System and method for estimating cardiac pump position - Patents.com

Abstract

To provide systems and methods for estimating a position of a heart pump system in a patient.SOLUTION: The system receives first data indicative of a time-varying motor current during a first time period. The motor current corresponds to an amount of current delivered to a motor, while the heart pump system is operating in the patient. The system receives second data indicative of a time-varying differential pressure during the first time period. The differential pressure is indicative of a position of the heart pump system relative to the patient's heart. The system receives third data indicative of time-varying motor current during a second time period, and determines an estimate of the differential pressure during the second period of time from the third data and from a relationship between the first data and the second data. The estimate is usable to predict the position of the heart pump system in the patient.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 644,240, entitled "SYSTEMS AND METHODS FOR ESTIMATING A POSITION OF A HEART PUMP," filed March 16, 2018, and is related to U.S. Patent Application No. 16 / 354,595, entitled "SYSTEMS AND METHODS FOR ESTIMATING A POSITION OF A HEART PUMP," filed March 15, 2019. The entire contents of the above-referenced applications are incorporated herein by reference. [Background technology]

[0002] background Acute and chronic cardiovascular conditions reduce quality of life and life expectancy. A variety of therapeutic modalities have been developed for cardiac health, ranging from pharmaceuticals to mechanical devices to transplants. Temporary cardiac support devices, such as cardiac pump systems, provide hemodynamic support to promote cardiac recovery. Some cardiac pump systems, such as the IMPELLA® family of devices (Abiomed, Inc., Danvers MA), can be inserted percutaneously into the heart and run in parallel with the patient's native heart to supplement cardiac output. Such cardiac pump systems may measure and / or calculate cardiac pump parameters that are useful for determining the patient's health and for judging the operation of the cardiac pump system.

[0003] These measurements may be collected through sensors, but sensors are prone to failure. When a sensor in a heart pump system fails, the clinician loses many valuable measurements, such as estimated flow, position monitoring, and suction alarms. When a sensor fails, the clinician often removes the heart pump system from the patient, even if the pump itself is functioning properly. Removal and replacement of the heart pump system is undesirable, especially if the pump is functioning properly, as it increases the risk of introducing bacteria to the patient. Replacement of the heart pump system can be expensive and leads to the heart pump system being "wasted." Furthermore, removal and replacement of the heart pump system takes away valuable time for the patient's blood pump support and therefore recovery. Summary of the Invention

[0004] overview The systems, devices, and methods described herein estimate the position of a heart pump when placed within a patient's heart. Specifically, the systems and methods of the present invention determine a relationship between motor current and differential pressure signals for a native heart pump system, and then use this relationship to determine an estimate of a time-varying differential pressure from subsequently received motor current data. From the estimated differential pressure, the heart pump system estimates pump flow, triggers a suction alarm, and triggers a placement alarm.

[0005] A controller may be configured to perform any of the embodiments, aspects, and methods described herein. For example, the controller may 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 connected to the motor; a pump housing at least partially surrounding the rotor such that operation of the motor drives the rotor and pumps blood through the pump housing; one or more sensors including a differential pressure sensor; and the controller. For example, the heart pump system may include an Impella RP heart pump or an Impella 5.0 heart pump from Abiomed, Inc. connected to an AIC or any other suitable system.

[0006] The heart pump system may include a pump having a pump housing and a rotor. The rotor is at least partially disposed within the pump housing such that during operation of the system, a motor drives the rotor and the rotor pumps blood through the pump housing. The heart pump system includes a cannula having a proximal end that interfaces with a distal end of the pump housing and a distal end. The pump may be configured to be positioned such that the cannula extends across the aortic valve of the patient with the distal end located within the left ventricle of the patient and the proximal end located within the aorta of the patient. In some embodiments, an elongated catheter extends proximally of the pump housing. The elongated catheter may be coupled to the pump housing at its distal end. In one example, a drive cable may extend through the elongated catheter. In one example, the elongated catheter may house an electrical connection connecting the pump to a controller. In some embodiments, the pump further includes a flexible protrusion extending distally from the distal end of the cannula, such as a pigtail-shaped flexible protrusion.

[0007] The heart pump system includes one or more sensors that measure pressure, such as a differential pressure sensor. In one example, the differential pressure sensor measures the difference between the pressure outside the pump and the pressure inside the pump. For example, when the cannula is placed across the aortic valve, the top (outer surface) of the sensor is exposed to aortic pressure and the bottom (inner surface) of the sensor is exposed to ventricular pressure.

[0008] A controller operatively connected to the heart pump system estimates a position of the heart pump based on baseline data and updated data. The baseline data is received during a first time period and provides a basis for the controller to determine a relationship between two parameters during normal operation of the pump. The first time period may be 20 seconds, 40 seconds, 1 minute, 2 minutes, 10 minutes, 20 minutes, or any other suitable time period. The first time period may correspond to a number of samples taken at a given frequency. For example, the first time period may correspond to 500 samples, 1000 samples, 2000 samples, 5000 samples, or any other suitable number of samples. Generally, during the first time period, the heart pump system operates within the patient, and sensors on the heart pump system and / or sensors not on the system acquire data regarding the operation of the system (e.g., motor current, pump location, or any other motor or system parameter) and / or data regarding the health of the patient (e.g., aortic pressure, differential pressure, or any other hemodynamic or patient parameter). This data is used to identify a relationship between certain parameters. In the event of a failure of one or more sensors (e.g., differential pressure), the controller may estimate the signal from the faulty sensor based on the in-service sensor (e.g., motor current) and the relationship between the signals from the faulty and in-service sensors. During a first period, the pump may operate at a single performance level (e.g., corresponding to a particular rotor speed) or may operate at a range of performance levels.

[0009] The controller receives first data indicative of a time-varying motor current in the heart pump system during a first time period and receives second data indicative of a time-varying differential pressure for the patient during the first time period. The time-varying motor current corresponds to an amount of current delivered to a motor of the heart pump system while the heart pump system is operating in the patient. For example, the motor current may be varied to keep a rotor speed of the heart pump system constant. Operating a motor of the heart pump system (e.g., the motor contained in the motor housing 102 of FIG. 1) to maintain a constant rotor speed is desirable in many medical situations, but generally requires a varying amount of current to be provided to the motor because the load on the motor varies at different stages during the cardiac cycle. Thus, when the differential pressure in the patient's heart changes, the motor current also changes to keep the rotor speed constant. For example, when the flow rate of blood entering the aorta increases (e.g., during systole), the current required to operate the motor increases. This increase in motor current may be used to characterize cardiac function, as described in more detail below. The time-varying differential pressure corresponds to the pressure difference between the interior portion of the heart pump system and the exterior of the heart pump system, and further indicates the position of the heart pump system relative to the patient's heart. The differential pressure signal indicates pressure over time, and the displayed measurement may be derived from a pressure sensor on the intravascular pump during operation of the pump. For example, the sensor may detect an electrical signal proportional to the difference between the aortic pressure and the ventricular pressure (also referred to as a differential pressure signal), which may be displayed by the heart pump system. As described below, the systems and methods described herein determine a relationship between the time-varying motor current and the time-varying differential pressure. The relationship between the motor current and the differential pressure may be used in conjunction with the motor current data to estimate the differential pressure at other times (e.g., after the first period described above). This is particularly useful when the pressure sensor fails or when it is desirable to verify the operation of the pressure sensor.

[0010] During a second time period that is later than the first time period, the controller receives third data indicative of the time-varying motor current. For example, the second time period may be 1 second, 2 seconds, 10 seconds, 30 seconds, 1 minute, 2 minutes, 10 minutes, or any suitable length of time. For example, the controller receives data related to the time-varying motor current and differential pressure at a first time and then receives additional motor current data during a second time period. The data from the first time period may be used to determine a relationship between the first data (indicative of the motor current during the first time period) and the second data (indicative of the differential pressure during the first time period).

[0011] The controller determines an estimate of the time-varying differential pressure during the second time period from the third data and from a relationship between the first data (indicative of the motor current during the first time period) and the second data (indicative of the differential pressure during the first time period). For example, the relationship between the first data and the second data may be a multiple linear fit of a mapping between the motor current information and the differential pressure information obtained during the first time period. The relationship between the motor current and the differential pressure may be characteristic of a given heart pump system - i.e., at a particular performance level, the relationship between the motor current and the differential pressure may be substantially similar at different times, and the relationship itself may be "scalable" between different performance levels. Thus, by determining the relationship between the motor current and the differential pressure during the first time period, the systems and methods described herein may be able to characterize the heart pump system and may be able to use the relationship at later times and at different performance levels.

