: heart rate, blood pressure, arterial oxygen saturation, mixed venous oxygen saturation, central venous oxygen saturation, arterial blood pressure, mean arterial pressure, right arterial pressure, central venous pressure, right ventricular pressure, pulmonary artery pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, left atrial pressure, aortic pressure, pressure gradient, left ventricular end pressure, stroke volume, stroke volume index, stroke volume change, systemic vascular resistance, systemic vascular resistance index, pulmonary vascular resistance, pulmonary vascular resistance Index, pulmonary vascular resistance, pulmonary vascular resistance index, left ventricular stroke work, left ventricular stroke work index, right ventricular stroke work, right ventricular stroke work index, coronary perfusion pressure, right ventricular end-diastolic volume, right ventricular end-diastolic volume index, right ventricular end-systolic volume, right ventricular ejection fraction, arterial oxygen content, venous oxygen content, arteriovenous oxygen content difference, oxygen delivery, oxygen delivery index, oxygen consumption, oxygen consumption index, oxygen extraction fraction, oxygen extraction index, total peripheral resistance, CO, cardiac index and CPO.

[0014] In some embodiments, the hemodynamic parameter is aortic pressure. Multiple aortic pressure measurements can be performed at corresponding different times, and the results are used to detect the position and performance of the pump and configure the pump to be used for operation. In some embodiments, three or more aortic pressure measurements are detected, and all measurements can be in the diastole of the same heart beat of the multiple beats or during different beats or times. If the blood pump is a left heart system, the pressure measurement value during diastole can be optimal because the only major flow through the aorta during diastole is facilitated by the blood pump. Therefore, it is easier to determine the pump performance and its contribution to the heart.

[0015] In some embodiments, at least three blood flow rates pumped by the intravascular blood pump are determined at corresponding three different times. p ) can be determined by the speed of the pump (in revolutions per minute or RPM) and the motor current supplied to the pump to maintain the pump speed. The technical relationship between the pump speed and the motor current allows the flow rate to be estimated by a mathematical correlation or a lookup table, where the pump speed and the motor current are indices into the lookup table. The flow values ​​in the lookup table can be pre-filled by bench testing. Another way to determine the flow rate output from the pump is to determine the flow rate for a subset of possible combinations of pump speed and motor current values ​​before the pump (or a similar pump) is placed in the patient's body. For example, if the flow rate at a pump speed of 40,000RPM and a motor current of 500mA is represented by i1, and the flow rate at a pump speed of 40,000RPM and a motor current of 510mA is represented by i2, the flow rate at a pump speed of 40,000RPM and a motor current of 505mA can be calculated by taking the average of i1 and i2.

[0016] CO is determined based on multiple aortic pressure measurements and blood flow rates. Some adaptations use at least three aortic pressure measurements and at least three corresponding blood flow rates. In an example, a vascular system is simulated using a Windkessel model having two current sources i connected in parallel to each other. h and i p And has resistance R and compliance C. The governing equation of the technical relationship reflected in this model is:

[0017]

[0018] Where C is compliance, P is pressure, R is systemic vascular resistance, i h is the flow from native heart operation, and i p is the flow from the pump. During diastole, the aortic valve is closed, so the only flow through the left ventricle comes from the pump located across the valve. By neglecting the cardiac current source and assuming a constant pump flow, the model can be simplified as follows:

[0019]

[0020] Where P0 is the exponential decay term of diastolic pressure For example, the proportional factor P0 may be proportional to the inverse of the corresponding pump speed, such that Where P 01 is the proportional factor at the first pump speed speed1, and P 02 is the scaling factor at the second pump speed speed2. Therefore, once P has been clinically determined for a single pump speed x, 0x , the proportionality factor P can be extrapolated for a range of pump speeds 0x In some embodiments, the flow rate from the pump is estimated based on the current to the motor of the heart pump system to maintain a constant speed. p The pressure P may be measured at various points within a single diastolic period to characterize and deconstruct the pressure waveform. For example, the pressure may be known (e.g., measured) at multiple times, and in the case of the Winkessel model, the pressure may be known at three different times. The flow rate i may be estimated at the same time as the pressure measurement. p Setting up multiple pressure equations, one for each of the times at which pressure is measured, the R and C values ​​can be calculated based on equation (2). In some embodiments, the heart pump is operated at a constant speed.

[0021] Systemic vascular resistance and compliance values ​​can be used to calculate other metrics indicative of cardiac performance. For example, once R and C have been determined using the Windkessel model described above, the calculated R and C values ​​can be calculated by inserting them into equation (1) above and applying the equation h The CO of the heart is determined by solving to determine the volume flow contributed by the native heart function. This can be determined by taking the total heart flow (i) over a desired time period (e.g., 5 seconds, 10 seconds, 30 seconds, etc.). h +i p ) to calculate CO.

[0022] In some embodiments, other metrics indicative of cardiac performance may be determined. For example, a metric indicative of cardiac performance may be ventricular resistance, ventricular compliance, CO, CPO, stroke volume, stroke work, ejection fraction, cardiac index, or a prediction of patient survivability. Many metrics indicative of cardiac performance are interrelated. For example, CO is determined based on the flow rate of blood passing through and through the pump. Stroke volume is an index of left ventricular function, and its formula is SV=CO / HR, where SV is stroke volume, CO is cardiac output, and HR is heart rate. Stroke work is the work done by the ventricle to eject a certain volume of blood, and can be calculated from stroke volume according to the equation SW=SV*MAP, where SW is stroke work, SV is stroke volume, and MAP is mean arterial pressure. Cardiac work is calculated by multiplying the stroke work and heart rate. CPO is a measure of cardiac function that represents the pumping capacity of the heart in watts. CPO is calculated using the equation CPO = mAoP * CO / 451, where CPO is cardiac power output, mAoP is mean aortic pressure, CO is cardiac output, and 451 is a constant used to convert mmHg x L / min to Watts. Ejection fraction can be calculated by dividing stroke volume by the volume of blood in the ventricle. Other parameters such as chamber pressure, preload state, afterload state, cardiac recovery, flow load state, variable volume load state, and / or cardiac cycle flow state can be calculated from these values ​​or determined via these parameters.

[0023] The operation of the pump may be adjusted based on the metric indicative of cardiac performance. Adjusting the pump operation may include increasing the pump speed, decreasing the pump speed, adjusting pump placement, shutting off the pump, or any other suitable adjustment. For example, if the total blood volume pumped is below a threshold, the pump speed may be increased, and if the blood volume is above a threshold, the pump speed may be decreased.

[0024] In some embodiments, multiple aortic pressure measurements are detected during the diastolic decline during a specific beat in the multiple beats. For example, the pressure can be sampled at a rate of 1, 2, 3, 10, 20, 30, 100, 200, 300, 1000, 2000, 3000 or any other suitable number of samples per second. In some examples, only the aortic pressure is sampled during the diastolic decline. In some examples, the aortic pressure is measured constantly or periodically. In some examples, the sampling rate of the aortic pressure is changed during the diastolic decline. In some embodiments, when cardiac output occurs only by the operation of the blood pump, at least one aortic pressure measurement is obtained at the end of diastole. In some embodiments, the multiple aortic pressure measurements can be obtained via a pressure sensor. For example, the pressure sensor can be part of an intravascular blood pump that provides hemodynamic support to the heart, or the pressure sensor can be separated from the intravascular blood pump.

