Method for tracing root cause of suction event based on dual sensors and catheter pump system

Abstract

Disclosed in the present application is a catheter pump system. A measured intraventricular pressure and a measured intravascular pressure are measured by means of dual sensors, respectively, and an estimated intraventricular pressure is calculated by using the measured intravascular pressure, a motor current, and a motor rotation speed. When it is determined that a suction event occurs in a pump assembly by using at least one of the estimated intraventricular pressure, the measured intravascular pressure, and the motor current, the root cause of the suction event is further determined by using the positive or negative characteristics of the measured intraventricular pressure.

Description

Method for tracing root cause of suction event based on dual sensors and catheter pump system TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, and in particular to a method for tracing root cause of suction event based on dual sensors and a catheter pump system. BACKGROUND

[0002] As has been clarified by CN116829072A, medical imaging technology can only help doctors confirm whether the catheter pump has been positioned at the desired position of the patient's heart before the catheter pump is operated. During the operation of the catheter pump, the displacement of the pump in the patient's body due to vibration when the pump is operated, patient movement, etc., and whether the catheter pump is still properly positioned after the displacement, are difficult to confirm by medical imaging technology.

[0003] However, whether the catheter pump is properly positioned during operation not only concerns whether the pump can perform its auxiliary function to the patient's heart with normal performance, but also affects the risk of damage that the pump may cause to the patient. For example, improper positioning of the catheter pump can cause the catheter pump to pierce the ventricular wall of the patient, thereby causing serious accidents including left ventricular perforation or free wall rupture, high blood pressure, insufficient blood flow, and even patient death.

[0004] In addition, improper positioning of the catheter pump can also cause suction events, leading to problems such as increased hemolysis and decreased pump flow.

[0005] It is worth noting that improper positioning of the catheter pump is only one of the reasons for causing suction events. In fact, different causes of suction events correspond to different treatment methods, which directly affects the effect of catheter pump assistance and treatment.

[0006] Therefore, it is very important to trace the cause of the suction event. TECHNICAL PROBLEM

[0007] Therefore, the present application provides a method for tracing root cause of suction event based on dual sensors and a catheter pump system, which can accurately trace the root cause of the suction event of the catheter pump system. TECHNICAL SOLUTION

[0008] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0009] The catheter pump system comprises a pump assembly arranged at a distal end of a catheter and deliverable to a heart of a patient by the catheter, two sensors and a controller. The two sensors have sensing heads adjacent to an inlet and an outlet of the pump assembly respectively, and the controller is connected with the two sensors and a motor for driving the pump assembly, and is configured to receive a measured intraventricular pressure and a measured intravascular pressure measured by the two sensors. An estimated intraventricular pressure is calculated according to the measured intravascular pressure, a motor current and a motor speed. Whether a suction event occurs in the pump assembly is determined according to at least one of the estimated intraventricular pressure, the measured intravascular pressure and the motor current. When the determination result is yes, a root cause of the suction event is determined according to a positive or negative nature of the measured intraventricular pressure.

[0010] The method for determining a root cause of a suction event of a dual-sensor traceable catheter pump system comprises receiving a measured intraventricular pressure and a measured intravascular pressure measured by two sensors. An estimated intraventricular pressure is calculated according to the measured intravascular pressure, a motor current and a motor speed. Whether a suction event occurs in the pump assembly is determined according to at least one of the estimated intraventricular pressure, the measured intravascular pressure and the motor current. When the determination result is yes, a root cause of the suction event is determined according to a positive or negative nature of the measured intraventricular pressure. Advantages

[0011] The present application provides a method for determining a root cause of a suction event and a catheter pump system, which can accurately trace a root cause of a suction event of a catheter pump system. BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 is a user interface for a heart pump controller when an intermittent suction event occurs in a catheter pump in the prior art;

[0013] Fig. 2 is a user interface for a heart pump controller when a continuous suction event occurs in a catheter pump in the prior art;

[0014] Fig. 3 is a pressure-volume relationship at end-systole and end-diastole in the prior art;

[0015] Fig. 4 is a typical pressure-volume loop during a therapeutic intervention in the prior art;

[0016] Fig. 5 is a calculation logic diagram when a suction event is determined in the prior art;

[0017] Fig. 6 is a schematic diagram of an in-vitro simulation of pump inlet occlusion / endothelialization;

[0018] Fig. 7 is a schematic diagram of an in-vitro simulation of insufficient preload;

[0019] Fig. 8 is a schematic diagram of a catheter pump system according to an embodiment of the present application;

[0020] Fig. 9A and Fig. 9B are schematic diagrams of the pump assembly in Fig. 8;

[0021] Figure 10 is a process diagram of tracing the suction source in an embodiment of the present application;

[0022] Figure 11 is a curve of the differential pressure ΔP formed by the pump inlet pressure and the pump outlet pressure versus the pump flow rate in three cases;

[0023] Figure 12 is a partial structure diagram of a cleaning liquid seal in the prior art;

[0024] Figure 13 is a curve of the dynamic seal load current decaying over time;

[0025] Figure 14 is a module diagram of a controller in an embodiment of the present application. Embodiments of the present application

[0026] The terms "first", "second", and the like in the present application are used to distinguish similar objects, and are not intended to describe a particular order or sequence. The orientation terms "near", "far", "front", and "back" are relative to the physician who is manipulating the catheter pump. "Near" and "back" refer to the parts that are relatively close to the physician, and "far" and "front" refer to the parts that are relatively far from the physician. For example, the extracorporeal part of the catheter is at the near or back end, and the pump assembly is at the far or front end. It should be understood that these orientation terms are defined for the convenience of description. Since the catheter pump can be used in many directions and positions, these orientation terms are not restrictive and absolute.

[0027] As described in CN110312535A, suction events are mostly caused by device position abnormalities or insufficient preload. The treatment methods for suction events caused by these two reasons are different, so it is very important to trace the root cause of the suction event. For example, if the suction event is caused by device position abnormalities, the catheter pump needs to be repositioned. If the suction event is caused by insufficient preload, it is speculated that the patient may have right heart failure or low blood volume, and the patient needs to be treated with fluid infusion or the pump speed needs to be reduced. However, this scheme can only determine whether the suction event occurs in the diastolic phase (intermittent suction event) or in the systole (continuous suction event), and cannot completely determine which of the two causes the two types of suction events.