[0012] The estimate of the differential pressure can be used to predict the location of the cardiac pump system within the patient. For example, the controller may use the relationship between the motor current and the differential pressure in conjunction with more recently obtained third data (indicative of the motor current during the second time period) to construct an estimated differential pressure signal for a second time period. The controller may use the estimated differential pressure signal to determine the location of the cardiac pump system within the patient.

[0013] In some embodiments, the systems, methods, and devices described herein determine a correlation between the motor current and the time-varying differential pressure for each time point. In some embodiments, the controller may calculate a multiple linear fit of the correlation. The multiple linear fit is indicative of the operational characteristics of the heart pump system. For example, for each measurement of the motor current at each time point within a first time period, the respective differential pressure measurements at the same time point may be plotted. This plot may be used to determine a multiple linear fit represented by a function or series of functions that may differ between individual heart pump systems. For example, a first heart pump system may have a completely different multiple linear fit than a second heart pump system. As described below, the correlation between the motor current and the time-varying differential pressure may be scaled (linearly or using any suitable scale) between different performance levels for the same heart pump system. After the controller determines the correlation between the motor current and the differential pressure, the correlation may later be used to characterize the patient's health and parameters of the system operation. This is particularly useful in the event of a sensor (e.g., a pressure sensor) failure; the correlation may be used to estimate parameters that can no longer be measured directly from the sensor.

[0014] In some embodiments, the second data (indicative of the time-varying differential pressure) is received from a differential pressure sensor on the heart pump system. For example, when the heart pump system is in an operating position within the patient's heart, one side or surface of the differential pressure sensor may be exposed to aortic pressure, a second side or surface of the differential pressure sensor may be exposed to ventricular pressure, and the differential pressure sensor may measure the difference between the aortic pressure and the ventricular pressure. The placement of the pressure sensor and the type of sensor are not limiting. For example, the second data may be collated from multiple sensors that may or may not be on the heart pump system.

[0015] The differential pressure sensor may fail or break. In some embodiments, if the differential pressure sensor fails, the controller determines an estimate of the time-varying differential pressure during the second time period in response to determining that the sensor has failed. In some embodiments, the controller may determine that the differential pressure sensor has failed if no data is received from the differential pressure sensor during the second time period. If the pressure sensor fails or breaks, the controller may no longer receive data directly related to the pressure within the patient's heart. For systems in which placement of the heart pump system within the patient's heart is determined from a pressure signal, failure or breakage of the pressure sensor means that it is difficult or impossible to know whether the heart pump system is properly positioned within the patient's heart (e.g., extending across the aortic valve into the left ventricle). Thus, rather than measuring the differential pressure directly, the differential pressure is estimated, and the estimate is used to determine placement of the heart pump system.

[0016] In some embodiments, the systems, methods, and devices described herein determine an estimate of the time-varying differential pressure during the second time period; the determining step includes determining a time series of the estimate points by determining whether the third data corresponds to a first phase or a second phase in the relationship between the first data and the second data. For example, the first phase may be phase A and the second phase may be phase B. For a given motor current value, there may be two corresponding differential pressure values ​​determined by the relationship between the first data and the second data (e.g., as shown in FIG. 3). Of the two corresponding differential pressure values, one value may correspond to phase A and the other value may correspond to phase B.

[0017] Whether the motor current is in the first phase (e.g., phase A) or the second phase (e.g., phase B) may be determined by examining the diastole. In some embodiments, the systems, methods, and devices described herein determine the diastole in the additional data (e.g., during the second time period described above). The diastole begins at a start point and ends at an end point. The slope of the additional data between the start point and the end point indicates the first or second phase. If the slope is positive, the additional data corresponds to the first phase. If the slope is negative, the additional data corresponds to the second phase. Thus, by examining the diastole of the patient's heart, the systems described herein may be able to properly determine which of the two pressure values ​​(phase A or phase B) is correct for a given motor current value.

[0018] In some embodiments, the systems, methods, and devices described herein determine at least one of flow, position, and suction associated with a heart pump system based on an estimate of the time-varying differential pressure. The time-varying differential pressure, motor current, and / or the estimate of the time-varying differential pressure may be displayed. In one example, the controller may simultaneously display the time-varying differential pressure, the motor current, and the estimate of the time-varying differential pressure. In one example, the controller may simultaneously display the motor current and one of the time-varying differential pressure or the estimate of the time-varying differential pressure. In one example, the user may select which signal they wish to view. Since the determination of flow, position, and suction, etc., is based on the measurement or estimate of the differential pressure, it is essential that the differential pressure value is known and correct for a given time. If the differential pressure sensor on the heart pump system fails and no estimate of pressure can be determined, the flow, position, and suction of the system are also lost. Thus, the systems and methods described herein provide differential pressure estimates, allowing flow, position, and suction estimation to continue in the event of a sensor failure, thereby providing the clinician with a clearer picture of the patient's health and the operation of the heart pump.

[0019] In some embodiments, the systems, methods, and devices described herein provide a first and / or second indication of differential pressure sensor failure and estimated time-varying differential pressure. The first indication indicates that the differential pressure sensor has failed. In one example, the controller may display a warning indication on a user interface conveying that the sensor data is unreliable. The second indication indicates that an estimate of the time-varying differential pressure during a second period has been simulated or estimated. In one example, the controller may simultaneously display an alarm warning that the differential pressure sensor has failed and an alarm warning that an estimate of the time-varying differential pressure is displayed and is an estimate. The indications may be visual or audible.

[0020] In some embodiments, the systems, methods, and devices described herein determine whether the time-varying differential pressure is drifting by comparing the time-varying differential pressure to an estimate of the time-varying differential pressure for a second time period. Based on comparing the time-varying differential pressure to an estimate of the time-varying differential pressure, a difference between the time-varying differential pressure and the estimate of the time-varying differential pressure over the second time period is calculated. For example, the controller may display both the time-varying differential pressure and the estimate of the time-varying differential pressure and may calculate the difference between the two signals at multiple time points during the second time period. The difference is compared to a differential pressure signal threshold. The differential pressure signal threshold may be 10 mmHg, 15 mmHg, 20 mmHg, 40 mmHg, 60 mmHg, 80 mmHg, or any suitable quantity. If the difference is greater than the differential pressure signal threshold, the time-varying differential pressure is drifting. For example, at a first time point, the difference between the time-varying differential pressure and the estimate of the time-varying differential pressure may be 2 mmHg. At a second time point, which is later than the first time point, the difference may be 5 mmHg. At a third time point, later than the second time point, the difference may be 27 mmHg. In this example, the differential pressure signal threshold may be 25 mmHg, in which case the controller determines that the time-varying differential pressure has drifted at the third time point. The systems and methods described herein provide a check that the sensor is working properly by determining if the differential pressure signal has drifted. For example, if the sensor is degraded, the pressure signal may drift, providing an incorrect reading to the clinician. If the estimated and measured differential pressures differ significantly, such drift may be notified to the clinician, providing the clinician with an opportunity to correct or further investigate the pressure reading.

[0021] In some embodiments, if the time-varying differential pressure has drifted, the systems, methods, and devices described herein display a notification indicating that the differential pressure sensor needs to be recalibrated. The notification may be visual or audible. In one example, the controller may display a warning or alarm on a user interface stating that the time-varying differential pressure signal is unreliable and needs to be recalibrated. In one example, the controller may display a warning or alarm on a user interface stating that the time-varying differential pressure signal is drifting. In some embodiments, if the time-varying differential pressure has drifted, the differential pressure sensor is automatically reconfigured. In one example, the controller may zero the differential pressure sensor for recalibration. Recalibration can help ensure that the sensor provides accurate data to the clinician or controller, thereby increasing the effectiveness of the treatment.