[0025] In some embodiments, determining the cardiac output of the patient's heart includes processing multiple cardiac output values ​​for a single heart beat or several heart beats. For example, as described above, multiple aortic pressure measurements can be obtained during diastole of a particular heart beat. For each pressure measurement in the multiple aortic pressure measurements, the pressure can be measured and the flow can be estimated. The pressure and flow values ​​combined with the known measurement time can be compared between two times to calculate cardiac parameters (such as vascular resistance and compliance), and then used to determine CO. Even within a single heart beat, the entire CO value calculated across the diastolic decline can vary due to fluctuations in the patient's heart and differences in flow estimates. Processing the multiple CO values ​​may include performing at least one of summing, averaging, or linear regression on the multiple determined cardiac output values ​​to calculate a first cumulative indicator of the heart's cardiac output. By processing multiple CO values ​​of multiple aortic pressure measurements in a single heart, the systems and methods described herein provide an accurate representation of the heart's CO (and heart performance). In some embodiments, the first cumulative indicator of cardiac output of the heart is indicative of cardiac performance or overall patient health during a particular heart beat.

[0026] In some embodiments, the systems and methods herein can determine cardiac performance by calculating CO for multiple heart beats, and the measured and determined values ​​of CO can be evaluated to identify a cumulative index of cardiac performance of the heart. In some embodiments, after the specific heart beat discussed above, a second cumulative index of cardiac output of the heart is determined for a second heart beat - that is, the first cumulative index of cardiac output can represent the first heart beat at the first time, and the second cumulative cardiac output can represent the second heart beat at a second time later than the first time. In some embodiments, the second heart beat is directly after the first heart beat. In some embodiments, a period of time has passed between the end of the first heart beat and the start of the second heart beat. The time period can be 1 second, 1 minute, 10 minutes, 1 hour, 10 hours, or any other suitable length of time. For example, a first cumulative metric can be calculated for a heart beat that starts at time 12:00 PM, and the indicated second cumulative metric can be calculated for a heart beat that starts at 1:00 PM on the same day. Investigating the cardiac output of heart beats at different time points can allow clinicians or computer systems to find overall trends in patient health.

[0027] In some embodiments, the first cumulative indicator of cardiac output is compared to a second cumulative indicator of cardiac output. Similar to the first cumulative indicator described above, the second cumulative indicator can be determined by calculating a second plurality of cardiac output values, wherein each cardiac output value in the second plurality of cardiac output values ​​corresponds to a beat in the second set of beats. Summing, averaging, or linear regression is applied to the determined plurality of cardiac output values ​​to calculate the second cumulative indicator, which can indicate overall cardiac performance of the patient's heart.

[0028] Based on a comparison between the first cumulative indicator and the second cumulative indicator, it is determined whether (i) the cardiac performance of the heart has improved or (ii) the cardiac performance of the heart has decreased. The improvement or decrease in cardiac performance may be indicative of the patient's cardiac or overall health. Similarly, CO values ​​may be determined for multiple heart beats of the patient and may be used to track cardiac performance over time. The hemodynamic support provided to the patient may be adjusted based on determining whether the cardiac performance of the heart has improved or decreased over time. The indicator may be used to identify when to apply or adjust the level of mechanical circulatory support and to what extent. In some embodiments, if an improvement in cardiac performance is observed, the hemodynamic support provided to the patient may be reduced; however, if a decrease in cardiac performance is observed, the hemodynamic support provided to the patient may be increased.

[0029] In some aspects, the hemodynamic parameters are monitored during operation of the heart pump at the first pump speed. In some embodiments, the pump is an intravascular blood pump device placed in the patient's heart via percutaneous insertion. The pump may be introduced to the patient because the patient is in cardiogenic shock or is otherwise experiencing a decline in health. The pump may be positioned across the aortic valve so that the blood inlet of the pump (e.g., Figure 1 The blood inlet 172 of the pump is in the left ventricle and the pump outlet (e.g., Figure 1 The outlet opening 170 of the pump is in the aorta. The pump facilitates the operation of the native heart so that the CO from the heart equals the native CO plus the pump output.

[0030] A hemodynamic parameter may be any parameter related to blood flow within organs and tissues of the body. For example, a hemodynamic parameter may include at least one of the following: heart rate, blood pressure, arterial oxygen saturation, mixed venous oxygen saturation, central venous oxygen saturation, arterial blood pressure, mean arterial pressure, right arterial pressure, central venous pressure, right ventricular pressure, pulmonary artery pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, left atrial pressure, aortic pressure, pressure gradient, left ventricular end pressure, stroke volume, stroke volume index, stroke volume variation, systemic vascular resistance, systemic vascular resistance index, pulmonary vascular resistance, pulmonary vascular resistance index, pulmonary vascular The pump speed is the operating speed of the pump and corresponds to the amount of blood flow provided by the operation of the pump. In some embodiments, the pump speed may correspond to the rotational speed of the rotor. For example, the pump speed can be 10,000 RPM, 20,000 RPM, 30,000 RPM, 40,000 RPM, 50,000 RPM, 60,000 RPM, 70,000 RPM, 80,000 RPM, 90,000 RPM, 100,000 RPM, or any suitable speed. The pump speed can correspond to a power level or P level, as described above with respect to Figure 1 As described herein. For example, the pump speed can be P-1, P-2, P-3, P-4, P-5, P-6, P-7, P-8 or P-9 or any other suitable value. In some embodiments, the pump speed can instead correspond to the rate at which the chamber of the pump fills and releases blood. By monitoring the hemodynamic parameters, the systems and methods described herein can investigate changes in the hemodynamic parameters over time. This comparison can be used to quantify cardiac performance.

[0031] In some embodiments, the diastolic phase of the cardiac cycle is identified based on the shape of the hemodynamic parameters over time. In particular, the dicrotic notch (evident in the aortic pressure waveform, e.g. Figure 3The notch 310) indicates the onset of diastole. If the patient's heart rhythm is relatively stable, the onset of the heart beat can be accurately predicted. When the heart beat completes contraction, the aortic pressure decreases before increasing to form the dicrotic notch. Identifying this waveform shape allows the system to determine the onset of diastole. Diastole is the time when the heart completes relaxation - diastole is the stage of the heart beat when the heart muscles relax and allow the chambers to fill with blood. For example, diastole can be 0.05 seconds, 0.1 seconds, 0.2 seconds, 0.3 seconds, 0.4 seconds, 0.5 seconds, 0.6 seconds, 0.7 seconds, 0.8 seconds, 0.9 seconds, 1 second, or any suitable length of time.

[0032] In some embodiments, a time-varying relationship between aortic pressure and blood flow during diastole is determined. The time-varying relationship may be a Windkessel model having two current sources i connected in parallel to each other. h and i p and has resistance R and compliance C. The governing equation for this model is:

[0033]

[0034] Where C is compliance, P is pressure, R is vascular resistance, i h is the flow from native heart operation, and i p is the flow from the pump. However, during diastole, the aortic valve is closed, so the only flow through the left ventricle comes from the pump positioned across the valve. By neglecting the cardiac current source and assuming a constant pump flow, the model can be simplified as follows:

[0035]

[0036] Where P0 is the scaling factor for the exponential decay portion of the diastolic pressure. In some embodiments, the flow rate from the pump is estimated based on the current to the motor of the heart pump system to maintain a constant speed. p The pressure P may be measured at various points within a single diastolic period to characterize and deconstruct the pressure waveform. For example, the pressure may be known at a first, second, and third time. The flow rate i may also be estimated at a first, second, and third time. p Setting up three pressure equations, one for each of the three times, based on equation (2), the R and C values ​​can be calculated. In some embodiments, the heart pump is operated at a constant speed.

