Position Sensing for Circulatory Assist Devices - Patent application

Abstract

A method and apparatus are provided for determining whether a circulatory assist device is properly positioned within a patient's heart. The method includes receiving a motor current signal from a motor of the circulatory assist device, receiving a pressure signal from a pressure sensor arranged on the circulatory assist device, generating a normalized motor current signal based at least in part on the pressure signal, determining a pulsatility of the normalized motor current signal, determining whether the circulatory assist device is properly positioned within the patient's heart based at least in part on the pulsatility of the normalized motor current signal, and outputting an alarm when it is determined that the circulatory assist device is not properly positioned within the patient's heart.

Description

[Technical field]

[0001] The subject application relates to position sensing, and more particularly, to position sensing for circulatory assist devices. [Background technology]

[0002] Fluid pumps, such as blood pumps, are used in the medical field for a wide range of applications and purposes. An intravascular blood pump is a pump that can be advanced through a patient's vasculature, i.e., veins and / or arteries, to one location within the patient's heart or another location within the patient's circulatory system. For example, an intravascular blood pump can be inserted via a catheter and positioned to span a heart valve. The intravascular blood pump is typically located at the end of the catheter. Once in position, the pump can be used to assist the heart and pump blood through the circulatory system, thus temporarily reducing the workload on the patient's heart, such as to allow the heart to recover after a heart attack. An exemplary intravascular blood pump is available from ABIOMED, ​​Inc. (Danvers, MA) under the trade name Impella® Heart Pump.

[0003] Such a pump can be positioned within a chamber of the heart, such as the left ventricle, to assist the heart. In this case, the blood pump can be inserted via the femoral artery using a hollow catheter and guided up to and into the left ventricle of the patient's heart. From this position, the blood pump inlet draws in blood and the blood pump outlet ejects blood into the aorta. In this way, the function of the heart can be replaced, or at least assisted, by the action of the pump.

[0004] Intravascular blood pumps are typically connected to a separate external heart pump controller that controls the heart pump, such as motor speed, and collects and displays operational data about the blood pump, such as cardiac signal levels, battery temperature, blood flow rate, and tubing integrity. An exemplary heart pump controller is available from ABIOMED, ​​Inc. under the trade name Automated Impella Controller®. The controller issues an alarm when an operational data value exceeds a predetermined value or range, e.g., if leakage, aspiration, and / or pump malfunction is detected. The controller may include a video display screen on which a graphical user interface configured to display the operational data and / or alarms is displayed. Summary of the Invention [Means for solving the problem]

[0005] Described herein are systems and methods for determining the position of a mechanical circulatory device within a patient's heart.

[0006] In some embodiments of the present technology, a method of determining whether a circulatory assist device is properly positioned within a patient's heart is provided, the method including receiving a motor current signal from a motor of the circulatory assist device, receiving a pressure signal from a pressure sensor arranged on the circulatory assist device, generating a normalized motor current signal based at least in part on the pressure signal, determining a pulsatility of the normalized motor current signal, determining whether the circulatory assist device is properly positioned within the patient's heart based at least in part on the pulsatility of the normalized motor current signal, and outputting an alarm when it is determined that the circulatory assist device is not properly positioned within the patient's heart.

[0007] In one aspect, the method further includes determining a maximum pressure value of the pressure signal within a time window of a predetermined length, and generating a normalized motor current signal based at least in part on the pressure signal includes generating a normalized motor current signal based at least in part on the maximum pressure value.

[0008] In one aspect, generating a normalized motor current signal based at least in part on the maximum pressure value includes dividing a value of the motor current signal by the maximum pressure value.

[0009] In one aspect, the pressure sensor comprises an optical pressure sensor.

[0010] In one aspect, the method further includes filtering the motor current signal, and generating the normalized motor current signal is based at least in part on the filtered motor current signal.

[0011] In one aspect, filtering the motor current signal includes filtering the motor current signal with a bandpass filter.

[0012] In one aspect, the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

[0013] In one aspect, the bandpass filter is configured to cut off frequencies below 0.65 Hz.

[0014] In one aspect, filtering the motor current signal includes filtering the motor current signal with a low pass filter.

[0015] In one aspect, the method further includes filtering the pressure signal, and generating the normalized motor current signal is based at least in part on the filtered pressure signal.

[0016] In one aspect, the method further includes determining a maximum pressure value of the filtered pressure signal within a time window of a predetermined length, and generating a normalized motor current signal based at least in part on the filtered pressure signal includes generating a normalized motor current signal based at least in part on the maximum pressure value.

[0017] In one aspect, filtering the pressure signal includes filtering the pressure signal with a low pass filter.

[0018] In one aspect, the low pass filter is configured to cut off frequencies above 5 Hz.

[0019] In one aspect, the method further includes determining a differential pressure signal based, at least in part, on the pressure signal, and determining whether the circulatory assist device is properly positioned within the patient's heart is further based, at least in part, on the differential pressure signal.

[0020] In one aspect, the method further includes determining a minimum pressure value of the pressure signal with a time window of a predetermined length and determining that the circulatory assist device is not correctly positioned within the patient's heart when the pulsatility of the normalized motor current signal is above a first threshold, the minimum pressure value is below a second threshold, the minimum value of the differential pressure signal within the time window is above a third threshold, or the maximum value of the differential pressure signal within the time window is above a fourth threshold.

[0021] In one aspect, the method further includes determining a pulsatility of the pressure signal, and determining whether the circulatory assist device is properly positioned within the patient's heart is further based, at least in part, on the pulsatility of the pressure signal.

[0022] In one aspect, the method further includes determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a third threshold when the pulsatility of the normalized motor current signal is less than a first threshold and the pulsatility of the pressure signal is less than a second threshold, and determining that the circulatory assist device is not correctly positioned in the patient's heart when the minimum pressure value within the time window is less than the third threshold.

[0023] In one aspect, the method further includes determining that the circulatory assist device is located within an aorta of the patient's heart when the minimum pressure value within the time window is less than a third threshold, and outputting the alarm includes outputting an alarm that the circulatory assist device is located within the aorta.

[0024] In one aspect, the method further includes filtering the pressure signal, and determining the pulsatility of the pressure signal includes determining the pulsatility of the filtered pressure signal.

[0025] In one aspect, filtering the pressure signal includes filtering the pressure signal with a bandpass filter.

[0026] In one aspect, the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

[0027] In one aspect, the bandpass filter is configured to cut off frequencies below 0.65 Hz.

[0028] In one aspect, the method further includes determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a second threshold, and determining that the circulatory assist device is properly positioned within the patient's heart when the pulsatility of the normalized motor current signal is less than the first threshold and the minimum pressure value within the time window exceeds the second threshold.

[0029] In one aspect, the method further includes determining that the circulatory assist device is not correctly positioned within the patient's heart when the pulsatility of the normalized motor current signal is above a first threshold and / or when the minimum pressure value within the time window is less than a second threshold.

