Detection of hypertension in LVAD patients using rotational speed changes

Abstract

The present disclosure relates to detecting hypertension in LVAD patients using rotational speed changes. A method of detecting hypertension in a patient having an implantable blood pump includes operating the implantable blood pump at a first pump set speed during a first time period. A first flow rate minimum during a cardiac cycle of the patient is measured during the first time period. During a second time period following the first time period, the first pump set speed is reduced by at least 200 rpm to a second pump set speed, the second time period being less than the first time period. A second flow rate minimum is measured during the cardiac cycle during the second time period. If the second flow rate minimum decreases by more than a predetermined amount at the second pump set speed during the second time period, an alert is generated indicating the presence of hypertension.

Description

[0001] This application is a divisional application of the invention patent application with an international application date of 2020-02-11, an international application number of PCT / US2020 / 017587, an application number entering the Chinese national phase of 202080016660.2, and titled "Detecting Hypertension in LVAD Patients Using Speed ​​Changes". Technical Field

[0002] This technology generally involves the detection of hypertension in ventricular assist devices and patients. Background Art

[0003] Patients with ventricular assist devices (VADs) must monitor their blood pressure regularly to maximize the benefit from such devices and to reduce the risk of adverse events associated with hypertension. Unlike some adverse events, such as aspiration in an implantable blood pump, hypertension cannot be resolved by reducing the speed of the pump. However, under normal pump operating conditions, it is difficult to distinguish between aspiration conditions that can be resolved by reducing the pump speed and hypertension that cannot be resolved. Summary of the invention

[0004] The technology disclosed herein generally relates to a method for detecting hypertension in a patient with a ventricular assist device, particularly an implantable blood pump. The method includes operating an implantable blood pump at a first pump set speed during a first time period. At least one of the group consisting of a first flow rate pulsatility and a first current pulsatility is measured during the first time period. During a second time period after the first time period, the first pump set speed is reduced to a second pump set speed. At least one of the group consisting of a second flow rate pulsatility and a second current pulsatility is measured during the second time period. If at least one of the group consisting of the second flow rate pulsatility and the second current pulsatility increases during the second time period at the second pump set speed compared to at least one of the group consisting of the first flow rate pulsatility and the first current pulsatility at the first pump set speed during the first time period, an alarm is generated indicating the presence of hypertension.

[0005] In another aspect, if an alarm is generated indicating the presence of hypertension, the method further includes identifying at least one of the group consisting of a first flow rate pulsatility and a first current pulsatility as a non-pumping waveform at a first pump setting speed during a first time period.

[0006] In another aspect, the second pump speed setting is at least 200 rpm lower than the first pump speed setting.

[0007] In another aspect, the second time period is less than the first time period.

[0008] In another aspect, the first time period and the second time period are continuous during continuous operation of the implantable blood pump.

[0009] In another aspect, the first time period and the second time period are periodic at predetermined time intervals.

[0010] In another aspect, the implantable blood pump is a centrifugal flow blood pump.

[0011] In another aspect, the implantable blood pump is an axial flow blood pump.

[0012] In another aspect, a first flow rate pulsatility and a second flow rate pulsatility are measured.

[0013] In another aspect, a first current ripple property and a second current ripple property are measured.

[0014] In another aspect, the first flow rate pulsatility and the second flow rate pulsatility are determined from at least one of the group consisting of an average and a median of a plurality of cardiac cycles during a respective one of the first time period and the second time period.

[0015] In another aspect, the first current pulsatility and the second current pulsatility are determined from at least one of the group consisting of an average value and a median value of a plurality of cardiac cycles during a respective one of the first time period and the second time period.