[0022] In some embodiments, the systems, methods, and devices described herein change the operation of the heart pump system from a first operating level to a second operating level. Based on changing the operation of the heart pump system to the second level, the relationship between the first data and the second data may be scaled to account for the second operating level. The estimate of the time-varying differential pressure may be based on the scaling of the relationship. In one example, during a first time period, the heart pump system may operate at an operating level P-8, while during a second time period, the heart pump system may operate at an operating level P-9. The controller may determine the relationship between the first data and the second data for the operating level P-8. During the second time period, the controller may calculate an estimate of the time-varying differential pressure by determining a value or set of values ​​using the relationship calculated for the first time period and then linearly scaling the value or set of values. Thus, if the P-level used to collect the motor current data and the differential pressure signal data during the first time period is different than the level used to collect additional motor current data during the second time period, the relationship between the motor current data and the differential pressure sensor data may be scaled to account for the change in P-level. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 illustrates an exemplary heart pump system configured to estimate cardiovascular parameters according to certain embodiments. [Diagram 2] FIG. 1 illustrates a process for estimating the position of a cardiac pump system within a patient according to certain embodiments. [Diagram 3] 1 is a plot of differential pressure signal versus motor current for a heart pump system operating at a range of performance levels according to certain embodiments. [Figure 4] FIG. 2 is a plot of motor current, differential pressure signal, and flow over a period of time according to certain embodiments. [Diagram 5] 1 is a plot of differential pressure signal versus motor current for a heart pump system according to certain embodiments. [Figure 6] FIG. 13 is a plot of motor current over time for the first phase according to certain embodiments. [Figure 7] FIG. 13 illustrates a plot of motor current over time for the second phase according to certain embodiments. [Figure 8] FIG. 13 is a plot of differential pressure signal versus motor current over first and second phases for a heart pump system according to certain embodiments. [Figure 9] FIG. 2 is a plot of an actual differential pressure signal, a simulated differential pressure signal, and a first phase simulated differential pressure signal during a period of first phase operation according to certain embodiments. [Figure 10] FIG. 2 is a plot of actual differential pressure signals, simulated differential pressure signals, and simulated differential pressure signals of the first phase during a period of second phase operation according to certain embodiments. [Figure 11]FIG. 1 is a plot of differential pressure signal, motor current, and rotations per minute (RPM) for a heart pump system as the performance level of the heart pump system changes between two levels, according to certain embodiments. [Figure 12] FIG. 2 is a plot of differential pressure signal and motor current at a first performance level over a period of time according to certain embodiments. [Figure 13] FIG. 13 is a plot of differential pressure signal and motor current at a second performance level over a period of time according to certain embodiments. [Figure 14] FIG. 13 is a plot of differential pressure signal drift versus motor current over time according to certain embodiments. [Figure 15] FIG. 13 is a plot of differential pressure signal drift versus estimated differential pressure signal over a period of time according to certain embodiments. [Figure 16] 4 is a histogram of average estimated flow error according to certain embodiments. [Figure 17] 4 is a histogram of maximum estimated flow error according to certain embodiments. [Figure 18] 4 is a histogram of minimum estimated flow error according to certain embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Detailed Description Certain exemplary aspects will be described so that the systems, methods, and devices described herein may be generally understood. Although the aspects and features described herein are specifically described for use in connection with a patient's cardiac health, it will be understood that all components and other features outlined below may be combined with one another in any suitable manner, and may be adapted and applied to other types of medical treatments and patient health conditions.

[0025] The systems, devices, and methods described herein use a relationship between historical motor current data and differential pressure data in a heart pump system to determine an estimate of a time-varying differential pressure from the motor current data. The differential pressure signal is indicative of pressure over time, and the displayed measurement may be derived from a pressure sensor on an intravascular pump (such as heart pump 100 in FIG. 1) during operation of the pump. For example, the sensor may detect an electrical signal proportional to the difference between the pressure outside the pump and the pressure inside the pump (also referred to as a differential pressure signal), which may be displayed by the heart pump system.

[0026] The differential pressure signal may be used by a clinician to determine the placement of the pump within the heart by monitoring the measured pressure to determine when the pump is properly placed within the heart. When the heart pump is properly placed across the aortic valve, the top (outer surface) of the sensor is exposed to aortic pressure and the bottom (inner surface) of the sensor is exposed to ventricular pressure. The heart pump system may be considered properly placed when the cannula of the heart pump straddles the aortic valve such that the blood inlet to the pump is in the left ventricle and the outlet from the pump is in the aorta. When the heart pump system is properly placed within the heart, a pulsatile differential pressure signal results from pressure changes associated with the cardiac cycle. During diastole, a large pressure difference between the aorta and the left ventricle creates a large differential pressure signal. At the peak of systole, when the aortic valve opens, the pressure difference between the aorta and the left ventricle (and thus the differential pressure signal) is zero. Thus, the continuous pressure changes associated with the cardiac cycle result in a pulsatile waveform when properly placed. When the heart pump system is not properly placed across the aortic valve, or is entirely within the aorta or entirely within the ventricle, the pressure outside and inside the cannula will be the same throughout the cardiac cycle. As a result, the pressure will be the same on either side of the sensor membrane, resulting in a flat differential pressure signal. For example, when properly placed, the differential pressure signal may fluctuate periodically and / or have a peak-to-trough value of 60 mmHg, 40 mmHg, or another generally high value. When not properly placed, the differential pressure signal may have a peak-to-trough value of 0 mmHg, 2 mmHg, or another generally low value.

[0027] The motor current signal represents a measurement of the current drawn by the motor in the heart pump system over time. A heart pump system (e.g., heart pump system 100) may be designed to provide a constant heart pump motor speed at a particular performance level. Operating the heart pump system's motor (e.g., the motor contained in motor housing 102 of FIG. 1) to maintain a constant rotor speed is desirable in many medical situations, but generally requires that a varying amount of current be supplied to the motor; the load on the motor varies at different stages during the cardiac cycle. Thus, when the differential pressure within the patient's heart changes, the motor current also changes to keep the rotor speed constant. For example, when the flow rate of blood entering the aorta increases (e.g., during systole), the current required to operate the motor increases. This change in motor current can therefore be used to help characterize cardiac function, as described in more detail below with respect to the accompanying figures. The motor current signal may be derived from measurements by a sensor on the pump motor within the pump, or may be derived from the processor or controller itself. Even if the differential pressure at a given time is not known, the rotor speed at that time is known, and the motor current is tuned to ensure that the rotor speed is stable. The systems and methods described herein establish a relationship between past motor current and differential pressure signal data for a particular heart pump system during a first time period, and then use this relationship to determine an estimated differential pressure signal from newly received motor current data during a second time period. The motor current / differential pressure signal relationship is determined for a unique heart pump system and is characteristic of that unique heart pump system.

[0028] Once the relationship between the motor current and the differential pressure signal has been determined, the motor current is used to determine an estimate of the differential pressure signal. However, for a given motor current value, there may be two corresponding differential pressure signal values: a value for the first phase (also referred to herein as "phase A") and a value for the second phase (also referred to herein as "phase B"). As described in more detail below, the systems and methods described herein may determine whether the heart pump system is in phase A or phase B, and may determine an estimate of the differential pressure signal accordingly.

[0029] Because the motor current and the relationship can be used to determine an estimate of the time-varying differential pressure, the systems and methods described herein may be particularly useful when a differential pressure sensor fails and the measured differential pressure signal data becomes unavailable or unreliable due to drift, as described below with respect to FIGS. 14-15. In some aspects, an estimate of the time-varying differential pressure may be determined in response to determining that the differential pressure sensor has failed. In some aspects, the cardiac pump system may issue an alarm if the differential pressure sensor has failed. In some aspects, an estimate of the differential pressure may be determined regardless of whether the differential pressure sensor has failed. By comparing the measured differential pressure signal to the estimated differential pressure signal, the systems and methods described herein may also be used to determine that the measured differential pressure signal has drifted and needs to be recalibrated.

[0030] The heart pump system of the present invention is at least partially inserted into the heart of a patient. A heart pump system compatible with the present disclosure is disclosed in US Patent Application Publication No. 2018-0078159-A1, the entire contents of which are incorporated herein by reference. Generally, any other heart pump system or system for obtaining physiological data from a patient may be used with the present disclosure. For example, differential pressure signal data and motor current data may be displayed on an interface connected to or part of the heart pump system, such as an Automated Impella Controller (AIC). Raw features may be extracted from the heart pump system signals. The heart pump system may have a display, such as an indwelling screen that displays real-time operating data for the heart pump system. Such an indwelling screen may display the waveforms of the differential pressure signal and motor current, as well as the maximum / minimum and average values ​​for each waveform, in a central display area of ​​the screen.

[0031] In some embodiments, the systems and methods described herein may be associated with the Impella 5.0 device, which is part of the IMPELLA® family of devices (Abiomed, Inc., Danvers MA).

[0032] FIG. 1 illustrates an exemplary heart pump system inserted into a patient's blood vessel and configured to estimate cardiovascular parameters, according to certain embodiments. The heart pump system 100 may operate intracardially, partially intracardially, extracardially, partially extracardially, partially extravascularly, or at any other suitable location in the patient's vascular system. The heart pump system may be considered "in position" when a cannula 173 is placed across the aortic valve such that a blood inlet to the pump (e.g., blood inlet 172) is in the left ventricle and an outlet from 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 a controller unit separate / remote from the heart pump 106. In some embodiments, the control system 104 is internal to 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 on which pump elements are 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. An impeller blade on the drive shaft may be rotated within the pump housing 134 to induce a flow of blood into the cannula 173 at a suction head 174. The suction head 174 provides a blood inlet 172 at a distal end portion 171 of the cannula 173. A flow of blood 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.