[0030] In some embodiments of the present technology, a circulatory assist device is provided comprising: a rotor, a motor configured to drive rotation of the rotor at one or more speeds, a pressure sensor configured to detect a pressure signal, and at least one controller configured to receive a motor current signal from the motor, receive the pressure signal from the pressure sensor, generate a normalized motor current signal based at least in part on the pressure signal, determine a pulsatility of the normalized motor current signal, determine whether the circulatory assist device is correctly positioned within the patient's heart based at least in part on the pulsatility of the normalized motor current signal, and output an alarm when it is determined that the circulatory assist device is not correctly positioned within the patient's heart.

[0031] In one aspect, the at least one controller is further configured to determine a maximum pressure value of the pressure signal within a time window of a predetermined length, and generating a normalized motor current signal based at least in part on the pressure signal includes generating a normalized motor current signal based at least in part on the maximum pressure value.

[0032] In one aspect, generating a normalized motor current signal based at least in part on the maximum pressure value includes dividing a value of the motor current signal by the maximum pressure value.

[0033] In one aspect, the pressure sensor comprises an optical pressure sensor.

[0034] In one aspect, the at least one controller is further configured to filter the motor current signal, and generating the normalized motor current signal is based at least in part on the filtered motor current signal.

[0035] In one aspect, filtering the motor current signal includes filtering the motor current signal with a bandpass filter.

[0036] In one aspect, the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

[0037] In one aspect, the bandpass filter is configured to cut off frequencies below 0.65 Hz.

[0038] In one aspect, filtering the motor current signal includes filtering the motor current signal with a low pass filter.

[0039] In one aspect, the at least one controller is further configured to filter the pressure signal, and generating the normalized motor current signal is based at least in part on the filtered pressure signal.

[0040] In one aspect, the at least one controller is further configured to determine a maximum pressure value of the filtered pressure signal within a time window of a predetermined length, and generating a normalized motor current signal based at least in part on the filtered pressure signal includes generating a normalized motor current signal based at least in part on the maximum pressure value.

[0041] In one aspect, filtering the pressure signal includes filtering the pressure signal with a low pass filter.

[0042] In one aspect, the low pass filter is configured to cut off frequencies above 5 Hz.

[0043] In one aspect, the at least one controller is further configured to determine a differential pressure signal based, at least in part, on the pressure signal, and determining whether the circulatory assist device is correctly positioned within the patient's heart is further based, at least in part, on the differential pressure signal.

[0044] In one aspect, the at least one controller is further configured to determine a minimum pressure value of the pressure signal with a time window of a predetermined length and determine that the circulatory assist device is not correctly positioned within the patient's heart when the pulsatility of the normalized motor current signal exceeds a first threshold, the minimum pressure value is less than a second threshold, and the minimum value of the differential pressure signal within the time window exceeds a third threshold or the maximum value of the differential pressure signal within the time window exceeds a fourth threshold.

[0045] In one aspect, the at least one controller is further configured to determine a pulsatility of the pressure signal, and determining whether the circulatory assist device is correctly positioned within the patient's heart is further based, at least in part, on the pulsatility of the pressure signal.

[0046] In one aspect, the at least one controller is further configured to determine whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a third threshold when the pulsatility of the normalized motor current signal is less than a first threshold and the pulsatility of the pressure signal is less than a second threshold, and to determine that the circulatory assist device is not correctly positioned in the patient's heart when the minimum pressure value within the time window is less than the third threshold.

[0047] In one aspect, the at least one controller is further configured to determine that the circulatory assist device is located within an aorta of the patient's heart when the minimum pressure value within the time window is less than a third threshold, and outputting the alarm includes outputting an alarm that the circulatory assist device is located within the aorta.

[0048] In one aspect, the at least one controller is further configured to filter the pressure signal, and determining the pulsatility of the pressure signal includes determining the pulsatility of the filtered pressure signal.

[0049] In one aspect, filtering the pressure signal includes filtering the pressure signal with a bandpass filter.

[0050] In one aspect, the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

[0051] In one aspect, the bandpass filter is configured to cut off frequencies below 0.65 Hz.

[0052] In one aspect, the at least one controller is further configured to determine whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a second threshold, and determine that the circulatory assist device is correctly positioned within the patient's heart when the pulsatility of the normalized motor current signal is less than the first threshold and the minimum pressure value within the time window exceeds the second threshold.

[0053] In one aspect, the at least one controller is further configured to determine that the circulatory assist device is not correctly positioned within the patient's heart when the pulsatility of the normalized motor current signal is above a first threshold and / or when the minimum pressure value within the time window is less than a second threshold.

[0054] In some embodiments, a method for determining whether a circulatory assist device is properly positioned within a patient's heart is provided. The method includes receiving a motor current signal from a motor of the circulatory assist device, filtering the motor current signal with a bandpass filter to generate a filtered motor current signal, receiving a pressure signal from a pressure sensor arranged on the circulatory assist device, filtering the pressure signal to generate a filtered pressure signal, generating a normalized motor current signal based at least in part on the filtered motor current signal and the filtered pressure signal, determining a pulsatility of the normalized motor current signal, determining a pulsatility of the filtered pressure signal, determining a differential pressure signal based at least in part on the filtered pressure signal, determining that the circulatory assist device is not correctly positioned in the patient's heart when the pulsatility of the normalized motor current signal is less than a first threshold, the pulsatility of the filtered pressure signal is less than a second threshold, a maximum value of the differential pressure signal within a time window of a predetermined length exceeds a third threshold, or a minimum value of the differential pressure signal within the time window exceeds a fourth threshold, and outputting an alarm when it is determined that the circulatory assist device is not correctly positioned in the patient's heart. [Brief description of the drawings]

[0055] [Figure 1A] FIG. 1A shows an illustrative circulatory assist device that may be used according to some embodiments.

[0056] [Figure 1B] FIG. 1B illustrates the circulatory assist device of FIG. 1A positioned within a patient's heart.

[0057] [Figure 1C] FIG. 1C illustrates a ventricular assist system that includes the circulatory assist device of FIG. 1A.

[0058] [Diagram 2] FIG. 2 illustrates a display on which one or more alerts associated with position detection of the circulatory assist device of FIG. 1A may be shown, according to some embodiments.

[0059] [Figure 3A] FIG. 3A illustrates a truth table representing an algorithm for determining the position of a circulatory assist device.

[0060] [Figure 3B] FIG. 3B illustrates a confusion matrix comparing the predicted and actual locations of a circulatory assist device when the algorithm of FIG. 3A is used to predict the location of the device.

[0061] [Figure 4A] FIG. 4A illustrates a truth table for an improved algorithm for determining the position of a circulatory assist device, according to some embodiments.

[0062] [Figure 4B] FIG. 4B illustrates a confusion matrix comparing the predicted and actual positions of a circulatory assist device when the improved algorithm of FIG. 4A is used to predict the position of the device.

[0063] [Diagram 5] FIG. 5 illustrates a flowchart of a process for determining the position of a circulatory assist device, according to some embodiments.

[0064] [Figure 6A] 6A-6B illustrate bar graphs of classification performed using the algorithm of FIG. 3A at different motor speeds. [Figure 6B] 6A-6B illustrate bar graphs of classification performed using the algorithm of FIG. 3A at different motor speeds.