[0037] In some embodiments, the total blood volume pumped per heart beat, which represents cardiac performance, is calculated based on the time-varying relationship between aortic pressure and blood flow during diastole. For example, once R and C have been determined, the total blood volume pumped per heart beat, which represents cardiac performance, can be calculated by plugging the calculated R and C values ​​into equation (1) above and applying the equation hThe CO of the heart is determined by solving to determine the volume flow contributed by the native heart function.

[0038] In some embodiments, other metrics indicative of cardiac performance may be calculated. For example, a metric indicative of cardiac performance may be ventricular resistance, ventricular compliance, CO, CPO, stroke volume, stroke work, ejection fraction, cardiac index, or a prediction of patient survivability. Many metrics indicative of cardiac performance are interrelated. For example, CO is determined based on the flow rate of blood passing through and through the pump. Stroke volume is an index of left ventricular function, and its formula is SV=CO / HR, where SV is stroke volume, CO is cardiac output, and HR is heart rate. Stroke work is the work done by the ventricle to eject a certain volume of blood, and can be calculated from stroke volume according to the equation SW=SV*MAP, where SW is stroke work, SV is stroke volume, and MAP is mean arterial pressure. Cardiac work is calculated by multiplying stroke work and heart rate. CPO is a measure of cardiac function that represents the pumping capacity of the heart in watts. CPO is calculated using the equation CPO = mAoP * CO / 451, where CPO is cardiac power output, mAoP is mean aortic pressure, CO is cardiac output, and 451 is a constant used to convert mmHg x L / min to Watts. Ejection fraction can be calculated by dividing stroke volume by the volume of blood in the ventricle. Other parameters such as chamber pressure, preload state, afterload state, cardiac recovery, flow load state, variable volume load state, and / or cardiac cycle flow state can be calculated from these values ​​or determined via these parameters.

[0039] In some embodiments, the operation of the pump is adjusted based on a metric indicative of cardiac performance. Adjusting the pump operation may include increasing the pump speed, decreasing the pump speed, adjusting pump placement, shutting down the pump, or any other suitable adjustment. For example, if the total blood volume pumped is below a threshold, the pump speed may be increased, and if the blood volume is above a threshold, the pump speed may be decreased.

[0040] In some embodiments, the method described above includes: actuating a blood pump within the patient's vasculature; and determining a cardiac output of the patient's heart using any of the aforementioned systems and sensors. The pumping rate of the blood pump can be adjusted based on the determined cardiac output. In some embodiments, the applied hemodynamic support can be based on determining whether the cardiac performance of the heart improves or decreases over time.

[0041] In some embodiments, a vascular sensor is provided. The vascular sensor may include a system for inducing blood flow in a patient's blood vessel. The system may be an intravascular system. The system may include a motor and an impeller. In some embodiments, the system for inducing blood flow in a patient's blood vessel includes: a cannula configured to extend within the left ventricle of the heart; and a pressure sensor configured to detect at least one of the following: aortic pressure, left ventricular pressure, or a pressure difference. The system for inducing blood flow in a patient's blood vessel may be an intracardiac blood pump incorporating an impeller into a shield. For example, the shield may be a pump housing. The shield may be sized to pass through a patient's blood vessel and may be coupled to a motor or other pump element. The shield may include one or more blood discharge orifices or outlets.

[0042] The blood vessel sensor may further include a controller. The controller may be configured to detect changes in resistance to impeller rotation within the blood vessel. In some embodiments, a constant impeller rotation speed is maintained based on the detected resistance to impeller rotation.

[0043] In some embodiments, a transfer function can be used to calculate vascular compliance and vascular resistance based on the change in resistance to impeller rotation. In some embodiments, the transfer function is a Windkessel model. In some embodiments, pump operation data can be transmitted to a computing device. The computing device can be located separately from the controller or onboard the controller. For example, the computing device can be a remotely stored server. In some embodiments, the pump operation data includes at least one of a pressure measurement, a current measurement, a change in resistance to impeller rotation, and a flow estimate. In some embodiments, the controller is further configured to receive a pump operation command from the computing device, wherein the pump operation command is based on the pump operation data. For example, the computing device can calculate vascular resistance and compliance and change the pump operation accordingly.

[0044] In some embodiments, the controller or computing device is configured to determine a metric indicative of cardiac performance based on vascular compliance and vascular resistance. The metric indicative of cardiac performance can be at least one of: cardiac output, cardiac power output, stroke volume, stroke work, ejection fraction, cardiac contractility, ventricular elastance, cardiac index, prediction of patient survivability, or any suitable metric.

[0045] In some embodiments, the controller is configured to adjust the impeller rotation speed based on at least one of: vascular resistance, vascular compliance, or cardiac output. For example, the impeller rotation speed can be increased or decreased to provide more or less blood flow based on the patient's heart or vascular health.

[0046] In some embodiments, the controller is configured to receive measurements indicative of aortic pressure over a period of time, detect current delivered to the pump, and determine a blood flow rate pumped by the system over the period of time based on the current delivered to the pump. Calculations of vascular compliance and vascular resistance may be based on measurements indicative of aortic pressure and blood flow rate.

[0047] In some embodiments, the controller is configured to perform any of the embodiments, aspects, and methods described herein. For example, the controller can be an automated Impella controller (AIC) from Abiomed, Inc, or any other suitable controller. In some embodiments, the heart pump system includes: a catheter; a motor; a rotor operatively coupled to the motor; a pump housing at least partially surrounding the rotor so that an actuated motor drives the rotor and pumps blood through the pump housing; one or more sensors, including a differential pressure sensor; and a controller. For example, the heart pump system may include an Impella 5.0 heart pump from Abiomed, Inc, connected to the AIC, or any other suitable system.

[0048] In some embodiments, the controller includes a display. Any of the aforementioned calculations or features can be configured for display. For example, an aortic pressure waveform can be presented on a graphical user interface. A clinician can observe such a display and adjust the operation of the pump based on their observations of hemodynamic parameters over time. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 An illustrative heart pump system is shown inserted into a blood vessel of a patient;

[0050] Figure 2 illustrates a process for determining the volume of blood pumped per heart beat in accordance with certain embodiments;

[0051] Figure 3 shows a graph of pressure versus time for a heart pump system according to certain embodiments;

[0052] Figure 4 shows a CO sensor coupled to a patient according to certain embodiments;

[0053] Figure 5 illustrates a process for determining the total volume of blood pumped per heart beat in accordance with certain embodiments;

[0054] Figure 6 illustrates a process for determining cardiac output according to certain embodiments; and

[0055] Figure 7 Shown are graphs of pressure versus time and flow versus time for a heart pump system in accordance with certain embodiments. DETAILED DESCRIPTION

[0056] In order to provide a comprehensive understanding of the systems and methods described herein, certain illustrative embodiments will be described. Although the embodiments and features described herein are specifically described for use in conjunction with a percutaneous heart pump system, it will be understood that all of the components and other features outlined below can be combined with each other in any suitable manner and can be adapted and applied to other types of cardiac therapy and heart pump systems, including heart pump systems that are implanted using surgical incisions, etc.

[0057] The systems, devices and methods described herein enable a support device that resides completely or partially within an organ to assess the function of the organ. In particular, these systems, devices and methods enable a mechanical circulatory support system (such as a percutaneous ventricular assist device) to be used to assess the function of the heart. For example, a support device (such as a blood pump) can be used to treat cardiogenic shock, heart disease, or to support the heart generally during coronary intervention.