[0028] CN115814262A describes in detail the two types of suction events, and determines the cause of the two types of suction events based on the aortic pressure measured by the pressure sensor arranged at the pump outlet and the left ventricular pressure indirectly estimated based on the aortic pressure and the motor current.

[0029] As shown in FIG. 1 and FIG. 2, are exemplary user interfaces 101', 108' for a heart pump controller when intermittent suction and continuous suction events are detected, respectively, in accordance with the above-described scheme. The user interfaces 101', 108' each include a first area 104', 110' showing aortic pressure waveform 102', 109' and left ventricular LVP waveform 103', 111', a second area 105', 112' showing motor current waveform, an aortic pressure indication 106', 113' including minimum and maximum values on the aortic pressure waveform 102', 109', and an LVP indication 107', 114' including minimum and maximum values on the left ventricular LVP waveform 103', 111'.

[0030] As can be seen from FIG. 1, a typical feature of intermittent suction event is that the LVP waveform 103' drops below 0 in early diastole but recovers before the end-diastolic pressure point. Specifically, the maximum value of the LVP indication 107' is normal, greater than the maximum value of the aortic pressure indication 106', but the minimum value is abnormal, less than a set threshold value, e.g., -40 mmHg. As can be seen from FIG. 2, a typical feature of continuous suction event is that the LVP waveform 111' drops below 0 during diastole and fails to rise above the aortic pressure waveform 109' during systole. Specifically, the LVP waveform 111' and the aortic pressure waveform 109' show a clear decoupling, i.e., both the maximum and minimum values of the LVP indication 114' are abnormal: the maximum value is lower than the maximum value of the aortic pressure indication 113', and the minimum value is also lower than a set threshold value, e.g., -40 mmHg.

[0031] It can be seen that when the systolic portion of the LVP waveform is at or above the highest level of the aortic pressure waveform (as shown in FIG. 1), but a drop in left ventricular diastolic pressure is observed, the problem is considered to be with the ventricular preload. If the preload is further reduced and drops below a set threshold value, e.g., -40 mmHg, then a diastolic / intermittent suction is determined to have occurred. On the other hand, if the systolic portion of the LVP waveform is below the highest level of the aortic pressure waveform (as shown in FIG. 2), then a systolic / continuous suction is determined to have occurred.

[0032] Therefore, the conclusion given by the existing scheme is that diastolic / intermittent suction events are caused by insufficient preload, and systolic / continuous suction events are caused by poor positioning of the pump or blockage of the pump inlet.

[0033] However, after extensive research, the applicant found and confirmed the following fact, which is different from the above conclusion: the diastolic / intermittent suction event is indeed only caused by insufficient preload. However, the systolic / continuous suction event is not necessarily only caused by poor positioning of the pump or blockage of the pump inlet, but it can also be caused by insufficient preload. That is, using the existing scheme, only the inducing cause of the diastolic / intermittent suction event can be determined, but the inducing cause of the systolic / continuous suction event cannot be determined. The reason is as follows:

[0034] According to various known documents (such as US10960118B2), the minimum point of the isovolumic diastolic period is the point of minimum left ventricular pressure in the entire cardiac cycle (generally 0-10 mmHg). This also means that at the minimum point of the isovolumic diastolic period, the blood volume in the left ventricle is the smallest.

[0035] According to the records of various known documents (for example, Adam L. Gottula et al., Impella in Transport: Physiology, Mechanics, Complications, and Transport Considerations, Air Medical Journal 41 (2022) 114-127), in the case of isolated left ventricular failure, the intervention support of the mechanical circulatory assistance device will cause the continuous reduction of the cardiac load. The effect of the continuous unloading of the heart will cause the PV loop (i.e. the pressure-volume loop) to move leftward and downward, forming a triangle. Intuitively, the left lower corner point of the minimum pressure and volume in the PV loop moves to the left lower corner, as shown in FIG. 3. When the left lower corner point moves below the horizontal axis, that is, the left ventricular pressure is less than 0, the LVP waveform 103' of FIG. 1 described above will occur.

[0036] Now assume an extreme case that the diastolic / intermittent suction event is not caused by insufficient preload, but by pump inlet occlusion. According to various known literatures (e.g., Nanna L. J. Udesen et al., Impact of concomitant vasoactive treatment and mechanical left ventricular unloading in a porcine model of profound cardiogenic shock, doi: 10.1186 / s13054-020-2816-8, 2020 Mar 18), the mechanical circulatory assistance is reduced or lost, which causes the PV loop to move right up and the area SW in the PV loop to decrease, as shown in FIG. 4. At this time, the left lower corner point with the minimum pressure and volume in the PV loop is larger than the normal value, which is obviously inconsistent with the LVP waveform 103' in FIG. 1.

[0037] In addition, the same conclusion can also be obtained from theoretical derivation. If the pump inlet is occluded, which means that the amount of blood extracted from the left ventricle is reduced, the amount of blood remaining in the left ventricle increases, which will cause the pressure in the left ventricle to increase. However, in the LVP waveform 103' of FIG. 1, the lowest point is lower than the normal case, which is obviously inconsistent with the actual situation.

[0038] Therefore, the diastolic / intermittent suction event can only be caused by insufficient preload, and cannot be caused by poor positioning or pump inlet occlusion. Among them, insufficient preload can be caused by insufficient blood supply to the left ventricle (e.g., the patient is also accompanied by right heart failure), or the speed of the catheter pump is too fast, and the support flow provided exceeds the blood supply of the left ventricle.

