Method for extracting and quantifying the end-diastolic point / mitral valve closure point from the flow waveform estimated from the hvad

Abstract

A control circuit for a sensorless implantable blood pump configured to determine mitral regurgitation includes processing circuitry configured to generate an estimated blood flow waveform from the sensorless implantable blood pump and generate an alert if a measured amplitude of the estimated blood flow waveform does not include an inflection point between end diastole and initial systole.

Description

Technical Field

[0001] This application generally relates to a system for determining mitral valve function and cardiac preload in patients with implantable blood pumps. Background Technology

[0002] Implantable blood pumps can be used to help patients with advanced heart disease. A blood pump operates by drawing blood from the patient's vascular system and pushing it back into the vascular system. By increasing the momentum and pressure of the blood flow, the blood pump can augment or replace the heart's pumping action. For example, a blood pump can be configured as a ventricular assist device (VAD). In the case of using a VAD to assist the pumping action of the left ventricle, the device draws blood from the left ventricle of the heart and drains it into the aorta.

[0003] In cardiac physiology, preload is defined as the initial stretch of cardiomyocytes before contraction. Since sarcomere length cannot be directly measured, other preload indices such as left atrial pressure (LAP), left ventricular end-diastolic pressure, and ventricular end-diastolic volume (EDV) are used to define preload. In a failing heart, preload does not necessarily increase stroke volume because the ventricles cannot be stretched further, leading to systemic congestion or edema. In mechanical circulatory support (MCS) therapy, a VAD is placed in the left and / or right ventricles to assist the failing ventricles in diverting available / remaining blood from the ventricles into the systemic / pulmonary circulation for proper perfusion. Operating the pump at a predetermined set rate maintains physiologically appropriate output and prevents ventricular overfilling / pumping due to under- or over-pumping. However, current-loaded VAD devices lack effective preload tracking methods to obtain preload information or are configured to determine mitral regurgitation without direct sensor use. Summary of the Invention

[0004] The techniques disclosed herein generally relate to predicting mitral valve status using the rising phase from the trough to the peak of an HVAD-estimated flow waveform. Under normal physiological conditions, the mitral valve closing point, recorded by a notch in the waveform, varies based on ventricular pressure. At higher pulmonary capillary wedge pressures (PCWP), the mitral valve must resist greater pressure, causing a shift in the point. Therefore, the distance between the notch and the waveform trough can be used as a proxy for ventricular volume or preload. The proposed method provides a non-invasive way to extract preload information from an HVAD current waveform that reflects preload variations in its morphology.

[0005] In one aspect, a control circuit for a sensorless implantable blood pump configured to determine mitral regurgitation includes processing circuitry configured to generate an estimated blood flow waveform from the sensorless implantable blood pump and to generate an alarm if the measured amplitude of the estimated blood flow waveform does not include an inflection point between end-diastole and early-systole.

[0006] In another aspect of this embodiment, the blood flow waveform is estimated based on the current supplied to the sensorless implantable blood pump.

[0007] In another aspect of this embodiment, the sensorless implantable blood pump is a ventricular assist device.

[0008] In another aspect of this embodiment, the sensorless implantable blood pump is a centrifugal pump.

[0009] In another aspect of this embodiment, the sensorless implantable blood pump is electrically connected to at least one of the group consisting of an implantable controller and an external controller.

[0010] In another aspect of this embodiment, the control circuit is further configured to periodically measure the amplitude of the estimated blood flow between the end of diastole and the beginning of systole.

[0011] In another aspect of this embodiment, the absence of the inflection point indicates mitral regurgitation.

[0012] In another aspect of this embodiment, the generated alerts include prompts to adjust the speed of the sensorless implantable blood pump.

[0013] In another embodiment, a control circuit for a sensorless implantable blood pump includes processing circuitry configured to generate at least one of a group consisting of estimated current waveforms and flow waveforms from the sensorless implantable blood pump; determine a mitral valve closure point from at least one of the estimated current waveforms and flow waveforms from the sensorless implantable blood pump; calculate a preload relative index; compare the preload relative index with a normal baseline preload relative index; and adjust the pump speed based on the comparison.