[0058] Using a mechanical circulatory support system to assess the function of the heart can alert health care professionals to changes in heart function and allow the degree / level of support provided by the assist device (i.e., the flow rate of blood pumped by the device) to be customized to suit the needs of a particular patient. For example, the degree of support can be increased as the patient's heart function deteriorates, or the degree of support can be reduced as the patient's heart function recovers and returns to a baseline of normal heart function. This can allow the device to dynamically respond to changes in heart function to promote heart recovery, and can allow the patient to gradually wean off treatment. In addition, an assessment of heart function can indicate when it is appropriate to terminate the use of the heart pump system. Although some of the embodiments presented herein relate to a heart pump system that is implanted across the aortic valve and resides partially in the left ventricle, these concepts can be applied to devices in the heart, cardiovascular system, or other areas of the body.

[0059] The assessment of cardiac function may include utilizing cardiac device interaction to determine cardiac parameters. The systems and methods described herein determine cardiac output based on aortic pressure measurements and flow output from a blood pump system. The flow may be a measured value or an estimated value determined based on the motor current supplied to the motor at a given pump speed in an intravascular blood pump system. At least one advantage of the systems and methods described herein is that they allow the heart pump system to assess cardiac function without changing the operation of the pump (e.g., pump speed), thereby minimizing the risks associated with changing the pump speed. A reduction in pump speed involves a reduction in patient support, while an increase in pump speed may lead to aspiration or other risks. Frequent and / or rapid changes in pump speed may also lead to hemolysis or a reduction in pump / motor performance. Using an intravascular blood pump system to measure or estimate the necessary parameters to determine metrics indicating cardiac performance also allows for continuous measurement of cardiac performance, because these metrics are obtained by a blood pump system already placed in the patient's vascular system.

[0060] Continuously measuring vascular and cardiac performance by utilizing the action of the heart pump system is a key step in providing additional clinical data to help adjust (titration) appropriate device support. However, more importantly, the system and method described herein demonstrate the impact and potential of device-artery connection to determine the state of the heart and blood vessels. Unlike some invasive heart pump systems that shunt blood from the heart, the heart pump system presented herein resides in the heart and works in parallel with native ventricular function. Unlike some more invasive devices, this allows the heart pump system presented herein to be sensitive enough to detect native ventricular function. Therefore, these systems, devices and methods enable the heart pump system to be used not only as a support device, but also as a diagnostic and prognostic tool. The heart pump system can basically play the function of an active catheter, which extracts information about heart function by being hydraulically connected to the heart. In some embodiments, the heart pump system operates at a constant level (e.g., a constant rotation speed of the rotor) while measuring the power delivered to the auxiliary device. In certain embodiments, the speed of the rotor of the heart pump system can be varied (e.g., as a delta function, a step or a ramp function) to further detect native heart function.

[0061] Figure 1 An illustrative heart pump system is shown inserted into a patient's blood vessel. A heart pump system compatible with the present disclosure is disclosed in U.S. Patent Application Publication No. 2018-0078159-A1, the contents of which are incorporated herein by reference in their entirety. In general, any other heart pump system or system for obtaining physiological data from a patient may be used with the present disclosure. In some embodiments, the systems and methods described herein may involve Abiomed, Inc., Danvers, Mass.

[0062] The heart pump system 100 can be operated in the heart, partially in the heart, outside the heart, partially outside the heart, partially outside the vascular system, or in any other suitable location in the patient's vascular system. The heart pump system can be considered to be "in place" when the cannula 173 is placed across the aortic valve so that the blood inlet of the pump (e.g., blood inlet 172) is in the left ventricle and the outlet of the pump (e.g., outlet opening 170) is in the aorta. The heart pump system 100 includes a heart pump 106 and a control system 104. All or part of the control system 104 may be in a controller unit that is separate from / away from the heart pump 106. In some embodiments, the control system 104 is inside the heart pump 106. The control system 104 and the heart pump 106 are not shown to scale. The pump system 100 includes an elongated catheter body 105, a motor housing 102, and a drive shaft in which a pump element is formed. The pump 100 includes a pump housing 134 and a motor housing 102 coupled to a cannula 173 at a distal end 111 of the motor housing 102. Impeller blades on a drive shaft can rotate within the pump housing 134 to induce blood to flow into the cannula 173 at a suction head 174. The suction head 174 provides a blood inlet 172 at a distal portion 171 of the cannula 173. The blood flow 109 passes through the cannula 173 in a first direction 108 and exits the cannula 173 at one or more outlet openings 170 of the cannula 173.

[0063] The rotation of the drive shaft within the pump housing 134 may also cause the pump element to rotate within the bearing gap. The hemocompatible fluid may be delivered through the motor housing 102 via the elongated conduit 105 to the proximal portion of the cannula 173 where the fluid is pressurized by the rotation of the pump element. The flow of the hemocompatible fluid has a second direction 122 through the bearing gap of the pump. After leaving the bearing gap, the hemocompatible fluid may follow a flow direction 123 and become entrained in the blood stream and flow with the blood into the aorta.

[0064] Heart pump 100 is inserted into the patient's blood vessel through sheath 175. Pump housing 134 can enclose the rotor and internal bearings and can be sized for percutaneous insertion into the patient's blood vessel. In some embodiments, the pump can be advanced through the vasculature and over the aortic arch 164. Although the pump is shown in the left ventricle, the pump can alternatively be placed in the right heart so that blood is pumped from the patient's inferior vena cava or right atrium through the right ventricle into the pulmonary artery.

[0065] A flexible protrusion 176 may also be included at the distal portion 171 of the cannula 173, distal to the suction head 174, so as to optimally position the heart pump 100 in a vessel or chamber of the heart. The flexible protrusion 176 may prevent the suction head 174 from approaching the vessel wall, where it may become stuck due to suction. The flexible protrusion 176 may extend the pump 100 mechanically rather than hydraulically because the flexible protrusion 176 may be non-absorbent. In some embodiments, the flexible protrusion may be formed as a pigtail. In some aspects, the pump need not include a flexible protrusion.

[0066] The elongated conduit 105 houses a connector 126, which may include a fluid supply line and may also house an electrical connection cable. The connector 126 may supply a hemocompatible fluid from a fluid reservoir, which may be contained within the control system 104, to the pump.

[0067] The control system 104 includes a controller 182 to control the pump 106, including, for example, controlling power to the motor or controlling motor speed. In some embodiments, the control system 104 includes a display screen to show measurements such as a differential pressure signal and motor current. The control system 104 may include circuitry for monitoring the motor current for a drop in current (indicating air in the line), a change in the differential pressure signal, flow position, suction, or any other suitable measurement. The control system 104 may include an alarm sound, light, or indicator to alert an operator to a sensor failure, a disconnection or disconnection in the connector 126, or a sudden change in the patient's health.

[0068] The motor 108 can be operated at a speed required to maintain the rotor at a set speed. As a result, and as further described below, the motor current drawn by the motor to maintain the rotor speed can be monitored and used to understand the underlying heart state. For example, the motor current can be used to determine the flow through the heart.

[0069] The heart pump can be operated at various pump speeds or P levels. The P level is the performance level of the heart pump system and is related to the flow control of the system. As the P level increases, the flow rate, motor current, and revolutions per minute associated with the heart pump system increase; therefore, a higher P level corresponds to a higher flow rate and revolutions per minute associated with the heart pump system. For example, power level P-1 may correspond to a first revolution per minute (RPM) of the rotor, while power level P-2 corresponds to a second RPM number. In some examples, the pump operates at ten different power levels ranging from P-0 to P-9. These P levels may correspond to 0 RPM to 100,000 RPM or any suitable number. Changing the speed of the rotor changes the CO of the heart.