[0039] The above scheme misjudges the cause of the induction of the systolic / continuous suction event, which is due to the algorithm setting. Specifically, in this scheme, the left ventricular pressure LVP is not actually measured, but is estimated based on the estimation. The error estimation of LVP and further taking it as the initial condition and basis to determine the cause of the suction event ultimately leads to the above misjudgment. The specific explanation is as follows:

[0040] The LVP estimation algorithm is as follows:

[0041] △P = AOP - LVP → LVP = AOP - △P

[0042] According to the scheme provided by CN115814262A or US7010954B2, the pressure difference △P is determined according to the motor current and the motor speed. At a given motor speed, the motor current is inversely related to △P.

[0043] According to the scheme provided in CN117282016A, at a given motor speed, for an inflatable cable-driven blood pump (such as the known embodiment provided in US20240149050A1), the motor current decreases as the pump flow increases. While for a non-inflatable blood pump (such as the known embodiment provided in US9550017B2), the motor current increases as the flow increases.

[0044] When a contraction / suction event occurs in the catheter pump, regardless of the cause, it will lead to a decrease in pump flow and aortic pressure AOP. The decrease in pump flow will cause the motor current I to decrease, further causing the estimated ΔP to increase according to the estimation model. As a result, the measured AOP decreases, the estimated ΔP increases, and the final estimated LVP decreases significantly, as shown in the entire logical process in FIG. 5.

[0045] Therefore, according to the scheme provided in CN115814262A, regardless of the cause of the contraction / suction event, the final result is a decrease in LVP, which leads to the inability to distinguish and identify the true cause.

[0046] The prior art determines the inducing cause of the contraction / suction event as poor positioning or pump inlet blockage, which can be caused by the following reasons:

[0047] During the systolic phase of the heart, the blood volume in the left ventricle is filled, and it is basically impossible to have a preload deficiency. This is because, as described above, a preload deficiency is mainly caused by two reasons: the patient is accompanied by right heart failure, and the pump is rotating too fast. Among them, it is a small probability event for a left heart failure patient to be accompanied by right heart failure. However, a too fast rotating pump generally does not occur in clinical practice, because before the operation is performed, the doctor will make a full assessment of the patient to determine the appropriate auxiliary flow to be applied to him.

[0048] Therefore, this clinically possible event is ultimately identified as the inducing cause of the contraction / suction event. However, according to the above reasoning, the above small probability event of a left heart failure patient accompanied by right heart failure cannot be excluded as a possible cause of the contraction / suction event.

[0049] In order to verify the above reasoning, the applicant further carried out the following tests and verifications.

[0050] FIG. 6 shows the in-vitro experimental simulation of blockage / adhesion to simulate the suction event caused by pump inlet blockage. The data of the normal condition (a) and the blockage condition (b) are as follows:

[0051] (a) The blood inlet is not blocked, and the speed of the catheter pump is opened to the maximum (35000rmp). It is measured that P1=23.4mmHg, P2=61.9mmHg, △P=P2-P1=38.5mmHg, Q=3.4L / min.

[0052] (b) The speed of the pump is unchanged, and the pump inlet is simulated to be blocked by using adhesive tape. In this embodiment, the simulated pump inlet blockage rate is 80%. It is measured that P1=30.4mmHg, P2=48.8mmHg, △P=18.4mmHg, Q=2.28L / min.

[0053] Wherein, P1 is the left ventricular pressure, P2 is the aortic pressure, △P is the pressure difference, and Q is the pump flow. It can be seen that, compared with the normal case (a), in the case of pump inlet blockage (b), the pressure difference △P and the pump flow Q decrease at the same time, which is reflected in that the pump flow Q is lower than expected at this speed setting.

[0054] Figure 7 is a simulation of the situation that the suction event is caused by insufficient blood volume in the left ventricle (insufficient preload). The data of the normal case (c) and the insufficient preload case (d) are as follows:

[0055] (c) Normal operation, by adjusting the motor speed, the pump flow Q is maintained at 3.5L / min. It is measured that P1=22mmHg, P2=60mmHg, △P=38mmHg.

[0056] (d) By controlling the inflow (for example, hemostatic forceps clamping the supplied hose), the pump flow Q is reduced to 1.5L / min at the same motor speed. It is measured that P1=-56mmHg, P2=30mmHg, △P=86mmHg.

[0057] It can be seen that, in the case of insufficient preload, the pump will suck the left ventricle into negative pressure, △P increases, and Q decreases.

[0058] The above verification results show that, in the two cases, the measured pump flow Q and aortic pressure AOP are reduced. However, in the case of pump inlet blockage, the pressure difference △P decreases compared with the normal case. In the case of insufficient preload, the pressure difference △P increases compared with the normal case. This also means that different types of suction events and possible causes do not have a one-to-one correspondence as described in the above prior art. Therefore, using the above prior art scheme, it is impossible to accurately trace the root cause of the suction event, especially the continuous / systolic suction event.

[0059] As shown in FIG. 8, FIG. 9A and FIG. 9B, to solve the above problems, the catheter pump system 3000 provided by the embodiment includes a catheter pump 1000 and a controller 2000 for controlling the catheter pump 1000. The catheter pump 1000 includes a catheter 100, a pump assembly 900 arranged at the distal end of the catheter 100 and deliverable by the catheter 100 to the heart of a patient, a distal sensor 600 and a proximal sensor 300 arranged on the pump assembly 900. The pump assembly 900 has a blood inlet 421 located in the ventricle of the patient when it is correctly positioned and a blood outlet 411 located in the vessel of the patient. Specifically, the pump assembly 900 includes a fluid cannula 400, a blood inlet window 420 and a blood outlet window 410 connected to the distal end and the proximal end of the fluid cannula 400 respectively, an impeller 800 arranged in the blood outlet window 410, and a motor 200 connected between the catheter 100 and the blood outlet window 410. The blood inlet 421 is formed on the blood inlet window 420, and the blood outlet 411 is formed on the blood outlet window 410.

