Patent Description:
Patients with ventricular assist devices, VADs, must routinely have their blood pressure monitored to maximize the benefits received from such devices and reduce the risk of adverse events associated with hypertension. Unlike some adverse events, such as suction 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 a suction condition, which can be resolved by reducing pump speed, versus hypertension which cannot.

Relevant prior art is for instance disclosed in documents <CIT>, <CIT> and <CIT>.

A system according to the present invention comprises the technical features as defined in independent claim <NUM>.

The techniques of this disclosure generally relate to a method (not claimed) of detecting hypertension in a patient having a ventricular assist device, and in particular an implantable blood pump. The method includes operating the implantable blood pump at a first pump set speed during a first period of time. At least one from the group consisting of a first flow rate pulsatility and a first current pulsatility is measured during the first period of time. The first pump set speed is reduced during a second period of time after the first period of time to a second pump set speed. At least one from the group consisting of a second flow rate pulsatility and a second current pulsatility is measured during the second period of time. If the at least one from the group consisting of the second flow rate pulsatility and the second current pulsatility increases during the second period of time at the second pump set speed compared to the at least one from the group consisting of the first flow rate pulsatility and the first current pulsatility at the first pump set speed during the first period of time, an alert is generated indicating a presence of hypertension.

In another aspect, if the alert is generated indicating the presence of hypertension, the method further includes identifying the at least one from the group consisting of the first flow rate pulsatility and the first current pulsatility at the first pump set speed during the first period of time as a non-suction waveform.

In another aspect, the second pump set speed is at least <NUM> rpm less that the first pump set speed.

In another aspect, the second period of time is less than the first period of time.

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

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

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

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

In another aspect, the first flow rate pulsatility and the second flow rate pulsatility are measured.

In another aspect, the first current pulsatility and the second current pulsatility are measured.

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

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

In one aspect, a system for detecting hypertension in a patient having a ventricular assist device, the ventricular assist device including an implantable blood pump, includes a controller in communication with the implantable blood pump, the controller having a processor having processing circuity, the processing circuitry being configured to operate the implantable blood pump at a first pump set speed during a first period of time. At least one from the group consisting of a first flow rate minimum and a first current minimum is measured during a first period of time. The first pump set speed is reduced during a second period of time after the first period of time to a second pump set speed. At least one from the group consisting of a second flow rate minimum and a second current minimum is measured during the second period of time. If the at least one from the group consisting of the second flow rate minimum and the second current minimum decreases during the second period of time at the second pump set speed more than a predetermined amount, the controller is configured to at least one from the group consisting of increase the second pump set speed to the first pump set speed and generate an alert indicating a presence of hypertension.

In another aspect, if the alert is generated indicating the presence of hypertension, the processing circuity is further configured to identify the at least one from the group consisting of the first flow rate minimum and the first current minimum at the first pump set speed during the first period of time as a non-suction waveform.

In another aspect, the first flow rate minimum and the second flow rate minimum are determined from at least one from the group consisting of a mean and a median from a plurality of cardiac cycles during the respective one of the first period of time and the second period of time.

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

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

Referring now to the drawings in which like reference designators refer to like elements there is shown in <FIG> an exemplary ventricular assist device, and in particular, an implantable blood pump constructed in accordance with the principles of the present application and designated generally "<NUM>. " The blood pump <NUM>, according to one embodiment of the disclosure, includes a static structure or housing <NUM> which houses the components of the blood pump <NUM>. In one configuration, the housing <NUM> includes a lower housing or first portion <NUM>, an upper housing or second portion <NUM>, and an inlet element <NUM> or inflow cannula <NUM> which includes an outer tube 18a and an inner tube 18b. The first portion <NUM> and the second portion <NUM> cooperatively define a volute shaped chamber <NUM> having a major longitudinal axis <NUM> extending through the first portion <NUM> and the inflow cannula <NUM>. The chamber <NUM> defines a radius that increases progressively around the axis <NUM> to an outlet location on the periphery of the chamber <NUM>. The first portion <NUM> and the second portion <NUM> define an outlet <NUM> in communication with chamber <NUM>. The first portion <NUM> and the second portion <NUM> also define isolated chambers (not shown) separated from the volute chamber <NUM> by magnetically permeable walls. The inflow cannula <NUM> is generally cylindrical and extends generally from the first portion <NUM> along the axis <NUM>. The inflow cannula <NUM> has an upstream end or proximal end <NUM> remote from second portion <NUM> and a downstream end or distal end <NUM> proximate the chamber <NUM>.