[0033] Rotation of the drive shaft within the pump housing 134 may also rotate the pump elements within the bearing gap. A hemocompatible fluid may be delivered through the elongated catheter 105 and through the motor housing 102 to the proximal end portion of the cannula 173, whereupon the fluid is pressurized by the rotation of the pump elements. The flow of the hemocompatible fluid has a second direction 122 through the bearing gap of the pump. After exiting the bearing gap, the hemocompatible fluid may follow a flow direction 123 and may be entrained in the flow of blood and flow with the blood into the aorta.

[0034] The heart pump 100 is inserted into the patient's vasculature through the sheath 175. The pump housing 134 may enclose the rotor and internal bearings and may be sized for percutaneous insertion into the patient's vasculature. In some embodiments, the pump may be advanced through the vasculature and past the aortic arch 164. Although the pump is shown in the left ventricle, alternatively, the pump may be placed in the right heart such that blood is pumped from the patient's inferior vena cava or right atrium through the right ventricle and into the pulmonary artery.

[0035] A flexible protrusion 176 may also be included at the distal end portion 171 of the cannula 173, distal to the suction head 174, for optimal placement of the heart pump 100 within a vessel or ventricle. The flexible protrusion 176 may prevent the suction head 174 from approaching the vessel wall, which may become wedged in the vessel wall by suction. The flexible protrusion 176 may be non-suctioning, so that the flexible protrusion 176 may extend the pump 100 mechanically but not hydraulically. In some embodiments, the flexible protrusion may be formed as a pigtail. In some aspects, the pump may not include a flexible protrusion.

[0036] The elongated catheter 105 houses a connection 126 that may comprise a fluid supply line, and may also house an electrical connection cable. The connection 126 may supply a hemocompatible fluid from a fluid reservoir, which may be contained within the control system 104, to the pump.

[0037] The control system 104 includes a controller 182 that controls the pump 106, for example by controlling power to the motor or controlling the motor speed, and may also include a cardiac parameter estimator 116. In some embodiments, the control system 104 includes a display screen to show measurements such as differential pressure signal and motor current. The control system 104 may include circuitry to monitor the motor current for air in the lines or a drop in current indicating a change in the differential pressure signal, flow position, suction, or any other suitable measurement. The control system 104 may include warning sounds, lights, or indicators to alert the operator to a failed sensor, a disconnected or broken connection 126, or a sudden change in the patient's health.

[0038] The control system 104 may include a current sensor (not shown). The controller 182 provides current to the motor 108 by a connection 126, such as through one or more wires. The current provided to the motor 108 via the connection 126 is measured by the current sensor. The load on the motor of a mechanical pump is the pressure head, or the difference between the aortic pressure and the left ventricular pressure. The heart pump 106 experiences a rated load during steady state operation for a given pressure head, and variations from this rated load occur as a result of changing external load conditions, such as the dynamics of left ventricular contraction. Changing dynamic load conditions vary the motor current required to operate the pump rotor at a constant or substantially constant speed. The motor may operate at a speed required to maintain the rotor at a set speed. Thus, and as described in more detail below, the current drawn by the motor to maintain the rotor speed may be monitored and used to understand the underlying cardiac condition. By simultaneously monitoring the pressure head during the cardiac cycle using the pressure sensor 112, the cardiac condition may be more precisely quantified and understood. The cardiac 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 the current and pressure signals to characterize the function of the heart. The cardiac parameter estimator 185 may access a stored lookup table to obtain additional information to characterize the function of the heart based on the pressure and current signals. For example, the cardiac parameter estimator 185 may receive the aortic pressure from the pressure sensor 112 and use the aortic pressure to determine the delta pressure using the lookup table.

[0039] The pressure sensor is a flexible membrane integrated within the cannula 172. As described above, one side of the sensor is exposed to the blood pressure on the outside of the cannula, and the other side is exposed to the pressure of the blood inside the cannula. The sensor generates an electrical signal (differential pressure signal) proportional to the difference between the pressure outside and inside the cannula, which may be displayed by the heart pump system. When the heart pump system is correctly positioned 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. Thus, the differential pressure signal is approximately equal to the difference between the aortic pressure and the ventricular pressure.

[0040] FIG. 2 illustrates a process 200 for determining an estimate of a time-varying differential pressure based on a motor current, according to certain embodiments. The process 200 may be performed using any suitable heart pump system, such as the one described in FIG. 1. In step 210, first data indicative of a time-varying motor current during a first time period is received. The first data (also referred to as motor current data) may be part of a motor current signal. The motor current data, as described above, describes a current delivered to a motor in the heart pump system. For example, the motor may be operated at a rotational speed required to keep the rotational speed of the rotor constant or substantially constant. The current may be measured using a current sensor (e.g., the current sensor described with respect to FIG. 1) or by any other suitable means. In step 212, second data indicative of a time-varying differential pressure during a first time period is received. The second data (also referred to as differential pressure signal data) may be part of a differential pressure signal. In some embodiments, the differential pressure signal data describes a change in pressure measured by a differential pressure sensor (e.g., pressure sensor 112). The differential pressure sensor may be an optical pressure sensor, an electrical pressure sensor, a MEMS sensor, or any other suitable pressure sensor. The differential pressure signal may be used by a clinician to monitor the position of the heart pump relative to the patient's aortic valve. The differential pressure signal and the motor current signal may be displayed to a clinician or other operator of the heart pump system. In some aspects, the first data and the second data are received or obtained from a heart pump system that may be at least partially located within the patient's heart during a first period of time.

[0041] A relationship between differential pressure and motor current is determined for the heart pump system. The relationship is determined using training data, which may include motor current data and differential pressure signal data received in steps 210 and 212 as described above. In some aspects, the motor current data and differential pressure signal data are obtained while the heart pump system is operating at a single P level. The P level is a performance level of the heart pump system, which is related to the flow control of the system and indicates the motor speed. Higher P levels increase the flow rate, motor current, and revolutions per minute associated with the heart pump system. For example, the motor current data and differential pressure signal data may each include 1000 sample points (with a frequency of real-time data collection of 25 Hz) corresponding to a 40 second period during which the heart pump system is operating at a P level of P-8.

[0042] The systems and methods described herein may calculate a model representative of the training data. In some aspects, the systems and methods described herein calculate a representative relationship between the motor current and the differential pressure signal by plotting differential pressure signal data values ​​against motor current data values ​​and / or determining a multiple linear regression of the resulting curve. The curve and associated multiple linear regression are representative of the relationship between the motor current and the differential pressure signal for the heart pump system from which the motor current and differential pressure signal data were obtained. The curve and associated multiple linear regression may represent the operating characteristics of the unique heart pump system from which the first and second data (related to the motor current and differential pressure, respectively) were obtained. For example, these operating characteristics may include minimum and maximum differential pressure, minimum and maximum motor current, and inflection points between the first and second phases of operation at a given performance level.

[0043] In optional step 216, the systems and methods described herein determine that the pressure sensor has failed. In some aspects, the systems and methods of the present invention may determine that the pressure sensor has failed when the system is no longer receiving differential pressure signal data or when no data is received from the differential pressure sensor during a second time period. In some aspects, the systems and methods described herein may determine that the pressure sensor needs to be recalibrated, as described in more detail below with respect to FIGS. 14-15. After it is determined that the pressure sensor needs to be recalibrated, an estimate of the differential pressure signal, as described below in step 220, may be relied upon in further calculations of suction, flow, position, etc., rather than a measured differential pressure signal.

[0044] In step 218, third data indicative of the time-varying motor current during a second time period after the first time period is received. The third data (hereinafter also referred to as additional motor current data) is measured by the same sensors of the same heart pump system as described above with respect to the motor current data of step 210. The additional motor current data may represent a time period after the time period represented by the motor current data received in step 210. In some aspects, the additional motor current data may have been obtained at a different P-level than the motor current data of step 210. For example, the additional motor data may represent a two second period during which the heart pump system is operating at a P level P-6.

