Patent Publication Number: US-2023149694-A1

Title: Mechanical circulatory support device

Description:
TECHNICAL FIELD 
     This disclosure is related to a medical mechanical circulatory support device. 
     BACKGROUND 
     A mechanical circulatory support device is configured to aid a heart of a patient with pumping blood to the body. An example mechanical circulatory support device is a ventricular assist device, which is configured to assist the pumping action of a heart and may include an inlet, an outlet, and a blood pump arranged to pump blood flow from the inlet to the outlet. The inlet may be fluidically connected to a chamber of the heart of a patient and the outlet may be fluidically connected to an artery, such as an aorta or a pulmonary artery. A blood pump of the ventricular assist device is configured to drive blood from the inlet towards the outlet and thus assists blood flow from the chamber of the heart into the artery. In patients with some degree of heart failure, the ventricular assist device may augment the pumping of the heart to provide blood flow at a sufficient rate to meet the demands of the body. The ventricular assist device may serve as, for example, a bridge to recovery, a bridge to transplantation, or destination therapy for the patient. 
     SUMMARY 
     This disclosure describes a mechanical circulatory support device configured to provide a pulsating blood flow to aid a heart of a patient in pumping blood to the body. A medical pump of the mechanical circulatory support device includes an impeller configured to impart energy to the blood flow when the impeller rotates around an eye axis of an impeller eye defined by the impeller. The blood pump includes a magnetic bearing configured such that, as the impeller rotates around the eye axis, the eye axis translates around (e.g., orbits) around a post axis defined by a post mechanically supported by the pump housing. The translation of the eye axis around the post axis as the impeller rotates transfers energy to the blood flow and imparts energy to the blood flow, which enables the mechanical circulatory support device to generate a pulsating blood flow. The pulsing blood flow can be generated, for example, without changing a speed of rotation of the impeller. 
     In an example, a mechanical circulatory support device comprises: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a post mechanically supported by the housing within the volume, wherein the post defines a post axis, and wherein the post mechanically supports an inner ring; and an impeller mechanically supporting an outer ring, wherein the impeller defines an eye surrounding the post and an eye axis extending through the eye, wherein the inner ring is configured to magnetically interact with the outer ring to establish a radial clearance between the inner ring and the outer ring, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the eye axis to translate around the post axis as the impeller rotates around the eye axis when the impeller imparts energy to a fluid flowing from the fluid inlet to the fluid outlet. 
     In an example, a heart pump comprises: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a stator configured to generate a stator magnetic field; a post mechanically supported by the housing within the volume, wherein the post mechanically supports an inner ring; and an impeller configured to impart energy to a fluid flowing from the fluid inlet to the fluid outlet, wherein the impeller defines an outer radial clearance between an outer perimeter of the impeller and the housing, and wherein the inner ring is configured to magnetically interact with an outer ring mechanically supported by the impeller to cause the outer radial clearance to vary. 
     In an example, a method comprises: controlling, by control circuitry, an impeller of a medical pump to rotate within a housing, the medical pump comprising: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a post mechanically supported by the housing within the volume, wherein the post defines a post axis, and wherein the post mechanically supports an inner ring; and the impeller mechanically supporting an outer ring, wherein the impeller defines an eye surrounding the post and an eye axis extending through the eye, wherein the inner ring is configured to magnetically interact with the outer ring to establish a radial clearance between the inner ring and the outer ring, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the eye axis to translate around the post axis as the impeller rotates around the eye axis when the impeller imparts energy to a fluid flowing from the fluid inlet to the fluid outlet; and modifying, by the control circuitry, a magnetic field causing the magnetic interaction between the inner ring and the outer ring. 
     The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a conceptual diagram illustrating an example medical system configured to assist the pumping action of a heart, the medical system including a mechanical circulatory support device. 
         FIG.  2 A  is a perspective illustration of an example mechanical circulatory support device in a first configuration. 
         FIG.  2 B  is a perspective illustration of the mechanical circulatory support device of  FIG.  2 A  in a second configuration. 
         FIG.  3    illustrates an example pressure waveform of a pulsating flow. 
         FIG.  4 A  is a schematic illustration of an example impeller of an example mechanical circulatory support device in a first rotational position within a pump housing. 
         FIG.  4 B  is a schematic illustration of the impeller of  FIG.  4 A  in a second rotational position within the pump housing of  FIG.  4 A . 
         FIG.  4 C  is a schematic illustration of the impeller of  FIG.  4 A- 4 B  in a third rotational position within the pump housing of  FIG.  4 A . 
         FIG.  4 D  is a schematic illustration of the impeller of  FIG.  4 A- 4 C  in a fourth rotational position within the pump housing of  FIG.  4 A- 4 C . 
         FIG.  5    is a conceptual diagram illustrating a cross-section of an example pump, the cross-section being taken through a post axis defined by the pump. 
         FIG.  6    is a schematic block diagram of the example medical system. 
         FIG.  7    is a flow diagram of an example technique of using a mechanical circulatory support device described herein. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes example medical systems configured to augment the pumping of a heart of a patient, e.g., to provide blood flow to meet the demands of the body of a patient during, for example, treatment of heart failure. The medical system includes a mechanical circulatory support device (“MCS device”) including a medical pump (also referred to herein more generally as a “pump”) configured to pump fluid (e.g., blood), which aids a heart of the patient in pumping blood to the body. In some examples, the MCS device is a ventricular assist device (“VAD”). In some examples, the MCS device may be implanted in the body of the patient and powered by an electrical power source inside or outside the body. 
     The pump is configured to drive blood flow from an inlet of the MCS device to an outlet of the MCS device. Blood may be introduced into the inlet from any suitable location in a body of a patient and blood may be introduced into any suitable part of the body via the outlet. For example, the medical system may include an inflow line (e.g., an inflow cannula) connected to a chamber (e.g., a ventricle) of the heart of the patient and to an inlet of the MCS device, and an outflow line (e.g., an outflow cannula) connected to an artery, such as an aorta or a pulmonary artery, and to an outlet of the MCS device. The pump is configured to drive blood from the inflow line towards the outflow line and thus assist blood flow from the chamber of the heart into the artery. 
     The pump is configured to provide a pulsating flow when the pump drives blood from the inflow line towards the outflow line. The pulsating flow may define a substantially continuous pressure waveform which substantially oscillates between a maximum pressure and a minimum pressure. The pump may be configured to produce the pulsating flow by at least varying a radial clearance between an impeller and a pump housing substantially surrounding the impeller as the impeller rotates and imparts energy to the blood flow. The varying radial clearance may at least in part cause the pump to produce the pulsating flow. Hence, in some examples, the pump is configured to produce the pulsating flow when the impeller rotates at a substantially constant rotational speed (e.g., constant or nearly constant to the extent permitted by device tolerances). In some examples, in addition to or instead of varying the radial clearance, the pump varies the rotational speed of the impeller to produce the pulsating flow. 
     The pulsating flow may help assist and/or substantially mimic the pulsatile flow naturally produced by the heart. The pulsating flow may, for example, complement the ejection of blood by the heart in systole, which may help relieve the work of the heart. As the heart relaxes in diastole, the pulsating flow may assist in increasing blood pressure when the pulsating flow provides blood to the aorta. The improved perfusion and reduced work performed by the heart may improve the performance of the heart, improving circulation for the entire body of the patient. In addition, in some cases, the pulsating flow provided by the MCS device may help disrupt flow in a ventricle of the patient and/or help wash the pump, which can help minimize thrombus ingestion by the pump. 
     The pump includes an impeller configured to generate the pulsating fluid flow when the impeller rotates to impart energy to a blood flow in the MCS device. In addition to or instead of achieving a pulsating flow by varying a speed of the pump (e.g., a speed of rotation of the impeller), the MCS devices described herein are configured to achieving a pulsating fluid flow by at least modifying the path the impeller takes as it rotates within a pump housing of the pump. The impeller is magnetically and/or hydrodynamically suspended within a pump housing of the pump, such that the impeller maintains a radial and axial clearance from the pump housing as the impeller rotates. Rather than rotating concentrically around a center post and maintaining a constant gap between the impeller and the pump housing, the pumps described herein are configured such that the radial clearance from the pump housing varies as the impeller rotates. That is, as the magnetically suspended impeller rotates, an axis of rotation of the impeller may vary relative to a post axis defined by the center post, such that the radial clearances between an outer perimeter of the impeller and the pump housing vary. In examples, the axis of rotation of the magnetically suspended impeller translates around (e.g., substantially orbits) the post axis as the magnetically suspended impeller rotates (e.g., as a fixed body) around the axis of rotation. As a result, the forces imparted by the impeller on fluid flowing through the pump housing are non-homogenous, and impeller motion may cause variations in the pressure of the fluid flowing through the pump housing. 
     Varying a speed of rotation of the impeller (also referred to herein as pump speed) may be useful for achieving a pulsatile flow through the pump, but changing the speed of rotation of the impeller relatively quickly can be relatively difficult to achieve due to limitations of the hardware. In addition, varying the pump speed to achieve pulsatile blood flow may consume more power than modifying the path the impeller takes as it rotates within a pump housing of the pump to achieve pulsatile flow by a MCS device. 
     The pumps described herein are configured such that, as the impeller rotates around an eye axis extending through an impeller eye defined by the impeller, the eye axis translates around (e.g., orbits) around a post axis defined by a post mechanically supported by the pump housing. The post can be, for example, fixed or integral with the pump housing and stationary relative to the pump housing during operation of the pump. In examples, the impeller eye surrounds the post when the impeller rotates within the pump housing. The translation of the eye axis around the post axis as the impeller transfers energy to the blood flow (e.g., increases a velocity of the flow) may cause the pump to generate a pulsating blood flow. In examples, the pumps described herein cause an increase in pressure (e.g., a static pressure) of the blood flow in regions where the translation of the eye axis around the post axis causes a decrease in the radial clearance between the impeller and the pump housing. The pumps described herein may cause an decrease in pressure (e.g., a static pressure) of the blood flow in regions where the translation of the eye axis around the post axis causes an increase in the radial clearance between the impeller and the pump housing. The varying pressure resulting from the varying radial clearance may generate the pulsating flow. Thus, the pumps described herein are configured to provide a pulsating (e.g., pulsatile) blood flow, even while the pump is operating at a substantially constant pump speed (e.g., constant or nearly constant to the extent permitted by manufacturing tolerances). 
     The pump includes a magnetic bearing (e.g., part of the impeller suspension system) configured to enable the eye axis to translate around the post axis as the impeller rotates. In some examples, the magnetic bearing includes an inner ring mechanically supported by the post and an outer ring mechanically supported by the impeller. The magnetic bearing is configured to generate a magnetic field (“bearing magnetic field”) to cause the inner ring to magnetically interact with the outer ring. In examples, the inner ring and the outer ring define the bearing magnetic field. The magnetic interaction may cause magnetic forces (e.g., attractive or repulsive forces) between inner ring and the outer ring. The inner ring may be configured to transmit some portion of the magnetic forces to the post and the outer ring may be configured to transmit some portion of the magnetic forces to the impeller, such that the magnetic forces establish an inner radial clearance between the post and the impeller (e.g., a radial clearance substantially perpendicular to the eye axis and/or post axis). In some examples, the magnetic bearing is configured to generate the bearing magnetic field such that the magnetic forces cause the inner radial clearance between the impeller and the post axis to vary around a perimeter defined by the post (e.g., a perimeter in a plane substantially perpendicular to the post axis). The magnetic forces may cause the inner radial clearance to vary such that, when the magnetic bearing establishes the inner radial clearance, the eye axis substantially offsets from the post axis, such that the eye axis translates around post axis when the impeller rotates to impart energy to a blood flow through the MCS device. 