The parts of the housing <NUM> mentioned above are fixedly connected to one another so that the housing <NUM> as a whole defines a continuous enclosed flow path. The flow path extends from the upstream end <NUM> at the upstream end of the flow path to the outlet <NUM> at the downstream end of the flow path. The upstream and downstream directions along the flow path are indicated in by the arrows U and D, respectively. A post <NUM> is mounted to the first portion <NUM> along the axis <NUM>. A generally disc shaped ferromagnetic rotor <NUM> with a central hole <NUM> is mounted within the chamber <NUM> for rotation about the axis <NUM>. The rotor <NUM> includes a permanent magnet and flow channels for transferring blood from adjacent the center of the rotor <NUM> to the periphery of the rotor <NUM>. In the assembled condition, the post <NUM> is received in the central hole of the rotor <NUM>.

A first stator or motor <NUM> having a plurality of coils may be disposed within the first portion <NUM> downstream from the rotor <NUM>. The first stator <NUM> may be axially aligned with the rotor along the axis <NUM> such that when a current is applied to the coils in the first stator <NUM>, the electromagnetic forces generated by the first stator <NUM> rotate the rotor <NUM> and pump blood. A second stator or motor <NUM> may be disposed within the second portion <NUM> upstream from the rotor <NUM>. The second stator <NUM> may be configured to operate in conjunction with or independently of the first stator <NUM> to rotate the rotor <NUM>.

Electrical connectors <NUM> and <NUM> (<FIG>) are provided on the first portion <NUM> and the second portion <NUM>, respectively, for connecting the coils to a source of power, such as a controller (not shown). The controller is arranged to apply power to the coils of the pump to create a rotating magnetic field which spins the rotor <NUM> around the axis <NUM> in a predetermined first direction of rotation, such as the direction R indicated by the arrow which is counterclockwise as seen from the upstream end of the inflow cannula <NUM>. In other configurations of the blood pump <NUM>, the first direction may be clockwise. Rotation of the rotor <NUM> impels blood downstream along the flow path so that the blood, moves in a downstream direction D along the flow path, and exits through the outlet <NUM>. During rotation, hydrodynamic and magnetic bearings (not shown) support the rotor <NUM> and maintain the rotor <NUM> out of contact with the surfaces of the elements of the first portion <NUM> and the second portion <NUM> during operation.

A first non-ferromagnetic disk <NUM> may be disposed within the first portion <NUM> upstream from the rotor <NUM> between the first stator <NUM> and the rotor <NUM> and a second non-ferromagnetic disk <NUM> may be disposed downstream from the rotor <NUM> within the second portion <NUM> between the second stator <NUM> and the rotor <NUM>. The rotor <NUM> is configured to rotate between the first disk <NUM> and the second disk <NUM> without contacting either disk. The general arrangement of the components described above may be similar to the blood pump <NUM> used in the MCSD sold under the designation HVAD® by HeartWare, Inc. , assignee of the present application. The arrangement of components such as the magnets, electromagnetic coils, and hydrodynamic bearings used in such a pump and variants of the same general design are described in <CIT>; <CIT>; <CIT>; and <CIT>.

Other implantable blood pumps <NUM> contemplated by this disclosure are those disclosed in <CIT> and <CIT>, and are axial flow blood pumps The MVAD™ pump is currently not for sale.