[0016] In one aspect, a system for detecting hypertension in a patient with a ventricular assist device, the ventricular assist device including an implantable blood pump, the system including a controller in communication with the implantable blood pump, the controller having a processor, the processor having processing circuitry, the processing circuitry configured to operate the implantable blood pump at a first pump setting speed during a first time period. At least one of the group consisting of a first flow rate minimum and a first current minimum is measured during the first time period. During a second time period after the first time period, the first pump setting speed is reduced to a second pump setting speed. At least one of the group consisting of a second flow rate minimum and a second current minimum is measured during the second time period. If at least one of the group consisting of the second flow rate minimum and the second current minimum decreases by more than a predetermined amount at the second pump setting speed during the second time period, the controller is configured to at least one of the group consisting of increasing the second pump setting speed to the first pump setting speed, and generating an alarm indicating the presence of hypertension.

[0017] In another aspect, if an alarm is generated indicating the presence of hypertension, the processing circuit is further configured to identify at least one of the group consisting of a first flow rate minimum and a first current minimum at a first pump setting speed during a first time period as a non-pumping waveform.

[0018] In another aspect, the second pump speed setting is at least 200 rpm lower than the first pump speed setting.

[0019] In another aspect, the second time period is less than the first time period.

[0020] In another aspect, the first time period and the second time period are continuous during continuous operation of the implantable blood pump.

[0021] In another aspect, the first time period and the second time period are periodic at predetermined time intervals.

[0022] In another aspect, the implantable blood pump is a centrifugal flow blood pump.

[0023] In another aspect, the implantable blood pump is an axial flow blood pump.

[0024] In another aspect, the first flow velocity minimum value and the second flow velocity minimum value are determined from at least one of the group consisting of an average value and a median value of a plurality of cardiac cycles during a respective one of the first time period and the second time period.

[0025] In another aspect, the first current minimum and the second current minimum are determined from at least one of the group consisting of an average and a median of a plurality of cardiac cycles during a respective one of the first time period and the second time period.

[0026] In one aspect, a method for detecting hypertension in a patient having a ventricular assist device, the ventricular assist device including an implantable blood pump, the method comprising operating the implantable blood pump at a first pump set speed during a first time period. Measuring a first flow rate minimum during a cardiac cycle of the patient during the first time period. During a second time period after the first time period, the first pump set speed is reduced by at least 200 rpm to a second pump set speed, the second time period being less than the first time period. Measuring a second flow rate minimum during a cardiac cycle during the second time period. If the second flow rate minimum decreases by more than a predetermined amount at the second pump set speed during the second time period, an alarm is generated indicating the presence of hypertension.

[0027] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] A more complete understanding of the present invention and its attendant advantages and features will be more readily appreciated by referring to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0029] Figure 1 is an exploded view of an implantable blood pump configured according to the principles of the present application;

[0030] Figure 2 is a block diagram illustrating various components of the controller of the present application;

[0031] Figure 3 is a flow chart illustrating a method for detecting hypertension in a patient with an implantable blood pump according to one aspect of the present application;

[0032] Figure 4 is a graph showing HQ curves for an exemplary ventricular assist device at various predetermined pump speed settings;

[0033] Figure 5 is a graph showing exemplary flow rate and current waveforms for a patient with normal blood pressure and corresponding pulsatility at a first predetermined pump setting speed and a second predetermined pump setting speed;

[0034] Figure 6 is a graph showing exemplary flow rate and current waveforms for a patient with normal hypertension and corresponding pulsatility at a first predetermined pump setting speed and a second predetermined pump setting speed;

[0035] Figure 7 is a graph showing the relationship between flow rate pulsatility at a first set rotation speed and a reduced rotation speed that can identify the development of hypertension over a long period of time; and

[0036] Figure 8 is a graph showing the resolution of the suction condition when the impeller speed decreases. DETAILED DESCRIPTION

[0037] It should be understood that the various aspects disclosed herein may be combined in combinations different from those specifically presented in the specification and drawings. It should also be understood that, depending on the example, certain actions or events of any of the processes or methods described herein may be performed in different sequences, may be added, merged, or omitted entirely (e.g., all described actions or events may not be necessary for performing these techniques). In addition, for the purpose of clarity, although certain aspects of the present disclosure are described as being performed by a single module or unit, it should be understood that the techniques of the present disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0038] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored in the form of one or more instructions or codes on a computer-readable medium and may be executed by a hardware-based processing unit. A computer-readable medium may include a non-transitory computer-readable medium, which corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer).