     For example, in some examples, the magnetic bearing is configured such that a first magnetic force causes an inner radial clearance between the post and the impeller in a first radial direction (e.g., a direction substantially perpendicular to the post axis). The magnetic bearing may further be configured such that a second magnetic force causes an inner radial clearance between the post and the impeller in a second direction substantially opposite the first direction. The second magnetic force may be less than the first magnetic force. For example, the second magnetic force may be less than about 90% of the first magnetic force, such as less than about 70% or 50% of the first magnetic force, or less than some other percentage of the first magnetic force sufficient to cause the offset between the eye axis and the post axis. The differing magnetic forces may cause the eye axis to translate around post axis when the impeller rotates to impart energy to the blood flow, such that pump provides a pulsating blood flow. 
     The pump is configured such that the magnetic forces between the impeller and the post vary around the perimeter defined by the post and/or the inner ring. For example, in some examples, the inner ring and/or the outer ring includes a permanent magnet configured to cause the magnetic forces between the impeller and the post to vary around the perimeter defined by the post. In some cases, the permanent magnet defines a structural feature (e.g., a notch in the permanent magnet) configured to cause the magnetic forces to vary. In addition or instead, in some examples, the inner ring and/or the outer ring includes an electromagnet configured to cause the magnetic forces to vary. In some examples, the electromagnet includes a winding configured to generate an electromagnetic field to generate the magnetic forces, and the winding is configured to cause the magnetic forces to vary around the perimeter defined by the post and/or the inner ring. 
     The pump housing defines a fluid inlet and a fluid outlet. The impeller is configured to rotate within the pump housing to impart energy to the blood between the fluid inlet and the fluid outlet. The impeller may be configured to impart energy to the blood flow by at least accelerating the blood flow toward an outer perimeter (“impeller outer perimeter”) defined by the impeller as the impeller rotates. The impeller outer perimeter may be defined by, for example, one or more vane tips of the impeller. The pump housing may define a volume (e.g., a volute) fluidically coupling the fluid inlet and the fluid outlet and configured to receive the blood flow accelerated by the impeller. In some examples, the fluid inlet is fluidically coupled to the inflow line and the fluid outlet is fluidically coupled to the outflow line, such that rotation of the impeller drives blood from the inflow line towards the outflow line. The eye axis about which the impeller is configured to rotate may be extend through an impeller eye defined by the impeller. The pump may be configured such that the eye axis defines the axis of rotation for the impeller when the impeller rotates to accelerate the blood flow. 
     In examples, the pump is configured to generate a pulsating flow wherein a pressure of the flow within the pump housing (e.g., at the fluid outlet) cyclically varies over a pressure range defined by a maximum pressure and a minimum pressure as the impeller rotates within the housing. In examples, during one full translation of the eye axis around the post axis, the pressure of the flow within the pump housing varies between the maximum and minimum pressures. The pulsating flow may define a substantially continuous pressure waveform which substantially oscillates between the maximum pressure and the minimum pressure. In examples, the pressure waveform defines a wave period. 
     In some examples, the medical system is configured to control the maximum pressure, the minimum pressure, and/or the wave period by at least controlling the motion of the impeller. For example, the maximum and/or minimum pressure may be a function of a radial clearance between the impeller and the pump housing as the impeller rotates around the eye axis. Control circuitry of the medical system (e.g., of the MCS device or another device) may be configured to control the wave period by at least controlling a rotational speed of the impeller around the eye axis. In some examples, the control circuitry is configured to receive a signal indicative of a physiological parameter of a patient and cause the pump to alter the pulsating flow based on the physiological parameter. The signal may be received directly or indirectly from a physiological sensor. The physiological parameter may be, for example, a cardiac signal such as an electrocardiogram (ECG), an electrogram (EGM), a signal indicative of an activity level of the patient (e.g., a signal generated by an accelerometer), a mechanical wave of the heart, a signal indicative of a respiratory rate, or another physiological parameter. Hence, the medical system may be configured to alter the pulsating flow provided by the MCS device to augment the pumping of a heart of a patient based on a sensed physiological condition of the patient. 
     During operation of the pump, an outer radial clearance between the pump housing and the impeller outer perimeter varies as the impeller rotates to generate the pulsating flow. The pump may be configured such that the translation of the eye axis around the post axis causes the outer radial clearance to vary. For example, at an initial point in time, with the impeller rotating around the eye axis and the eye axis translating (e.g., orbiting) round the post axis, the pump may define a first outer radial clearance between the impeller and the pump housing in a first radial direction and a second outer radial clearance between the impeller and the pump housing in a second radial direction opposite the first radial direction. The first outer radial clearance may be less than the second outer radial clearance. At a subsequent point in time, with the impeller having rotated by some degree around the eye axis and the eye axis having translated by some degree round the post axis, the impeller may have altered its orientation relative to the pump housing such that the first outer radial clearance is greater than the second radial outer displacement. The radial clearance can be measured in a direction orthogonal to the post axis. 
     In some examples, the pump is configured such that the translation of the eye axis around the post axis cause the first outer radial clearance to cyclically vary from a minimum first radial clearance to a maximum first radial clearance as the eye axis translates around the post axis. In examples, as the eye axis translates around the post axis, the first radial clearance defines a substantially continuous first displacement waveform which oscillates between the maximum first radial clearance and the minimum first radial clearance. The first displacement waveform defines a first displacement wave period. In examples, the pump is configured such that the first displacement wave period is substantially equal to the wave period of the pressure waveform defined by the pulsating flow. In similar manner, the pump may be configured such that the translation of the eye axis around the post axis cause the second outer radial clearance to cyclically vary from a minimum second radial clearance to a maximum second radial clearance as the eye axis translates around the post axis. The second radial clearance defines a substantially continuous second displacement waveform which oscillates between the maximum second radial clearance and the minimum second radial clearance as the eye axis translates around the post axis. The second displacement waveform defines a second displacement wave period. The pump may be configured such that the second displacement wave period is substantially equal to the wave period of the pressure waveform defined by the pulsating flow and/or the first displacement wave period. 
     In some examples, the pump is configured such that the pump housing and the varying magnetic forces between the inner and outer ring cause a side thrust on the impeller when the impeller rotates to impart energy (e.g., a velocity) to the blood flow and enable the pump to generate a pulsating (e.g., pulsatile) fluid flow. The side thrust causes the eye axis to translate around (e.g., orbit) the post axis. The side thrust may, for example, cause the first outer radial clearance and/or the second outer radial clearance to vary from its respective maximum to its respective minimum. In examples, the pump housing and the bearing magnetic field are configured to cause a side thrust on the impeller in a direction from the first outer radial clearance toward the second outer radial clearance when the first outer radial clearance is less than the second outer radial clearance. The pump housing and the bearing magnetic field may be configured to cause a side thrust on the impeller in a direction from the second outer radial clearance toward the first outer radial clearance when the second outer radial clearance is less than the first outer radial clearance. The side thrust causing the eye axis to translate around the post axis as the impeller imparts energy to the blood flow may cause the impeller to generate the pulsating blood flow, such that a pressure of the blood flow at the fluid outlet of the housing cyclically varies substantially from a maximum pressure to a minimum pressure (and vice-versa) as the impeller rotates. 
     In some examples, for a given MCS device, the bearing magnetic field is modifiable, e.g., to achieve different amounts of fluid pulsations, which may have different physiological effects on the patient. For example, a medical system including the MCS device can include control circuitry configured to control the bearing magnetic field based on user input, based on one or more sensed physiological parameters, or based on other factors or combination thereof. In some examples, the control circuitry is configured to vary the bearing magnetic field in a radial direction (e.g., substantially perpendicular to the eye axis and/or post axis) to cause the magnetic field strength of the magnetic field to vary around the perimeter defined around the post axis. The control circuitry may be configured to alter an operation of the pump (e.g., by at least altering the bearing magnetic field) to control a pressure range exhibited by the pulsations as the impeller generates the pulsating flow. For example, in some examples, the control circuitry is configured to alter the bearing magnetic field to increase a difference between the minimum first radial clearance and the maximum first radial clearance as the eye axis translates around the post axis to, for example, increase the pressure range exhibited by the pulsations. As another example, the control circuitry can be configured to alter the bearing magnetic field to decrease a difference between the minimum first radial clearance and the maximum first radial clearance as the eye axis translates around the post axis to, for example, decrease the pressure range exhibited by the pulsations. Hence, the medical system may be configured to alter the pressure range exhibited by the pulsations depending on the needs of the patient. 
     In some examples, the medical system includes a programming computing device or the like that is configured to communicate with the control circuitry. A user can interact with the programming computing device to provide user input that causes the control circuitry to modify the pressure range, e.g., by directly specifying different bearing magnetic fields, different pressure ranges, or the like. The control circuitry of the MCS device is configured to, in response to receiving the user input, modify the pressure range, such as by modifying the bearing magnetic field or taking another action described herein that has an impact on the pressure range. In this way, once implanted in the patient, the operation of the MCS device can be modified to accommodate the needs of the patient and provide better therapeutic outcomes, e.g., as the patient condition changes over time without requiring explanation of the device from the patient. 
     The MCS device is configured to cause the impeller to rotate around the eye axis as the eye axis translates around the post axis. In some examples, the pump defines a stator configured to cause the impeller to rotate around the eye axis. The stator can be, for example, mechanically supported by the pump housing. In examples, the stator and the impeller are configured to magnetically interact to cause the impeller to rotate around the eye axis. The stator and the impeller may define a motor (e.g., a brushless DC motor) configured to exert a torque on the impeller causing the impeller to rotate around the eye axis. In examples, the stator and/or the impeller are configured to define a magnetic field of the motor (“motor magnetic field”) to cause the impeller to rotate around the eye axis. For example, the stator may be configured to generate a rotating motor magnetic field (e.g., rotating substantially around the post axis) to cause the impeller to rotate around the eye axis. The control circuitry of the pump may be configured to control a rotational speed of the impeller by at least, for example, controlling a rotational speed of the motor magnetic field and/or the torque exerted on the impeller (e.g., by controlling a strength of the motor magnetic field). In examples, the pump is configured such that the motor magnetic field and/or hydrodynamic forces from the blood flow cause an axial displacement between the pump housing and the impeller, such that the impeller may rotate within the pump housing to cause the pulsating flow without contacting the pump housing. 
     In some examples, the control circuitry of the medical system is configured to control an operation of the pump based on a sensed physiological parameter of the patient. For example, the medical system may include a monitor (e.g., an implantable, wearable, or other monitor) including sensing circuitry configured to generate an output (e.g., an electrical signal) indicative of a physiological parameter of a patient (e.g., a cardiac signal such as an ECG, ECM, a signal indicative of an activity level of the patient, a signal indicative of a respiratory rate, a mechanical wave of the heart, or another physiological parameter). The monitor may be configured to communicate a signal indicative of the physiological parameter to the control circuitry. The control circuitry may receive the signal and alter an operation of the pump (e.g., alter the bearing magnetic field and/or the motor magnetic field) based on the received signal. For example, the control circuitry may alter the bearing magnetic field and/or motor magnetic field to alter the radial clearances exhibited between the impeller and the pump housing to, for example, increase or decrease a pressure range of the pulsating flow based on the indicative signal, or for another reason. As another example, the control circuitry may alter the bearing magnetic field and/or motor magnetic field (e.g., a rotation of the motor magnetic field) to alter a rotational speed of the impeller to, for example, increase or decrease a wave period of the pulsating flow based on the indicative signal, alter a flow rate of the blood flow through the pump, or for other reasons. 