[0070] The control system 104 may include a current sensor (not shown). The controller 182 supplies current to the motor 108 via the connector 126 (such as, through one or more wires). The current supplied to the motor 108 via the connector 126 is measured by the current sensor. The load experienced by the motor of the mechanical pump is the pressure head or the difference between the aortic pressure and the left ventricular pressure. The heart pump 106 experiences a nominal load during steady-state operation at a given pressure head, and changes from this nominal load are the result of changes in external load conditions, such as the dynamics of left ventricular contraction. Changes in dynamic load conditions change the motor current required to operate the pump rotor at a constant or substantially constant speed. As described above, the motor can be operated at a speed required to maintain the rotor at a set speed, and the motor current drawn by the motor to maintain the rotor speed can be monitored and used to understand the underlying heart state. By using the pressure sensor 112 to monitor the pressure head simultaneously during the heart beat cycle, the heart state can be quantified and understood even more accurately. The heart parameter estimator 185 receives the current signal from the current sensor and the pressure signal from the pressure sensor 112. The cardiac parameter estimator 185 uses these current and pressure signals to characterize cardiac function. The cardiac parameter estimator 185 may access a stored lookup table to obtain additional information to characterize cardiac function based on the pressure signal and the current signal. For example, the cardiac parameter estimator 185 may receive the aortic pressure from the pressure sensor 112 and, using a lookup table, may use the motor current and pump speed to determine the delta pressure between the aorta and the ventricle.

[0071] In some embodiments, the pressure sensor 112 is an aortic pressure sensor. In some embodiments, the pressure sensor 112 is a flexible membrane integrated into the cannula 172, which is configured to measure the pressure difference. One side of the sensor is exposed to the blood pressure outside the cannula, and the other side is exposed to the blood pressure inside the cannula. The sensor generates an electrical signal (pressure difference signal) proportional to the difference between the pressure outside the cannula and the internal pressure, which can be displayed by the heart pump system. When the heart pump system is placed in the correct position across the aortic valve, the top (outer surface) of the sensor is exposed to the aortic pressure, and the bottom (inner surface) of the sensor is exposed to the ventricular pressure. Therefore, the pressure difference signal is approximately equal to the difference between the aortic pressure and the ventricular pressure. In some embodiments, the system includes both the pressure difference sensor and the aortic pressure sensor.

[0072] Figure 2 A process 200 for determining cardiac output is illustrated. Figure 1Process 200 is performed using a heart pump system 100 or any other suitable pump. In some embodiments, the pump is an intravascular blood pump device that is placed in the patient's heart via percutaneous insertion. The pump may be introduced to the patient because the patient is in cardiogenic shock or is otherwise experiencing a decline in health. The pump may be positioned across the aortic valve so that the blood inlet of the pump (e.g., Figure 1 The blood inlet 172 of the pump is in the left ventricle and the pump outlet (e.g., Figure 1 The outlet opening 170 of the pump is in the aorta. The pump facilitates the operation of the native heart so that the CO from the heart equals the native CO plus the pump output.

[0073] In step 202, hemodynamic support is applied to the heart at a first pumping rate. In some embodiments, the pumping rate may correspond to the rotational speed of the rotor. For example, the pump speed may be 10,000 RPM, 20,000 RPM, 30,000 RPM, 40,000 RPM, 50,000 RPM, 60,000 RPM, 70,000 RPM, 80,000 RPM, 90,000 RPM, 100,000 RPM, or any suitable speed. The pump speed may correspond to a power level or P level, as described below with respect to Figure 1 As described. For example, the pump speed can be P-1, P-2, P-3, P-4, P-5, P-6, P-7, P-8 or P-9. In some embodiments, the pumping rate can be changed to correspond to the rate at which the chamber of the pump fills and releases blood. The pumping rate is supplied by multiple heart beats of the heart. Each heart beat includes a systolic rise, a dicrotic notch, and a diastolic fall that occurs after the dicrotic notch.

[0074] In step 204, at least three aortic pressure measurements are detected during the diastolic descent of a particular beat in the plurality of beats. In some embodiments, the aortic pressure is measured continuously or sampled periodically, and a plurality of aortic pressure measurements are detected. For example, the pressure may be sampled at a rate of 1, 2, 3, 10, 20, 30, 100, 200, 300, 1000, 2000, 3000, or any other suitable number of samples per second. In some examples, the aortic pressure is sampled only during the diastolic descent. In some examples, the aortic pressure is measured constantly or periodically.

[0075] In step 206, at least three blood flow rates pumped by the intravascular blood pump are determined. Figure 3As shown in and as described above, pressure can be measured at a series of points during the diastolic time period. For each of these pressure measurements, the pressure is measured, and the flow rate can be estimated based on the current supplied to the pump to maintain the rotor speed. This mathematical relationship between the pump speed and the motor current can be implemented by setting a lookup table, wherein the pump speed and the motor current are indexes of the table, and the flow values ​​in the table are pre-filled by bench testing. Another way is to predetermine the flow rate for a subset of possible combinations of pump speed and motor current. For example, if the flow rate at a pump speed of 40,000RPM and a motor current of 500mA and the flow rate at a pump speed of 40,000RPM and a motor current of 510mA are referred to as i1 and i2, respectively, the flow rate at a pump speed of 40,000RPM and a motor current of 505mA can be calculated by taking the average of i1 and i2. In conjunction with the known measurement time, the pressure and flow measurements are compared between the two times to calculate cardiac parameters (such as systemic vascular resistance and compliance).

[0076] In step 208, the cardiac output during a particular beat is determined based on the aortic pressure and blood flow measurements. Aortic pressure can be simulated using a Windkessel model, which has two current sources i connected in parallel to each other. h and i p and has resistance R and compliance C. The governing equation for this model is:

[0077]

[0078] Where C is compliance, P is pressure, R is vascular resistance, i h is the flow from native heart operation, and i p is the flow from the pump. However, during diastole, the aortic valve is closed, so the only flow through the left ventricle comes from the pump positioned across the valve. By neglecting the cardiac current source and assuming a constant pump flow, the model can be simplified as follows:

[0079]

[0080] Where P0 is the initial aortic pressure during diastole. In some embodiments, the flow rate from the pump is estimated based on the current to the motor of the heart pump system to maintain a constant speed. p The pressure P can be measured at various points within a single diastole to characterize and deconstruct the pressure waveform, such as Figure 3 As shown in and described below. For example, the pressure may be known at at least three times. The flow rate i may also be estimated at the same three times. pSetting up three pressure equations, one for each of the three times, based on equation (2), R and C values ​​can be calculated. For example, once R and C have been determined using the Windkessel model described above, the calculated R and C values ​​can be calculated by inserting them into equation (1) above and applying the equations to i h The CO of the heart is determined by solving to determine the volume flow contributed by the native heart function.

[0081] The operation of the pump may be adjusted based on the calculated CO value. Adjusting the pump operation may include increasing the pump speed, decreasing the pump speed, adjusting pump placement, shutting off the pump, or any other suitable adjustment. For example, if the CO is below a threshold, the pump speed may be increased, and if the CO is above a threshold, the pump speed may be decreased.

[0082] Figure 3 A graph 300 of pressure versus time for a heart pump system according to certain embodiments is shown. The y-axis of graph 300 represents aortic pressure in mmHg, while the x-axis represents time as a percentage of the length of a heart beat. In particular, graph 300 shows that pressure can be measured at a series of points P0-P5 during the diastole of a heart beat. Δt1 represents the time of a first heart beat, and Δt2 represents the time of a second heart beat after the first heart beat. When the heart pump system is at least partially placed in the patient's heart, time periods Δt1 and Δt2 occur. Point 310 represents the dicrotic notch during the first heart beat, and point 320 represents the dicrotic notch during the second heart beat. The diastolic time period Δt3 represents the diastole of the second heart beat. During time periods Δt1, Δt2, and Δt3, the pump operates at a first pump speed. In some embodiments, the pump operates at a second pump speed during time period Δt3. For example, the pump speed can be increased during time period Δt3. At higher pump speeds, measured aortic pressure and total flow were higher compared to lower pump speeds.