[0045] In step 220, an estimate of the time-varying differential pressure during the second time period is determined from the third data and the relationship between the first data (motor current data) and the second data (differential pressure signal data) described above. If the P-levels used to collect the motor current data and the differential pressure signal data are different from those used to collect the additional motor current data, the relationship must be scaled to account for the change in P-level, as described below with respect to FIG. 4. Once the relationship is scaled, the systems and methods described herein determine whether the heart pump system is in "phase A" or "phase B" for the additional motor current data, as described below with respect to FIG. 3. The phase determination depends on the motor current values ​​at the beginning and end of the diastolic phase of the cardiac cycle, which in turn depends on the patient's pressure and P-level. Each value of the additional motor current data is then mapped to a corresponding phase A or phase B differential pressure signal value. In some embodiments, this simulation occurs in near real time and may be displayed for the heart pump system operator. In the event of a pressure sensor failure, an estimated differential pressure signal may be displayed instead of the measured differential pressure signal, allowing the clinician to still view the differential pressure signal data even if the pressure sensor fails. In some aspects, the heart pump system may display a notice indicating that the differential pressure sensor has failed or is unreliable. In some aspects, the heart pump system may display a notice that an estimate of the time-varying differential pressure has been simulated and / or that the heart pump system is displaying an estimate of the differential pressure signal rather than a measured differential pressure signal.

[0046] An accurate differential pressure signal can be used to properly position the heart pump system within the patient, as well as to determine additional metrics such as flow, position, suction, drift, and cardiac output (which can be calculated from flow). Flow is the rate at which blood flows through the pump in the heart pump system. Flow can be used to calculate cardiac output for a patient and provides a measure of the mechanical assistance provided to the heart by the heart pump. Blood flow through a healthy heart averages about 5 liters / minute, and blood flow through the heart pump system may be at a similar or different rate. Suction occurs when there is insufficient or restricted blood volume available to the heart pump system. Suction limits the amount of support the heart pump system can provide and is very important to monitor because it limits the amount of support the heart pump system can provide and can indicate that the heart pump is blocked if, for example, the pump inlet area becomes lodged in patient tissue. Position is the actual placement of the heart pump within the patient's heart and is important for proper operation of the heart pump system. Drift is when the measured differential pressure signal drifts above or below an expected or consistent value. If the differential pressure signal begins to drift, it may be necessary to recalibrate the pressure sensor. In some embodiments, the system of the present invention may determine that the pressure sensor needs to be recalibrated, and the system of the present invention may display a warning or signal to the user to recalibrate accordingly, or may automatically recalibrate the sensor.

[0047] As described above, the differential pressure signal may be used to determine if the heart pump system is properly positioned within the patient's heart. When the heart pump system is properly positioned across the aortic valve, a pulsatile differential pressure signal results from pressure changes associated with the cardiac cycle. When the heart pump system is not properly positioned across the aortic valve, or is entirely within the aorta or entirely within the ventricle, the pressure outside and inside the cannula will be the same throughout the cardiac cycle. As a result, the pressure will be the same on either side of the sensor membrane, resulting in a flat differential pressure signal. However, if the differential pressure signal is unreliable, it may be difficult for a clinician to determine if the system is properly positioned, in which case an estimated differential pressure signal may be very useful.

[0048] The heart pump system may be operated to achieve the maximum possible flow without inducing suction. Flow rate may vary due to incorrect positioning or suction. If the blood volume available to the heart pump is insufficient or limited, the heart pump system may trigger a suction alarm. Suction limits the amount of support the heart pump system can provide to the patient, thereby reducing arterial pressure and cardiac output; can damage blood cells leading to hemolysis; and may be an indicator of right heart failure. Therefore, it is important to monitor suction during operation of the heart pump system.

[0049] 3-18 further illustrate various embodiments and example results of the present disclosure. FIG. 3 shows an example of a differential pressure vs. motor current relationship for an intrinsic heart pump at different performance levels. The curves shown in FIG. 3 were calculated using motor current and differential pressure signal data, such as those described above with respect to stages 210 and 212. FIG. 4 shows an example of training data, such as those described above with respect to stages 210 and 212. FIG. 5 shows an example of a differential pressure vs. motor current relationship for an intrinsic heart pump at a single performance level operating in only the first phase. FIG. 6 shows an example of motor current data, such as those described above with respect to stage 210, during operation in the first phase. FIG. 7 shows an example of motor current data, such as those described above with respect to stage 210, during operation in the second phase. FIG. 8 shows an example of a differential pressure vs. motor current relationship for an intrinsic heart pump at a single performance level for both the first and second phases. The curve shown in FIG. 8 may be one example of the curves shown in FIG. 3. 9-10 show measured differential pressure signal data and an estimate of the differential pressure signal, as described above in connection with steps 218 and 220, respectively. FIG. 11 shows the measured differential pressure signal, the estimate of the differential pressure signal (such as described in step 220), the motor current (such as described in step 218), and the revolutions per minute (such as described above with respect to FIG. 1) of the rotor of the heart pump motor. FIGS. 12-13 show the measured differential pressure signal, the estimate of the differential pressure signal (such as described in step 220), and the motor current (such as described in step 218) resulting from training at the first P level and testing at the first and second P levels. FIGS. 14-15 show the drift of the measured differential pressure signal in comparison with the motor current data (such as in step 210 or step 218) and the estimate of the differential pressure signal (such as in step 220). As described in more detail below with respect to Figures 14-15, the estimated differential pressure signal may also be used to determine if the differential pressure signal is drifting or has drifted and whether the sensor needs to be recalibrated.16-18 show results of the validity of estimates of flow rate calculated using an estimated differential pressure signal (such as in step 220) as compared to flow rate calculated using a measured differential pressure signal.

[0050] 3 illustrates a plot 300 of differential pressure signal versus motor current for a heart pump system operating at nine different performance levels according to certain embodiments. The y-axis of plot 300 represents the differential pressure signal in mmHg, while the x-axis represents the motor current in mA. Each curve from P-1 to P-9 illustrates a representative curve for the same heart pump system operating at a different performance level or P level (e.g., curve P-1 corresponds to operation at performance level P-1); the P level relates to the flow control of the heart pump system. Higher P levels correspond to higher flow rates and revolutions per minute associated with the heart pump system.

[0051] As depicted in FIG. 3, the differential pressure vs. motor current relationship for a heart pump system is scaled across performance levels. Thus, once the differential pressure vs. motor current relationship for a given heart pump system is determined at a first P level (e.g., P-8), the differential pressure vs. motor current relationship for the heart pump system may be scaled to determine the differential pressure vs. motor current relationship for the heart pump system at a second P level (e.g., P-6). For example, in the case shown in FIG. 3, differential pressure signal data and motor current data for a heart pump system were collected at P-8. This data is partially represented by points 310, 312, 314, 316, and 318. The dashed lines 302, 304, and 308 represent the linear scaling of the differential pressure vs. motor current relationship. Specifically, line 302 represents the linear scaling of the maximum differential pressure signal between P levels. The maximum differential pressure signal increases with increasing P level. Line 304 represents the linear scaling of the inflection point of the differential pressure vs. motor current relationship between P levels. The inflection points increase linearly with increasing P levels. Line 308 represents the linear scaling of the minimum differential pressure signal between P levels. The minimum differential pressure signal decreases with increasing P levels. For example, by determining the maximum and minimum differential pressure signal and inflection point at P-8, the maximum and minimum differential pressure signals and inflection points can be calculated for P-1 through P-7 and P-9. In some embodiments, the scaling between P levels may be achieved using a scaling factor. To determine the scaling factor, the maximum, minimum and inflection points at all P levels are found for a set of N heart pump systems. All N heart pump systems are of the same type of heart pump system operating under similar conditions. A linear fit is calculated for the maximum, minimum and inflection points across all P levels for the data of all N heart pump systems. These linear fits are then used to determine the scaling factors for the maximum, minimum and inflection points of the N heart pump systems.The three scaling factors for the N pumps are very similar and are then averaged to determine a general scaling factor for all pumps of that pump type.

[0052] As can be seen in each of the curves P-1 through P-9, even for a single performance level curve, there may be multiple corresponding differential pressure signals for a given motor current value. The differential pressure signal values ​​corresponding to a single motor current value are classified as either "Phase A" or "Phase B." Values ​​plotted above the inflection line 304 from P-1 through P-9 are classified as Phase B values. Values ​​plotted below the inflection line 304 from P-1 through P-9 are classified as Phase A values. For example, points 310, 312, 314, 316, and 318 are Phase A values ​​for P level P-8. As discussed above, when determining an estimate of the time-varying differential pressure, the systems and methods described herein determine whether the motor current signal is in Phase A or Phase B, and determine an estimate of the corresponding differential pressure signal value accordingly. For example, if the measured motor current during operation at P level P-8 is 600 mA, the corresponding differential pressure signal value is 42 mmHg if the measured motor current is in phase A and 110 mmHg if the measured motor current is in phase B. A method for distinguishing between phase A and phase B from the measured motor current value is described below with respect to Figures 6-7.