[0039] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, the term "processor" as used herein may refer to any of the foregoing structures or any other physical structure suitable for implementing the described techniques. Moreover, the techniques may be fully implemented in one or more circuits or logic elements.

[0040] Referring now to the drawings, wherein like reference numerals refer to like elements throughout, Figure 1 An exemplary ventricular assist device, and in particular, an implantable blood pump configured in accordance with the principles of the present application, is shown in FIG. 1 and is generally designated “10”. According to one embodiment of the present disclosure, the blood pump 10 includes a static structure or housing 12 that houses components of the blood pump 10. In one configuration, the housing 12 includes a lower housing or first portion 14, an upper housing or second portion 16, and an inlet element 18 or inflow cannula 18 that includes an outer tube 18a and an inner tube 18b. The first portion 14 and the second portion 16 together define a volute-shaped chamber 20 having a main longitudinal axis 22 extending through the first portion 14 and the inflow cannula 18. The chamber 20 defines a radius that gradually increases about the axis 22 to an outlet location on the periphery of the chamber 20. The first portion 14 and the second portion 16 define an outlet 24 that communicates with the chamber 20. The first portion 14 and the second portion 16 also define an isolation chamber (not shown) that is separated from the volute chamber 20 by a magnetically conductive wall. The inflow cannula 18 is generally cylindrical and extends generally from the first portion 14 along an axis 22. The inflow cannula 18 has an upstream or proximal end 26 distal from the second portion 16 and a downstream or distal end 28 proximate to the chamber 20.

[0041] The various parts of the housing 12 described above are fixedly connected to each other so that the housing 12 as a whole defines a continuous closed flow path. The flow path extends from an upstream end 26 at the upstream end of the flow path to an outlet 24 at the downstream end of the flow path. The upstream and downstream directions along the flow path are indicated by arrows U and D, respectively. A post 30 is mounted to the first part 14 along the axis 22. A generally disc-shaped ferromagnetic rotor 32 having a central hole 34 is mounted in the chamber 20 for rotation about the axis 22. The rotor 32 includes a permanent magnet and a flow channel, which is used to transfer blood from the center adjacent to the rotor 32 to the periphery of the rotor 32. In the assembled state, the post 30 is received in the central hole of the rotor 32.

[0042] A first stator or motor 36 having a plurality of coils may be disposed within the first portion 14 downstream of the rotor 32. The first stator 36 may be axially aligned with the rotor along the axis 22 such that when current is applied to the coils in the first stator 36, the electromagnetic force generated by the first stator 36 rotates the rotor 32 and pumps blood. A second stator or motor 38 may be disposed within the second portion 16 upstream of the rotor 32. The second stator 38 may be configured to operate in conjunction with or independently of the first stator 36 to rotate the rotor 32.

[0043] Electrical connectors 41 and 43 ( Figure 1 ) are respectively disposed on the first portion 14 and the second portion 16 for connecting the coil to a power source, such as a controller (not shown). The controller is arranged to apply power to the coil of the pump to generate a rotating magnetic field, which causes the rotor 32 to rotate about the axis 22 in a predetermined first rotational direction (as shown by the arrow in the counterclockwise direction R as viewed from the upstream end of the inflow cannula 18). In other configurations of the blood pump 10, the first direction may be a clockwise direction. The rotation of the rotor 32 propels blood to flow downstream along the flow path, so that the blood moves in the downstream direction D along the flow path and exits through the outlet 24. During rotation, fluid dynamic bearings and magnetic bearings (not shown) support the rotor 32 and maintain the rotor 32 from contacting the surfaces of the elements of the first portion 14 and the second portion 16 during operation.