     In some examples, instead of or in addition to controlling operation of the pump based on one or more sensed physiological parameters, the medical system is configured to monitor a blood flow through the pump and alter the operation of the pump based on the monitored blood flow. For example, the medical system may include a pump thrombosis detection system including circuitry configured to detect a pump thrombosis within the pump. The pump thrombosis detection system may be configured to communicate a thrombosis signal indicative of the pump thrombosis to the control circuitry. The control circuitry may be configured to alter an operation of the pump (e.g., alter the bearing magnetic field and/or the motor magnetic field) based on the thrombosis signal. For example, the control circuitry may be configured to alter the bearing magnetic field and/or the motor magnetic field to generate a mechanical vibration in the impeller to try to clear the pump thrombosis. 
       FIG.  1    is a conceptual and schematic diagram illustrating an example medical system  100  configured to assist the pumping action of a heart  101  of a patient  103  using a mechanical circulatory support device  102  (“MCS device  102 ”). MCS device  102  includes a pump  104 . Medical system  100  includes an inflow line  105 , an outflow line  106 , and a driveline  108 . Inflow line  105  and/or outflow line  106  may be, for example, cannulas or other structures configured to define a fluid pathway for blood. A first end of inflow line  105  is fluidically coupled to a fluid inlet  110  of pump  104  either directly or indirectly. A second end of inflow line  105  is fluidically coupled to heart  101 , e.g., grafted to heart  101 , such as the left ventricle  112  of heart  101 . The second end of inflow line  105  may define an MCS inlet  109  fluidically coupled to fluid inlet  110 . In some examples, the second end of inflow line  105  includes a ventricular connector (not shown). A first end of outflow line  106  is fluidically coupled to fluid outlet  114  of pump  104  either directly or indirectly. A second end of outflow line  106  may be grafted or otherwise fluidically coupled to an artery of patient  103 , e.g., aorta  116 . The second end of outflow line  106  may define an MCS outlet  107  fluidically coupled to fluid outlet  114 . Driveline  108  is configured to provide electrical and/or mechanical power to pump  104 . 
     Pump  104  is configured to draw blood from a chamber of heart  101  and pump the blood to other portions of the body of patient  103 . In examples, pump  104  includes a pump housing  117  and an impeller  118  configured to rotate within pump housing  117  to draw blood from the chamber of heart  101  and pump the blood to other portions of the body of patient  103 . Impeller  118  is configured impart energy to a blood flow flowing from inflow line  105  to outflow line  106  when impeller  118  rotates within pump housing  117 . In examples, pump  104  is configured to cause impeller  118  to generate a pulsating flow as the blood flow flows from inflow line  105  to outflow line  106 . The pulsating flow may define a substantially continuous pressure waveform (e.g., at fluid outlet  114 ) which oscillates between a maximum pressure and a minimum pressure. 
     Driveline  108  is configured to provide electrical and/or mechanical power to pump  104  to, for example, cause impeller  118  to impart energy to the blood flow. In the example shown in  FIG.  1   , medical system  100  includes control circuitry  120  configured to supply and/or control the power supplied by driveline  108 . In some examples, control circuitry  120  or other control circuitry of system  100  is configured to control a bearing magnetic field and/or a stator magnetic field generated within pump  104 . Thus, while control circuitry  120  is primarily referred to herein for ease of description, in other examples, system  100  can include other control circuitry configured to perform some or all of the functions described with respect to control circuitry  120 . 
     Control circuitry  120  is configured to communicate with pump  104  (e.g., using driveline  108  and/or another communication link) to alter an operation of pump  104 . For example, control circuitry  120  may be configured to alter the operation of pump  104  to control a pressure range exhibited by the pulsations of the pulsating flow as impeller  118  imparts energy to the blood flow flowing from inflow line  105  to outflow line  106 . As another example, in some examples, control circuitry  120  is configured to alter the operation of pump  104  (e.g., a rotational speed of impeller  118 ) to control a wave period of the pulsating flow as impeller  118  imparts energy to the blood flow flowing from inflow line  105  to outflow line  106 . Control circuitry  120  may be configured to alter the operation of the bearing magnetic field and/or the stator magnetic field within pump  104  to alter the operation of pump  104 . 
     In examples, control circuitry  120  is configured to monitor MCS device  102  (e.g., pump  104 ) and/or a blood flow produced by MCS device to evaluate the pulsating flow and, in some examples, control pump  104  accordingly. For example, control circuitry  120  may be configured to monitor MCS device  102  to evaluate when pump  104  is operating in a condition causing the eye axis defined by impeller  118  to translate around the post axis as impeller  118  rotates around the eye axis (e.g., when the eye axis is an axis of rotation of impeller  118 ). In addition, or alternatively, control circuitry  120  may be configured to monitor MCS device  102  to evaluate when pump  104  is operating in a condition causing the radial clearance between impeller  118  and pump housing  117  to vary as impeller  118  rotates around the eye axis. Control circuitry  120  may be configured to alter and/or establish an operating condition of MCS device  102  (e.g., pump  104 ) to cause MCS device to produce the pulsating flow. Control circuitry  120  may be configured to evaluate a waveform (e.g., a continuous, discontinuous, and/or discrete waveform) generated by MCS device  102  and indicative of a pulsating flow to evaluate a sufficiency of the pulsating flow. Control circuitry  120  may be configured to alter and/or establish an operating condition of MCS device  102  based on the evaluation of the waveform, e.g., to modify the waveform. 
     In examples, MCS device  102  includes a sensor  121  including sensing circuitry configured to monitor the pulsating flow generated by MCS device  102  and/or a characteristic of MCS device  102  (e.g., pump  104 ) indicating a pulsating flow. Sensor  121  is configured to generate a flow signal indicative of the pulsating flow and/or the characteristic of MCS device  102  indicating the pulsating flow. For example, sensor  121  may be configured to measure a flow rate and/or pressure of the blood flow in a particular portion of MCS device  102  (e.g., fluid outlet  114 , outflow line  106 , or another portion) and provide a flow signal indicative of the flow rate and/or pressure to control circuitry  120 . In addition to or instead, sensor  121  may be configured to measure a position of impeller  118  (e.g., a position relative to pump housing  117 ) and/or an electrical characteristic of pump  104  (e.g., a current and/or voltage demand) and provide a flow signal indicative of the position and/or the electrical characteristic to control circuitry  120 . In some examples, sensor  121  is configured to generate a flow signal representative of a mechanical wave generated by MCS device  102 . The mechanical wave may, for example, include an acoustic wave, a mechanical vibration, an electrical field, or another parameter representative of a mechanical wave generated by an operation of MCS device  102 . Control circuitry  120  may be configured to evaluate the flow signal to indicate MCS device  102  is producing a pulsating flow (e.g., based on the variance and/or oscillation of a wave form exhibited by the flow signal). In examples, control circuitry  120  may evaluate the pulsating flow generated by MCS device  102  by evaluating a plurality of frequency peaks, periods, or other characteristics of the wave form of the flow signal. 
     In the example shown in  FIG.  1   , the one or more components of system  100  are powered by a power source  122 . Power source  122  may be, for example, one or more batteries, or another power source configured to deliver electrical power to control circuitry  120 , pump  104 , as well as other components of system  100 . In examples, power source  122  is separately housed from control circuitry  120 . Power source  122  may be electrically coupled to control circuitry  120  by a power cord  124 . In the illustrated example, control circuitry  120  and power source  122  are removably attached to a carrier  126 . Carrier  126  may be configured to be wearable by patient  103 , such that patient  103  may remain ambulatory while using medical system  100 . 
     In some examples, as shown in  FIG.  1   , medical system  100  includes a monitor  128 , a computing device  130 , and user interface  132 . In examples, monitor  128  includes sensing circuitry configured to generate a signal indicative of a physiological parameter of a patient (e.g., a cardiac signal such as an ECG, ECM, an activity level of patient  103 , a respiratory rate, a mechanical wave of heart  101 , an electrical field of heart  101 , or another physiological parameter). Monitor  128  is configured to communicate the signal indicative of the physiological parameter to another device, such as computing device  130  (e.g., via a wired or wireless communication link  134 ) and/or control circuitry  120 . In examples, computing device  130  is configured to communicate with control circuitry  120  via, for example, a wired or wireless link  136 . Control circuitry  120  may be configured to alter an operation of pump  104  based on the indicative signal from monitor  128  and/or a communication from computing device  130 . 
     User interface  132  is communicatively coupled to computing device  130  via a wired or wireless link  138 . User interface  132  may be configured to communicate information indicative of the operation of pump  104  or another component of medical system  100  to a user (e.g., patient  103 , a caregiver, and/or a clinician) or another entity, such as a remote server system. In addition, user interface  132  can be configured to receive user input, such as user input requesting a change to an operation of pump  104 . 
     In some examples, medical system  100  is configured to cause pump  104  to control or alter a pressure range exhibited by the pulsations of the pulsating flow based on a communication from monitor  128  and/or computing device  130 . For example, medical system  100  may be configured to cause pump  104  to control or alter a wave period of the pulsating flow based on a communication from monitor  128  and/or computing device  130 . In some examples, monitor  128  is configured to detect a pump thrombosis within pump  104  and communicate a thrombosis signal to computing device  130  and/or control circuitry  120 . Control circuitry  120  may be configured to alter the operation of pump  104  based on the thrombosis signal to, for example, generate a mechanical vibration of impeller  118  to attempt to clear the pump thrombosis. Further, although shown in  FIG.  1    as separate devices, in other examples, one or more of monitor  128 , computing device  130 , and/or user interface  132  may be included in the same device. Monitor  128 , computing device  130 , and/or user interface  132  may be portable, e.g., able to be carried on or implanted in patient  103  to, for example, enable patient  103  to remain ambulatory while using medical system  100 . 
       FIG.  2 A  schematically illustrates a perspective view of an example pump  104  with pump housing  117  in a first configuration.  FIG.  2 B  illustrates the example pump  104  with pump housing  117  is a second configuration, in which pump housing  117  is open to illustrate impeller  118  positioned within pump housing  117 . Pump housing  117  defines fluid inlet  110  and fluid outlet  114 . Also shown in  FIGS.  2 A and  2 B  is inflow line  105 , which defines a lumen  140  (“inflow line lumen  140 ”) and MCS inlet  109  opening to inflow line lumen  140 . Fluid inlet  110  may be fluidically coupled to MCS inlet  109  through inflow line lumen  140 . In examples, MCS device  102  is configured to receive a blood flow from heart  101  ( FIG.  1   ) via inflow MCS inlet  109  and deliver the blood flow to pump  104  via inflow line lumen  140 . Inflow line  105  can be integrally formed with pump housing  117  or can be physical separate from and mechanically connected to pump housing  117 . 