[0065] [Figure 7A]7A-7B illustrate bar graphs of classification performed using the improved algorithm of FIG. 4A at different motor speeds. [Figure 7B] 7A-7B illustrate bar graphs of classification performed using the improved algorithm of FIG. 4A at different motor speeds. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Detailed Description Circulatory assist devices (also referred to herein as "heart pumps" or simply "pumps") are percutaneous, catheter-based devices that provide hemodynamic support to a patient's heart. For heart pumps to function properly, they should be correctly positioned within a patient's heart with an inlet portion of the pump located within the left ventricle and an outlet portion of the pump located within the aorta, thereby spanning the aortic valve of the patient's heart. As shown in FIG. 1A, the heart pump 110 may include a pigtail 111, an inlet area 112, a cannula 113, a pressure sensor 114, an outlet area 115, a motor housing 116, and / or a catheter tube 117. The pigtail 111 may help stabilize the heart pump 110 within the patient's heart. It should be understood that some embodiments of the heart pump 110 may not include the pigtail 111 and the heart pump 110 may be stabilized in other ways or not stabilized at all. During operation, blood may be drawn into one or more openings in the inlet area 112 by a motor (not shown) disposed within the motor housing 116, channeled through the cannula 113, and discharged through one or more openings in the outlet area 115. In some implementations, the pressure sensor 114 may include a flexible membrane integrated into the cannula 113. One side of the pressure sensor 114 may be exposed to blood pressure on the outside of the cannula 113, and the other side may be exposed to the pressure of blood inside the cannula 113. In some such implementations, the pressure sensor 114 may generate an electrical signal proportional to the difference between the pressure outside the cannula 113 and the pressure inside the cannula 113. In some implementations, the pressure difference measured by the pressure sensor 114 may be used, at least in part, to position the heart pump 110 within the patient's heart. In some implementations, the pressure sensor 114 is an optical pressure sensor. The catheter tubing 117 may provide one or more fluid and / or electrical connections between the heart pump 110 and one or more other devices of a ventricular assist system, an example of which is shown in FIG. 1C.

[0067] As shown in FIG. 1B , the heart pump 110 may be positioned within the patient's heart 120. For example, the heart pump 110 may be inserted percutaneously via the femoral artery 122, into the ascending aorta 124, across the aortic valve 126, and into the left ventricle 128. In other implementations, the heart pump may be inserted percutaneously via the axillary artery 123, into the ascending aorta 124, across the aortic valve 126, and into the left ventricle 128. In other implementations, the heart pump may be inserted directly into the ascending aorta 124, across the aortic valve 126, and into the left ventricle 128, for example. During operation, the heart pump 110 takes in blood from the left ventricle 128 and expels blood into the ascending aorta 124. As a result, the blood pump 110 performs some of the work normally performed by the patient's heart 120. The hemodynamic effects of the heart pump include improved coronary blood flow resulting in increased cardiac output, left ventricular end-diastolic pressure, pulmonary capillary wedge pressure, myocardial work, and reduced oxygen consumption.

[0068] As shown in FIG. 1C, the heart pump 110 may form part of a ventricular assist system 100. The ventricular assist system 100 also includes a controller 130 (e.g., Automated Impella Controller® from ABIOMED, ​​Inc., Danvers, Mass.), a display 140, a purge subsystem 150, a connector cable 160, a plug 170, and a repositioning unit 180. As shown, the controller 130 includes the display 140. The controller 130 monitors and controls the operation of the heart pump 110. During operation, the purge subsystem 150 is configured to deliver a purge fluid to the heart pump 110 through the catheter tube 117 to prevent blood from entering the motor (not shown) in the motor housing 116. In some implementations, the purge fluid is a glucose solution (e.g., 5% glucose in water with 25 or 50 IU / mL of heparin). A connector cable 160 provides an electrical connection between the heart pump 110 and the controller 130. A plug 170 connects the catheter tube 117, the purge subsystem 150, and the connector cable 160. In some implementations, the plug 170 includes a storage device (e.g., memory) configured to store, for example, operating parameters to facilitate patient transition to another controller, if needed. A repositioning unit 180 may be used to reposition the heart pump 110 within the patient's heart.

[0069] As shown, the purge subsystem 150 includes a container 151, a supply line 152, a purge cassette 153, a purge disk 154, purge tubing 155, a check valve 156, a pressure reservoir 157, an infusion filter 158, and a side arm 159. The container 151 may be, for example, a bag or a bottle. A purge fluid is stored in the container 151. The supply line 152 provides a fluid connection between the container 151 and the purge cassette 153. The purge cassette 153 may control how the purge fluid in the container 151 is delivered to the heart pump 110. For example, the purge cassette 153 may include one or more valves for controlling the pressure and / or flow rate of the purge fluid. The purge disk 154 may include one or more pressure and / or flow sensors for measuring the pressure and / or flow rate of the purge fluid. As shown, the controller 130 includes a purge cassette 153 and a purge disk 154. Purge tubing 155 provides a fluid connection between the purge disk 154 and a check valve 156. A pressure reservoir 157 provides additional fill volume during purge fluid exchange. In some implementations, the pressure reservoir 157 includes a flexible rubber diaphragm that provides additional fill volume with an expansion chamber. An infusion filter 158 helps prevent bacterial contamination and air from entering the catheter tube 117. A side arm 159 provides a fluid connection between the infusion filter 158 and a plug 170.

[0070] During operation, the controller 130 may be configured to receive measurements from the pressure sensor 114 and the purge disk 154 and control the operation of the motor (not shown) and the purge cassette 153 in the motor housing 116. As described above, the controller 130 is configured to control and measure the pressure and / or flow rate of the purge fluid through the purge cassette 153 and the purge disk 154. During operation, after exiting the purge subsystem 150 through the side arm 159, the purge fluid is directed through the catheter tube 117 and a purge lumen (not shown) in the plug 170. The catheter tube 117, the connector cable 160, and the sensor cable (not shown) in the plug 170 provide electrical connections between the pressure sensor 114 and the controller 130. The catheter tube 117, the connector cable 160, and the motor cable (not shown) in the plug 170 provide electrical connections between the motor in the motor housing 116 and the controller 130. During operation, the controller 130 is configured to receive measurements from the pressure sensor 114 through the sensor cable and control power delivered through the motor cable to the motor in the motor housing 116. By controlling the power delivered to the motor in the motor housing 116, the controller 130 is operable to control the speed of the motor in the motor housing 116.

[0071] Various modifications can be made to the ventricular assist system 100 and one or more of its components. For example, one or more additional sensors can be added to the heart pump 100. In another example, a signal generator can be added to the heart pump 100 to generate a signal indicative of the rotational speed of the motor in the motor housing 116. As yet another example, a second pressure sensor can be added to the heart pump 110 near the inlet area 112, and the second pressure sensor can be configured to measure left ventricular blood pressure. In such an implementation, an additional sensor cable can be disposed within the catheter tube 117, the connector cable 160, and the plug 170 to provide an electrical connection between the one or more additional sensors and the controller 130. As yet another example, one or more components of the ventricular assist system 100 can be separated. For example, the display 140 can be incorporated into another device that communicates with the controller 130 (e.g., wirelessly or through one or more electrical cables).