[0053] FIG. 4 shows plots of motor current, differential pressure signal, and flow over time according to certain embodiments. The y-axis of plot 410 shows the measured motor current in milliamps (mA), the y-axis of plot 420 shows the measured differential pressure signal in millimeters of mercury (mmHg), and the y-axis of plot 430 shows the flow in liters per minute (L / m). Plots 410, 420, 430 are representative plots for the same time period measured at sample numbers along the plots' respective x-axes. The plots fluctuate in a somewhat periodic manner such that each plot has alternating peaks and troughs. Peaks in motor current 410 correspond with troughs in differential pressure signal 420 and peaks in flow 430. For example, at the 100 sample mark, motor current 410 is at a local maximum while differential pressure signal 420 is at a local minimum at the same time.

[0054] Plots 410 and 420 represent measured data from a current sensor and a pressure sensor, respectively, for a single heart pump system, such as that described above with respect to FIG. 1. Each "dot" along the plots represents a measured data point. The measured data points are best-fitted to provide plots 410 and 420. The data represented by plots 410 and 420 is used as training data to build a representative model of the relationship between differential pressure and motor current for that heart pump system, as described above.

[0055] FIG. 5 illustrates a plot of differential pressure signal versus motor current for a native heart pump system according to certain embodiments. The y-axis of plot 500 represents the differential pressure signal in mmHg, while the x-axis represents the motor current in mA. At specific time points, the differential pressure signal and the motor current are measured for a particular heart pump. These two measurements are marked by dots in plot 500. For example, data points from plots 410 and 420 of FIG. 4 described above may be represented by dots in plot 500. A multiple linear approximation may be used to determine a best fit curve 510 to represent the training data. The best fit curve 510 is a representative curve of the native heart pump system used in this example to obtain the data shown in FIGS. 4 and 5.

[0056] The systems and methods described herein may determine whether a heart pump system is in phase A or phase B from plots depicting motor current over time, such as FIGS. 6 and 7. The slope of a line directly between the beginning and end of diastole indicates whether the system is in phase A or phase B. A positive slope indicates phase A, while a negative slope indicates phase B. In phase B, a local minimum in motor current occurs just before contraction, while in phase A, a local minimum in motor current occurs just after contraction. Whether a heart pump system is in phase A or phase B depends on the patient's pressure and P level. Phase B is more likely to occur at lower P levels (and lower motor current values). Higher differential pressure signal values ​​occur in phase B.

[0057] 6 shows a plot of motor current over time for phase A according to certain embodiments. The y-axis of plot 600 represents motor current in mA, while the x-axis represents time in samples. Circle 602 indicates the start of diastole. Circle 604 indicates the end of diastole. The slope between circles 602 and 604 is positive, indicating that the heart pump system is in phase A.

[0058] 7 shows a plot of motor current over time for phase B according to certain embodiments. The y-axis of plot 700 represents motor current in mA, while the x-axis represents time in samples. Circle 702 indicates the start of diastole. Circle 704 indicates the end of diastole. The slope between circles 602 and 604 is negative, indicating that the heart pump system is in phase B.

[0059] FIG. 8 shows a plot of the differential pressure signal versus motor current for a heart pump system according to certain embodiments. The y-axis of the plot 800 represents the differential pressure signal in mmHg, while the x-axis represents the motor current in mA. Line 810 marks the boundary of the motor current value of 710 mA. An inflection point 840 at approximately 50 mmHg marks the "change" from phase A to phase B. Points above inflection point 840 are in phase B, while points below inflection point 840 are in phase A. At higher motor current values ​​(greater than approximately 730 mA), the heart pump system operates in phase A and the corresponding phase B value is no longer present. Circles 820 and 830 show two possible differential pressure signal values ​​corresponding to the motor current value of 710 mA shown by line 810. Circle 820 marks a value of approximately 40 mmHg and is in phase A. Circle 830 marks the corresponding phase B value of approximately 90 mmHg.

[0060] FIG. 9 illustrates a plot of an actual differential pressure signal, a simulated differential pressure signal, and a simulated differential pressure signal for phase A over time according to certain embodiments. The y-axis of plot 900 represents the differential pressure signal in mmHg, while the x-axis represents time in number of samples. Curve 910 illustrates a differential pressure signal measured by a differential pressure sensor of a heart pump system. The curve of the simulated differential pressure signal is an estimated differential pressure signal simulated by the systems and methods described herein, and it completely overlaps with curve 912. Thus, the simulated curve is not visible in plot 900. Curve 912 illustrates a "phase A" differential pressure signal simulation according to the systems and methods described herein. As can be seen by the positive slope during the diastolic phase, the heart pump system was operating entirely in phase A during this time frame, so the simulated differential pressure signal 912 for phase A matches entirely with the simulated differential pressure signal. Plot 900 may be used to validate the performance of a simulated differential pressure signal. As can be seen in plot 900, the actual differential pressure signal 910 and the simulated differential pressure signal 912 match fairly closely. The periods, mean values, maximum values, and minimum values ​​of the two signals 910 and 912 are particularly close. These values ​​are critical metrics used in flow, placement, and suction calculations. The minimum value of the differential pressure signal is used to determine the maximum value of the flow; the maximum value of the differential pressure signal is used to determine the minimum value of the flow; and the mean value of the differential pressure signal is used to determine the average value of the flow. The average, maximum, and minimum values ​​of the flow may be displayed to the clinician through a user interface.

[0061] FIG. 10 shows a plot of an actual differential pressure signal, a simulated differential pressure signal, and a simulated differential pressure signal for phase A over time according to certain embodiments. The y-axis of plot 1000 represents the differential pressure signal in mmHg, while the x-axis represents time in number of samples. Curve 1010 shows a differential pressure signal measured by a differential pressure sensor of a heart pump system. Curve 1012 shows an estimated differential pressure signal simulated by the systems and methods described herein. Curve 1014 partially overlaps with curve 1012 and shows a "phase A" differential pressure signal simulation according to the systems and methods described herein. As can be seen by the negative slope during the diastolic cycle, the heart pump system was at least partially operating in phase B during this time frame, so the simulated differential pressure signal 1014 for phase A does not match the simulated differential pressure signal 1012 completely (they diverge mostly around the peak). Plot 1000 shows the importance of determining whether the heart pump system is operating in phase A or phase B. The simulated signal 1014 of phase A matched fairly closely with the actual values ​​of period and minimum, but did not match the maximum or average values ​​measured by the differential pressure sensor and shown by curve 1010. Although the simulated curve 1012 does not fully overlap with the actual signal 1010, taking phase B into account can provide a sufficiently good estimate of the actual differential pressure signal (especially the minimum and maximum values), which can be used for flow calculations and position / suction alarms.

[0062] FIG. 11 shows plots of differential pressure signal, motor current, and revolutions per minute (RPM) for a heart pump system as its performance level is changed according to certain embodiments. Plot 1110 shows validation of the differential pressure signal, plot 1120 shows motor current over time, and plot 1130 shows RPM over time. The three plots 1110, 1120, 1130 show simultaneous measurements of the same heart pump system operated over the same period of time. The y-axis of plot 1110 represents the differential pressure signal in mmHg, while the x-axis represents time in number of samples. Curve 1112 represents the differential pressure signal measured by the differential pressure sensor. Curve 1114 represents an estimate of the differential pressure signal. The y-axis of plot 1120 represents motor current in mA, while the x-axis represents time in number of samples. Curve 1122 represents the motor current over time measured by the heart pump system. The y-axis of plot 1130 represents RPM while the x-axis represents time in number of samples. Curve 1132 represents RPM over time as measured by the heart pump system. Boxes 1116, 1126, 1136 represent periods of operation of the heart pump system at a first P level. Boxes 1118, 1128, 1138 represent periods of operation of the heart pump system at a second P level. The second P level is lower than the first P level. As the P level was reduced between boxes 1116, 1126, 1136 and boxes 1118, 1128, 1138, the RPM and motor current all decreased.