[0044] The first non-ferrous magnetic disk 40 may be disposed in the first portion 14 upstream of the rotor 32 between the first stator 36 and the rotor 32, and the second non-ferrous magnetic disk 42 may be disposed in the second portion 16 downstream of the rotor 32 between the second stator 38 and the rotor 32. The rotor 32 is configured to rotate between the first disk 40 and the second disk 42 without contacting either disk. The general arrangement of the above components may be similar to that described in the invention by HeartWare, Inc. (the assignee of the present application) and The blood pump 10 used in the MCSD is sold under the name of . The arrangement of components such as magnets, solenoid coils and hydrodynamic bearings used in such pumps and variations of the same general design are described in U.S. Patent Nos. 6,688,861; 7,575,423; 7,976,271; and 8,419,609.

[0045] Other implantable blood pumps 10 contemplated by the present disclosure are those disclosed in U.S. Patent Nos. 8,007,254 and 9,561,313 and are axial flow blood pumps. TM The pump is not currently for sale.

[0046] Reference now Figure 2, the implantable blood pump 10 can communicate with a controller 44 having a control circuit 46 having control circuitry for monitoring and controlling the activation and subsequent operation of one or more motors of the implantable blood pump 10. The controller 44 can also include a processor 48 having processing circuitry, a memory 50, and an interface 52. The memory 50 stores information accessible by the processor 48 and the processing circuitry, including instructions 54 (e.g., a motor control module 55 and a motor monitoring module 57 executable by the processor 20) and / or data 56, which can include, but is not limited to, current 58 supplied to one or more motors of one or more phase motors and pump data 60, which can include flow rate data that can be retrieved, manipulated, and / or stored by the processor 20. The controller 44 can communicate with a power source 58 (e.g., a battery 62) external to the patient.

[0047] Reference now Figure 3 During operation of pump 10, controller 44 may operate implantable blood pump 10 at a first pump set speed S1 of impeller 32 during a first time period (step S100). First pump set speed S1 may be in a range between 1800 rpm and 4000 rpm, for example, and may be a function of the particular pump (whether a centrifugal flow pump or an axial flow pump). For example, Figure 4 As shown in , for each first pump set speed S1, the pump 10 exhibits a specific HQ curve, which generally shows that during normal use, regardless of the set speed, the fluid flow through the pump increases as the pressure head decreases. The fluid flow is also a function of the patient's cardiac cycle, where during diastole, the pressure head is higher and the fluid flow through the pump 10 decreases, while during systole, the pressure head decreases and the fluid flow through the pump 10 increases. During normal operation at the first pump set speed S1, the current waveform and the flow rate waveform can be measured in real time and monitored by the controller 44 (step S102). As used herein, "hypertension" or "hypertensive" refers to high blood pressure or surgery in the flat region of the HQ curve.

[0048] In one configuration, such as Figure 5 As shown in FIG. 1 , during a first time period T1 at a first pump setting speed S1 of 2600 RPM, a patient with normal blood pressure exhibits a first flow pulsatility of about 3.9 L / min and a first current pulsatility of about 0.25 A. In one configuration, as Figure 6 As shown in FIG. 1 , during the first time period T1 at the first pump setting speed S1 2400 RPM, the patient with hypertension exhibits a first flow rate pulsatility of about 5.7 L / min and a first current pulsatility of about 0.35 A. Therefore, the patient with hypertension has a greater flow rate and current pulsatility than the patient with normal blood pressure. For example, Figure 5 and Figure 6 As shown in FIG. 1 , the controller 44 may reduce the speed of the impeller 32 by a predetermined amount to a second pump set speed S2 of the impeller 32 during the second time period T2 (step S104). Figure 5 and Figure 6 As shown in FIG. 1 , the first pump set speed S1 is reduced by 200 RPM, to a second pump set speed S2 of 2200 RPM and 2400 RPM, respectively. The second time period T2 may be less than, equal to, or longer than the first time period T1. Optionally, the time period T1 during which the set speed is normal and the time period T2 during which the set speed is reduced may be operated periodically and / or continuously as part of the normal operation of the blood pump or as part of a normal impeller 32 cleaning cycle in which the impeller 32 speed is reduced and then increased to prevent the formation of blood clots on the impeller 32.