[0072] As should be understood from the foregoing description, proper positioning of the heart pump 110 across the patient's aortic valve is important to ensure that the heart pump 110 operates properly to support the patient's cardiac function. Because the position of the heart pump 110 within the patient's heart is typically not precisely known during insertion of the heart pump 110 into the patient's heart or during its operation while within the patient's heart, the position of the heart pump 110 is inferred in some embodiments from sensor information provided by one or more sensors (e.g., pressure sensor 114, motor current sensor (not shown), etc.) coupled to the heart pump 110. The sensor information may be provided to the controller 130, which may be configured to determine the position of the heart pump 110 within the patient's heart based, at least in part, on the sensor information. In some embodiments, the controller 130 may be configured to output an alert to the display 140 to indicate whether the heart pump 110 is in a desired position (e.g., with the inlet area 112 located within the patient's left ventricle and the outlet area 115 located within the patient's aorta), for example, as shown in FIG. 2. As shown, once the heart pump is properly positioned across the aortic valve (261), the display 140 may be configured to display an indication 251 of proper positioning of the heart pump. Additionally or alternatively, once the controller 130 determines that the position of the heart pump 110 is not in the desired position, the controller 130 may be configured to output one or more alerts to the display 140 to indicate incorrect positioning of the heart pump 110. Reporting such alerts may be important to ensure that a medical professional (e.g., a physician) inserting and / or monitoring the functioning of the heart pump 110 during operation is informed of the incorrect placement and may take corrective action to adjust the position of the heart pump 110 within the patient's heart.

[0073] In some embodiments, the controller 130 may be configured to control the display 140 to output one of a number of types of alerts when the heart pump 110 is improperly positioned within the patient's heart. For example, as shown in FIG. 3A, the controller 130 may be configured to determine whether the heart pump is properly positioned (e.g., OK) or improperly positioned (e.g., located in the ventricle, located in the aorta, unknown) based at least in part on the motor current signal I and the pressure signal P. One or more of the alerts corresponding to an indication that the heart pump is improperly positioned may be associated with a different alert level corresponding to a risk associated with the current positioning of the heart pump. For example, an indication that the heart pump is located in the ventricle or in the aorta may be associated with a higher (e.g., more dangerous) alert level compared to an indication that the installation signal (e.g., from an optical pressure sensor) is low or the pulsatility of the motor current signal is low for an unknown reason. It should be understood that any suitable number of alert levels may be assigned. Assigning an alert level to a pump position alert may encourage a medical professional monitoring the operation of the heart pump to take appropriate emergency action when such a pump position alert is provided on display 140.

[0074] In the example shown in Figure 3A, the pump position is determined based on three comparisons: pulsatility I of the motor current signal within a given time window (e.g., 2 seconds), as shown in the leftmost column of Figure 3A; mod_actual is the first threshold I modulation When the heart pump is properly positioned across the aortic valve, the motor current signal sensed from the pump motor fluctuates in a pulsatile manner as the pump motor operates in coordination with the pumping cycle of the patient's heart. Thus, as shown in FIG. 3A, the pulsatility I of the motor current signal mod_actual is the threshold I modulationWhen the pressure sensor signal P (e.g., from an optical pressure sensor) is greater than 0.05, the position of the heart pump may be determined to be OK or unknown. The distinction between these two types of position determination is min_actual and the second threshold P min As shown, the minimum pressure sensor value P within a given time window (e.g., 2 seconds) of the pressure sensor signal is min_actual is the threshold P min If the minimum pressure sensor value P min_actual is the threshold P min If it is less than this, it may be determined that the pressure sensor signal is too low so that the position of the pump cannot be accurately determined. In such an instance, an alert may be output indicating a low pressure signal reading.

[0075] Continuing with the example shown in FIG. 3A, the pulsation of the motor current signal I mod_actual is the threshold I modulation When the motor current signal falls below , the position of the heart pump may be determined to be in an incorrect position (e.g., located in the ventricle, located in the aorta), or unknown. Distinguishing between these types of position determinations may be further based on the pressure sensor signal P. Similar to the motor current signal, the pressure sensor signal (e.g., from an optical pressure sensor) may vary in a pulsatile manner depending on the location of the pressure sensor within the heart. As shown, the pulsatility P of the pressure sensor signal within a given time window (e.g., 2 seconds) mod_actual is the third threshold P mod When the pulsatility of the pressure signal is too low to make an accurate determination of the pump location, an unknown alert is generated. mod_actual is the third threshold P mod When the pressure sensor signal P (e.g., from an optical pressure sensor) as described above is exceeded, it is determined that the heart pump is mispositioned to be located in the aorta or in the ventricle. min_actual and the second threshold P minAs shown, the minimum pressure sensor value P within a predetermined time window (e.g., 2 seconds) of the pressure sensor signal is determined based on a comparison of min_actual is the threshold P min However, if the minimum pressure sensor value P min_actual is the threshold P min If it is less than 0.05, it may be determined that the position of the pump is located within the ventricle. Improper positioning of the heart pump within the heart or aorta may represent a more serious event for which a medical professional monitoring the heart pump operation may wish to take immediate corrective action. Thus, as explained above, such an alert may be associated with an alert level that indicates the urgency of the event to a user of the ventricular assist system.

[0076] The inventors have recognized and appreciated that accurate reporting of the positioning of the heart pump via alerts provided to a user of the ventricular assist system is important to ensure that medical professionals monitoring the heart pump operation take appropriate action. While false negatives (e.g., not accurately detecting that the heart pump is in the aorta or ventricle) may be the most serious type of positioning error, generating too many false positives (e.g., detecting that the heart pump is in the aorta or ventricle when it is properly positioned) may also have negative consequences. For example, if such false positive alerts are generated frequently, medical professionals may begin to ignore the alerts rather than take action when needed, or alternatively perform unnecessary medical procedures (e.g., imaging the heart using ultrasound) when in fact the pump is properly positioned. In addition, because aortic and / or ventricular alerts may be associated with a higher alert level, patients may become anxious or stressed when such alerts are displayed frequently, resulting in an unpleasant patient experience.

[0077] FIG. 3B shows a confusion matrix comparing the results of the predicted position of the heart pump based on the algorithm and metrics shown in FIG. 3A (horizontal axis) and the actual position of the heart pump as verified by a human operator (vertical axis). It should be understood that if the algorithm of FIG. 3A had performed error-free location detection on the human-labeled data, all of the values ​​would be located along the diagonal from the top left to the bottom right of the confusion matrix of FIG. 3B. However, as shown, applying the algorithm of FIG. 3A resulted in a substantial number (16.2%) of false positive intra-aortic alerts and, to a lesser extent, numerous false positive unknown low pulse and PS low alerts when the heart pump was in fact properly positioned. As discussed above, the occurrence of false positive alerts when the heart pump is properly positioned has multiple negative consequences. To this end, some embodiments are directed to techniques for improving the accuracy of heart pump position estimation based on motor current and pressure sensor signals.

[0078] The inventors have recognized and appreciated that multiple adjustments to the algorithm diagrammatically illustrated in Figure 3A may be made to improve the accuracy of cardiac pump position detection. In some embodiments, all of the adjustments described herein may be used, while in other embodiments, only one or a subset of the adjustments may be used, and embodiments of the present disclosure are not limited in this respect.