[0083] At a given known time point t within the diastolic period Δt3 02 At the pressure P(t 02 ) is known; at the second known time point t within the diastolic period Δt3 03 At the pressure P(t 03 ) is known; and at a third known time point t within the diastolic period Δt3 04 At the pressure P(t 04 ) is known. At each of these times within the diastolic period Δt3, the pump flow is known from the motor current supplied to the pump motor at that point in time. Therefore, P0, R, and C can be calculated using the following equations:

[0084]

[0085] These steps can be repeated for each time point within the diastolic period t3. 02 and t 04 ,t 02 and t 03 In some embodiments, the R and C values ​​calculated by the patient may be slightly different (e.g., R and C values ​​calculated by the patient's heart rate monitoring system, such as heart rate monitoring system, heart rate monitoring system, heart rate monitoring system, heart rate monitoring system, heart rate monitoring system, etc.). The measured R and C values ​​may be averaged to obtain representative systemic vascular resistance and compliance values ​​for the heart. In some embodiments, R and C values ​​may be calculated periodically to determine how these values ​​change over time while the patient is receiving treatment. In some embodiments, the calculated R and C values ​​may be used to determine cardiac output. For example, determining cardiac output may include: determining cardiac output for multiple specific beats within the multiple beats, and applying at least one of summing, averaging, or linear regression to the determined cardiac output to determine a cumulative indicator of cardiac output for the heart.

[0086] Figure 4 A compliance sensor 410 is shown coupled to a patient 400. The compliance sensor 410 may include various hardware elements configured to perform the methods described herein, as well as additional processes. In some embodiments, the compliance sensor includes an intravascular blood pump (e.g., Figure 1 Pump 202). The intravascular blood pump may be configured to be placed at least partially within the patient's heart. In some embodiments, the intravascular blood pump includes: a cannula; an impeller configured to rotate within a blood vessel and pump blood through the cannula; and a drive mechanism configured to impart power to rotate the impeller. In some embodiments, the cannula may be configured to extend across the aortic valve so that the distal end of the cannula is within the left ventricle and the proximal end of the cannula is within the aorta. For example, the heart pump system may be considered to be "in place" when the cannula is placed across the aortic valve so that the blood inlet of the pump is within the left ventricle and the outlet of the pump is within the aorta. The drive mechanism may include an onboard motor, a drive cable, a drive shaft, or any other suitable element or combination thereof.

[0087] In some embodiments, the compliance sensor 410 includes an elongated catheter body coupled to the cannula. The elongated catheter may include a drive cable, electrical wiring connecting the blood pump to a control system, any suitable element, or any combination thereof. In some embodiments, the blood pump includes a pump housing and a motor housing coupled to the cannula at a distal end of the motor housing. An impeller may rotate within the pump housing to induce blood to flow into the cannula.

[0088] The compliance sensor 410 includes a pressure sensor configured to detect a pressure within a blood vessel, the pressure being caused at least in part by the pumping of blood within the blood vessel. For example, the pressure sensor can be a differential pressure sensor as part of a blood pump. One side or surface of the differential pressure sensor can be exposed to aortic pressure, a second side or surface of the differential pressure sensor can be exposed to ventricular pressure, and the differential pressure sensor can measure the difference between the aortic pressure and the ventricular pressure. As another example, the pressure sensor 412 can include a pressure measurement lumen configured to measure aortic pressure.

[0089] The compliance sensor 410 includes a controller 414. The controller 414 is coupled to the pressure sensor 412. The controller 414 may be coupled to the pressure sensor 412 directly or indirectly. For example, the controller 414 may be connected to the pressure sensor 412 via electrical wiring, wireless signals, or any other suitable means. The controller 414 is configured to detect a signal indicative of blood pressure from the pressure sensor. All or a portion of the controller 414 may be in a controller unit separate from / remote from the intravascular blood pump. In some embodiments, the control system is internal to the intravascular blood pump.

[0090] In some embodiments, the controller 414 is configured to detect changes in resistance to the rotation of the impeller within the blood vessel. For example, the resistance may be calculated at various time points based on pressure and flow measurements of the heart, as described above with respect to Figure 1 described.

[0091] In some embodiments, the controller 414 is configured to maintain a constant impeller rotation speed based on the detected resistance to impeller rotation. The current supplied to the impeller motor can be varied based on the necessary current required to maintain the motor speed. Thus, the motor current can be related to the flow through the heart.

[0092] In some embodiments, the controller 414 is configured to calculate vascular compliance and vascular resistance based on the change in resistance to impeller rotation using a transfer function. Figure 3 In another example, while maintaining the pump speed at a constant speed (speed1), for a set of times (eg, t equals t1 01 、t1 02 、t1 03 The controller may then set the pump to a different constant speed (speed2) and for a second set of times (e.g., t equals t2 01 , t2 02 , t2 03The difference between the two sets of pressure measurements P1(t) and P2(t) and the difference between the two sets of pump flows i1(t) and i2(t) can be used to calculate vascular resistance via the following equation:

[0093]

[0094] Figure 5 A process 500 for determining the total volume of blood pumped per heart beat is illustrated. Figure 1 Process 500 is performed using a heart pump system 100 or any other suitable pump. In some embodiments, the pump is an intravascular blood pump device that is placed in the patient's heart via percutaneous insertion. In some embodiments, the pump can be a surgically implanted device, a left ventricular assist device, a counterpulsation device, an expandable heart pump, or any other suitable device. The pump can be introduced to the patient because the patient is in cardiogenic shock or is otherwise experiencing a decline in health. The pump can be positioned across the aortic valve so that the blood inlet of the pump (e.g., Figure 1 The blood inlet 172 of the pump is in the left ventricle and the pump outlet (e.g., Figure 1 The outlet opening 170 of the pump is in the aorta. The pump facilitates the operation of the native heart so that the CO from the heart equals the native CO plus the pump output.

[0095] In step 502, hemodynamic parameters are monitored during operation of the heart pump at a first pump speed. Hemodynamic parameters may be any parameters related to blood flow within organs and tissues of the body. For example, the hemodynamic parameters may include at least one of the following: heart rate, blood pressure, arterial oxygen saturation, mixed venous oxygen saturation, central venous oxygen saturation, arterial blood pressure, mean arterial pressure, right arterial pressure, central venous pressure, right ventricular pressure, pulmonary artery pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, left atrial pressure, aortic pressure, pressure gradient, left ventricular end pressure, stroke volume, stroke volume index, stroke volume variation, systemic vascular resistance, systemic vascular resistance index, pulmonary vascular resistance, pulmonary vascular resistance index , pulmonary vascular resistance, pulmonary vascular resistance index, left ventricular stroke work, left ventricular stroke work index, right ventricular stroke work, right ventricular stroke work index, coronary perfusion pressure, right ventricular end-diastolic volume, right ventricular end-diastolic volume index, right ventricular end-systolic volume, right ventricular ejection fraction, arterial blood oxygen content, venous blood oxygen content, arteriovenous blood oxygen content difference, oxygen delivery, oxygen delivery index, oxygen consumption, oxygen consumption index, oxygen extraction fraction, oxygen extraction index, total peripheral resistance, CO, cardiac index, and CPO. The pump speed is the operating speed of the pump and corresponds to the amount of blood flow provided by the operation of the pump. In some embodiments, the pump speed may correspond to the rotational speed of the rotor. For example, the pump speed can be 10,000 RPM, 20,000 RPM, 30,000 RPM, 40,000 RPM, 50,000 RPM, 60,000 RPM, 70,000 RPM, 80,000 RPM, 90,000 RPM, 100,000 RPM, or any suitable speed. The pump speed can correspond to a power level or P level, as described above with respect to Figure 1 For example, the pump speed may be P-1, P-2, P-3, P-4, P-5, P-6, P-7, P-8, or P-9 or any other suitable value. In some embodiments, the pump speed may instead correspond to the rate at which the chamber of the pump fills and releases blood.