[0014] In another aspect of this embodiment, the processing circuit is configured to calculate the relative preload index by dividing the measured amplitude between the mitral valve shut-off point and at least one trough estimated in the group consisting of current waveforms and flow waveforms by the measured amplitude between at least one peak and trough in the group consisting of current waveforms and flow waveforms.

[0015] In another aspect of this embodiment, the sensorless implantable blood pump is a ventricular assist device.

[0016] In another aspect of this embodiment, the sensorless implantable blood pump is a centrifugal pump.

[0017] In another aspect of this embodiment, the processing circuitry is configured to generate an alarm if the preload index deviates from the normal baseline preload relative index by a predetermined percentage.

[0018] In another aspect of this embodiment, the processing circuit is configured to increase the pump speed if the relative preload index is greater than a predetermined percentage of the normal baseline relative preload index.

[0019] In another aspect of this embodiment, the predetermined percentage is between 5% and 15%.

[0020] In another aspect of this embodiment, the processing circuit is configured to reduce the pump speed if the relative preload index is less than a predetermined percentage of the normal baseline preload.

[0021] In another aspect of this embodiment, the predetermined percentage is between 5% and 15%.

[0022] In another embodiment, a control circuit for a sensorless implantable blood pump includes processing circuitry configured to: generate at least one from a group consisting of estimated current and flow waveforms from the sensorless implantable blood pump; determine a mitral valve closure point from the at least one estimated from the group consisting of current and flow waveforms from the sensorless implantable blood pump; calculate a relative preload index by dividing the measured amplitude between the mitral valve closure point and a trough of the at least one estimated from the group consisting of current and flow waveforms by the measured amplitude between a peak and a trough of the at least one from the group consisting of current and flow waveforms; compare the relative preload index with a normal baseline preload; and generate an alarm if the relative preload index deviates from the normal baseline preload by 5% to 15%.

[0023] Details of one or more aspects of this disclosure are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the technology described in this disclosure will be apparent from the description and drawings and from the claims. Attached Figure Description

[0024] A more complete understanding of the invention, along with its accompanying advantages and features, will be more readily apparent when considered in conjunction with the accompanying drawings, by referring to the following detailed description, in which:

[0025] Figure 1 This is an exploded view of an implantable blood pump constructed based on the principles of this application;

[0026] Figure 2 It is a graph showing the estimated flow waveform and the position of the mitral valve closure point as exercise increases under various training conditions;

[0027] Figure 3It is a graph showing the estimated flow waveform in a patient with moderate mitral regurgitation;

[0028] Figure 4 It is a graph showing the estimated flow waveform in a patient with mild mitral regurgitation;

[0029] Figure 5 This is a graph showing the estimated return of the preload to normal after the pump speed is increased;

[0030] Figure 6 It is a graph showing the calculation of the relative index of the front load; and

[0031] Figure 7 This is a flowchart illustrating the steps for determining cardiac preload in a patient with an implantable blood pump. Detailed Implementation

[0032] In one or more instances, the technology may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include non-transitory computer-readable media, which corresponds to tangible media such as data storage media (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 is accessible by a computer).

[0033] The instructions can 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 arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the term "processor" as used herein can refer to any of the foregoing structures or any other physical structure suitable for implementing the technology. Furthermore, the technology can be fully implemented in one or more circuit or logic elements.

[0034] Referring now to the accompanying drawings, in which the same reference numerals denote the same elements, Figure 1An exemplary sensorless blood pump constructed according to the principles of this application is shown, generally designated "10". The blood pump 10 according to one embodiment of this disclosure includes a static structure or housing 12 housing the 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 portion or inflow sleeve 18 including an outer tube 18a and an inner tube 18b. The first portion 14 and the second portion 16 cooperatively define a spiral chamber 20 having a main longitudinal axis 22 extending through the first portion and the inflow sleeve 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 communicating with the chamber 20. The first portion 14 and the second portion 16 also define an isolation cavity (not shown) separated from the spiral chamber 20 by a magnetically conductive wall.