     Pump  104  is configured to impart energy (e.g., a velocity) to a blood flow flowing from fluid inlet  110  to fluid outlet  114  when impeller  118  rotates within pump housing  117  (e.g., in the first configuration of  FIG.  2 A ). Impeller  118  includes an impeller eye  144  configured to substantially surround (e.g., surround a majority of) a post  146  when impeller  118  rotates within pump housing  117 . In examples, impeller  118  includes an inner surface  147  (“impeller inner surface  147 ”) forming the boundary of impeller eye  144 . Impeller eye  144  and impeller inner surface  147  may define a volume  149  (“eye volume  149 ”) ( FIGS.  4 A- 4 D ) configured to receive post  146  when impeller eye  144  substantially surrounds post  146 . Post  146  is positioned within pump housing  117  and can be mechanically supported by pump housing  117 . Post  146  can be integrally formed with pump housing  117  or physically separate from and mechanically connected to pump housing  117 . 
     Pump  104  may be configured to impart energy to the blood flow by increasing a velocity of the blood flow, increasing a static pressure of the blood flow, and/or increasing a dynamic pressure of the blood flow. In examples, pump  104  (e.g., impeller  118 ) is configured to increase a velocity of the blood flow and then decrease the velocity of the blood flow (e.g., using pump housing  117 ) to cause an increase in the static pressure of the blood flow. Pump  104  may be configured to impart kinetic energy to the blood flow using impeller  118  and convert the kinetic energy to pressure energy using pump housing  117 . 
     Impeller  118  may be configured to impart energy to the blood flow by accelerating the blood flow toward an impeller outer perimeter P 1  defined by impeller  118  as impeller  118  rotates. Impeller outer perimeter P 1  may be defined by, for example, one or more vane tips of impeller  118 , such as vane tip  148  of impeller vane  150 , and the path vane tip  148  takes as impeller  118  rotates within pump housing  117 . Impeller  118  may be configured such that rotational motion of impeller  118  generates centrifugal forces in a direction from impeller inner surface  147  toward impeller outer perimeter P 1 . Impeller  118  may be configured to impart the centrifugal forces to a fluid flowing from impeller eye  144  toward impeller outer perimeter P 1  (e.g., using one or vanes, such as vane  150 ), such that impeller  118  imparts energy to the fluid. Impeller  118  may comprise, for example, a radial impeller, a mixed flow impeller, an axial flow impeller, a peripheral impeller, a free flow impeller, or some other impeller configured to impart energy to a fluid flow. 
     Pump housing  117  is configured to fluidically couple fluid inlet  110  and fluid outlet  114  (e.g., when in the first configuration of  FIG.  2 A ). Pump housing  117  may be configured to receive and direct the blood flow accelerated by impeller  118  toward fluid outlet  114 . In examples, pump housing  117  is configured to increase a static pressure of the accelerated blood flow as the blood flow flows toward fluid outlet  114 . In examples, pump housing  117  defines a volume  152  fluidically coupling the fluid inlet and the fluid outlet. Volume  152  may define, for example, a volute or a diffuser. In examples, pump housing  117  defines a boundary (e.g., a pressure boundary and/or fluid boundary) between volume  152  and an exterior of pump  104 , such that MCS device  102  may more effectively generate a blood flow from MCS inlet  109  to MCS outlet  107 . In examples, an inner surface  154  of pump housing  117  (“housing inner surface  154 ”) defines volume  152 . 
     Pump housing  117  has any suitable configuration and is configured for implantation in a patient in some examples. In some examples, pump housing  117  includes an upper housing  153  configured to mechanically engage a lower housing  155  to define volume  152 . Upper housing  153  and lower housing  155  may be configured to mechanically disengage to, for example, allow access to portions of volume  152  during assembly or for other reasons. In some examples, pump housing  117  is a unified body defining volume  152 . Pump housing  117  may comprise, for example, titanium, a ceramic material, and/or another suitable biocompatible material. In examples, pump housing  117  comprises a non-magnetic material. 
     Pump  104  is configured to magnetically and/or hydrodynamically suspend impeller  118  within pump housing  117 , such that impeller  118  maintains an outer radial clearance (e.g., the first outer radial clearance R 1 ) between impeller  118  and housing inner surface  154  as impeller  118  imparts energy to the blood flow. Pump  104  may be configured to maintain an outer radial clearance between impeller  118  and housing inner surface  154  circumferentially around the impeller outer perimeter P 1  as impeller  118  rotates. 
     Pump  104  includes a magnetic bearing  156  configured to establish an inner radial clearance between impeller  118  and post  146  as impeller  118  rotates. In examples, magnetic bearing  156  includes an inner ring (not shown in  FIGS.  2 A and  2 B ) mechanically supported by post  146  and configured to magnetically interact with an outer ring (not shown in  FIGS.  2 A and  2 B ) mechanically supported by impeller  118  to maintain the inner radial clearance. Magnetic bearing  156  may be configured to cause magnetic forces between the inner ring and the outer ring which vary around an inner perimeter (e.g., inner perimeter P 2  ( FIGS.  4 A- 4 D )) defined by post  146  and/or an inner ring of magnetic bearing  156  (e.g., inner ring  166  ( FIG.  6   )). 
     Pump  104  also includes a stator  158  configured to cause impeller  118  to rotate within pump housing  117 . In examples, pump  104  defines a second stator  160 . Stator  158  and/or second stator  160  may be mechanically supported by pump housing  117  and can be integrally formed with pump housing  117  or separate from and attached to pump housing  117 . In examples, impeller  118  and stator  158  and/or second stator  160  are configured to magnetically interact to cause impeller  118  to rotate within pump housing  117 . Impeller  118  and stator  158  and/or stator  160  may define a motor (e.g., a brushless DC motor) and a motor magnetic field configured to exert a torque on impeller  118  to cause impeller  118  to rotate within pump housing  117 . Driveline  108  may be configured to provide electrical power to pump  104  to power magnetic bearing  156 , stator  158 , second stator  160 , and/or other components of pump  104 . 
     Pump  104  is configured to generate a pulsating blood flow (e.g., at fluid outlet  114 ) when impeller  118  rotates within pump housing  117  to impart energy to the blood flow at a given rate of rotation (e.g., pump speed). In examples, pump  104  is configured to generate the pulsating flow by at least causing a displacement defined by an outer radial clearance (e.g., defined by first outer radial clearance R 1 ) to vary as impeller  118  rotates within pump housing  117 . In some examples, pump  104  is configured to cause first outer radial clearance R 1  to cyclically vary over a range between and including a minimum first radial clearance and a maximum first radial clearance as impeller  118  rotates within pump housing  117 . For example, pump  104  may be configured such that the varying magnetic forces caused by the bearing magnetic field and/or fluid momentum forces imparted to impeller  118  cause an eye axis AE defined by impeller  118  to translate around (e.g., orbit) a post axis AP when impeller  118  rotates around eye axis AE. Post  146  may define post axis AP extending through post  146  and impeller eye  144  may define an eye axis AE extending through impeller eye  144 . Eye axis AE may be substantially parallel (e.g., parallel or nearly parallel to the extent permitted by manufacturing tolerances) to post axis AP in some examples. Pump  104  may be configured to cause impeller  118  to rotate around eye axis AE (e.g., as an axis of rotation) when impeller  118  rotates within pump housing  117 . Translation of the eye axis AE around post axis AP as impeller  118  rotates may cause first outer radial clearance R 1  to cyclically vary, such that impeller  118  generates the pulsating flow. 
       FIG.  3    illustrates an example of a pressure waveform P which may be generated when pump  104  provides the pulsating flow.  FIG.  3    illustrates exemplary pressures of pressure waveform P, however pressure waveform P may exhibit any pressures sufficient for the operation of MCS device  102 . Pump  104  may be configured to generate the pressure waveform P within, for example, pump housing  117 , outflow line  106 , and/or within some other portion of MCS device  102 . 
     Pressure waveform P may substantially oscillate over a range defined between a maximum pressure PMAX and a minimum pressure PMIN. Pressure waveform P may define a pressure wave period PWP as pressure waveform P substantially oscillates over a range defined between a maximum pressure PMAX and a minimum pressure PMIN. In examples, pressure waveform P substantially oscillates over the range between maximum pressure PMAX and minimum pressure PMIN as the eye axis AE translates around (e.g., substantially orbits) the post axis AP. In some examples, pressure waveform P substantially oscillates over the range in a substantially synchronized manner with the translations of the eye axis AE around the post axis AP, such that a full translation of the eye axis AE around the post axis AP (labeled  1 . 00 ,  2 . 00 ,  3 . 00 , etc. in  FIG.  3   ) causes pressure waveform P to substantially oscillates over the range between maximum pressure PMAX and minimum pressure PMIN. In some examples, a rotation of impellor  118  around eye axis AE is synchronized with the translation of the eye axis AE around the post axis AP. For example, in some examples, for each full translation of eye axis AE around post axis AP, impeller  118  may complete a substantially full rotation around eye axis AE. 
       FIGS.  4 A- 4 D  schematically illustrate impeller  118  rotating around eye axis AE (e.g., rotating with eye axis AE as an axis of rotation) as eye axis AE translates around (e.g., orbits) post axis AP. In  FIGS.  4 A- 4 D , eye axis AE and post axis AP are depicted perpendicular to the page.  FIGS.  4 A- 4 D  depict rotation of impeller  118  around eye axis AE as a sequence, such that  FIG.  4 B  is temporally subsequent to the position depicted at  FIG.  4 A ,  FIG.  4 C  is temporally subsequent to the position depicted at  FIG.  4 B , and  FIG.  4 D  is temporally subsequent to the position depicted at  FIG.  4 C . Magnetic bearing  156  generates magnetic forces which vary around inner perimeter P 2  surrounding post  146 . Impeller  118  rotates in a rotational direction W to impart energy to a blood flow by accelerating the blood flow toward housing inner surface  154  of pump housing  117  using, for example, impeller vane  150 . 
     Pump  104  is configured such the varying magnetic forces of magnetic bearing  156  and/or fluid momentum forces on impeller  118  (e.g., as impeller  118  accelerates the blood flow toward housing inner surface  154 ) causes eye axis AE to translate around post axis AP when impeller  118  rotates around eye axis AE. For example, as impeller  118  from the impeller position depicted at  FIG.  4 A  to the impeller position depicted at  FIG.  4 B , eye axis AE may translate around post axis AP from the position depicted at  FIG.  4 A  to the position depicted at  FIG.  4 B . As impeller  118  rotates from the impeller position depicted at  FIG.  4 B  to the impeller position depicted at  FIG.  4 C , eye axis AE may translate around post axis AP from the position depicted at  FIG.  4 B  to the position depicted at  FIG.  4 C . As impeller  118  rotates from the impeller position depicted at  FIG.  4 C  to the impeller position depicted at  FIG.  4 D , eye axis AE may translate around post axis AP from the position depicted at  FIG.  4 C  to the position depicted at  FIG.  4 D . Impeller  118  may subsequently rotate from the impeller position depicted at  FIG.  4 D  to substantially return to the impeller position depicted at  FIG.  4 A , such that eye axis AE translates around post axis AP from the position depicted at  FIG.  4 D  to the position depicted at  FIG.  4 A . Hence, pump  104  may be configured to cause eye axis AE to translate around (e.g., orbit) post axis AP as impeller  118  rotates around eye axis AE to impart energy to a blood flow within pump housing  117 . 