[0096] At step 504, the diastolic period of the cardiac cycle is identified based on the shape of the hemodynamic parameter over time. The diastolic period is the time when the heart is completing relaxation - the phase of the heart beat when the heart muscles relax and allow the chambers to fill with blood. For example, the diastolic period can be 0.05 seconds, 0.1 seconds, 0.2 seconds, 0.3 seconds, 0.4 seconds, 0.5 seconds, 0.6 seconds, 0.7 seconds, 0.8 seconds, 0.9 seconds, 1 second, or any suitable length of time.

[0097] At step 506, a time-varying relationship between aortic pressure and blood flow during diastole is determined. The time-varying relationship may be a Windkessel model having two current sources i connected in parallel to each other. h and ip and has resistance R and compliance C. The governing equation for this model is:

[0098]

[0099] Where C is compliance, P is pressure, R is systemic vascular resistance, i h is the flow from native heart operation, and i p is the flow from the pump. However, during diastole, the aortic valve is closed, so the only flow through the left ventricle comes from the pump positioned across the valve. By neglecting the cardiac current source and assuming a constant pump flow, the model can be simplified as follows:

[0100]

[0101] Where P0 is the initial aortic pressure during diastole. In some embodiments, the flow rate from the pump is estimated based on the current to the motor of the heart pump system to maintain a constant speed. p The pressure P can be measured at various points within a single diastole to characterize and deconstruct the pressure waveform, as described below with respect to Figure 3 In some embodiments, the heart pump operates at a constant speed. In some embodiments described herein, the speed of the pump can be changed to "ping" the heart.

[0102] At step 508, the total blood volume pumped per heart beat, representative of cardiac performance, is calculated based on the time-varying relationship between aortic pressure and blood flow during diastole. For example, once R and C have been determined, the CO of the heart may be determined (e.g., as described below with respect to Figure 7Described). In some embodiments, other metrics indicative of cardiac performance may be calculated. For example, a metric indicative of cardiac performance may be ventricular resistance, ventricular compliance, CO, CPO, stroke volume, stroke work, ejection fraction, cardiac index, or a prediction of patient survivability. Many metrics indicative of cardiac performance are interrelated. For example, CO is determined based on the flow rate of blood passing through and through the pump. Stroke volume is an index of left ventricular function and is given by the formula SV=CO / HR, where SV is stroke volume, CO is cardiac output, and HR is heart rate. Stroke work is the work done by the ventricle to eject a certain volume of blood and can be calculated from stroke volume according to the equation SW=SV*MAP, where SW is stroke work, SV is stroke volume, and MAP is mean arterial pressure. Cardiac work is calculated by multiplying the stroke work and heart rate. CPO is a measure of cardiac function that represents the pumping capacity of the heart in watts. CPO is calculated using the equation CPO = mAoP * CO / 451, where CPO is cardiac power output, mAoP is mean aortic pressure, CO is cardiac output, and 451 is a constant used to convert mmHg x L / min to Watts. Ejection fraction can be calculated by dividing stroke volume by the volume of blood in the ventricle. Other parameters such as chamber pressure, preload state, afterload state, cardiac recovery, flow load state, variable volume load state, and / or cardiac cycle flow state can be calculated from these values ​​or determined via these parameters.

[0103] In some embodiments, the operation of the pump is adjusted based on a metric indicative of cardiac performance. Adjusting the pump operation may include increasing the pump speed, decreasing the pump speed, adjusting pump placement, shutting down the pump, or any other suitable adjustment. For example, if the total blood volume pumped is below a threshold, the pump speed may be increased, and if the blood volume is above a threshold, the pump speed may be decreased.

[0104] In some embodiments, the method described above includes: actuating a blood pump within the patient's vasculature; and determining a cardiac output of the patient's heart using any of the aforementioned systems and sensors. The pumping speed of the blood pump may be adjusted based on the determined cardiac output.

[0105] Figure 6 A process 600 for determining cardiac output is illustrated. Figure 1 Process 600 is performed using the heart pump system 100 or any other suitable pump. In some embodiments, the pump is an intravascular blood pump device that is placed in the patient's heart via percutaneous insertion. The pump may be introduced to the patient because the patient is in cardiogenic shock or is otherwise experiencing a decline in health. The pump may be positioned across the aortic valve so that the blood inlet of the pump (e.g., Figure 1 The blood inlet 172 of the pump is in the left ventricle and the pump outlet (e.g., Figure 1The outlet opening 170 of the pump is in the aorta. The pump facilitates the operation of the native heart so that the CO from the heart equals the native CO plus the pump output.

[0106] In step 602, hemodynamic support is applied to the heart at a first pumping rate. The hemodynamic pumping rate is supplied through multiple heart beats of the heart. Each heart beat includes a systolic rise, a dicrotic notch, and a diastolic fall that occurs after the dicrotic notch. For example, the hemodynamic pumping rate may be provided over a range of two, three, four, ten, twenty, thirty, one hundred, two hundred, or any other suitable number of heart beats.

[0107] In step 604, a plurality of aortic pressure measurements are detected during the diastolic descent of a particular beat in the plurality of beats. For example, the pressure may be sampled at a rate of 1, 2, 3, 10, 20, 30, 100, 200, 300, 1000, 2000, 3000, or any other suitable number of samples per second. In some examples, the aortic pressure is sampled only during the diastolic descent. In some examples, the aortic pressure is measured constantly or periodically. In some examples, the sampling rate of the aortic pressure is changed during the diastolic descent.

[0108] In step 606, a first of the plurality of aortic pressure measurements is compared to a second of the plurality of aortic pressure measurements in a time-dependent, nonlinear model of the vascular system to determine systemic vascular resistance and compliance. In some embodiments, at least one aortic pressure measurement is obtained at the end of diastole when cardiac output occurs solely through operation of the blood pump. For example, Figure 3 As shown in and described above, pressure can be measured at a series of points during the diastolic period. For each of these pressure measurements, pressure can be measured and flow can be estimated. In conjunction with the known measurement time, pressure and flow measurements can be compared between two times to calculate cardiac parameters (such as aortic resistance and compliance).

[0109] In step 608, the cardiac output during a particular beat is determined based on the determined systemic vascular resistance and compliance. In some embodiments, determining the cardiac output includes determining the cardiac output for a plurality of particular beats within the plurality of beats, and applying at least one of summing, averaging, or linear regression to the determined cardiac outputs to determine a cumulative indicator of the cardiac output of the heart. The cumulative indicator of the cardiac output of the heart may be indicative of cardiac performance or overall patient health.