[0035] The inflow sleeve 18 is generally cylindrical and extends from the first portion 14 and generally along axis 22. The inflow sleeve 18 has an upstream end or proximal end 26 away from the second portion 16 and a downstream end or distal end 28 near the chamber 20. The components of the aforementioned housing 12 are fixedly connected to each other such that the housing 12 as a whole defines a continuous, closed flow path. The flow path extends from the upstream end 26 at the upstream end of the flow path to the outlet 24 at the downstream end of the flow path. Along the upstream and downstream directions of the flow path... Figure 1 The arrows U and D represent the axes 22, respectively. A column 30 is mounted to the first portion 14 along axis 22. A generally disc-shaped ferromagnetic rotor 32, having a central bore 34, is mounted within the chamber 20 for rotation about axis 22. The rotor 32 includes permanent magnets and flow channels for transferring blood from near the center of the rotor 32 to its periphery. In the assembled state, the column 30 is received in the central bore of the rotor 32. A first stator 36 having multiple 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 axis 22 such that when current is applied to the multiple coils in the first stator 36, the electromagnetic force generated by the first stator 36 causes the rotor 32 to rotate and pump blood. A second stator 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 to rotate the rotor 32.

[0036] Electrical connectors 41 and 43 are respectively disposed on the first stator 36 and the second stator 38 for connecting the coils to a power source (e.g., a controller 45), which may be implanted inside or outside the patient's body. The controller 45 is arranged to apply power to the pump's coils to generate a rotating magnetic field that causes the rotor 32 to rotate about axis 22 in a predetermined first rotational direction, for example by... Figure 1The direction R indicated by the middle arrow, i.e., from the upstream end of the inflow sleeve 18, is counterclockwise. In other configurations of the blood pump 10, the first direction may be clockwise. Rotation of the rotor 32 causes blood to flow downstream along the flow path, such that the blood moves downstream in the flow path in the downstream direction D and exits through the outlet 24. During rotation, a hydrodynamic bearing and a magnetic bearing (not shown) support the rotor 32 and keep the rotor 32 from contacting the elements of the first part 14 and the second part 16 during operation, as discussed in more detail below. The overall arrangement of the above-described components may be similar to the blood pump 10 used in the MCSD sold by HeartWare, Inc. under the name HVAD, the assignee of this application. The arrangement of components such as magnets, electromagnetic coils, and hydrodynamic bearings used in such pumps, as well as variations of the same overall design, are described in U.S. Patent Nos. 6,688,861, 7,575,423, 7,976,271, and 8,419,609, the disclosure of which is incorporated herein by reference.

[0037] Now for reference Figure 2 In one configuration, controller 45 is configured to provide 50Hz high-resolution data of pump 10 parameters, such as speed, current, and voltage, as well as flow estimation calculations. In another configuration, controller 45 maintains a constant pump set speed for impeller 32, selected by the user. The pump set speed is set to provide sufficient positive flow through the pump, i.e., pump 10 generates sufficient pressure to overcome the systemic pressure of positive flow. An increase in pump preload, i.e., a larger volume in the ventricles or a decrease in systemic resistance, can contribute to positive flow because in both cases, the pressure differential across the pump decreases. During a normal cardiac cycle, pump flow will increase as the pressure differential decreases (i.e., cardiac contraction) and decrease as the pressure differential across the pump increases (i.e., cardiac diastole). Additionally, aortic and mitral valve operations can cause changes in flow patterns, which can be reflected in the morphology of the estimated flow waveform, and can be used as a marker to identify the valve operational state. For example, as... Figure 2 As shown, under normal physiological conditions, the mitral valve closure point, based on ventricular pressure, is represented by the change in the estimated flow rate slope, which... Figure 2 The box is represented by a notch. At higher pulmonary capillary wedge pressures (PCWP), the mitral valve must resist more pressure, causing a shift in the mitral valve closure point. Therefore, the slope change and the distance to the estimated flow waveform trough can be used as a substitute for ventricular volume or preload, as discussed in more detail below.

[0038] Now for reference Figures 3 to 4Abnormalities, such as mitral regurgitation associated with mitral valve dysfunction, can also be reflected in the estimated flow waveform. The waveform morphology changes based on the severity of the regurgitation. Based on available clinical data, the severity of mitral regurgitation (MR) is categorized as control / mild (no MR), mild, and mild-moderate. As severity increases, the mitral closure point disappears because the valve does not close completely, and the trough appears flat and does not include an inflection point or notch. In other words, when mitral valve function is normal, the amplitude of the estimated flow waveform includes the inflection point between end-diastole and early systole. When mitral valve function is abnormal, the inflection point disappears.