Referring now to <FIG>, implantable blood pump <NUM> may be in communication with a controller <NUM> having a control circuit <NUM> having control circuitry for monitoring and controlling startup and subsequent operation of one or more motors of the implanted blood pump <NUM>. The controller <NUM> may also include a processor <NUM> having processing circuitry, a memory <NUM>, and an interface <NUM>. The memory <NUM> stores information accessible by the processor <NUM> and processing circuitry, including instructions <NUM>, for example, motor control modules <NUM> and motor monitoring modules <NUM> executable by the processor <NUM> and/or data <NUM>, which may include by its not limited to, current <NUM> supplied to the one or more motors in one or more phases motors and pump data <NUM>, which may include flow rate date, that may be retrieved, manipulated, and/or stored by the processor <NUM>. The controller <NUM> may be in communication with a power supply <NUM> which may be external to the patient, for example, a battery <NUM>.

Referring now to <FIG>, during operating of the pump <NUM>, the controller <NUM> may operate the implantable blood pump <NUM> at a first pump set speed S<NUM> of the impeller <NUM> during a first period of time (Step S100). The first pump set speed S<NUM> may range between, for example, 1800rpm and 4000rpm, and may be a function of the particular pump, whether a centrifugal flow pump or an axial flow pump. For example, as shown in <FIG> for each first pump set speed, S<NUM>, the pump <NUM> exhibits a particular HQ curve that generally shows that during normal use fluid flow out through the pump increases as the pressure head decreases regardless of the set speed. Fluid flow is also a function of a patient's cardiac cycle, where during diastole the pressure head is higher and fluid flow decreases out through the pump <NUM> and during systole the pressure head decreases and fluid flow increases out through the pump <NUM>. During normal operation at the first pump set speed, S<NUM>, the current waveform and the flow rate waveform may be measured in real time and monitored by the controller <NUM> (Step S102). As used herein, "hypertension" or "hypertensive" refers to hypertension or operation in the flat region of the HQ curve.

In one configuration, as shown in <FIG>, a patient with a normal blood pressure exhibits a first flow pulsatility of about <NUM>/min, and a first current pulsatility of around <NUM>. 25A, during a first time period T<NUM> at the first pump set speed, S1 <NUM> RPM. In one configuration, a patient with hypertension, as shown in <FIG>, exhibits a first flow pulsatility of about <NUM>/min, and a first current pulsatility of about <NUM>. 35A, during a first time period T<NUM> at the first pump set speed, S1 <NUM> RPM. Thus, a hypertensive patient has greater pulsatility of flow rate and current than a patient with normal blood pressure. For example, as shown in both <FIG> and <FIG>, the controller <NUM> may reduce the speed of the impeller <NUM> by a predetermined amount to a second pump set speed S<NUM> of the impeller <NUM> during a second period of time T<NUM> (Step S104). For example, as shown in <FIG> and <FIG>, the first pump set speed, S<NUM> is reduced by 200RPM to the second pump set speeds S<NUM> of 2200RPM and 2400RPM, respectively. The second period of time T<NUM> may be the less than, the same, or longer than the first period of time T<NUM>. Optionally, the time periods T<NUM>, where the set speed is normal, and T<NUM>, where the set speed is reduced, may be run periodically and/or continually as part of normal operation of the blood pump or as part of a normal impeller <NUM> wash cycle, in which the speed of the impeller <NUM> is decreased then increased to prevent thrombus formation on the impeller <NUM>.

During the second period of time T<NUM> at the reduced set speed S<NUM>, the flow rate and the current are measured (Step S106). If a second flow rate pulsatility or a second current pulsatility increases during the second period of time, T<NUM>, at the second pump set speed, S<NUM>, compared to respective one of the first flow rate pulsatility or the first current pulsatility at the first pump set speed during S<NUM>, the first period of time, T<NUM>, the controller <NUM> may determine that the patient is exhibiting hypertension (Step <NUM>). For example, as shown in <FIG>, the second flow rate pulsatility during the second period of time, T<NUM> at the second pump set speed, S<NUM>, decreases from <NUM>/min to <NUM>/min and the second current pulsatility during the second period of time, T2 at the second pump set speed, S2, decreases from <NUM>. 25A to <NUM>. This decrease in pulsatility of current and/or flow rate is indicative of a patient with normal blood pressure. However, as shown in <FIG>, the second flow rate pulsatility during the second period of time, T<NUM> at the second pump set speed, S<NUM>, increases from an already higher than normal <NUM>/min to <NUM>. <NUM>/min, and the second current pulsatility during the second period of time, T2 at the second pump set speed, S2, increases from an already higher than normal <NUM>. 35A to <NUM>. This increase in pulsatility of current and/or flow rate is indicative of hypertension, which can be determined by the controller <NUM>. The measured flow rate pulsatility or current pulsatility may further be based on a measured mean or median of the respective pulsatility over T<NUM> and/or T<NUM>.