[0110] Figure 7Two graphs are shown for the same ten second period, one graph of aortic pressure and one graph of cardiac flow. The y-axis of the upper graph represents aortic pressure in mmHg, while the x-axis represents time in seconds. The y-axis of the lower graph represents the calculated total cardiac flow in liters per minute, while the x-axis represents time in seconds. In this example, systemic vascular resistance R and compliance C are known. For example, R and C can be calculated using aortic pressure measurements obtained during the depicted ten second time period in combination with pump data as described above. The total cardiac flow i is calculated using R, C, and the aortic pressure waveform by applying equation (1) h +i p :

[0111]

[0112] The total cardiac flow i generated by equation (1) over a period of time (e.g., 5 seconds, 10 seconds, or 30 seconds) can be calculated by taking the total cardiac flow i h +i p The average value of CO is used to calculate CO. Figure 7 In the example in , the time period is 10 seconds. The average R value for this time period is 0.6143 mmHg*sec / ml, and the average C value is 1.5 mL / mmHg, resulting in a calculated CO of 6.9 L / min.

[0113] The foregoing is merely illustrative of the principles of the present disclosure, and the device may be practiced in other aspects than those described, which are presented for purposes of illustration and not limitation. It will be understood that the device disclosed herein, although shown for percutaneous insertion of a heart pump, may be applied to devices in other applications requiring hemostasis.

[0114] After reviewing this disclosure, variations and modifications will occur to those skilled in the art. The disclosed features may be implemented in any combination and subcombination (including multiple dependent combinations and subcombinations) with one or more other features described herein. The various features described or illustrated above (including any components thereof) may be combined or integrated in other systems. In addition, certain features may be omitted or not implemented.

[0115] The described systems and methods may be implemented locally on a heart pump system or a controller of a heart pump system (such as an AIC). The heart pump system may include a data processing device. The systems and methods described herein may be implemented remotely on an independent data processing device. The independent data processing device may be directly or indirectly connected to the heart pump system via a cloud application. The heart pump system may communicate with the independent data processing device in real time (or near real time).

[0116] In general, aspects of the subject matter and functional operations described in this specification may be implemented in digital electronic circuits or in computer software, firmware or hardware, including the structures disclosed in this specification and their structural equivalents, or in a combination of one or more of them. Aspects of the subject matter described in this specification may be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium, for execution by a data processing device or to control the operation of a data processing device. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, a material combination that affects a machine-readable propagation signal, or a combination of one or more of them. The term "data processing device" encompasses all devices, devices, and machines for processing data, including, as examples, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, a device may also include code that creates an execution environment for the computer program in question, for example, code that constitutes a processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, for example, a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to a suitable receiver device.

[0117] A computer program (also referred to as a program, software, software application, script, or code) may be written in any form of programming language, including compiled or interpreted languages, and it may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store multiple portions of one or more modules, subroutines, or code). A computer program may be deployed to execute on one computer, or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0118] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuits, and the device can also be implemented as special purpose logic circuits, such as FPGAs (field programmable gate arrays) or ASICs (application specific integrated circuits).

[0119] As an example, processors suitable for executing computer programs include both general-purpose microprocessors and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, or be operatively connected to receive data from the mass storage device or transfer data to the mass storage device. However, a computer need not have such a device.

[0120] Examples of changes, substitutions, and alterations are ascertainable by those skilled in the art and may be made without departing from the scope of the information disclosed herein.All references cited herein are incorporated by reference in their entirety and constitute a part of this application.

Claims

1. A method for determining cardiac performance of a heart, the method comprising: monitoring a hemodynamic parameter during operation of the mechanical circulatory support device at a first device operating parameter; identifying a diastolic phase of a cardiac cycle based on a shape of the hemodynamic parameter over time; establishing a time-varying relationship between aortic pressure and blood flow during said diastolic period; as well as Based on the time-varying relationship between aortic pressure and blood flow during the diastolic phase, the total blood volume induced per heart beat by the mechanical circulatory support device is calculated to indicate cardiac performance.

2. The method according to claim 1, wherein: The mechanical circulatory support device is an intravascular blood pump, and wherein monitoring occurs while operating the pump at a first pump speed.

3. The method according to any one of claims 1 to 2, wherein: The hemodynamic parameter is aortic pressure.

4. The method according to claim 1, wherein: Calculating the total volume of blood pumped with each heart beat includes: determining vascular compliance and vascular resistance of systemic vasculature based on a mathematical formula representing the hemodynamic parameter over time; and Using the determined vascular compliance and vascular resistance, stroke volume of the systemic vasculature is calculated.

5. A blood vessel sensor, comprising: a system for inducing blood flow in a blood vessel of a patient, the system comprising a motor and an impeller; as well as A controller configured to: detecting a change in resistance to rotation of an impeller in the blood vessel; maintaining a constant impeller rotational speed based on the detected resistance to impeller rotation; Vascular compliance and vascular resistance were calculated based on the change in resistance with impeller rotation using a transfer function.

6. The blood vessel sensor according to claim 5, wherein: The transfer function is a Windkessel model.

7. The blood vessel sensor according to claim 5, wherein: The controller is configured to determine a metric indicative of cardiac performance based on the vascular compliance and the vascular resistance.

8. The blood vessel sensor according to claim 7, 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 survivability.

9. The blood vessel sensor according to claim 8, wherein: The controller is configured to adjust the impeller rotational speed based on at least one of: vascular resistance, vascular compliance, or cardiac output.

10. The blood vessel sensor according to claim 5, wherein: The controller is configured to: receiving a measurement indicative of aortic pressure over a period of time; detecting current delivered to the motor; and determining a blood flow rate pumped by the system during the time period based on the current delivered to the motor, Therein, the calculation of the vascular compliance and the vascular resistance is further based on the measured values ​​indicative of aortic pressure and the blood flow rate.

11. The blood vessel sensor according to claim 5, wherein: The system for inducing blood flow in a blood vessel of the patient includes: a cannula configured to extend within a left ventricle of a heart; and a pressure sensor configured to detect at least one of: aortic pressure, left ventricular pressure, or a pressure gradient.

12. The blood vessel sensor according to claim 5, wherein: The system for inducing blood flow within a vessel of the patient is an intracardiac blood pump incorporating the impeller within a shroud.

13. A blood vessel sensor, comprising: a system for inducing blood flow within a patient's blood vessels; a hemodynamic sensor configured to detect changes in a hemodynamic parameter resulting from said induced blood flow; and A controller is configured to receive the sensor signal and calculate the resistance of the blood vessel based on the blood flow in the blood vessel and the aortic pressure.

14. The blood vessel sensor according to claim 13, wherein: The system comprises a pump comprising a motor and an impeller, and wherein the controller is configured to: detecting a change in resistance to rotation of an impeller in the blood vessel; maintaining a constant impeller rotational speed based on the detected resistance to impeller rotation; and The pump operation data is transmitted to a computing device.

15. The blood vessel sensor according to claim 14, wherein: The pump operation data includes at least one of: a pressure measurement, an electric current measurement, a change in resistance to impeller rotation, and a flow rate estimate.

16. The blood vessel sensor according to claim 14, wherein: The controller is configured to: receiving 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 decline of a heart beat; determining a first blood flow rate pumped by the pump at the first time and a second blood flow rate pumped by the pump at the second time; and A time-dependent nonlinear model of the vascular system is calculated using (i) the first aortic pressure measurement, (ii) the second aortic pressure measurement, (iii) the first blood flow rate, and (iv) the second blood flow rate to determine systemic vascular resistance and compliance.

17. The blood vessel sensor according to claim 16, wherein: The time-dependent nonlinear model is the Windkessel model.

18. The blood vessel sensor according to claim 16, wherein: The controller is further configured to determine cardiac output based on the first aortic pressure measurement, the second aortic pressure measurement, the first blood flow rate, and the second blood flow rate.

19. The blood vessel sensor according to claim 16, wherein: The controller is configured to receive operating commands for a pump from the computing device, wherein the operating commands are based on operating data of the pump.

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