[0060] In an exemplary application scenario, the catheter pump system 3000 is used to provide left ventricular assistance for a patient. The pump assembly 900 can be inserted into the subject through percutaneous puncture, pushed forward by the catheter 100 in the aorta AO of the subject until the distal end of the pump assembly 900 passes through the aortic valve AV into the left ventricle LV, so that the fluid cannula 400 spans the aortic valve AV, the blood inlet 421 is located in the left ventricle LV, and the blood outlet 411 is located in the aorta AO. The impeller 800 is connected to the distal end of the drive shaft of the motor 200, so as to be driven to rotate by the motor 200, so as to suck the blood in the left ventricle LV into the fluid cannula 400 through the blood inlet window 420, and pump the blood from the blood outlet window 410 to the aorta AO, so as to assist the pumping function of the heart and reduce the burden on the heart.

[0061] It is worth noting that the catheter pump system 3000 for left ventricular assistance is only one of its possible application scenarios. In other possible and not explicitly excluded scenarios, the catheter pump system 3000 can also be used as right ventricular assistance, and the pump assembly 900 can be intervened into the right ventricle so that the blood inlet 421 is located in the right ventricle and the blood outlet 411 is located in the pulmonary artery. Therefore, the pressures measured by the sensors 600, 300 adjacent to the blood inlet 421 and the blood outlet 411 are different according to different application scenarios. When the catheter pump system 3000 is used for left ventricular assistance, the sensors 300, 600 measure the aortic pressure and the left ventricular pressure respectively. When the catheter pump system 3000 is used for right ventricular assistance, the sensors 300, 600 measure the pulmonary artery pressure and the right ventricular pressure respectively. Hereinafter, the scenario in which the catheter pump 1000 is used for left ventricular assistance is mainly described. However, it can be known from the above description that the protection scope of the embodiment of the application is not limited in this way.

[0062] In the above embodiments, the catheter pump 1000 employs an in-line motor 200 which is formed as part of the pump assembly 900 structure. In other possible embodiments, the motor 200 can also not be part of the pump assembly 900, for example the motor 200 can be an extracorporeal motor. In this case, the motor 200 is connected to the proximal end of the catheter 100 and is located outside the patient's body when the catheter pump 1000 is in operation, and the rotation is transmitted to the impeller 800 through a flexible shaft which is threaded through the catheter 100.

[0063] A cable 500 is threaded through the catheter 100 for electrical and signal connection between the catheter pump 1000 and the controller 2000. The cable 500 includes wires connected to the motor 200 for transmitting electrical signals to the motor 200 to drive the rotation of the motor 200. The cable 500 also includes signal wires connected to the sensors 300, 600 for transmitting the signals measured by the sensors 600, 300 to the controller 2000. The controller 2000 can store the current signals of the motor 200 and the pressure signals measured by the sensors 600, 300 in a memory, and can display the current signals and the pressure signals in association with time, forming waveforms similar to those shown in Figures 1 and 2.

[0064] The sensors 600, 300 can employ any suitable existing configuration, including but not limited to piezoelectric pressure sensors, piezoresistive pressure sensors, fiber-optic pressure sensors, etc., and the present embodiments are not limited in this regard. Corresponding to the various types of pressure sensors described above, the signal wires are cables, cables, and optical fibers, respectively.

[0065] As shown in Figures 9A and 9B, the sensing head of the sensor 600 is adjacent to the blood inlet 421, and the sensing head of the sensor 300 is adjacent to the blood outlet 411. After the pump assembly 900 is properly positioned, the sensor 600 is used to measure the actual pressure LVP in the left ventricle LV at the location of the blood inlet 421, and the sensor 300 is used to measure the actual pressure AOP in the aorta AO at the location of the blood outlet 411. The distal sensor 600 can be disposed outside the blood inlet window 420 and proximal to the blood inlet 421, and the proximal sensor 300 can be disposed outside the blood outlet window 410 and distal to the blood outlet 411.

[0066] In some embodiments, the sensors 600, 300 can not be integrated on the catheter pump 1000, but instead be delivered to the heart chamber with a Swan-Ganz catheter, as long as they can be configured to measure the pressure inside the heart chamber and the pressure inside the vessel, respectively. Preferably, at least one of the sensors 600, 300 is provided on the pump assembly 900 according to the above described arrangement, and more preferably both of the sensors 600, 300 are provided on the pump assembly 900. This integrated design has the additional benefit that the sensors 600, 300 can be delivered to the patient together with the pump assembly 900, and be positioned at the same time when the pump assembly 900 is properly positioned. This eliminates the additional procedure of externally placing the catheter, which is advantageous for reducing the patient's pain and achieving a fast deployment of the procedure. At the same time, the elimination of the external catheter reduces the risk of infection caused by the external catheter.

[0067] Fig. 10 illustrates a procedure 4000 for tracing the source of suction, which can be performed using the catheter pump system 3000 illustrated in Figs. 8, 9A and 9B, specifically by the controller 2000.

[0068] At step 4001, the sensor 300 measures the measured pressure AOP inside the vessel. In the present embodiment, the catheter pump system 3000 is used as a left ventricular assist device, and the measured pressure AOP inside the vessel is the measured pressure in the aorta AO. At step 4002, the distal sensor 600 measures the measured pressure LVP inside the heart chamber. In this case, the measured pressure LVP inside the heart chamber is specifically the measured pressure in the left ventricle LV.

[0069] At step 4003, the estimated pressure LVP' in the left ventricle is obtained using the measured pressure AOP in the aorta, the motor current I and the motor speed ω. The motor current I and the motor speed ω can be obtained by any suitable prior art method, for example, the current I can be measured using a current sensor, and the speed ω can be obtained from the periodic relationship between the current or voltage supplied to the motor and the speed. The estimated pressure LVP' in the left ventricle obtained from the measured AOP, the motor current I and the motor speed ω has been described above and will not be repeated here.

[0070] At step 4004, it is determined whether a suction event has occurred based on a comparison of the estimated pressure LVP' in the left ventricle with a set threshold value (for example, -40 mmHg). If the LVP' is not lower than the set threshold value, it is determined that no suction event has occurred. Otherwise, it is determined that a suction event has occurred. In this case, it is necessary to further determine the source of the suction event.