[0079] The first adjustment involves normalizing the motor current signal and using the normalized motor current signal, rather than the raw (or otherwise unnormalized) motor current signal, to determine the motor current pulsatility within a predetermined time window (e.g., 2 seconds). In some embodiments, the normalization of the motor current signal is based, at least in part, on a pressure sensor signal (e.g., as determined from an optical pressure sensor). The inventors have recognized and appreciated that the motor current signal is more pulsative at higher pressures and less pulsative at lower pressures, even when the heart pump is properly positioned across the aortic valve. By normalizing the motor current signal based on the measured pressure sensor signal, the patient's actual pressure value is taken into account, which allows the motor current signal to more accurately reflect the patient's true condition prior to assessing the pulsatility of the motor current signal.

[0080] The normalization factor used to normalize the motor current signal based on the measured pressure sensor signal may be determined in any suitable manner. In some embodiments, the normalization factor corresponds to the pulsatility of the pressure sensor signal measured within a predetermined time window. In other embodiments, the normalization factor corresponds to the mean arterial pressure (MAP) as measured within a predetermined time window of the pressure sensor signal. In yet other embodiments, the normalization factor corresponds to the maximum pressure value P as measured within a predetermined time window of the pressure sensor signal. max In some cases, the maximum pressure value P max may be used as a normalization factor because it is more tolerant to heart pump location. For example, using MAP as a normalization factor assumes that the pressure sensor located on the heart pump is in the aorta. However, if the pressure sensor is not located in the aorta, MAP may not be accurate. In contrast, even when the pressure sensor is not located in the aorta (e.g., the pressure sensor is located in the ventricle), P max would represent the true maximum pressure during systole.

[0081] As shown in FIG. 4A, in some embodiments, the normalized motor current signal is calculated by multiplying the motor current signal (or a processed version of the motor current signal) by the maximum pressure signal P determined within a time window of a predetermined length (e.g., 2 seconds). max The resulting pulsatility of the normalized motor current signal, I mod / P max (optionally multiplied by a scaling factor of 100) is then used, at least in part, to determine whether the heart pump is properly positioned within the patient's heart.

[0082] The inventors have recognized and appreciated that the motor current signal and / or the pressure sensor signal may drift over time. Thus, in a second adjustment of the algorithm of FIG. 3A, the motor current signal (or a processed version of the motor current signal) and / or the pressure sensor signal (or a processed version of the pressure sensor signal) are filtered prior to being used to estimate pump position. In some embodiments, the motor current signal is filtered and the filtered motor current signal is then normalized using one or more of the normalization techniques described herein.

[0083] Any suitable filter may be applied to filter the motor current signal and / or the pressure sensor signal. The inventors have recognized and appreciated that respiratory effects, coughing, and / or other factors may contribute to the calculated pulsatility of the motor current signal and / or the pressure sensor signal. To adjust for such factors, one or both of the motor current signal and the pressure sensor signal may be filtered using a bandpass filter configured to perform baseline correction of the corresponding signal. Any suitable cutoff frequency may be used. In some embodiments, the bandpass filter may have a lower cutoff of 0.5 Hz and an upper cutoff of 5 Hz. In other embodiments, the bandpass filter may have a lower cutoff of 0.65 Hz. In some embodiments, the cutoff frequencies may be selected to include a typical range of heart rates observed by patients who may use a heart pump. In some embodiments, the pressure sensor signal may be filtered and a normalized motor current may be generated based, at least in part, on the filtered pressure sensor signal. For example, a normalization factor (e.g., MAP, P max , etc.) may be determined based on the filtered pressure sensor signal. Any suitable filter may be applied to filter the pressure sensor signal. For example, in some embodiments, the pressure sensor signal is filtered using a low pass filter. Any suitable cutoff frequency may be used for the low pass filter. For example, in some embodiments, the low pass filter has a cutoff frequency of 5 Hz. In some embodiments, the pressure sensor signal may be filtered differently depending on the pressure metric desired to be calculated from the filtered pressure sensor signal. For example, to calculate the pulsatility of the pressure sensor signal, the pressure sensor signal may first be filtered using a band pass filter (as described above) and a maximum pressure value P max or minimum pressure value P min_actual(or any other absolute parameter, for example), the pressure sensor signal may first be filtered using a low pass filter. In this manner, one or more filtered motor current signals and / or pressure sensor signals may be generated based on the desired corresponding motor current and / or pressure metric to be determined.

[0084] The inventors have recognized and appreciated that at higher pump speeds, when the pump is doing most of the pumping for the heart and therefore the valves are less open, separation of the aortic and ventricular signals results in a dampened left ventricular signal that is present and appears similar to a suction condition. Under such circumstances, it cannot be determined whether a suction condition has occurred or whether the heart pump is in a desired position, so in some embodiments, a third adjustment of the algorithm of FIG. 3A is to perform one or more additional checks when the heart pump position is determined to be improperly positioned (e.g., located in the aorta or located in the ventricle) and / or when the pump position is determined to be unknown.

[0085] According to one such additional check, a differential pressure signal dP across the aortic valve is determined based, at least in part, on the pressure sensor signal. As described above in connection with FIGS. 1A-1C, the heart pump may include a pressure sensor (e.g., an optical pressure sensor) configured to detect the patient's aortic pressure when the heart pump is properly positioned within the patient's heart. The heart pump may not include a separate pressure sensor configured to detect the patient's ventricular pressure. In such cases, the differential pressure signal dP may be determined indirectly using the measured aortic pressure, the measured motor current, and a look-up table that maps the motor current value to a dP value for the heart pump. In some embodiments, the left ventricular pressure (LVP) may also be determined indirectly. For example, the LVP may be determined using the measured aortic pressure signal and a known pressure differential dP across the aortic valve. Decoupling of the dP and LVP signals suggests that a suction event has occurred, and an alert indicative thereof may be displayed via the display 140 to inform a medical professional monitoring the operation of the heart pump to move the heart pump to correct the suction condition.

[0086] In some embodiments, one or more additional checks include determining the minimum value dP of the dP signal within a time range of a predetermined length (e.g., 2 seconds). min In some embodiments, one or more additional checks include determining whether the maximum dP of the dP signal within a time range of a predetermined length (e.g., 2 seconds) is greater than a threshold value. max exceeds a threshold. Based on one or more additional checks, appropriate alerts may be generated in an attempt to further reduce false positives regarding positioning of the heart pump within the aorta or ventricle.

[0087] FIG. 4B shows a confusion matrix comparing the results of the predicted position of the heart pump based on the algorithm and metrics shown in FIG. 4A (horizontal axis) and the actual position of the heart pump as verified by a human operator (vertical axis). Compared to the confusion matrix shown in FIG. 3B, it can be observed that the number of false positive intra-aortic alerts was substantially reduced (0.4% in FIG. 4B compared to 16.2% in FIG. 3B), thereby demonstrating the effectiveness of the improved algorithm. Moderate improvements in other cases were also observed. For example, the false positive rate for PS low alerts was reduced from 7.9% using the algorithm of FIG. 3A to 0.8% using the algorithm of FIG. 4A. Notably, the false negative rate did not change substantially for intra-aortic and intra-ventricular, two conditions that indicate improper placement of the heart pump in the heart.