[0049] During the second time period T2 of the reduced set speed S2, the flow rate and the current are measured (step S106). If the second flow rate pulsatility or the second current pulsatility increases at the second pump set speed S2 during the second time period T2, the controller 44 may determine that the patient exhibits hypertension (step 108) as compared to the first flow rate pulsatility or the first current pulsatility at the first pump set speed S1 during the first time period T1. For example, if Figure 5 As shown in FIG. 1 , during the second time period T2 at the second pump setting speed S2, the second flow rate pulsatility decreases from 3.9 L / min to 3.1 L / min, and during the second time period T2 at the second pump setting speed S2, the second current pulsatility decreases from 0.25 A to 0.24 A. This decrease in current and / or flow rate pulsatility indicates that the patient has normal blood pressure. However, as Figure 6 As shown in FIG. 4 , during the second time period T2 at the second pump setting speed S2, the second flow rate pulsatility increases from 5.7 L / min, which is already higher than the normal value, to 7.1 L / min, and during the second time period T2 at the second pump setting speed S2, the second current pulsatility increases from 0.35 A, which is already higher than the normal value, to 0.38 A. This increase in current and / or flow rate pulsatility indicates hypertension, which can be determined by the controller 44. The measured flow rate pulsatility or current pulsatility can also be based on the measured average or median value of the corresponding pulsatility at T1 and / or T2.

[0050] In another method of detecting hypertension, during operation of the blood pump 10, a minimum flow rate or current during T1 at a first pump setting speed S1 may be measured. The minimum flow rate or current may be measured during a single cardiac cycle during T1, may be an average of the minimum flow rate or minimum current detected from each of a plurality of cardiac cycles during T1, or may be a median of the minimum flow rate or minimum current detected from each of a plurality of cardiac cycles during T1. The controller 44 may then reduce the impeller 32 speed to S2 during T2, and then measure the minimum flow rate or current during T2, which may be measured during a single cardiac cycle during T2, may be an average of the minimum flow rate or minimum current detected from each of a plurality of cardiac cycles during T2, or may be a median of the minimum flow rate or minimum current detected from each of a plurality of cardiac cycles during T2, depending on how the minimum flow rate or current minimum is measured during T1. If the minimum flow rate or current minimum value measured at S2 decreases by more than a predetermined amount during T2, the controller 44 may indicate the presence of hypertension by generating an alarm as described above, and / or the controller may instruct the set speed of the impeller 32 to remain at S2 or return to a set speed equal to or greater than S1. The predetermined reduction in current may be based on empirical values ​​for patients with normal blood pressure. For example, Figure 5 As shown in FIG. 1 , the minimum flow or current value of a normotensive patient measured at S2 during T2 decreases less than the minimum flow or current value of a hypertensive patient measured at S2 during T2. Figure 5 In the experiment, the minimum flow rate under S2 during T2 was about 1 L / min, while during Figure 6 In patients with hypertension it is close to 0 L / min.

[0051] Reference now Figure 7 and Figure 8 If a suction condition exists, the increased pulsation of flow and / or current, and / or the decrease in the minimum value of flow and / or current, is measured by controller 44, and reducing the set speed of impeller 32 should resolve or not exacerbate the condition. For example, if Figure 8 As shown in FIG. 1 , when the impeller 32 speed is reduced, the measured flow rate pulsatility and current pulsatility decrease. However, if during T2 the pulsatility increases or the minimum flow rate or minimum current decreases at the reduced set speed, the controller 44 can mark the log file and / or generate an alarm in real time indicating the presence of hypertension, whether visual, tactile or audio, rather than the current or flow rate waveform associated with the puff, and notify other puff-related algorithms that hypertension is present. Therefore, such a determination may result in a modification of the puff detection criteria thereafter.