     A first outer radial clearance R 1  (e.g., R 1 - 1  ( FIG.  4 A ), R 1 - 2  ( FIG.  4 B ), R 1 - 3  ( FIG.  4 C ), and/or R 1 - 4  ( FIG.  4 D )) between impeller  118  and post  146  varies in magnitude as impeller  118  rotates. First outer radial clearance R 1  is measured at one location of pump  104 , such that it is measured at the same location in  FIGS.  4 A- 4 D . In some examples, pump  104  is configured such that the translation of eye axis AE around post axis AP causes the first outer radial clearance R 1  to cyclically vary from a maximum first radial clearance (e.g., radial clearance R 1 - 1  ( FIG.  4 A )) to a minimum first radial clearance (e.g., radial clearance R 1 - 3  ( FIG.  4 C )) as eye axis AE translates around post axis AP. For example, pump  104  may be configured to define a second outer radial clearance (e.g., radial clearance R 1 - 2  ( FIG.  4 B )) less than the maximum first radial clearance and greater than the minimum first radial clearance as impeller  118  rotates. Pump  104  may be configured to define the minimum first radial clearance (e.g., radial clearance R 1 - 3  ( FIG.  4 C )) as impeller  118  rotates. Pump  104  may be configured to define a fourth outer radial clearance (e.g., radial clearance R 1 - 4  ( FIG.  4 D )) greater than the minimum first radial clearance and less than the maximum first radial clearance as impeller  118  rotates. In examples, pump  104  is configured to cause impeller  118  and pump housing  117  (e.g., housing inner surface  154 ) to define the maximum first radial clearance, the second outer radial clearance, the minimum first radial clearance, and the fourth outer radial clearance substantially cyclically as impeller  118  rotates around eye axis AE. That is, as eye axis AE translates around post axis AP, impeller  118  moves such that it defines, relative to post  146 , The maximum first radial clearance (e.g., R 1 - 1 ), the second outer radial clearance (e.g.) R 1 - 2 , the minimum first outer radial clearance (e.g., R 1 - 3 ), and the fourth outer radial clearance (e.g., R 1 - 4 ). 
     The variation of the first outer radial clearance R 1  over the range between and including the maximum first radial clearance and the minimum first radial clearance may cause impeller  118  to generate a pulsating flow as impeller  118  imparts energy to the blood flow within pump housing  117 . 
     The translation of eye axis AE around post axis AP as impeller  118  rotates may cause an inner radial clearance RC between post  146  and impeller inner surface  147  (defining eye  144 ) to cyclically vary from a maximum inner radial clearance (e.g., radial clearance RC- 1  ( FIG.  4 A ) to a minimum inner radial clearance (e.g., RC- 3  ( FIG.  4 C )). For example, pump  104  may be configured to define a second inner radial clearance (e.g., radial clearance RC- 2  ( FIG.  4 B )) less than the maximum inner radial clearance and greater than the minimum inner radial clearance as impeller  118  rotates. Pump  104  may be configured to define the minimum inner radial clearance (e.g., radial clearance RC- 3  ( FIG.  4 C )) as impeller  118  rotates in the rotational direction W. Pump  104  may be configured to define a fourth inner radial clearance (e.g., radial clearance RC- 4  ( FIG.  4 D )) greater than the minimum inner radial clearance and less than the maximum inner radial clearance as impeller  118  rotates. In examples, pump  104  is configured to cause impeller  118  and post  146  to define the maximum inner radial clearance, the second inner radial clearance, the third inner radial clearance, and the minimum inner radial clearance substantially cyclically as impeller  118  rotates around eye axis AE. That is, as eye axis AE translates around post axis AP, impeller  118  moves such that it defines, relative to post  146 , the maximum inner radial clearance (e.g., RC- 1 ), the second inner radial clearance (e.g., RC- 2 ), the minimum first inner radial clearance (e.g., RC- 3 ), and the fourth inner radial clearance (e.g., RC- 4 ). Inner radial clearance RC (e.g., RC- 1 , RC- 2 , RC- 3 , and RC- 4 ) may be measured at one location of pump  104 , such that it is measured at the same location in  FIGS.  4 A- 4 D . 
     In examples, pump  104  is configured such that the inner radial clearance RC between impeller  118  and post  146  varies proportionally to the first radial clearance R 1  between the impeller and the housing. In examples, pump  104  defines the inner radial clearance RC in a direction substantially parallel to the direction of first outer radial clearance R 1 . In some examples, the first outer radial clearance R 1  defines a first displacement vector in a first direction, and the inner radial clearance RC defines a second displacement vector in the first direction. 
     In examples, the varying inner radial clearance RC causes eye volume  149  to describe a substantially non-uniform shape with respect to post axis P as impeller  118  rotates around eye axis AE and eye axis AE translates around post axis P. For example, eye volume  149  may be defined by a plurality of outer radii passing defined from the post axis AP to impeller inner surface  147  and passing through inner perimeter P 2  of post  146 . The plurality of outer radii may define a varying radial displacement between post axis AP and impeller inner surface  146  around the inner perimeter  146 , such that eye volume  149  describes a substantially non-uniform shape with respect to post axis AP. Magnetic bearing  156  may be configured to cause eye volume  149  to describe the substantially non-uniform shape as impeller  118  rotates around eye axis AE to impart energy to a fluid. 
     As used herein, when impeller  118  rotates around eye axis AE, this means that impeller  118  rotates as a fixed body around an axis of rotation. The axis of rotation may be substantially defined by and/or coincident with eye axis AE. When eye axis AE translates around post axis AP, this may mean that some portion of eye axis AE defines a closed perimeter around post axis AP as eye axis AE translates around post axis AP. In some examples, eye axis AE is substantially parallel with post axis AP when eye axis AE translates around post axis AP, although this is not required. The magnitudes of the maximum first radial clearance and the minimum first radial clearance may vary as impeller  118  proceeds from one rotation around eye axis AE to a subsequent rotation around eye axis AE. Hence, impeller  118  and pump housing  117  are configured to define an initial maximum first radial clearance and an initial minimum first radial clearance during an initial revolution of impeller  118  around eye axis AE, and define a subsequent maximum first radial clearance and a subsequent minimum first radial clearance during a subsequent revolution of impeller  118  around eye axis AE. The initial maximum first radial clearance may define a displacement (e.g., a length) different from the subsequent maximum first radial clearance and/or the initial minimum first radial clearance may define a displacement (e.g., a length) different from the subsequent minimum first radial clearance. 
       FIG.  5    illustrates a schematic cross-sectional view of example blood pump  104  configured to produce a pulsating flow as a blood flow flows from fluid inlet  110  to fluid outlet  114 . The cross-section is taken through a center of pump housing  117 , e.g., along post axis AP. Pump housing  117  is configured to house the components of pump  104 . In examples, pump housing  117  includes upper housing  153  and lower housing  155  configured to mechanically engage to define volume  152 . Post  146  is mechanically supported by pump housing  117  and defines post axis AP. Volume  152  may defines a radius RV between post axis AP and housing inner surface  154  that, in which example shown in  FIG.  5   , increases progressively (e.g., in a clockwise of counter-clockwise direction) around post axis AP to fluid outlet  114 . Upper housing  153  and lower housing  155  may be configured to mechanically engage to define fluid outlet  114 . 
     Inflow line  105  is configured to receive a blood flow via MCS inlet  109  and provide the provide the blood flow to impeller  118  via inflow line lumen  140  and fluid inlet  110 . In examples, pump housing  117  mechanically supports inflow line  105 . Pump housing  117  may mechanically support inflow line  105  such that post axis AP extends at least partially through fluid inlet  110  and/or inflow line lumen  140 . In examples, pump housing  117  (e.g., upper housing  153  and lower housing  155 ) and inflow fine  105  may be fixedly connected to define a continuous, enclosed flow path from MCS inlet  109  to fluid outlet  114 . In examples, inflow line  105  includes an outer surface  162  (“inflow outer surface  162 ”) and an inner surface  164  (“inflow inner surface  164 ”) opposite inflow outer surface  162 . Inflow inner surface  164  may define inflow line lumen  140 . 
     Impeller  118  is fully or partially enclosed by pump housing  117 . Impeller  118  is configured to receive a blood flow via fluid inlet  110  and impart energy to the blood flow as the blood flow flows from fluid inlet  110  to fluid outlet  114 . Impeller  118  is configured to rotate around eye axis AE defined by impeller eye  144  when impeller  118  is positioned within pump housing  117 . Eye axis AE extends through eye volume  149  defined by impeller eye  144 . In examples, impeller  118  is configured such that eye volume  149  receives post  146  when impeller  118  is positioned within pump housing  117 , such that impeller eye  144  substantially surrounds post  146 . In examples, impeller  118  is configured to receive a blood flow (e.g., from fluid inlet  110 ) into eye volume  149  and rotate around eye axis AE to impart energy by accelerating the blood flow housing inner surface  154 . Impeller  118  is configured to rotate to impart centrifugal forces to the blood flow flowing from impeller eye  144  toward housing inner surface  154 . 
     Pump  104  includes a magnetic bearing  156  configured to establish and/or maintain the inner radial clearance RC between impeller  118  (e.g., impeller inner surface  147 ) and post  146  (e.g., inner perimeter P 2 ). Magnetic bearing  156  may be configured to generate a bearing magnetic field which generate magnetic forces between impeller  118  and post  146 . Magnetic bearing  156  may be configured such that the magnetic forces (e.g., attractive or repulsive) maintain the inner radial clearance RC. In examples, magnetic bearing  156  is configured to cause the magnetic forces to act between impeller  118  and post  146  around some portion of or substantially all of a perimeter defined around post axis AP and/or eye axis AE, such that a first force vector acting in a first direction (e.g., on one of impeller  118  or post  146 ) substantially opposes a second force vector acting in a second direction (e.g., on the one of impeller  118  or post  146 ) opposite the first direction. For example, the first force vector and the second force vector may act through a closed perimeter in a plane substantially perpendicular to post axis AP. The opposition of the first force vector and the second force vector may act to establish and/or maintain the inner radial clearance RC between impeller  118  (e.g., impeller inner surface  147 ) and post  146 . 
     In the example shown in  FIG.  5   , magnetic bearing  156  includes an inner ring  166  and an outer ring  168  configured to establish and/or maintain the inner radial clearance RC. The bearing magnetic field generated by magnetic bearing  156  causes inner ring  166  to magnetically interact with outer ring  168 . Magnetic bearing  156  may be configured such that the magnetic interaction between inner ring  166  and outer ring  168  causes the magnetic force between impeller  118  and post  146 . In some examples, magnetic bearing  156  is configured to cause inner ring  166  to generate the magnetic field causing inner ring  166  to magnetically interact with outer ring  168 . In other examples, magnetic bearing  156  is configured to cause outer ring  168  to generate the magnetic field causing inner ring  166  to magnetically interact with outer ring  168 . Inner ring  166  may be configured to transmit some portion of the magnetic force to post  146 . Outer ring  168  may be configured to transmit some portion of the magnetic force to impeller  118 . In examples, inner ring  166  is mechanically supported by and/or integral with post  146 . Outer ring  168  may be mechanically supported by and/or integral with impeller  118 . 
     Magnetic bearing  156  is configured to cause the magnetic forces to vary around the perimeter defined around post axis AP and/or eye axis AE. In examples, magnetic bearing  156  may be configured to cause inner radial clearance RC to vary around inner perimeter P 2 . Magnetic bearing  156  may be configured such that the magnetic forces cause inner radial clearance RC to vary such that eye axis AE is substantially offset from post axis AP when the magnetic forces establish and/or maintain the inner radial clearance RC. 