[0088] FIG. 5 is a flowchart of a process 500 for an improved position detection technique, according to some embodiments. In act 502, a motor current signal associated with an operating state of a motor in a heart pump is received. Process 500 then proceeds to act 504, where the received motor current signal is filtered (e.g., using a bandpass filter as described above). In act 506, a pressure sensor signal (e.g., from an optical pressure sensor located on the heart pump) is received. Process 500 then proceeds to act 508, where the received pressure sensor signal is filtered (e.g., using a lowpass filter and / or a bandpass filter as described above). Process 500 then proceeds to act 510, where the filtered motor current signal and the filtered pressure signal are used to generate a normalized motor current signal. For example, as described above, the value of the filtered motor current signal is calculated based on the maximum pressure P determined within a predetermined time window of the pressure sensor signal. max It may be divided by

[0089] Process 500 then proceeds to act 512, where the pulsatility of the normalized motor current signal is determined and compared to a first threshold. If in act 512 it is determined that the pulsatility of the normalized motor current signal is less than the first threshold, process 500 then proceeds to act 514, where it is determined whether the measured minimum pressure value from the pressure sensor signal is above a second threshold. If in act 514 it is determined that the minimum pressure value is above the second threshold, process 500 proceeds to act 516, where it is determined that the position of the heart pump is OK. If in act 514 it is determined that the minimum pressure value is less than the second threshold, process 500 proceeds to act 518, where it is determined that the position of the heart pump is inconclusive. In response to determining that the position of the heart pump is inconclusive, one or more additional checks may be performed to assess whether the pump position is OK, as described above, despite the low pressure measurement.

[0090] If it is determined in act 512 that the pulsatility of the motor current signal is less than the first threshold, the process 500 proceeds to act 520, where the pulsatility of the filtered pressure sensor signal is determined and compared to a third threshold. If it is determined in act 520 that the pulsatility of the filtered pressure sensor signal does not exceed the third threshold, the process 500 proceeds to act 522, where it is determined that the heart pump position is inconclusive. One or more additional checks may be performed to determine whether the pump is correctly positioned despite the low pulsatility of the pressure signal, as described above. If it is determined in act 520 that the pulsatility of the pressure signal is greater than the third threshold, the process 500 proceeds to act 524, where it is determined whether the minimum pressure value measured from the pressure sensor signal is greater than a fourth threshold. If it is determined in act 524 that the minimum pressure value is greater than the fourth threshold, the process 500 proceeds to act 526, where it is determined that the heart pump position is in the aorta. As described above, in some embodiments, one or more additional checks are performed when the pump position is determined to be within the aorta in an attempt to avoid generating a false positive alert when the pump is correctly positioned. If in act 524 it is determined that the minimum pressure value is less than the fourth threshold, process 500 proceeds to act 528 where it is determined that the cardiac pump position is within the ventricle. In response to determining that the cardiac pump position is within the ventricle, one or more additional checks may be performed in an attempt to avoid generating a false positive alert when the pump is correctly positioned.

[0091] The first, second, third, and fourth thresholds may be set in any suitable manner. In some embodiments, at least some of the thresholds are set based on empirical data describing the type of error generated. Figures 6A-B illustrate bar graphs showing the distribution for different classifications made using the algorithm shown in Figure 3A. The vertical axis represents the number of classifications and the horizontal axis represents normalized motor current values. The motor of the heart pump may be configured to operate at one of a number of fixed speeds (e.g., designated as P1-P9), and the classifications that result at different motor speeds may also be different. Figures 6A-6B include separate bar graphs for each motor speed P1-P9. As discussed above, a motivating factor for improving the algorithm of Figure 3A was to reduce false positives, where the algorithm determined that the heart pump was located in the aorta when in fact it was properly positioned across the aortic valve. As shown in Figures 6A-6B, one way to conceptualize a solution to this problem is to determine a threshold value that separates cases where a false positive intra-aortic classification is determined by the algorithm from cases where a true intra-aortic classification is determined by the algorithm. For each motor speed P1-P9 depicted in Figures 6A-6B, a dotted line is shown that represents the threshold value that best separates the two populations described above. As should be understood from Figures 6A-6B, at many motor current speeds, the "false intra-aortic" and "true intra-aortic" classifications largely overlap, making the determination of an appropriate threshold value difficult. The overlap is even more pronounced at higher motor speeds (e.g., P8-P9) where the number of false positives for the intra-aortic classification is increased relative to the slower motor speeds.

[0092] 7A-B illustrate bar graphs showing distributions for different classifications made using the improved algorithm shown in FIG. 4A. Similar to the bar graphs shown in FIG. 6A-6B, thresholds designed to separate the false intra-aortic and true intra-aortic classifications for each motor speed P1-P9 are represented as dotted lines in FIG. 7A-7B. As should be understood from FIG. 7A-7B, the improved algorithm used to determine heart pump position according to some embodiments generates distributions of false intra-aortic and true intra-aortic classifications that are substantially non-overlapping. At higher motor speeds (e.g., P8-P9), the number of false positives for the intra-aortic classifications remains higher than at slower motor speeds, but their distribution as a function of normalized motor current is separated from the distribution of the true intra-aortic classifications, which can be achieved by setting an appropriate threshold (e.g., the "first threshold" described in act 512 of FIG. 5 or the I threshold shown in the algorithm of FIG. 4A). mod_norm_thresh ) is drawn between the two populations, making it possible to separate them for different motor speeds.

[0093] Having thus described several aspects and embodiments of the technology described in this disclosure, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the technology described herein. For example, one skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining one or more of the results and / or advantages described herein, and each such variation and / or modification is deemed to be within the scope of the embodiments described herein. One skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. Thus, it should be understood that the foregoing embodiments are presented by way of example only, and that within the scope of the appended claims and their equivalents, the embodiments of the invention may be practiced otherwise than as specifically described. In addition, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein is included within the scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0094] The embodiments described above can be implemented in any of a number of ways. One or more aspects and embodiments of the present disclosure involving the implementation of a process or method may utilize program instructions executable by a device (e.g., a computer, a processor, or other device) to perform or control the implementation of the process or method. In this regard, various inventive concepts may be embodied as a computer-readable storage medium (or multiple computer-readable storage media) (e.g., a computer memory, one or more floppy disks, compact disks, optical disks, magnetic tapes, flash memories, circuitry in field programmable gate arrays or other semiconductor devices, or other tangible computer storage media) encoded with one or more programs that, when executed on one or more computers or other processors, perform a method that implements one or more of the various embodiments described above. The computer-readable medium or media may be transportable such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various of the aspects described above. In some embodiments, the computer readable medium may be a non-transitory medium.

[0095] The above-described embodiments of the present technology can be implemented in any of a number of ways. For example, the embodiments may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers. It should be understood that any component or collection of components that performs the functions described above can generally be considered as a controller that controls the functions described above. The controller can be implemented in a number of ways, such as using dedicated hardware, or using general-purpose hardware (e.g., one or more processors) that is programmed using microcode or software to perform the functions listed above, and may be implemented in a combination of ways when the controller corresponds to multiple components of a system.