[0063] As depicted in FIGS. 11-13, the heart pump system was operated at a first P level to obtain training data including motor current data and differential pressure signal data. The training data was used to determine a relationship between the motor current data and the differential pressure signal data at that P level. That relationship was then used to determine an estimate of the differential pressure signal shown by curve 1114 in box 1116, which closely matched the measured differential pressure signal shown by curve 1112. The heart pump system was then operated at a second, lower P level. As described above with respect to FIG. 3, the relationship between differential pressure and motor current was scaled to account for the lower P level. The scaled and determined relationship was then used to determine an estimated differential pressure signal at this second P level. As shown in box 1118, the estimated differential pressure signal 1114 also closely matched the measured differential pressure signal 1112.

[0064] FIG. 12 illustrates a plot of differential pressure signal and motor current over time at a first P level according to certain embodiments. Plot 1210 is a zoomed-in view of box 1116 shown in FIG. 11. The y-axis of plot 1210 illustrates the differential pressure signal measured in mmHg. Plot 1220 is a zoomed-in view of box 1126 shown in FIG. 11. The y-axis of plot 1220 illustrates the motor current measured in mA. The x-axis of plots 1210 and 1220 illustrates time measured in number of samples over the same period of time. Plot 1210 displays a measured differential pressure signal curve 1212, a simulated dwell curve 1214, and a simulated differential pressure signal curve 1216 for phase A. The simulated differential pressure signal curve 1212 for phase A nearly overlaps with the simulated differential pressure signal curve 1214, indicating that the estimation of the differential pressure was accurate.

[0065] FIG. 13 illustrates plots of differential pressure signal and motor current over time at a second P level according to certain embodiments. Plot 1310 is a zoomed-in view of box 1118 shown in FIG. 11. The y-axis of plot 1310 illustrates the differential pressure signal measured in mmHg. Plot 1320 is a zoomed-in view of box 1128 shown in FIG. 11. The y-axis of plot 1220 illustrates the motor current measured in mA. The x-axis of plots 1310 and 1320 illustrates time measured in number of samples over the same period of time. Plot 1310 displays a measured differential pressure signal curve 1312, a simulated dwell curve 1314, and a simulated differential pressure signal curve 1316 for phase A. The simulated differential pressure signal curve 1312 for phase A nearly overlaps with the simulated differential pressure signal curve 1314, indicating that the estimation of the differential pressure was accurate.

[0066] Even though the relationship between differential pressure and motor current was not "built" using training data acquired at the second P level, the estimated differential pressure signal 1314 still closely matched the measured differential pressure signal 1312 at that P level. These results indicate that the scaling process used when switching between P levels is reliable and provides results comparable to those measured at the P levels used for training.

[0067] FIG. 14 shows a plot of differential pressure signal drift and motor current over time according to certain embodiments. The y-axis of plot 1410 represents the differential pressure signal in mmHg while the x-axis represents time in number of samples. The y-axis of plot 1420 represents motor current in mA while the x-axis represents time in number of samples over the same period of time as that represented in plot 1410. The motor current 1420 is maintained over time with approximately the same average value over the entire period. During this same period, the differential pressure signal (measured by the pressure sensor) significantly increased from an average value of about 20 mmHg to an average value of about 80 mmHg. When the average value of the motor current is stable over a significant period of time, the average differential pressure signal should also be stable over that period of time. In this case, the differential pressure signal 1410 is "drifting," indicating that the pressure sensor is no longer providing an accurate measurement.

[0068] FIG. 15 illustrates a plot of differential pressure signal drift and estimated differential pressure signal over time according to certain embodiments. The y-axis of plot 1500 represents the differential pressure signal in mmHg, while the x-axis represents time in number of samples. Curve 1510 represents the measured differential pressure signal, curve 1512 represents the average of the measured differential pressure signal, curve 1514 represents the simulated differential pressure signal, and curve 1516 represents the average of the simulated differential pressure signal. The measured differential pressure signal 1510 is drifting, while the estimate of the differential pressure signal (the simulated differential pressure signal) 1514 remains stable. If the measured differential pressure signal deviates from the simulated differential pressure signal, and particularly if that deviation occurs after a period of time during which the average 1512 of the measured differential pressure signal closely matches the average 1516 of the simulated differential pressure signal, the systems and methods described herein may determine that the pressure sensor (providing the measured differential pressure signal data) needs to be recalibrated. In some embodiments, the sensor may be recalibrated automatically. In some aspects, the heart pump system may display a notification to the user indicating that the sensor needs to be recalibrated.

[0069] In some embodiments, to determine if the differential pressure signal is drifting, the systems and methods described herein may calculate a difference between the differential pressure signal or average differential pressure signal (e.g., curve 1512) and an estimate of the differential pressure signal (e.g., curve 1516) or average estimate. This difference may be compared to a threshold. If the difference is above the threshold, the differential pressure signal has drifted. If the difference is below the threshold, the differential pressure signal has not drifted. The threshold may be 10 mmHg, 20 mmHg, or any suitable quantity. For example, the threshold may be 15 mmHg, and in FIG. 15, curve 1512 may be determined to be drifting at sample 4.000e+4. In some embodiments, the system may determine a first difference, which is the difference between the measured differential pressure signal at a first time and the estimate, and a second difference, which is the difference between the measured differential pressure signal at a second time and the estimate. If the second difference is substantially greater than the first difference, the system may determine that the measured pressure signal has drifted. In some embodiments, the difference between the measured differential pressure signal and the estimated value may be measured periodically or continuously monitored If the difference increases over time, the system may determine that the measured pressure signal is drifting.

[0070] 16-18 show metrics for measuring the success of an estimated flow based on a simulated differential pressure signal, such as a simulated differential pressure signal from the systems and methods described above, according to certain embodiments. FIGS. 16-18 are from validation testing performed using data from pumps with reliable differential pressure signals (e.g., pumps containing accurate differential pressure sensors that did not fail during testing). Flow is an important metric used by clinicians to determine how a pump is performing. Clinicians may need average, maximum, and minimum flow values ​​to understand the performance and status of the cardiac pump system, which may be displayed to the clinician through a user interface.

[0071] 16 shows a histogram of the average estimated flow error according to certain embodiments. Display 1600 includes a histogram of the average estimated flow, an estimated error distribution, a confidence interval distribution, and a table of results. The histogram of the average estimated flow error is centered around zero with a narrow peak, indicating a matching result with little error. The average estimated flow error represents the difference between the average value of the flow calculated from the measured differential pressure signal and the average value of the flow calculated from the estimated value of the differential pressure signal.

[0072] 17 shows a histogram of maximum estimated flow error according to certain embodiments. Display 1700 includes a bar graph of maximum estimated flow error, estimated error distribution, confidence interval distribution, and a table of results. The histogram of maximum estimated flow error is centered around zero with a narrow peak, indicating a matching result with little error. The maximum estimated flow error represents the difference between the local maximum of flow calculated from the measured differential pressure signal and the local maximum of flow calculated from the estimated differential pressure signal.

[0073] FIG. 18 shows a histogram of minimum estimated flow errors according to certain embodiments. Display 1800 includes a bar graph of minimum estimated flow errors, an estimated error distribution, a confidence interval distribution, and a table of results. The histogram of minimum estimated flow errors is centered around zero with a narrow peak, indicating a matching result with little error. The minimum estimated flow error represents the difference between the local minimum of flow calculated from the measured differential pressure signal and the local minimum of flow calculated from the estimated differential pressure signal.

[0074] In some aspects, the heart pump system may output suction and / or position alarms. The reliability of such alarms when relying on an estimated differential pressure signal rather than a measured differential pressure signal may be a useful metric for determining the validity of the estimated differential pressure signal. In some embodiments, a position alarm may be triggered when the pulsatility of the differential pressure signal is less than a threshold value. The alarm may indicate incorrect placement of the heart pump system within the patient's heart. For example, a position alarm may be triggered when the pulsatility of the differential pressure signal falls below 10 mmHg. The alarm may prompt the clinician to adjust the placement of the heart pump system. If the pressure sensor measuring the differential pressure signal fails, the heart pump system may rely on an estimated differential pressure signal (as determined by the system and method described above) to trigger a position alarm. To determine the reliability of the estimated differential pressure signal in triggering a position alarm, cases of actual alarms triggered by measured differential pressure signal values ​​were compared with the estimated differential pressure signal that triggered an alarm for the same cases. To trigger alarms with greater reliability, a tolerance of the differential pressure signal may be incorporated into the alarm calculation. In this case, this tolerance is built into the test environment to address cases that lead to false positive or false negative alarms when slightly above or slightly below the threshold. As shown in Table 1, the overall accuracy of the estimated differential pressure signal position alarm for the 20 case studies was 97.9%, while the recall of the position alarm was 100.0%.