     In some examples, magnetic bearing  156  is configured as a passive magnetic bearing including one or more permanent magnets. For example, inner ring  166  and/or the outer ring  168  may include a permanent magnet configured to cause magnetic forces between inner ring  166  and outer ring  168 . In some examples, one of inner ring  166  or outer ring  168  includes a permanent magnet and the other of inner ring  166  or outer ring  168  includes a ferromagnetic material configured to interact with a magnetic field generated by the permanent magnet. The permanent magnet may comprise, for example, iron, a steel, nickel, platinum, cobalt, samarium, boron, and/or other materials suitable for permanent magnetization. The ferromagnetic material may comprise, for example, iron, nickel, cobalt, a steel, a “soft iron” having a relatively low coercivity, or another suitable material. The permanent magnet may be configured to cause the magnetic forces between post  146  and impeller  118  to vary around the perimeter defined around post axis AP and/or eye axis AE. For example, the permanent magnet may be configured to generate a magnetic field exhibiting a varying magnetic flux density around the perimeter defined around post axis AP and/or eye axis AE. The varying magnetic flux density may cause the magnetic forces between post  146  and impeller  118  to vary around the perimeter defined around post axis AP and/or eye axis AE. In some examples, the permanent magnet defines a structural feature (e.g., a notch and/or face in the permanent magnet) configured to cause the magnetic flux density and/or the magnetic forces to vary. 
     In other examples, magnetic bearing  156  is configured as an active magnetic bearing including one or more electromagnets. For example, inner ring  166  and/or the outer ring  168  may include an electromagnet configured to cause magnetic forces (attractive or repulsive) between inner ring  166  and outer ring  168 . In examples, one of inner ring  166  or outer ring  168  includes an electromagnet and the other of inner ring  166  or outer ring  168  includes a ferromagnetic material configured to interact with a magnetic field generated by the electromagnet. The electromagnet may be configured to cause the magnetic forces between post  146  and impeller  118  to vary around the perimeter defined around post axis AP and/or eye axis AE. In examples, the electromagnet is configured to generate a magnetic field exhibiting a varying magnetic flux density around the perimeter defined around post axis AP and/or eye axis AE. The varying magnetic flux density may cause the magnetic forces between post  146  and impeller  118  to vary around the perimeter defined around post axis AP and/or eye axis AE. 
     In some examples, magnetic bearing  156  includes a winding configured to generate the magnetic field of the electromagnet. For example, inner ring  166  may include a winding  170  configured to cause inner ring  166  to generate a magnetic field. Outer ring  168  may include a winding  172  configured to cause outer ring  168  to generate a magnetic field. In examples, winding  170 ,  172  is configured to generate a magnetic field causing the magnetic forces between post  146  and impeller  118  to vary around the perimeter defined around post axis AP and/or eye axis AE. 
     As discussed, pump  104  is configured such that eye axis AE translates around (e.g., orbits) post axis AP when impeller  118  rotates around eye axis AE to impart energy to a blood flow within pump housing  117 . The translation of eye axis AE around post axis AP may cause the inner radial clearance RC to cyclically vary from a maximum inner radial clearance (e.g., radial clearance RC- 1  ( FIG.  4 A ) to a minimum inner radial clearance (e.g., RC- 3  ( FIG.  4 C )). Pump  104  may be configured such that a magnetic field (e.g., a magnetic field strength) generated by winding  170 ,  172  substantially controls the maximum inner radial clearance and/or the minimum inner radial clearance as eye axis AE translates around post axis AP. Pump  104  may be configured such that a pressure range exhibited by the pulsating flow (e.g., at fluid outlet  114 ) is controllable based on the difference between the minimum inner radial clearance and the maximum inner radial clearance. Hence, in examples, control circuitry  120  is configured to control a pressure range exhibited by the pulsating flow by at least controlling the maximum inner radial clearance and/or the minimum inner radial clearance caused by the magnetic field generated by winding  170 ,  172 . Control circuitry  120  may be configured to alter the pressure range exhibited by the pulsating flow by at least altering the magnetic field through, for example, altering electric power supplied to winding  170 ,  172 . 
     In similar manner, the translation of eye axis AE around post axis AP may cause the first outer radial clearance R 1  to cyclically vary from a maximum first radial clearance (e.g., radial clearance R 1 - 1  ( FIG.  4 A )) to a minimum first radial clearance (e.g., radial clearance R 1 - 3  ( FIG.  4 C )). In some examples, pump  104  is configured such that the magnetic field (e.g., the magnetic field strength) generated by winding  170 ,  172  substantially controls the maximum first radial clearance and/or the minimum first radial clearance. Pump  104  may be configured such that the pressure range exhibited by the pulsating flow is controllable based on the difference between the minimum first radial clearance and the maximum first radial clearance, such that control circuitry  120  may control the pressure range of the pulsating flow by at least controlling the maximum first radial clearance and/or the minimum first radial clearance caused by the magnetic field generated by winding  170 ,  172 . 
     In examples, control circuitry  120  is configured to control the magnetic field generated by winding  170 ,  172 . Control circuitry  120  may be configured to control the electric power supplied (e.g., via driveline  108  ( FIG.  1   )) to winding  170 ,  172  to control the magnetic field. For example, control circuitry  120  may be configured to control the magnetic field generated by winding  170 ,  172  to control and/or alter the maximum inner radial clearance, minimum inner radial clearance, minimum first radial clearance, and/or the maximum first radial clearance based on a signal (e.g., from monitor  128  ( FIG.  1   )) representative of a physiological parameter of heart  101 . Hence, control circuitry  120  may be configured to alter the characteristics of the pulsating flow depending on the needs of the patient. 
     In some examples, magnetic bearing  156  may be configured as a hybrid magnetic bearing including both one or more electromagnets and one or more permanent magnets. For example, inner ring  166  may include a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet. Outer ring  168  may include a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet. Control circuitry  120  may be configured to control the power supply to winding  170  to control the magnetic field generated by inner ring  166 , control the power supply to winding  172  to control the magnetic field generated by outer ring  168 , or control both the first power supply to winding  170  and the second power supply to winding  172 . 
     Pump  104  may include stator  158  and/or second stator  160  configured to cause impeller  118  to rotate around eye axis AE to impart energy to a blood flow within pump housing  117 . Stators  158 ,  160  may mechanically supported by pump housing  117 . Stators  158 ,  160  may be configured to generate a motor magnetic field to cause the rotation of impeller  118 . In examples, the motor magnetic field exerts a torque on impeller  118  causing the rotation of impeller  118 . In examples, stators  158 ,  160  are configured to generate a motor magnetic field rotating substantially around post axis PA and/or eye axis AE to cause impeller  118  to rotate. Pump  104  may be configured such that a rotational speed of the motor magnetic field controls the rotational speed of impeller  118  around eye axis AE. In examples, stator  158  includes one or more field elements such as field element  186  and field element  188 . Second stator  160  may include one or more field elements such as field element  190  and field element  192 . Field element  186 ,  188 ,  190 ,  192  may include one or more windings configured to generate an electromagnetic field. The one or more windings may be configured to generate the motor magnetic field using AC electric power or DC electric power (e.g., supplied via driveline  108  ( FIG.  1   )). In some examples, field element  186 ,  188 ,  190 ,  192  includes one or more permanent magnets configured to generate a magnetic field. 
     Control circuitry  120  ( FIG.  1   ) may be configured to control a rotational speed and/or magnetic field strength of the motor magnetic field to, for example, control a speed and/or generated torque of pump  104 . For example, control circuitry  120  may control the electric power supplied to stator  158 ,  160  (e.g., via driveline  108 ) to control the rotational speed and/or magnetic field strength of the motor magnetic field. Control circuitry  120  may be configured to alter the characteristics of the motor magnetic field to alter the pulsating flow produced by pump  104 . For example, pump  104  may be configured such that a pressure range and/or pressure wave period exhibited by the pulsating flow of pump  104  is controllable based on the speed of pump  104 . Control circuitry  120  may be configured to control the pressure range and/or pressure wave period by at least controlling the speed of pump  104 . In examples, control circuitry  120  is configured to control the motor magnetic field to alter a speed a pump  104  based on a signal (e.g., from monitor  128  ( FIG.  1   )) representative of a physiological parameter of patient  103 . In some examples, control circuitry  120  is configured to alter a generated torque of pump  104  to, for example, cause a mechanical vibration to impeller  118  to clear a thrombosis within pump  104 , or for other reasons. Hence, control circuitry  120  may be configured to alter the characteristics of the pulsating flow depending on the needs of the patient. 
     Pump  104  may be configured such that the motor magnetic field magnetically interacts with impeller  118  to cause impeller  118  to rotate around the eye axis. For example, impeller  118  may include one or more impeller pole pieces such as pole piece  178  and pole piece  180  configured to magnetically interact with the motor magnetic field. Pole piece  178 ,  180  may comprise, for example, a ferrous and/or ferromagnetic material. Pump  104  may be configured such that the magnetic interaction of impeller  118  with the motor magnetic field exerts a torque on impeller  118  causing impeller  118  to rotate around eye axis AE. In some examples, pole piece  178 ,  180  includes a permanent magnet configured to magnetically interact with the motor magnetic field. Impeller  118  may mechanically support pole pieces such that when the motor magnetic field causes a torque on pole piece  178 ,  180  around eye axis AE, pole piece  178 ,  180  transmits at least some portion of the torque to impeller  118  to cause the rotation of impeller  118  around eye axis AE. In some examples, stator  158 ,  160  and pole piece  178 ,  180  operate substantially as a brushless DC motor (BLDM) to cause the rotation of impeller  118  around eye axis AE. 
     In examples, pump  104  is configured such that impeller  118  is suspended within pump housing  117  when impeller  118  rotates to impart energy to a blood flow within pump housing  117 . Pump  104  may be configured to maintain an axial clearance between impeller  118  and pump housing  117  (e.g., a clearance in a direction substantially parallel to post axis AP and/or eye axis AE) when impeller  118  impart the energy to the blood flow. Pump  104  may be configured such that the motor magnetic field and/or hydrodynamic forces from the blood flow cause the axial displacement. In examples, rotation of impeller  118  causes some portion of the blood flow entering pump housing  117  via fluid inlet  110  to define one or more hydrodynamic bearings with impeller  118  to causes impeller  118  to axially suspend. Pump  104  may be configured such that the hydrodynamic bearing acts substantially as a thrust bearing for impeller  118  to, for example, assist impeller  118  in its rotation around eye axis AE. 
     For example, impeller  118  may define a first bearing surface  182  configured to allow a portion of the blood flow entering via fluid inlet  110  to flow between first bearing surface  182  and pump housing  117  when impeller  118  rotates around eye axis AE. Impeller  118  may define a second bearing surface  184  configured to allow a portion of the blood flow flowing into eye volume  149  to flow between second bearing surface  184  and pump housing  117  when impeller  118  rotates around eye axis AE. The blood flow flowing between pump housing  117  and first bearing surface  182  and/or second bearing surface  184  may support impeller  118  during rotation and help keep impeller  118  out of contact with pump housing  117  (e.g., upper housing  153  and/or lower housing  155 ). In examples, the blood flow flowing between pump housing  117  and first bearing surface  182  and/or second bearing surface  184  may substantially act as a thrust bearing for impeller  118  to resist axial loads on impeller  118  arising from magnetic forces between stator  158 ,  160  and pole piece  178 ,  180 . 