[0071] In other embodiments, the suction event can also be determined by comparing the motor current I or the measured aortic pressure AOP to their normal values (i.e. the values of the motor current and the aortic pressure when no suction event occurs). As described above, especially with reference to Fig. 5, when a suction event occurs, both the motor current I and the measured aortic pressure AOP decrease. Therefore, the motor current I and the measured aortic pressure AOP can also be used as a basis for determining whether a suction event occurs.

[0072] Since the estimated left ventricular pressure LVP' obtained by using the known parameters including the motor current I and the measured aortic pressure AOP also decreases when a suction event occurs, there is a correlation or linkage between the motor current I, the measured aortic pressure AOP and the estimated left ventricular pressure LVP'. That is, when a suction event occurs, all of them will decrease. Therefore, at least one of them can be used as a basis for determining whether a suction event occurs.

[0073] In the present embodiment, the normal motor current and the normal aortic pressure when no suction event occurs can be pre-stored in the controller 2000. For example, the controller 2000 can store a data table of the normal values of the motor current corresponding to different motor speeds and the normal values of the aortic pressure, which can be obtained by testing in vitro. Since the motor speed for maintaining the required flow rate is constant, the current motor speed can be looked up in the data table to match the same or the closest speed value, and the current motor current I or the measured aortic pressure AOP obtained can be compared with the normal values of the motor current and the normal values of the aortic pressure in the data table. If the measured values decrease compared with the normal values, it can be determined that a suction event occurs.

[0074] Alternatively, the normal values of the motor current and the normal values of the aortic pressure can also be the historical data of the current catheter pump collected and recorded locally in real time before a suction event occurs, and the determination principle is similar to the above. In actual clinical visualization, the waveforms of the historical data of the motor current I and the aortic pressure AOP displayed in real time on the display screen of the controller 2000 will suddenly decrease at a certain time, and maintain at a lower level compared with the time before that for a certain period of time after that.

[0075] It should be noted that the above two methods for determining the normal motor current and the normal aortic pressure when no suction event occurs can also be applied to the determination of other normal values. For example, the normal pressure difference, the normal pump pressure, etc. mentioned below.

[0076] In addition, since the load of the motor changes at different cardiac cycles due to the beating of the heart, maintaining a constant rotation speed usually requires supplying a varying current to the motor, which is manifested in clinical visualization as motor current is also fluctuating (see motor current waveforms 105', 112' in FIG. 1, FIG. 2). This fluctuation of motor current is independent of whether an aspiration event occurs or not, and the peak of the current is not constant but oscillates within a small range (e.g. 10%). Similarly, the valley of the current also follows the same or similar oscillation rule. Therefore, if the peak or valley of the current drops significantly, e.g. beyond the threshold range of 10% mentioned above, it is considered that an aspiration event has occurred. Among them, the threshold range is variable for patients with different blood viscosity and different running time of the pump, such as 8%, 12% or 15% or even 20% and the like.

[0077] The above is to use the drop range of the peak or valley of the current as the basis for judging whether an aspiration event occurs. In other feasible embodiments, the average value of the current can also be used as the basis for judgment. Among them, the calculation method of the current average value can be the average value of the current collected within one or several complete cardiac cycles, or the average value of the peak and valley of the current collected within one complete cardiac cycle. As mentioned above, under normal circumstances, the average value of the current should remain basically constant or slowly decrease within a short period of time (this is due to the gradual wear and tear of the relative rotating parts of the pump, and the decrease of other loads except blood, such as the dynamic sealing load as described below). Therefore, if the average value of the current drops sharply at a certain moment, it is considered that an aspiration event has occurred.

[0078] Referring to the aortic pressure waveforms 102', 109' in FIG. 1, FIG. 2, since the measured pressure AOP in the aorta has the same fluctuation independent of aspiration events as the motor current I. Therefore, using the measured AOP as the basis for judgment, it is also possible to judge whether an aspiration event occurs by comparing the drop range of the peak, valley or average value of AOP with the set threshold range. Among them, the average aortic pressure mAOP can refer to CN115814262A, which will not be repeated here.

[0079] When it is judged that an aspiration event occurs, the controller 2000 can control the operation of triggering the warning to be sent out, such as through the way of flashing or jumping words on the display screen, buzzer alarm, etc., to inform medical staff to take timely disposal measures. Of course, the disposal measures suggested to medical staff can be made according to the cause of the aspiration event as described below, and the cause of the aspiration event and the suggested disposal measures (4008, 4009 in FIG. 10) will be displayed in the form of words on the display screen.

[0080] At steps 4005 and 4006, the suction cause is determined according to the positive or negative of the measured intraventricular pressure LVP. When the value of the measured intraventricular pressure LVP is negative, it is determined that the root cause of the suction event is low preload. And the specific type of the suction event occurring at this time is diastolic / intermittent suction event, and the corresponding treatment means is to reduce the pump speed of 4008 or to supplement the patient with fluid.

[0081] When the value of the measured intraventricular pressure LVP is positive, it means that a systolic / continuous suction event occurs. Further comparison is needed with the normal data of the catheter pump 1000 when no suction event occurs to determine the cause. As introduced above, these normal data can be obtained by experimental means and pre-set locally, or can be real-time recorded and stored as historical data locally.

[0082] Table 1 Parameters of the catheter pump 1000 in normal state

[0083]

[0084] Table 2 Parameters of the simulated catheter pump 1000 under low preload

[0085]

[0086] Table 3 Parameters of the simulated catheter pump 1000 under pump inlet obstruction

[0087]

[0088] Figure 11 shows the curve relationship between the pressure difference ΔP formed by the pump inlet pressure and the pump outlet pressure and the pump flow of the catheter pump 1000 under three conditions of normal, low preload and pump inlet obstruction measured by the test, and the related data is shown in Tables 1 to 3. By comparing the pressure difference ΔP changes (indicated by the dashed arrow in Figure 11) of the catheter pump 1000 operating at the same gear, for example, all at the highest gear, under the three conditions, it can be known that compared with the normal condition, the ΔP increases when the preload is low. When the pump inlet is obstructed, the ΔP decreases. Therefore, according to the change of the ΔP compared with the normal condition, it can be identified whether the systolic / continuous suction event is caused by low preload or pump inlet obstruction.