[0075] In some aspects, a suction alarm may be triggered if the differential pressure signal is greater than the threshold for a period of time. The suction alarm may be triggered only when the cardiac pump system is operating at a certain P level. For example, a suction alarm may be triggered if the differential pressure signal is greater than the threshold for 10% of a 3-second window when operating at one of P levels P5-P9. To more reliably trigger an alarm, a suction tolerance may be incorporated into the alarm calculation. In this case, this tolerance is incorporated into the test environment to address cases where being slightly above or slightly below the threshold leads to false positive or false negative alarms. As shown in Table 1, the overall accuracy of the suction alarm for the estimated differential pressure signal for the 30 cases was 80.6%, while the recall of the position alarm was 93.2%.

[0076] [Table 1]

[0077] The foregoing is merely illustrative of the principles of the present disclosure, and the device of the present invention may be practiced outside the aspects of this description, which are presented for purposes of illustration and not limitation. It should be understood that the device disclosed herein, although shown for use in percutaneous insertion of a heart pump, may also be applied to devices in other applications requiring hemostasis.

[0078] Variations and modifications will occur to those skilled in the art after reviewing this disclosure. The features of the present disclosure may be implemented in any combination and subcombination (including multiple subordinate combinations and subcombinations) with one or more other features described herein. The various features described or illustrated above, including components thereof, may be combined or integrated into other systems. Additionally, certain features may be omitted or not implemented.

[0079] The systems and methods described herein may be implemented locally on the heart pump system or on a controller of the 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 a separate data processing device. The separate data processing device may be directly connected or indirectly connected to the heart pump system through a cloud application. The heart pump system may communicate in real time (or near real time) with the separate data processing device.

[0080] Generally, aspects of the subject matter and functional operations described herein may be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed herein and their structural equivalents, or in any combination of one or more of them. Aspects of the subject matter described herein may be implemented as one or more computer program products, i.e., as one or more modules of computer program instructions encoded on a computer-readable medium for execution by or for controlling the operation of a data processing apparatus. The computer-readable medium may be a machine-readable storage device, a machine-readable storage carrier, a memory device, a composition of matter affecting a machine-readable propagated signal, or any combination of one or more of them. The term "data processing apparatus" encompasses all apparatus, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, an apparatus may also include code that creates an execution environment for a subject computer program, such as code that constitutes a processor firmware, a protocol stack, a database management system, an operating system, or any combination of one or more of these. A propagated signal is an artificially generated signal, such as a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to a suitable receiving device.

[0081] A computer program (also known as a program, software, software application, script, or code) may be written in any programming language, including compiled or translated languages, and 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 as part 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 files associated with each other (e.g., a file storing one or more modules, subprograms, or portions of code). A computer program may be deployed to be executed on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communications network.

[0082] The processes and logic flows described herein may 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 may also be performed by, and an apparatus may be implemented as, special purpose logic circuitry, such as, for example, an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0083] Processors suitable for executing computer programs include, by way of example, general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from a read-only memory or a random access memory, or both. The essential elements of a computer are a processor for performing instructions, and one or more memory devices for storing instructions and data. Generally, a computer also includes one or more mass storage devices for storing data, such as, for example, magnetic disks, magneto-optical disks, or optical disks; or is operatively connected to such mass storage devices for receiving data from, transferring data to, or both. However, a computer need not have such devices.

[0084] Examples of changes, substitutions, and alterations are ascertainable by one of ordinary skill in the art and can be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made a part of this application.

Claims

1. 1. A method for automatically recalibrating a differential pressure sensor in a cardiac pump system, comprising: receiving, by a controller of the heart pump system, first data indicative of a time-varying motor current during a first time period, the time-varying motor current corresponding to an amount of current delivered to a motor of the heart pump system while the heart pump system is operating within a patient; receiving, by the controller, second data from a differential pressure sensor of the cardiac pump system indicative of a time-varying differential pressure during the first period; receiving, by the controller, third data indicative of a time-varying motor current during a second time period subsequent to the first time period; determining, by the controller, an estimate of a time-varying differential pressure during the second time period from the third data and from a relationship of the first data to the second data; receiving, by the controller, fourth data from the differential pressure sensor indicative of the time-varying differential pressure during the second time period; determining, by the controller, whether the time-varying differential pressure indicated by the fourth data is drifting based on a comparison between (a) the time-varying differential pressure during the second time period as indicated by the fourth data and (b) an estimate of the time-varying differential pressure during the second time period; automatically recalibrating the differential pressure sensor based on a determination that the time-varying differential pressure during the second time period has drifted; and The method includes:

2. The method of claim 1 , wherein determining the estimate of the time-varying differential pressure during the second period of time is responsive to determining that the differential pressure sensor has failed.

3. The method of claim 1 , wherein determining that the differential pressure sensor has failed occurs when no data is received from the differential pressure sensor during the second period of time.

4. providing, by the controller, a first indication that the differential pressure sensor has failed; providing, by the controller, a second indication that an estimate of the time-varying differential pressure during the second time period has been simulated; and The method of any one of claims 1 to 3, further comprising:

5. 5. The method of claim 1, wherein determining an estimate of the time-varying differential pressure during the second period comprises determining a time series of estimated points of differential pressure by determining whether the third data corresponds to a first phase or a second phase of the cardiac pump system in a relationship between the first data and the second data, wherein in the first phase, a given motor current value corresponds to a first differential pressure value and in the second phase, the given motor current value corresponds to a second differential pressure value.

6. Determining whether the third data corresponds to the first phase or the second phase determining, by the controller, a diastolic period within the third data beginning at a start point and ending at an end point; determining, by the controller, a slope of the third data between the start point and the end point; determining that the third data corresponds to the first phase in response to determining that the slope is positive; and determining that the third data corresponds to the second phase in response to determining that the slope is negative; and The method of claim 5 , comprising:

7. The method of any one of claims 1 to 6, further comprising determining, by the controller, at least one of a flow rate, a position, and a suction associated with the cardiac pump system based on an estimate of the time-varying differential pressure.

8. The method of any one of claims 1 to 7, further comprising displaying, by the controller, at least one of the time-varying differential pressure, the time-varying motor current, and an estimate of the time-varying differential pressure.

9. Determining that the time-varying differential pressure is drifting, calculating, by the controller, a difference between the time-varying differential pressure indicated by the fourth data over a second time period and an estimate of the time-varying differential pressure based on a comparison of (a) and (b); comparing, by the controller, the difference with a differential pressure signal threshold; determining, by the controller, that the difference is greater than the differential pressure signal threshold based on comparing the difference to the differential pressure signal threshold; The method according to any one of claims 1 to 8, comprising:

10. 10. The method of claim 1, further comprising displaying a notification, by the controller, indicating that the differential pressure sensor needs to be recalibrated based on determining that the time-varying differential pressure has drifted.

11. The method of any one of claims 1 to 10, wherein the time-varying differential pressure corresponds to a pressure difference between an interior portion of the heart pump system and an exterior of the heart pump system.

12. The relationship between the first data and the second data is determining, by the controller, a correlation between the time-varying motor current and the time-varying differential pressure for each time point within the first time period; calculating, by the controller, a multiple linear fit of the correlation indicative of an operational characteristic of the cardiac pump system; The method according to any one of claims 1 to 11, wherein the

13. the first data and the second data are representative of the heart pump system operating at a first operating level, the method comprising: changing, by the controller, operation of the heart pump system to a second operating level; scaling, by the controller, the relationship between the first data and the second data to take into account the second operation level upon changing operation of the cardiac pump system to a second operation level; Including, The method of any one of claims 1 to 12, wherein determining the estimate of the time-varying differential pressure is further based on scaling the relationship.

14. A system comprising a controller configured to perform the method of any one of claims 1 to 13.

15. a pump comprising a pump housing having a proximal end and a rotor; a cannula having a proximal end that interfaces with the distal end of the pump housing, and a distal end, the pump being configured to be actuated by a motor; an elongate catheter extending proximally from the pump housing; one or more sensors, including a differential pressure sensor; A controller configured to perform the method of any one of claims 1 to 13; A heart pump system comprising:

16. 16. The heart pump system of claim 15, wherein the pump is configured to be positioned such that the cannula extends across the aortic valve of the patient, the distal end being located within the left ventricle of the patient and the proximal end being located within the aorta of the patient.

17. The heart pump system of claim 15 , further comprising a flexible protrusion extending distally from the distal end of the cannula.

18. 16. The heart pump system of claim 15, wherein the elongated catheter is coupled at its distal end to the pump housing, and the pump further comprises a drive cable extending through the elongated catheter.

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