       FIG.  6    is a functional block diagram illustrating an example medical system  100  that includes MCS device  102 . As shown in  FIG.  6   , monitor  128 , computing device  130 , user interface  132 , and control circuitry  120  are optionally communicatively coupled to a network  200 . In some examples, fewer components (e.g., only computing device  130 ) may be coupled to network  200 . Network  200  represents any public or private communication network, for instance, based on Bluetooth, WiFi®, a proprietary protocol for communicating with IMDs, or other types of networks for transmitting data between computing systems, servers, and computing devices, both implanted within and external to a patient. Monitor  128 , computing device  130 , user interface  132 , control circuitry  120 , and MCS device  102  may each be operatively coupled to network  200  using respective network links  252 ,  254 ,  256 ,  258 , and  262 . Network links  252 ,  254 ,  256 ,  258 ,  262  may be any type of network connections, such as wired or wireless connections as discussed above. 
     Network  200  may provide selected devices, such as monitor  128 , computing device  130 , user interface  132 , control circuitry  120 , and MCS device  102  with access to the Internet, and may enable monitor  128 , computing device  130 , user interface  132 , control circuitry  120 , and MCS device  102  to communicate with each other. For example, rather than communicating via link  134 , monitor  128  and computing device  130  may communicate via network links  252  and  254 . Rather than communicating via link  136 , computing device  130  and control circuitry  120  may communicate via network links  254  and  258 . In some examples, computing device  130  is configured to communicate with MCS device  102  via link  260 , which may be configured similarly to links  252 ,  254 ,  256 ,  258 , and  262  described above. In some examples, rather than communicating via link  260 , MCS device  102  and computing device  130  may communicate via network links  262  and  254 . 
     In some examples, computing device  130  is configured to send data to MCS device  102  and/or control circuitry  120 , receive data from MCS device  102  and/or control circuitry  120 , or both via network  200 . For example, computing device  130  may send at least one of one or more signals (e.g., conditioned or unconditioned signals from monitor  128 ), MCS data, auxiliary cardiovascular data, and user data to MCS device  102  and/or control circuitry  120 . Computing device  130  also may receive data from MCS device  102  and/or control circuitry  120  including, for example, stored signals, stored indications (e.g., from sensor  121 ), stored user data, notification data (e.g., regarding indications of, for example, an operation and/or condition of MCS device  102 ), algorithm data (e.g., to update or modify algorithms used by computing device  130  or control circuitry  120  to, for example, control MCS device  102 ), and the like. Computing device  130  may collect and analyze one or more signals, indications of MCS device  102  operation, MCS data, auxiliary cardiovascular data, and user data from at least one of computing device  130  and/or control circuitry  120  to notify patient  103  of another user (e.g., via user interface  132 ) of an operation of and/or indication from MCS device  102 , such as a pump model, a pump of an identified age range, a pump with an identified operational history, a pump used in a patient with an identified medical history or treatment history, or the like. 
     In examples, computing device  130  includes storage components  270  to store data provided by monitor  128 , control circuitry  120 , sensor  121 , and/or other components of medical system  100 , or any combination thereof. Control circuitry  120  is configured to alter the operation of pump  104  based on the data provided by monitor  128  and/or control circuitry  120 , track the data provided by monitor  128  and/or control circuitry  120  over time, or both, e.g., directly or under the control of computing device  130 . In examples, computing device  130  may receive (e.g., from control circuitry  120 ) data associated with pump  104 , such as but is not limited to, the age and model type of one or more components of pump  104 , the age and usage of power source  122 , the power consumption of pump  104 , flow data associated with blood flow through pump  104 , a temperature of pump  104 , revolutions per minute of pump  104 , user input data from user interface  132 , or other data. 
     In some examples, monitor  128  is within or coupled to an implantable medical device (IMD). The IMD may include, but is not limited to, at least one of MCS device  102  or an insertable cardiac monitor. In some examples, monitor  128  may be within or coupled to a wearable device (e.g., an externally-wearable device) or other portable device, such as, for example, a mobile phone, patch, chest strap, or a Holter monitor. In examples, monitor  128  is configured to generate a signal (e.g., output) representative of a physiological parameter of patient  103  and provides the signal to computing device  130 , control circuitry  120 , user interface  132 , and/or a remote server. In some examples, monitor  128  may be configured to condition the signal prior to providing the signal to computing device  130 , control circuitry  120 , user interface  132 , and/or the remote server. Conditioning may include, but is not limited to, amplification, filtering, attenuation, isolation, and/or transformation such as Fast Fourier Transformation. In some examples, monitor  128  may provide an unconditioned signal to computing device  130 , control circuitry  120 , user interface  132 , and/or the remote server. Computing device  130 , control circuitry  120 , user interface  132 , and/or the remote server may condition the signal in some examples. 
     User interface  132  is configured to receive input from a user and/or communicate information to a user (e.g., patient  103 , a caregiver, and/or a clinician) or another entity, such as a remote server system. User interface system may include any suitable user input devices, such as, but not limited to, a display, a keyboard, buttons, a touchscreen, a speaker, a microphone, a gyroscope, an accelerometer, a vibration motor, or the like. In examples, user interface  132  is configured to generate an alert based on a communication received from computing device  130 , monitor  128 , and/or control circuitry  120 . In some examples, a display of user interface  132  may include a mobile device of the user. Similarly, computing device  130  includes one or more input components that receive tactile input, kinetic input, audio input, optical input, or the like from a user or another entity via user interface  132 . In this way, user interface  132  may receive user input from a user and send user input to computing device  130  or control circuitry  120 . For example, a user may provide user input to user interface  132 , which communicates the user input to computing device  130  or control circuitry  120  to control an operation of MCS device  102 . 
     In some, but not all, examples, medical system  100  includes drug delivery device  280 . Drug delivery device  280  is configured to deliver any suitable drug therapy to patient  103 . Drug delivery device may be communicatively coupled to computing device  130  via link  282 . Additionally or alternatively, drug delivery device  280  may be operatively coupled to network  200  via network link  284 . Link  282 ,  284  may be the same as or substantially similar to links  252 ,  254 ,  256 ,  258 ,  260 , and  262 , as discussed above, as discussed above. Computing device  130  may control drug delivery device  280  to deliver an intervention to a patient. For example, computing device  130  may control drug delivery device  280  to deliver or increase a rate of delivery of a thrombolytic agent to MCS device  102 , such as into a blood stream of a patient or directly to a component of MCS device  102 . The thrombolytic agent may be configured to breakup (e.g., at least partially dissolve) or dislodge a thrombus from MCS device  102  (e.g., medical pump  104 ). Medical system  100  may be communicatively coupled (e.g., connected) to one or more additional cardiovascular system monitoring devices. Cardiovascular system monitoring devices include, but are not limited to, pulse monitoring devices, blood oxygenation monitoring devices, blood pressure monitoring devices, prothrombin time monitoring devices, and additional user input devices. 
     Although computing device  130  of  FIG.  6    is shown separate from monitor  128 , user interface  132 , and control circuitry  120 , in some examples, computing device  130  may include one or more of monitor  128 , user interface  132 , and control circuitry  120 . For example, rather than being coupled by links, computing device  130  and user interface  132  may form an integrated device, such as a mobile phone or a wearable medical device monitor. In one example approach, computing device  130  includes processing circuitry  263 , one or more one or more input devices  264 , communications circuitry  266 , one or more output devices  268 , and one or more one or more storage components  270 . In some examples, computing device  130  may include additional components or fewer components than those illustrated in  FIG.  6   . 
     Control circuitry  120  and processing circuitry  263  may include various type of hardware, including, but not limited to, microprocessors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete or integrated logic circuitry, as well as combinations of such components. The term “processing circuitry” and “control circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. Control circuitry  120  and processing circuitry  263  may represent hardware that can be configured to implement firmware and/or software that sets forth one or more algorithms described herein. For example, processing circuitry  263  may be configured to implement functionality, process instructions, or both for execution within computing device  130  of processing instructions stored within storage components  270 . In some examples, processing circuitry  263  includes processing circuitry of an IMD and/or other devices of medical system  100 . 
     Input devices  264 , in some examples, are configured to receive input from a user through tactile, audio, or video sources. Examples of input devices  264  include user interface  132 , a mouse, a button, a keyboard, a voice responsive system, video camera, microphone, touchscreen, or any other type of device for detecting a command from a user. In some example approaches, user interface  132  includes all input devices  264  employed by computing device  130 . 
     Computing device  130  may utilize communications circuitry  266  to communicate with external devices (e.g., monitor  128 , control circuitry  120 , user interface  132 , and/or MCS device  102 ) via one or more networks, such as one or more wired or wireless networks. Communications circuitry  266  may include a communications interface, such as an Ethernet card, a radio frequency transceiver, cellular transceiver, a Bluetooth® interface card, USB interface, or any other type of device that can send and receive information. In some examples, computing device  130  utilizes communications circuitry  266  to wirelessly communicate with an external device such as a remote server system. 
     Computing device  130  may further include one or more output devices  268 . Output devices  246 , in some examples, are configured to provide output to a user using, for example, audio, video or tactile media. For example, output devices  246  may include user interface  132 , a sound card, a video graphics adapter card, or any other type of device for converting a signal into an appropriate form understandable to humans or machines. In some example approaches, user interface  132  includes all output devices  246  employed by computing device  130 . 
     One or more storage components  270  may be configured to store information within computing device  130  during operation. One or more storage components  270 , in some examples, include a computer-readable storage medium or computer-readable storage device. In some examples, one or more storage components  270  include a temporary memory, meaning that a primary purpose of one or more storage components  270  is not long-term storage. One or more storage components  270 , in some examples, include a volatile memory, meaning that one or more storage components  270  does not maintain stored contents when power is not provided to one or more storage components  270 . Examples of volatile memories include random access memories (RAM), dynamic random-access memories (DRAM), static random-access memories (SRAM), and other forms of volatile memories known in the art. In some examples, one or more storage components  270  are used to store program instructions for execution by processing circuitry  263 . One or more storage components  270 , in some examples, are used by software or applications running on computing device  130  to temporarily store information during program execution. In some examples, one or more storage components  270  may further include one or more storage components  270  configured for longer-term storage of information. In some examples, one or more storage components  270  include non-volatile storage elements. Examples of such non-volatile storage elements include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. 
     An example technique for connecting a generating a pulsating flow using a medical system is illustrated in  FIG.  7   . Although the technique is described mainly with reference to medical system  100  of  FIGS.  1 - 5   , and as being performed by control circuitry  120 , the technique may be performed by another system and/or other control circuitry of system  100  alone or in combination with control circuitry  120 . 
     The technique includes using controlling, by control circuitry  120 , impeller  118  to rotate within pump housing  117  of pump  104  to impart energy to a fluid ( 702 ). Impeller  118  rotates around an eye axis AE extending through an impeller eye  144  defined by impeller  118  to impart the energy to the fluid. In examples, a magnetic bearing  156  establishes an inner radial clearance RC between impeller  118  and a post  146  mechanically supported by pump housing  117  as impeller  118  rotates to impart the energy to the fluid. 