[0089] The existing scheme cannot identify the suction event when the pump is in the low gear, for two reasons: one is that the probability of suction in the low gear is low; the second is that the low gear means low flow and high pressure difference, in this case, the blood flow field is unstable, and the ΔP at this time is large, and the error of the estimated LVP is large, which leads to misjudgment. And the present application adopts the method of using both the measured LVP and the estimated LVP', so there is no problem of misjudgment caused by large error of estimated LVP' when the pump is in the low gear. Therefore, even in the low gear, the suction event and its cause can be accurately identified.

[0090] At step 4007, the root cause of the suction is determined according to whether the pressure difference ΔP decreases relative to the normal pressure difference value when no suction event occurs. The decrease of the pressure difference ΔP relative to the normal pressure difference determines that the pump is suctioned due to the occlusion of the blood inlet 421. Otherwise, it is determined that the pump is suctioned due to insufficient preload. One of the cases of occlusion of the blood inlet 421 is caused by abnormal positioning of the device as mentioned above, which is commonly known as wall sticking (abbreviated as sticking) of the blood inlet 421 on one side close to the inner wall of the ventricle. For this type of fault, the recommended treatment for medical staff is repositioning as in 4009.

[0091] Since the catheter pump 1000 operates at a substantially constant speed, the generated pump pressure is also substantially constant. Therefore, no matter which one or which several blood inlets are occluded, it will cause the flow rate of blood through other unoccluded blood inlets to increase, and thus the blood pressure on one side of the fluid cannula 400 corresponding to the unoccluded blood inlet 421 decreases. On the contrary, the blood pressure on the side of the fluid cannula 400 corresponding to the occluded blood inlet 421 increases.

[0092] Therefore, the position of the occluded blood inlet 421 can be determined according to the change of the pressure in the pump. Specifically, as shown in FIGS. 9A and 9B, there are multiple blood inlets 421, and at least one internal sensor 700 is arranged in the pump assembly 900 corresponding to each blood inlet 421. The internal sensor 700 can adopt any suitable existing structure, which can be referred to the description of the sensors 300, 600 above, and will not be repeated here.

[0093] The sensor 700 can be fixed on the inner wall of the blood inlet window 420 and located proximally to the corresponding blood inlet port 421. The sensor 700 is connected to the controller 2000 and used to test the blood pressure entering the fluid cannula 400 through the corresponding blood inlet port 421, i.e. the measured internal pressure MIP. Based on the MIP, the comparison between the steps 4010 and 4011 and the normal internal pressure NIP when no suction event occurs can determine the location of the blocked blood inlet port 421 to facilitate the doctor to perform the repositioning operation on the pump assembly 900 by rotating the catheter 100. When the MIP is increased compared with the NIP, it is determined that the blood inlet port 421 on the side where the sensor 700 is located is blocked. Conversely, it is determined that the blood inlet port 421 on the opposite side of the sensor 700 is blocked.

[0094] As can be seen from the above, the sensor 700 can be provided only one, which is arranged in the pump and corresponds to any one of the blood inlet ports 421. The comparison between the MIP and the NIP measured by the one sensor 700 can determine which position or which side of the blood inlet port 421 is blocked.

[0095] For example, as shown in FIG. 9A, the sensor 700 is provided only on the upper blood inlet port 421. When the upper blood inlet port 421 is blocked, the blood flow rate of the lower blood inlet port 421 shown in the figure will increase, and the blood flow rate of the upper blood inlet port 421 will slow down. At this time, the MIP will increase compared with the NIP, and it can be determined that the blood inlet port 421 on the side where the sensor 700 is located, i.e. the upper side, is blocked. Similarly, when the lower blood inlet port 421 shown in the figure is blocked, the same judgment can also be made.

[0096] In addition, the pump inlet wall is usually manifested as when one side of the blood inlet port 421 is blocked, the other side of the blood inlet port 421 opposite to it is not blocked. Therefore, the two MIPs on the opposite sides in the pump inlet often show exactly opposite changes compared with the NIP. Therefore, by using this rule, in some embodiments, the sensor 700 can be provided two and arranged in the pump in an axial symmetry. Then, the opposite changes of the MIPs measured by the two symmetrical sensors 700 compared with the NIP can more accurately identify the location of the blocked blood inlet port 421.

[0097] For example, as shown in FIG. 9B, the upper inlet 421 and the lower inlet 421 are both provided with sensors 700. If the upper inlet 421 is blocked, the blood flow rate of the lower inlet 421 increases, and the blood flow rate of the upper inlet 421 decreases. At this time, compared with the pressure value NIP when no suction occurs, the pressure value MIP2 detected by the lower sensor 700 decreases, and the pressure value MIP1 detected by the upper sensor 700 increases. Under normal circumstances, MIP1=MIP2=NIP when no suction occurs, so it can be determined that the inlet 421 on the side where the upper sensor 700 is located, i.e. the upper inlet 421, is blocked.

[0098] Of course, in other embodiments, a sensor 700 can be provided in the pump corresponding to each inlet 421. In this way, according to the above method, it can be accurately determined which inlet or inlets 421 are blocked.

[0099] The estimated intraventricular pressure LVP' is calculated based on the pressure difference △P calculated from the motor current I and the measured pressure AOP of the vessel, and the motor current I is affected by many factors. For example, in the prior art, only the effect of the pressure difference △P on the motor current I is considered, so in practice only abnormalities that cause changes in the pressure difference △P, such as suction events, can cause changes in the motor current I. Therefore, the pressure difference △P is also referred to as "pump load", which is the largest factor affecting the motor current I. However, the pressure difference △P is only the largest part of the "pump load". Other factors, such as the sealing scheme of the catheter pump 1000, often cannot be ignored in their effect on the motor current I.