[0052] Those skilled in the art will appreciate that the present invention is not limited to the contents specifically shown and described above. In addition, unless mentioned to the contrary above, it should be noted that all drawings are not drawn to scale. According to the above teachings, various modifications and variations can be made without departing from the scope and spirit of the present invention, and the scope and spirit of the present invention are limited only by the appended claims.

Claims

1. A system for detecting hypertension in a patient having a ventricular assist device, the ventricular assist device comprising an implantable blood pump, the system comprising: Memory; as well as a controller coupled to the memory, the controller comprising circuitry and configured to: operating the implantable blood pump at a first pump speed setting during a first time period; measuring a first pulsatility during the first time period, the first pulsatility corresponding to at least one of a first flow rate pulsatility or a first current pulsatility; reducing the first pump speed setting to a second pump speed setting during a second time period after the first time period; measuring a second pulsatility during the second time period, the second pulsatility corresponding to at least one of a second flow rate pulsatility or a second current pulsatility; as well as Responsive to the second pulsatility being increased at the second pump speed setting during the second time period as compared to the first pulsatility at the first pump speed setting during the first time period, it is identified that the patient is exhibiting hypertension.

2. The system of claim 1 , wherein the controller is further configured to generate an alarm identifying that the patient has exhibited hypertension in response to an increase in the second pulsatility at the second pump setting speed during the second time period as compared to the first pulsatility at the first pump setting speed during the first time period. 3 . The system of claim 1 , wherein the second pump speed setting is at least 200 rpm lower than the first pump speed setting. The system of claim 1 , wherein the second time period is less than the first time period.

5. The system of claim 1, wherein the first time period and the second time period are continuous during continuous operation of the implantable blood pump.

6. The system of claim 5, wherein the first time period and the second time period are periodic at predetermined time intervals.

7. The system of claim 1, wherein the implantable blood pump is a centrifugal blood pump.

8. The system of claim 1, wherein the implantable blood pump is an axial flow blood pump.

9. The system of claim 1, wherein the first pulsatility corresponds to the first flow rate pulsatility and the second pulsatility corresponds to the second flow rate pulsatility.

10. The system of claim 1, wherein the first pulsatility corresponds to the first current pulsatility, and the second pulsatility corresponds to the second current pulsatility.

11. A non-transitory computer readable medium comprising instructions executable by a processing unit to perform a method for detecting hypertension in a patient having a ventricular assist device, the ventricular assist device comprising an implantable blood pump, the method comprising: operating the implantable blood pump at a first pump speed setting during a first time period; determining a first minimum value during a first time period, the first minimum value corresponding to at least one of a first flow rate minimum value or a first current minimum value; reducing the first pump speed setting to a second pump speed setting during a second time period after the first time period; determining a second minimum value during the second time period, the second minimum value corresponding to at least one of a second flow rate minimum value or a second current minimum value; as well as Responsive to a decrease in the second minimum value during the second time period compared to the first minimum value during the first time period, identifying that the patient has exhibited hypertension.

12. The non-transitory computer readable medium of claim 11, wherein the method further comprises: In response to the second minimum value being decreased during the second period as compared to the first minimum value during the first period, the second pump speed setting is increased.

13. The non-transitory computer readable medium of claim 11, wherein the method further comprises: In response to the second minimum value decreasing during the second time period as compared to the first minimum value during the first time period, an alarm is generated.

14. The non-transitory computer-readable medium of claim 11, wherein the second time period is less than the first time period.

15. The non-transitory computer-readable medium of claim 11, wherein the first time period and the second time period are continuous during continuous operation of the implantable blood pump.

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