     Magnetic bearing  156  may include an inner ring  166  mechanically supported by post  146  and an outer ring  168  mechanically supported by impeller  118 . As discussed above, inner ring  166  and outer ring  168  may magnetically interact to establish the inner radial clearance RC. In examples, magnetic bearing  156  causes a first magnetic force between inner ring  166  and outer ring  168  in a first radial direction and a second magnetic force between inner ring  166  and outer ring  168  in a second direction substantially opposite the first direction, with the second magnetic force less than the first magnetic force. The differing magnetic forces caused by magnetic bearing  156  may cause the eye axis to translate around post axis when impeller  118  rotates to impart energy to the fluid, such that impeller  118  generates the pulsating flow. The magnetic interaction between inner ring  166  and outer ring  168  may cause the eye axis AE to translate around a post axis AP defined by post  146  when impeller  118  rotates around eye axis AE to impart the energy to the fluid. In examples, the magnetic interaction may cause the inner radial clearance RC to vary as impeller  118  imparts the energy to the fluid. In examples, the magnetic interaction may cause a first outer radial clearance R 1  between impeller  118  and pump housing  117  to vary as impeller  118  imparts the energy to the fluid. 
     The translation of eye axis AE around a post axis AP as impeller  118  imparts energy to the fluid may generate a pulsating flow of the fluid. The pulsating flow may define a substantially continuous pressure waveform which substantially oscillates between the maximum pressure and the minimum pressure. 
     Control circuitry  120  may be configured to alter the operation of pump  104  to control a pressure range exhibited by the pulsating flow as impeller  118  imparts the energy to the fluid. Control circuitry  120  may alter the operation of pump  104  (e.g., a rotational speed of impeller  118 ) to control a wave period of the pulsating flow as impeller  118  imparts energy to the fluid. Stator  158 ,  160  may magnetically interact with impeller  118  to cause impeller  118  to rotate around eye axis AE. In examples, the stator and/or the impeller define a motor magnetic field to cause the impeller to rotate around the eye axis. Control circuitry  120  may control a rotational speed and/or strength of the motor magnetic field to control a rotational speed of the impeller. 
     In the example shown in  FIG.  7   , control circuitry  120  modifies a bearing magnetic field of magnetic bearing  156  to modify an operation of MCS device  102  ( 704 ). In examples, control circuitry  120  may increase a current and/or voltage supplied to windings  170 ,  172  to modify the operation of MCS device  102  (e.g., pump  104 ). Control circuitry  120  may alter the bearing magnetic field to increase or decrease magnetic forces between impeller  118  and post  146  to modify the operation of MCS device  102 . For example, control circuitry may alter the bearing magnetic field to increase a first magnetic force acting in a first direction between impeller  118  and post  146  and decrease a second magnetic force acting in a second direction opposite the first direction to modify the operation of MCS device  102 . Control circuitry may modify the bearing magnetic field to modify the radial distribution (e.g., with respect to post axis AP) of the magnetic forces acting between impeller  118  and post  146 . In examples, control circuitry modifies the bearing magnetic field to increase and/or decrease a maximum outer radial clearance, minimum outer radial clearance, maximum inner radial clearance, and/or minimum inner radial clearance. Control circuitry  120  may modify the magnetic field strength of the bearing magnetic field to modify the operation of MCS device  102 . 
     Control circuitry  120  may receive a flow signal from sensor  121  and modify the bearing magnetic field and/or motor magnetic field based on the flow signal. Sensor  121  may generate a flow signal indicative of the pulsating flow and/or the characteristic of MCS device  102  indicating the pulsating flow, such as a flow rate of the blood flow, a pressure of the blood flow, a position of impeller  118 , an electrical characteristic of MCS  102  (e.g., pump  104 ), and/or a mechanical wave generated by MCS device  102 . Control circuitry  120  may analyze evaluate the flow signal to indicate MCS device  102  is producing a pulsating flow (e.g., based on the variance and/or oscillation of a wave form exhibited by the flow signal). In examples, control circuitry  120  may evaluate the pulsating flow generated by MCS device  102  by evaluating a plurality of frequency peaks, periods, or other characteristics of the wave form of the flow signal. 
     Control circuitry  120  may monitor MCS device  102  to evaluate, assess, determine, analyze, monitor, and or otherwise confirm that pump  104  is operating in a condition causing eye axis AE to translate around post axis AP as impeller  118  rotates around eye axis AE. Control circuitry  120  may evaluate, assess, analyze, and or otherwise monitor the flow signal to determine if MCS device  102  is producing a pulsating flow. Control circuitry  120  may alter an operating characteristic of pump  104  to cause the pulsating flow based on the flow signal. 
     Control circuitry  120  may control an operation of MCS device  102  based on a sensed physiological parameter of the patient  103 . Monitor  128  may detect a physiological parameter of patient  103  (e.g., a cardiac signal such as an ECG, ECM, an activity level of patient  103 , a mechanical wave of heart  101 , an electrical field of heart  101 , or another physiological parameter) and communicate a signal indicative of the physiological parameter to computing device  130  (e.g., via communication link  134 ) and/or control circuitry  120 . Control circuitry  120  may alter an operation of pump  104  based on the indicative signal from monitor  128  and/or a communication from computing device  130 . 
     The techniques described in this disclosure, including those attributed to system  100 , control circuitry  120 , computing device  130 , or various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry. The term “processor,” “processing circuitry,” “controller,” or “control circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. 
     Such hardware, software, firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, modules or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. 
     When implemented in software, the functionality ascribed to the systems, devices and techniques described in this disclosure may be embodied as instructions on a computer-readable medium such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions may be executed to support one or more aspects of the functionality described in this disclosure. 
     This disclosure includes the following non-limiting examples. 
     Example 1: A mechanical circulatory support device comprising: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a post mechanically supported by the housing within the volume, wherein the post defines a post axis, and wherein the post mechanically supports an inner ring; and an impeller mechanically supporting an outer ring, wherein the impeller defines an eye surrounding the post and an eye axis extending through the eye, wherein the inner ring is configured to magnetically interact with the outer ring to establish a radial clearance between the inner ring and the outer ring, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the eye axis to translate around the post axis as the impeller rotates around the eye axis when the impeller imparts energy to a fluid flowing from the fluid inlet to the fluid outlet. 
     Example 2: The mechanical circulatory support device of example 1, wherein the eye axis and the post axis are substantially parallel. 
     Example 3: The mechanical circulatory support device of example 1 or example 2, wherein the impeller defines an outer radial clearance between an outer perimeter of the impeller and the housing, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the outer radial clearance to vary as the impeller rotates around the eye axis. 
     Example 4: The mechanical circulatory support device of any of examples 1-3, wherein the impeller is configured to cause a pulsating flow of the fluid at the fluid outlet when the impeller imparts the velocity to the fluid. 
     Example 5: The mechanical circulatory support device of any of examples 1-4, wherein the inner ring and the outer ring are configured to define a magnetic field to cause the inner ring to magnetically interact with the outer ring, and wherein at least one of the inner ring or the outer ring is configured to cause the magnetic field to cause magnetic forces between the inner ring and the outer ring that vary around a perimeter defined by the inner ring. 
     Example 6: The mechanical circulatory support device of example 5, wherein at least one of the inner ring or the outer ring includes a permanent magnet, and wherein the permanent magnet defines a structural feature configured to cause the magnetic forces to vary around the perimeter defined by the inner ring. 
     Example 7: The mechanical circulatory support device of any of examples 1-6 wherein at least one of the inner ring or the outer ring includes a winding configured to generate an electromagnetic field configured to cause the inner ring to magnetically interact with the outer ring, wherein the control circuitry is configured to control a magnetic strength of the electromagnetic field using the winding. 
     Example 8: The mechanical circulatory support device of any of examples 1-7, wherein the impeller includes a pole piece, the pump further comprising a stator configured to generate a stator magnetic field, wherein the stator is configured to cause the stator magnetic field to magnetically interact with the pole piece to cause the impeller to rotate around the eye axis. 
     Example 9: The mechanical circulatory support device of any of examples 1-8, further comprising control circuitry, wherein the stator includes a stator winding configured to generate a rotating stator magnetic field, and wherein the control circuitry is configured to control a rotational speed of the rotating stator magnetic field using the stator winding. 
     Example 10: The mechanical circulatory support device of any of examples 1-8, wherein the inner ring is integrally formed with the post, the outer ring is integrally formed with the impeller, or the inner ring is integrally formed with the post and the outer ring is integrally formed with the impeller. 
     Example 11: The mechanical circulatory support device of any of examples 1-10, wherein the housing is configured to cause the fluid to flow through the radial clearance between the inner ring and the outer ring when the fluid flows from the fluid inlet to the fluid outlet. 
     Example 12: The mechanical circulatory support device of any of examples 1-11, further comprising: a sensor configured to provide a flow signal indicative of a flow of the fluid; and control circuitry configured to determine when the eye axis translates around the post axis based on the flow signal. 
     Example 13: The mechanical circulatory support device of any of examples 1-12, further comprising: an inflow line configured to receive a blood flow from a heart of a patient and provide the blood flow to the fluid inlet; and an outflow line configured to receive the blood flow from the fluid outlet and provide the blood flow to vasculature of the patient. 
     Example 14: The mechanical circulatory support device of example 13, further comprising control circuitry configured to: receive one or more signals indicative of a physiological parameter of the heart of the patient; and control at least one of the radial clearance or a rotational speed of the impeller based on the one or more signals. 
     Example 15: The mechanical circulatory support device of example 14, further comprising a display, wherein the control circuitry is configured to output, via the display, an indication of at least one of the physiological parameters of the heart, an operating condition of the pump, or a performance characteristic of the pump. 
     Example 16: A heart pump, comprising: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a stator configured to generate a stator magnetic field; a post mechanically supported by the housing within the volume, wherein the post mechanically supports an inner ring; and an impeller configured to impart energy to a fluid flowing from the fluid inlet to the fluid outlet, wherein the impeller defines an outer radial clearance between an outer perimeter of the impeller and the housing, and wherein the inner ring is configured to magnetically interact with an outer ring mechanically supported by the impeller to cause the outer radial clearance to vary. 
     Example 17: The heart pump of example 16, wherein the post defines a post axis, and wherein the impeller defines an eye surrounding the post and an eye axis extending through the eye, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the eye axis to translate around the post axis as the impeller rotates around the eye axis to impart velocity to the fluid. 
     Example 18: The heart pump of example 16 or example 17, wherein the inner ring is configured to magnetically interact with the outer ring to establish a radial clearance between the inner ring and the outer ring. 
     Example 19: A method, comprising: controlling, by control circuitry, an impeller of a medical pump to rotate within a housing, the medical pump comprising: a housing including a fluid inlet and a fluid outlet, wherein the housing defines a volume fluidically coupling the fluid inlet and the fluid outlet; a post mechanically supported by the housing within the volume, wherein the post defines a post axis, and wherein the post mechanically supports an inner ring; and the impeller mechanically supporting an outer ring, wherein the impeller defines an eye surrounding the post and an eye axis extending through the eye, wherein the inner ring is configured to magnetically interact with the outer ring to establish a radial clearance between the inner ring and the outer ring, and wherein the inner ring is configured to magnetically interact with the outer ring to cause the eye axis to translate around the post axis as the impeller rotates around the eye axis when the impeller imparts energy to a fluid flowing from the fluid inlet to the fluid outlet; and modifying, by the control circuitry, a magnetic field causing the magnetic interaction between the inner ring and the outer ring. 
     Example 20: The method of example 19, further comprising receiving, by the control circuitry, at least one of a flow signal indicative of a pressure of the fluid as the impeller imparts the velocity to the fluid or a physiological signal indicative of a physiological parameter of a patient, wherein modifying the magnetic field comprises modifying the magnetic field based on the flow signal or the physiological signal 
     Various examples of the disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following claims.