[0100] The known solution CN115814262A described above uses a cleaning fluid seal (although this solution does not explicitly state that it uses a cleaning fluid seal, it can be determined from the "cleaning menu" provided on the interface). For the cleaning fluid seal solution, see AU2022379554A1 or US9550017B2. As shown in FIG. 12, the general process of the cleaning fluid seal is as follows: the cleaning fluid is delivered from the cleaning line 122' in the catheter 121' to the motor 123', and after passing through and lubricating the proximal bearing 124' and the motor 123', it finally flows out from the distal bearing 125' to prevent blood from entering the motor 123' from the gap of the distal bearing 125', thereby achieving sealing of the blood. As can be seen, the implementation of this sealing solution has a relatively small impact on the "pump load" throughout the process.

[0101] Compared with the cleaning liquid seal, the dynamic seal has the advantages of simplified structure, low process difficulty, fast deployment of the operation, no cleaning liquid leakage, no blockage and no particle drop to the human body. Generally, the dynamic seal adopts one or more sealing lips to contact the shaft to achieve sealing. In order to achieve the sealing effect, the sealing lip needs to tightly hold the shaft with a certain pre-tightening force. Therefore, the use of the dynamic seal scheme will increase the overall "pump load", so that only part of the finally detected motor current I is used to overcome the differential pressure load. Therefore, for the catheter pump 1000 using the dynamic seal, in order to obtain the accurate differential pressure ΔP, the part of the motor current I' used to overcome the "pump load" (also referred to as the sealing load) due to the dynamic seal needs to be removed.

[0102] As shown in FIG. 13, the force of the sealing lip holding the shaft is not constant. With the passage of time of the pump operation, the wear of the shaft to the sealing lip and the gradual adaptation of the two, the force of the sealing lip holding the shaft gradually decreases and eventually reaches a constant. In addition, the rate of decrease of the holding force of the sealing lip to the shaft is positively correlated with the rotational speed of the shaft. Specifically, the faster the rotational speed of the shaft, the greater the slope of the decay curve. Therefore, the motor current I' used to overcome the sealing load has a decay curve as shown in FIG. 13 over time. The decay curve is obtained by means of in-vitro testing (operating the pump in an unloaded condition without pumping any liquid medium, recording the relationship between the current I' and the time t and the rotational speed of the motor), and is stored in the controller 2000 in the form of a preset data set or a correlation data table. The motor current I is corrected using the decay curve and the preset data set. Specifically, in combination with the current motor rotational speed ω, the rotational speed is matched or interpolated in the preset data set to obtain the same or the closest rotational speed. Then, the dynamic sealing load current I' is determined using the correlation between the obtained operating time t and the matched rotational speed.

[0103] In order to facilitate the explanation of the influence of the decay of the dynamic sealing load on the motor current, the catheter pump 1000 structure of FIGS. 8, 9A and 9B is taken as an example for illustration. In other embodiments, as long as the catheter pump 1000 adopts dynamic sealing, the method of the present application for correcting the motor current based on the dynamic sealing load current is applicable.

[0104] As shown in FIGS. 8, 9A and 9B, the pump assembly 900 includes a pump housing, a drive shaft and a dynamic sealing assembly. The drive shaft can be driven by the motor 200, and the distal end thereof extends from the pump housing for connection of the impeller 800, and the dynamic sealing assembly is arranged between the impeller 800 and the pump housing and surrounds the drive shaft, for preventing blood from entering the pump housing.

[0105] The pump housing and the drive shaft vary with the arrangement of the motor 200. When the motor 200 is in the built-in form as shown in FIGS. 8, 9A and 9B, the motor 200 is part of the structure of the pump assembly 900, and the pump housing is the motor housing and the drive shaft is the motor shaft. When the motor 200 is in the external form, the motor 200 is not part of the structure of the pump assembly 900, and the pump housing is the conduit 100 or a tubular member (generally referred to as a bearing chamber or a connecting tube) connecting the conduit 100 and the pump assembly 900, and the drive shaft is the flexible shaft passing through the conduit 100.

[0106] The dynamic sealing assembly can adopt a known embodiment as provided in CN117717705B or EP0961621B1, which will not be described herein.

[0107] Before the step 4003 of acquiring the motor current I and calculating the estimated intraventricular pressure LVP' based on the motor current I, the motor current I is corrected by performing the steps 4012-4014. That is, the motor current I measured based on the current sensor is subtracted by the current dynamic sealing load current I' to obtain the corrected motor current I only for overcoming the "pressure difference load", and the estimation of LVP' is performed based on the corrected motor current I. In this way, the estimation accuracy of LVP' can be improved, and the judgment accuracy of the subsequent steps, especially the step 4004 involving the motor current I or LVP', can be improved.

[0108] In the correction operation of the motor current I, first, the operation of acquiring the motor running time t in step 4012 is performed, which can be determined based on the time (i.e., the pump starting time) that the controller 2000 provides the motor with electric energy to drive its rotation and the current time. Subsequently, in step 4013, the current dynamic sealing load current I' of the dynamic sealing assembly is determined according to the running time t. Finally, in step 4014, the obtained current dynamic sealing load current I' is subtracted from the detected motor current to obtain the corrected motor current I.

[0109] The relationship between the running time t of the motor and the dynamic sealing load current I' can be calculated by fitting a corresponding function. According to the running time t, the current dynamic sealing load current I' corresponding to the running time t can be obtained by looking up in a mapping table including the corresponding relationship between the running time t and the dynamic sealing load current I'. As shown in FIG. 13, there is a curve relationship between the dynamic sealing load current I' and the running time t of the motor 200. As described above, the curve relationship can be stored locally in a preset data set or an associated data table, and a one-to-one mapping relationship between the dynamic sealing load current I' and the running time of the motor 200 is recorded. The curve or mapping relationship can be expressed as the following formula, and then the current dynamic sealing load current I' can be calculated according to the calculation formula.

[0110] I' = A * exp(-i * w * t) + B;

[0111] wherein I' is the current dynamic sealing load current, unit mA. When the conduit pump 1000 runs for a certain time length, the motor current required to overcome the stable holding force exerted on the shaft by the dynamic sealing does not change;

[0112] A and B are constants related to the performance of the dynamic sealing, mA;

[0113] i is a correction factor constant, dimensionless;

[0114] w is the motor speed, rpm;

[0115] t is the running time length, h.