[0039] In one configuration, the controller 45 has a control circuit 46 that includes processing circuitry configured to compare a first amplitude 47 of an estimated flow waveform at a predetermined interval, for example, during end-diastole, with a second amplitude 49 of an estimated flow waveform at a predetermined normal baseline during the same time period. Figure 2 For example, the normal baseline estimated flow waveform can be derived from a patient's or from a normally known baseline from a patient who does not exhibit MR. Such a baseline includes an inflection point in the amplitude between end-diastole and early systole. Control circuitry 46 is further configured to determine whether the first amplitude 47 includes an inflection point, for example, by a point between end-diastole and early systole where the amplitude becomes negative or flattens. If there is no point between end-diastole and early systole where the first amplitude 47 changes slope or becomes negative, control circuitry 46 can generate an alarm indicating MR. The evaluation of the first amplitude 47 for comparison can be performed during a single time cycle, during a single cardiac cycle, or at intervals between multiple cardiac cycles. Figures 3 to 4 As shown, the amplitude between end-diastole and early systole flattens as the severity of MR increases.

[0040] Now for reference Figure 5 Left ventricular pressure (LVP) is a factor driving the flow of pump 10, and the end-diastolic pressure point generates a change in slope in the estimated flow waveform, corresponding to the mitral valve closing point as discussed above. For a given preload, the pressure required to close the mitral valve depends on the LVP. As the preload increases, the mitral valve resists the increase in pressure to close, and the mitral valve closing point shifts upward in the waveform. The percentage or magnitude of the shift in the mitral valve closing point relative to the LVP change can be monitored to provide information about ventricular preload. For example, when a person exercises, the preload increases to accommodate the increased blood flow demand. Figure 5As shown, this graph illustrates the effect of impeller speed 32 on preload. Patients initially operated at a baseline impeller speed of 32 (2600 RPM), performing exercises at 0W, 15W, and 60W. For a given speed, the preload increased. When the speed was increased to 2920 RPM, the same exercise was performed again. The preload level decreased compared to the preload at the lower speed of 2600 RPM.

[0041] Now for reference Figures 6 to 7 Control circuit 46 can be configured to generate an estimated current or flow waveform from sensorless implantable blood pump 10 (step 100). In the non-MR patent, the estimated current or flow waveform can be obtained from measured current information from pump 10. Control circuit 46 can then extract the patient's cardiac systolic-diastolic cycle based on the estimated current or flow waveform and determine the mitral valve closure point. The mitral valve closure point can then be determined, and the amplitude of the estimated flow waveform or current waveform can be measured at the mitral valve closure point. Control circuit 46 can then calculate the patient preload relative index (PRI) (step 102), which is a relative index of preload for a specific patient, calculated using the following formula, such as... Figure 6 As shown:

[0042]

[0043] That is, PRI is equal to the amplitude of the current or flow between the mitral valve closure point and the trough divided by the current or flow from the peak to the trough. As preload increases, left atrial pressure increases, and the end-diastolic point of the heart shifts upward, and vice versa. The percentage increase or decrease in the calculated PRI is compared with the normal baseline preload relative index range to determine whether the speed of impeller 32 should be changed based on the calculated PRI. In particular, if the calculated PRI is greater than the normal baseline PRI range (step (104)) for example 5 to 15%, which means there is excess volume and therefore excess pressure in the ventricle, the control circuit 46 may increase the speed of impeller 32. If pump 10 is already running at maximum speed, PRI is remeasured after a predetermined cycle and compared with the normal baseline PRI range before making a speed change. If PRI is less than the normal baseline range (step 106), for example 5 to 15%, the speed of impeller 32 may be decreased. If pump 10 is already running at minimum speed, PRI is remeasured after a predetermined cycle and compared with the normal baseline PRI range before making a speed change.

[0044] Now refer to Figure 5 The above method can be used to restore a patient's preload index to normal baseline preload. For example, when measured at, say, 2600 RPM or 2920 RPM, the patient's preload increase due to exercise in watts is represented by the R...2 The values ​​show a high correlation with the predicted values ​​of the preload index compared to the methods described above. In particular, at 2920 RPM, the preload index returns to the normal baseline pressure as the impeller speed 32 increases.