In another method of detection hypertension, during operation of the blood pump <NUM>, the flow rate or current minimum during T<NUM> at the first pump set speed, S<NUM>, may be measured. The flow rate or current minimum may be measured during a single cardiac cycle during T<NUM>, may be the mean of the minimum flow rates or currents detected from each of a number of cardiac cycles during T<NUM>, or the median of the minimum flow rate or current detected from each of a number of cardiac cycles during T<NUM>. The controller <NUM> may then reduce the impeller <NUM> speed to S<NUM> during T<NUM> and the flow rate or current minimum is then measured during T<NUM>, which may be measured during a single cardiac cycle during T<NUM>, may be the mean of the minimum flow rates or currents detected from each of a number of cardiac cycles during T<NUM>, or the median of the minimum flow rates or currents detected from each of a number of cardiac cycles during T<NUM>, depending on how the minimum flow rate or current minimum is measured during T<NUM>. If the measured minimum flow rate or current minimum decreases during T<NUM> at S<NUM> by more than a predetermined amount, then the controller <NUM> may indicate the presence of hypertension by generating an alert as described above and/or the controller may direct the set speed of the impeller <NUM> to either stay at S<NUM> or return to a set speed equal to or greater than S<NUM>. The predetermined decrease in current may be based on empirical values of patients that have a normal blood pressure. For example, as shown in <FIG>, the measured flow or current minimum during T<NUM> at S<NUM> in a patient with normal blood pressure decreases by less than the measured flow or current minimum during T<NUM> at S<NUM> in a patient with hypertension. For example, in <FIG>, the flow rate minimum at its lowest during T<NUM> at S<NUM> is about <NUM>/min whereas in <FIG>, it approaches <NUM>/min in patient with hypertension.

Referring now to <FIG> and <FIG>, if a suction condition is present, the increased pulsatility of flow and/or current and/or the decreased the minimum of flow and/or current is measured by the controller <NUM>, and reducing the set speed of the impeller <NUM> should resolve or not exacerbate the condition. For example, as shown in <FIG>, when the impeller <NUM> speed is reduced the measured flow rate pulsatility and current pulsatility reduces. However, if pulsatility increases or the minimum of flow or current decreases during T<NUM> with a reduced set speed, the controller <NUM> may flag the log file and/or in real time generate an alert, whether visual, tactile, or audio indicating the presence of hypertension, and not a suction related current or flow rate waveform, and inform other suction related algorithms that hypertension is present. This determination may therefore result in modification of the suction detection criteria thereafter.

Claim 1:
A system for detecting hypertension in a patient having a ventricular assist device, the ventricular assist device including an implantable blood pump (<NUM>), the system comprising:
a controller (<NUM>) in communication with the implantable blood pump, the controller having a processor (<NUM>) having processing circuity, the processing circuity being configured to
operate the implantable blood pump at a first pump set speed during a first period of time;
measure at least one from the group consisting of a first flow rate minimum and a first current minimum during a first period of time;
reduce the first pump set speed during a second period of time after the first period of time to a second pump set speed;
measure at least one from the group consisting of a second flow rate minimum and a second current minimum during the second period of time;
if the at least one from the group consisting of the second flow rate minimum and the second current minimum decreases during the second period of time at the second pump set speed more than a predetermined amount, the controller is configured to generate an alert indicating a presence of hypertension and optionally to increase the second pump set speed to the first pump set speed.