[0096] Further, it should be understood that the computer may be embodied in any of a number of forms, such as, as non-limiting examples, a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. In addition, the computer may be embedded within devices that are not generally considered computers but with suitable processing capabilities, including a personal digital assistant (PDA), a smart phone, or any other suitable portable or fixed electronic device.

[0097] A computer may also have one or more input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include a printer or display screen for visual presentation of output, and a speaker or other sound generating device for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards and pointing devices such as mice, touchpads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or in other audible formats.

[0098] Such computers may be interconnected by one or more networks in any suitable form, including local or wide area networks, such as enterprise networks, and intelligent networks (INs) or the Internet. Such networks may be based on any suitable technology and operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks.

[0099] Also, as described, some aspects may be embodied as one or more methods. Acts performed as part of a method may be ordered in any suitable manner. Thus, embodiments may be constructed in which acts are performed in a different order than illustrated, which may include performing some acts simultaneously, even if shown as sequential acts in the illustrative embodiments.

[0100] All definitions, as defined and used herein, should be understood to take precedence over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0101] The indefinite articles "a" and "an," as used herein in the specification and claims, unless expressly indicated otherwise, should be understood to mean "at least one."

[0102] The phrase "and / or" as used herein in the specification and claims should be understood to mean "one or both" of the elements so conjoined, i.e., elements that are conjunctive in some cases and disjunctive in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., as "one or more" of the elements so conjoined. Other elements, whether related or unrelated to those elements specifically identified, may optionally be present other than the elements specifically identified by the "and / or" clause. Thus, as a non-limiting example, a reference to "A and / or B," when used in conjunction with open language such as "comprising," can refer in one embodiment to only A (optionally including elements other than B), in another embodiment to only B (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0103] As used herein in the specification and claims, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of every element specifically recited in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified elements in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. Thus, as non-limiting examples, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one A (and optionally including elements other than B), optionally including more than one, in which no B is present; in another embodiment to at least one B (and optionally including elements other than A), optionally including more than one, in which no A is present; in yet another embodiment to at least one A, optionally including more than one, and at least one B, optionally including more than one, in which case (and optionally including other elements); etc.

[0104] Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "with," and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof and additional items.

[0105] In the claims and the above specification, all transitional phrases such as "comprising," "including," "propagating," "having," "containing," "with," "holding," "consisting of," and the like, are intended to be open-ended, i.e., to mean "including, but not limited to." Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

[0106] The use of ordinal terms such as "first," "second," "third," etc. in the claims to modify claim elements does not, in itself, imply any priority, precedence, or ordering of one claim element relative to another, or the temporal order in which acts of a method are performed, but merely distinguishes one claim element having a certain name from another element having the same name (in the absence of the use of ordinal terms) and is used as a marker to distinguish the claim elements.

[0107] Claims

Claims

1. 1. A method for determining whether a circulatory assist device is properly positioned within a patient's heart, the method comprising: receiving a motor current signal from a motor of the circulatory assist device; receiving a pressure signal from a pressure sensor disposed on the circulatory assist device; generating a normalized motor current signal based at least in part on the pressure signal; determining a pulsatility of the normalized motor current signal; determining whether the circulatory assist device is properly positioned within the patient's heart based, at least in part, on the pulsatility of the normalized motor current signal; outputting an alarm when it is determined that the circulatory assist device is not properly positioned within the patient's heart. A method comprising:

2. determining a maximum pressure value of the pressure signal within a time window of a predetermined length; 2. The method of claim 1 , wherein generating the normalized motor current signal based at least in part on the pressure signal comprises generating the normalized motor current signal based at least in part on the maximum pressure value.

3. 3. The method of claim 2, wherein generating the normalized motor current signal based at least in part on the maximum pressure value comprises dividing a value of the motor current signal by the maximum pressure value.

4. The method of claim 1 , wherein the pressure sensor comprises an optical pressure sensor.

5. filtering the motor current signal; The method of claim 1 , wherein generating the normalized motor current signal is based at least in part on the filtered motor current signal.

6. The method of claim 5 , wherein filtering the motor current signal comprises filtering the motor current signal with a bandpass filter.

7. The method of claim 6 , wherein the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

8. The method of claim 7 , wherein the bandpass filter is configured to cut off frequencies below 0.65 Hz.

9. The method of claim 5 , wherein filtering the motor current signal comprises filtering the motor current signal with a low pass filter.

10. filtering the pressure signal; The method of claim 1 , wherein generating the normalized motor current signal is based at least in part on the filtered pressure signal.

11. determining a maximum pressure value of the filtered pressure signal within a time window of a predetermined length; 11. The method of claim 10, wherein generating the normalized motor current signal based at least in part on the filtered pressure signal comprises generating the normalized motor current signal based at least in part on the maximum pressure value.

12. The method of claim 10 , wherein filtering the pressure signal comprises filtering the pressure signal with a low pass filter.

13. The method of claim 12 , wherein the low pass filter is configured to cut off frequencies above 5 Hz.

14. determining a differential pressure signal based at least in part on the pressure signal; 10. The method of claim 1, wherein determining whether the circulatory assist device is properly positioned within the patient's heart is further based, at least in part, on the differential pressure signal.

15. determining a minimum pressure value of the pressure signal associated with a time window of a predetermined length; the pulsatility of the normalized motor current signal exceeds a first threshold; the minimum pressure value is less than a second threshold value; a minimum value of the differential pressure signal within the time window exceeds a third threshold value, or a maximum value of the differential pressure signal within the time window exceeds a fourth threshold value. determining that the circulatory assist device is not properly positioned within the patient's heart when ... properly positioned within the patient's heart when the circulatory assist device is properly positioned within the patient's heart when the circulatory assist device is properly positioned within the patient's heart when the The method of claim 14 further comprising:

16. determining a pulsatility of the pressure signal; 10. The method of claim 1, wherein determining whether the circulatory assist device is properly positioned within the patient's heart is further based, at least in part, on pulsatility of the pressure signal.

17. determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a third threshold when the pulsatility of the normalized motor current signal is less than a first threshold and the pulsatility of the pressure signal is less than the second threshold; determining that the circulatory assist device is not properly positioned within the patient's heart when the minimum pressure value within the time window is less than the third threshold value; and 20. The method of claim 16, further comprising:

18. determining that the circulatory assist device is located within an aorta of the patient's heart when the minimum pressure value within the time window is less than the third threshold; 20. The method of claim 17, wherein outputting an alarm includes outputting an alarm that the circulatory assist device is located within the aorta.

19. filtering the pressure signal; The method of claim 16 , wherein determining the pulsatility of the pressure signal comprises determining the pulsatility of the filtered pressure signal.

20. The method of claim 19 , wherein filtering the pressure signal comprises filtering the pressure signal with a bandpass filter.

21. 21. The method of claim 20, wherein the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

22. 22. The method of claim 21, wherein the bandpass filter is configured to cut off frequencies below 0.65 Hz.

23. determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a second threshold; determining that the circulatory assist device is properly positioned within the patient's heart when the pulsatility of the normalized motor current signal is less than the first threshold and the minimum pressure value within the time window is greater than the second threshold; The method of claim 1 further comprising:

24. 24. The method of claim 23, further comprising determining that the circulatory assist device is not correctly positioned in the patient's heart when pulsatility of the normalized motor current signal is above the first threshold and / or when the minimum pressure value within the time window is less than the second threshold.

25. 1. A circulatory assist device comprising: A rotor; a motor configured to drive rotation of the rotor at one or more speeds; a pressure sensor configured to detect a pressure signal; At least one controller, receiving a motor current signal from the motor; receiving a pressure signal from the pressure sensor; generating a normalized motor current signal based at least in part on the pressure signal; determining a pulsatility of the normalized motor current signal; determining whether the circulatory assist device is properly positioned within the patient's heart based, at least in part, on the pulsatility of the normalized motor current signal; outputting an alarm when it is determined that the circulatory assist device is not properly positioned within the patient's heart. At least one controller configured to: A circulatory support device comprising:

26. The at least one controller further comprises: configured to determine a maximum pressure value of the pressure signal within a time window of a predetermined length; generating the normalized motor current signal based at least in part on the pressure signal includes generating the normalized motor current signal based at least in part on the maximum pressure value.

26. The circulatory assist device of claim 25.

27. 27. The circulatory assist device of claim 26, wherein generating the normalized motor current signal based at least in part on the maximum pressure value comprises dividing a value of the motor current signal by the maximum pressure value.

28. 26. The circulatory assist device of claim 25, wherein the pressure sensor comprises an optical pressure sensor.

29. The at least one controller further comprises: configured to filter the motor current signal; generating the normalized motor current signal based, at least in part, on the filtered motor current signal.

26. The circulatory assist device of claim 25.

30. 30. The circulation assist device of claim 29, wherein filtering the motor current signal comprises filtering the motor current signal with a bandpass filter.

31. 31. The circulatory assist device of claim 30, wherein the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

32. 32. The circulatory assist device of claim 31 , wherein the bandpass filter is configured to cut off frequencies below 0.65 Hz.

33. 30. The circulation assist device of claim 29, wherein filtering the motor current signal comprises filtering the motor current signal with a low pass filter.

34. The at least one controller further comprises: configured to filter the pressure signal; generating the normalized motor current signal based, at least in part, on the filtered pressure signal; 26. The circulatory assist device of claim 25.

35. The at least one controller further comprises: configured to determine a maximum pressure value of the filtered pressure signal within a time window of a predetermined length; generating the normalized motor current signal based at least in part on the filtered pressure signal includes generating the normalized motor current signal based at least in part on the maximum pressure value.

35. The circulatory assist device of claim 34.

36. 36. The circulatory assist device of claim 35, wherein filtering the pressure signal comprises filtering the pressure signal with a low pass filter.

37. 37. The circulatory assist device of claim 36, wherein the low pass filter is configured to cut off frequencies above 5 Hz.

38. The at least one controller further comprises: configured to determine a differential pressure signal based at least in part on the pressure signal; determining whether the circulatory assist device is properly positioned within the patient's heart further comprises determining whether the circulatory assist device is properly positioned within the patient's heart based, at least in part, on the differential pressure signal; 26. The circulatory assist device of claim 25.

39. The at least one controller further comprises: determining a minimum pressure value of the pressure signal associated with a time window of a predetermined length; the pulsatility of the normalized motor current signal exceeds a first threshold; the minimum pressure value is less than a second threshold value; a minimum value of the differential pressure signal within the time window exceeds a third threshold value, or a maximum value of the differential pressure signal within the time window exceeds a fourth threshold value. determining that the circulatory assist device is not properly positioned within the patient's heart when ... properly positioned within the patient's heart when the circulatory assist device is properly positioned within the patient's heart when the circulatory assist device is properly positioned within the patient's heart when the 40. The circulatory assist device of claim 38, configured to:

40. The at least one controller further comprises: configured to determine the pulsatility of the pressure signal; determining whether the circulatory assist device is properly positioned within the patient's heart further comprises determining whether the circulatory assist device is properly positioned within the patient's heart based, at least in part, on a pulsatility of the pressure signal; 26. The circulatory assist device of claim 25.

41. The at least one controller further comprises: determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a third threshold when the pulsatility of the normalized motor current signal is less than a first threshold and the pulsatility of the pressure signal is less than the second threshold; determining that the circulatory assist device is not properly positioned within the patient's heart when the minimum pressure value within the time window is less than the third threshold value; and 41. The circulatory assist device of claim 40, configured to:

42. The at least one controller further comprises: configured to determine that the circulatory assist device is located within an aorta of the patient's heart when the minimum pressure value within the time window is less than the third threshold; and outputting an alarm including outputting an alarm that the circulatory assist device is located within the aorta.

42. The circulatory assist device of claim 41.

43. The at least one controller further comprises: configured to filter the pressure signal; determining the pulsatility of the pressure signal includes determining the pulsatility of the filtered pressure signal.

41. The circulatory assist device of claim 40.

44. 44. The circulatory assist device of claim 43, wherein filtering the pressure signal comprises filtering the pressure signal with a bandpass filter.

45. 45. The circulatory assist device of claim 44, wherein the bandpass filter is configured to cut off frequencies below 0.5 Hz and above 5 Hz.

46. 46. ​​The circulatory assist device of claim 45, wherein the bandpass filter is configured to cut off frequencies below 0.65 Hz.

47. The at least one controller further comprises: determining whether a minimum pressure value within a time window of a predetermined length of the pressure signal exceeds a second threshold; determining that the circulatory assist device is properly positioned within the patient's heart when the pulsatility of the normalized motor current signal is less than the first threshold and the minimum pressure value within the time window is greater than the second threshold; 26. The circulatory assist device of claim 25, configured to:

48. The at least one controller further comprises:

48. The circulatory assist device of claim 47, configured to determine that the circulatory assist device is not correctly positioned in the patient's heart when pulsatility of the normalized motor current signal is above the first threshold and / or when the minimum pressure value within the time window is less than the second threshold.

49. 1. A method for determining whether a circulatory assist device is properly positioned within a patient's heart, the method comprising: receiving a motor current signal from a motor of the circulatory assist device; filtering the motor current signal with a bandpass filter to generate a filtered motor current signal; receiving a pressure signal from a pressure sensor disposed on the circulatory assist device; filtering the pressure signal to generate a filtered pressure signal; generating a normalized motor current signal based at least in part on the filtered motor current signal and the filtered pressure signal; determining a pulsatility of the normalized motor current signal; determining a pulsatility of the filtered pressure signal; determining a differential pressure signal based at least in part on the filtered pressure signal; (i) the pulsatility of the normalized motor current signal is less than a first threshold; (ii) the pulsatility of the filtered pressure signal is less than a second threshold; (iii) a maximum value of the differential pressure signal within a time window of a predetermined length exceeds a third threshold; or (iv) the minimum value of the differential pressure signal within the time window exceeds a fourth threshold value. determining that the circulatory assist device is not properly positioned within the patient's heart when outputting an alarm when it is determined that the circulatory assist device is not properly positioned within the patient's heart. A method comprising:

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