[0045] Example 1. A control circuit for a sensorless implantable blood pump, comprising processing circuitry configured to generate at least one of a group consisting of estimated current waveforms and flow waveforms from the sensorless implantable blood pump; and to determine the mitral valve closure point from at least one of the estimated current waveforms and flow waveforms from the sensorless implantable blood pump.

[0046] Calculate the relative index of preload;

[0047] Compare the aforementioned preload relative index with the normal baseline preload relative index; and

[0048] The speed of the pump is adjusted based on the comparison.

[0049] Example 2. The control circuit according to Example 1, wherein the processing circuit is configured to calculate the preload relative index by dividing the measured amplitude between the mitral valve closure point and the trough of at least one of the estimated waveforms in the group consisting of current waveforms and flow waveforms by the measured amplitude between the peak value and the trough of at least one of the waveforms in the group consisting of current waveforms and flow waveforms.

[0050] Example 3. The control circuit according to any one of the above examples, wherein the sensorless implantable blood pump is a ventricular assist device.

[0051] Example 4. The control circuit according to any one of the above examples, wherein the sensorless implantable blood pump is a centrifugal pump.

[0052] Example 5. A control circuit according to any one of the above examples, wherein the processing circuit is configured to generate an alarm if the preload index deviates from the normal baseline preload relative index by a predetermined percentage.

[0053] Example 6. A control circuit according to any one of the preceding examples, wherein the processing circuit is configured to increase the speed of the pump if the relative preload index is greater than a predetermined percentage of the normal baseline relative preload index.

[0054] Example 7. The control circuit according to any one of the above examples, wherein the predetermined percentage is between 5% and 15%.

[0055] Example 8. A control circuit according to any one of the above examples, wherein the processing circuit is configured to reduce the speed of the pump if the relative preload index is less than a predetermined percentage of the normal baseline preload.

[0056] Example 9. A control circuit for a sensorless implantable blood pump, comprising:

[0057] Processing circuit, the processing circuit being configured to:

[0058] Generate at least one of the group consisting of estimated current waveforms and flow waveforms from a sensorless implantable blood pump;

[0059] The mitral valve closure point is determined by estimating at least one of the current and flow waveforms from a sensorless implantable blood pump.

[0060] The relative preload index is calculated by dividing the measured amplitude between the mitral valve closure point and the trough of at least one of the estimated waveforms in the group consisting of current and flow waveforms by the measured amplitude between the peak value and the trough of at least one of the waveforms in the group consisting of current and flow waveforms.

[0061] The relative preload index was compared to the normal baseline preload; and

[0062] An alarm is generated if the relative preload index deviates from the normal baseline preload by 5% to 15%.

[0063] Those skilled in the art will understand that the present invention is not limited to what has been specifically shown and described above. Furthermore, unless otherwise stated above, it should be noted that all drawings are not to scale. Various modifications and variations are possible based on the foregoing teachings without departing from the scope and spirit of the invention, the scope and spirit of which are defined only by the appended claims.

Claims

1. A control circuit for a sensorless implantable blood pump configured to determine mitral regurgitation, comprising: a processing circuit configured to: Estimated blood flow waveforms are generated from the sensorless implantable blood pump; An alarm is generated if the measured amplitude of the estimated blood flow waveform does not include the inflection point between the end of diastole and the beginning of systole.

2. The control circuit of claim 1, wherein the estimated blood flow waveform is based on the current supplied to the sensorless implantable blood pump.

3. The control circuit according to claim 1, wherein the sensorless implantable blood pump is a ventricular assist device.

4. The control circuit according to claim 1, wherein the sensorless implantable blood pump is a centrifugal pump.

5. The control circuit of claim 1, wherein the sensorless implantable blood pump is electrically connected to at least one of the group consisting of an implantable controller and an external controller.

6. The control circuit of claim 1, wherein the control circuit is further configured to periodically measure the amplitude of the estimated blood flow between the end of diastole and the beginning of systole.

7. The control circuit according to claim 1, wherein the absence of the inflection point indicates mitral regurgitation.

8. The control circuit of claim 1, wherein the generated alarm includes a prompt to adjust the speed of the sensorless implantable blood pump.

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