[0116] As shown in FIG. 14, the controller 2000 includes a processor 901 and a memory 902 connected with the processor 901 in communication. The memory 902 stores instructions executable by the processor 901, and the instructions are executed by the processor 901 to perform the above method steps.

[0117] Obviously, the above described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, other different forms of changes or variations can be made by those skilled in the art without creative labor, and all should belong to the protection scope of the present application.

Claims

1. A catheter pump system, comprising: a catheter; a pump assembly disposed at a distal end of the catheter, deliverable by the catheter to a heart of a patient, having a blood inlet located within a chamber of the patient when properly positioned and a blood outlet located within a vessel of the patient, an impeller drivable by a motor to pump blood from the blood inlet to the blood outlet; a distal sensor having a sensing head adjacent to the blood inlet for measuring a pressure within the chamber; a proximal sensor having a sensing head adjacent to the blood outlet for measuring a pressure within the vessel; a controller connected to the motor, the distal sensor, and the proximal sensor; wherein the controller is configured to: receive a measured pressure within the chamber measured by the distal sensor; receive a measured pressure within the vessel measured by the proximal sensor; obtain a motor current and a motor speed of the motor; calculate an estimated pressure within the chamber based on the measured pressure within the vessel, the motor current, and the motor speed; determine whether a suction event occurs to the pump assembly based on at least one of the estimated pressure within the chamber, the measured pressure within the vessel, and the motor current; when the determination is positive, determine a root cause of the suction event based on a sign of the measured pressure within the chamber.

2. The conduit pump system of claim 1, wherein, when the measured pressure within the chamber is negative, determine that the root cause of the suction event is an insufficient preload.

3. The conduit pump system of claim 1, wherein, when the measured pressure within the chamber is positive, determine the root cause of the suction event based on a change of a measured pressure difference compared to a normal pressure difference when no suction event occurs.

4. The conduit pump system of claim 3, wherein, when the measured pressure difference increases compared to the normal pressure difference, determine that the root cause of the suction event is an insufficient preload.

5. The conduit pump system of claim 3, wherein, when the measured pressure difference decreases compared to the normal pressure difference, determine that the root cause of the suction event is at least partial occlusion of the blood inlet.

6. The conduit pump system of claim 5, wherein, the blood inlet has a plurality of inlets, and the pump assembly has an internal sensor corresponding to at least one of the inlets; the internal sensor is connected to the controller and configured to measure a measured pump internal pressure of blood entering a fluid cannula through the corresponding inlet; the controller is further configured to determine a location of the occluded inlet based on a change of the measured pump internal pressure compared to a normal pump internal pressure when no suction event occurs.

7. The conduit pump system of claim 6, wherein, when the measured pump internal pressure increases compared to the normal pump internal pressure, determine that the inlet on a side where the internal sensor is located is occluded.

8. The conduit pump system of claim 6, wherein, when the measured pump internal pressure decreases compared to the normal pump internal pressure, determine that the inlet on an opposite side of the internal sensor is occluded.

9. The catheter pump system of claim 6, wherein: the internal sensor is two and axially symmetrically disposed within the pump assembly; or each of the inlets is provided with one internal sensor.

10. The conduit pump system of claim 1, wherein, the pump assembly comprises: a pump housing; a drive shaft drivable by the motor, a distal end of the drive shaft extending out of the pump housing for connection of the impeller. A dynamic seal assembly is provided between the impeller and the pump housing and around the drive shaft to prevent blood from entering the pump housing; The controller is further configured to: acquire a running time of the motor; determine a current dynamic seal load current of the dynamic seal assembly according to the running time; subtract the current dynamic seal load current from the motor current to correct the motor current.

11. The conduit pump system of claim 10, wherein, The controller is further configured to: find the current dynamic seal load current in a preset mapping relationship according to the running time, the mapping relationship including a corresponding relationship between running time and dynamic seal load current; or, calculate the current dynamic seal load current according to a calculation formula of running time and dynamic seal load current; The calculation formula is as follows: I'=A*exp(-i*w*t)+B; wherein I' is the current dynamic seal load current, mA; A and B are constants related to dynamic seal performance, mA; i is a correction factor constant, dimensionless; w is the motor speed, rpm; t is the running time, h.

12. The conduit pump system of claim 1, wherein, At least one of the proximal sensor and the distal sensor is provided on the pump assembly.

13. The conduit pump system of claim 1, wherein, The controller is configured to determine that the suction event occurs when the estimated intraventricular pressure is lower than a set threshold, and / or the measured intravascular pressure decreases compared to the normal pressure in the vessel when the suction event does not occur, and / or the motor current decreases compared to the normal motor current of the motor when the suction event does not occur.

14. The conduit pump system of claim 1, wherein, The catheter pump system is used for left ventricular assist; when the pump assembly is correctly positioned, the blood inlet is located in the left ventricle of the patient, and the blood outlet is located in the aorta of the patient.

15. A method for determining the root cause of a suction event of a dual-sensor traceable catheter pump system, the catheter pump system comprising: a catheter; a pump assembly provided at a distal end of the catheter and deliverable by the catheter to a heart of a patient, having a blood inlet located in a ventricle of the patient and a blood outlet located in a vessel of the patient when the pump assembly is correctly positioned, and an impeller driven by a motor to pump blood from the blood inlet to the blood outlet; a distal sensor having a sensing head adjacent to the blood inlet for measuring an intraventricular pressure; a proximal sensor having a sensing head adjacent to the blood outlet for measuring an intravascular pressure; The method comprises: receiving the measured intraventricular pressure measured by the distal sensor; receiving the measured intravascular pressure measured by the proximal sensor; acquiring a motor current and a motor speed of the motor; calculating an estimated intraventricular pressure according to the measured intravascular pressure, the motor current and the motor speed; determining whether the pump assembly has a suction event according to at least one of the estimated intraventricular pressure, the measured intravascular pressure and the motor current; when the determination result is yes, determining the root cause of the suction event according to the positive or negative nature of the measured intraventricular pressure.

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