Circulatory Assist Systems and Methods
Circulatory assist systems and related methods provide for pumping of blood from a ventricle to an artery. A circulatory assist system includes a ventricular assist device, a motor control circuit, a controller, a sensing circuit, and a blood flow cannula. The ventricular assist device includes a housing, a stator assembly, and a blood flow impeller. The blood flow impeller includes a first disk portion, a second disk portion, and vanes extending between the first disk portion and the second disk portion. Each of the first disk portion and the second disk portion includes embedded magnetic segments for rotation and levitation of the blood flow impeller. The first disk portion has central aperture configured for transit of a blood flow received through the blood flow inlet into the blood flow impeller for impelling radially outwardly between the first disk portion and the second disk portion via the vanes.
1 . A circulatory assist system comprising:
a centrifugal ventricular assist device configured to pump blood from a ventricle of a patient to an artery of the patient, wherein the centrifugal ventricular assist device comprises a housing, a stator assembly, and a blood flow impeller, wherein the housing defines a blood flow inlet and a blood flow outlet, wherein the stator assembly comprises stator coils, wherein the blood flow impeller comprises a first disk portion, a second disk portion, and vanes extending between and separating the first disk portion and the second disk portion, wherein each of the first disk portion and the second disk portion comprises embedded magnetic segments for rotation and levitation of the blood flow impeller, and wherein the first disk portion defines a first disk portion central aperture configured for transit of a blood flow received through the blood flow inlet into the blood flow impeller for impelling radially outwardly between the first disk portion and the second disk portion via the vanes for output from the blood flow outlet;
a motor control circuit operable to supply drive currents to the stator coils;
a controller configured for controlling operation of the motor control circuit;
a sensing circuit configured to generate a stator drive signal indicative of a magnitude of the drive currents supplied to the stator coils by the motor control circuit or a magnitude of a drive power supplied to the stator coils via the drive currents; and
a blood flow cannula configured for connecting the blood flow outlet with the artery.
2 . The circulatory assist system of claim 1 , wherein:
the housing defines a central hub;
the second disk portion defines a second disk portion central aperture; and
the central hub extends at least partially through the second disk portion central aperture.
3 . The circulatory assist system of claim 1 , wherein:
the blood flow impeller has a rotation axis; and
the blood flow impeller is magnetically suspended parallel to the rotation axis during operation of the centrifugal ventricular assist device via the embedded magnetic segments.
4 . The circulatory assist system of claim 1 , wherein the housing defines a volute region that extends circumferentially and is configured to receive the blood flow from the blood flow impeller and redirect the blood flow to the blood flow outlet.
5 . The circulatory assist system of claim 1 , further comprising a battery pack for supplying electrical power for operation of the centrifugal ventricular assist device.
6 . The circulatory assist system of claim 1 , wherein the controller is configured to:
process the stator drive signal to determine a speed synchronization start point at which time a rotation rate of the blood flow impeller will begin a predetermined rotation rate variation that is synchronized with a patient's cardiac cycle; and
control the motor control circuit to modulate the rotation rate of the blood flow impeller to implement the predetermined rotation rate variation.
7 . The circulatory assist system of claim 6 , wherein:
the controller is configured to process the stator drive signal to determine an estimated current cardiac cycle pulse period for the patient; and
the controller is configured to determine the speed synchronization start point based on the estimated current cardiac cycle pulse period for the patient.
8 . The circulatory assist system of claim 7 , wherein the controller is configured to:
process the stator drive signal to determine at least two prior cardiac cycle pulse periods for the patient; and
determine the estimated current cardiac cycle pulse period for the patient based on the at least two prior cardiac cycle pulse periods.
9 . The circulatory assist system of claim 6 , wherein the stator drive signal is indicative of the magnitude of the drive currents supplied to the stator coils by the motor control circuit.
10 . The circulatory assist system of claim 6 , wherein the stator drive signal is indicative of the magnitude of the drive power supplied to the stator coils via the drive currents.
11 . The circulatory assist system of claim 6 , wherein the controller is configured to filter the stator drive signal to remove frequencies above 5 Hz.
12 . The circulatory assist system of claim 6 , wherein the controller is configured to process the stator drive signal to identify cardiac cycle features of the patient.
13 . The circulatory assist system of claim 12 , wherein the predetermined rotation rate variation begins prior to a systolic phase for the ventricle and ends before completion of the systolic phase for the ventricle.
14 . The circulatory assist system of claim 13 , wherein the controller is configured to control the motor control circuit to rotate the blood flow impeller at a constant rotational rate between implementations of the predetermined rotation rate variation.
15 . The circulatory assist system of claim 14 , wherein the rotation rate of the blood flow impeller during the predetermined rotation rate variation is higher than the constant rotation rate.
16 . The circulatory assist system of claim 6 , wherein the predetermined rotation rate variation is specified by a clinician.
17 . A method of pumping blood from a ventricle of a patient to an artery of a patient, the method comprising:
operating a motor drive circuit of a centrifugal ventricular assist device to supply drive currents to stator coils of a motor stator to generate a magnetic field to drive rotation of a blood flow impeller that comprises a first disk portion, a second disk portion, and vanes extending between and separating the first disk portion and the second disk portion, wherein each of the first disk portion and the second disk portion comprises embedded magnetic segments for rotation and levitation of the blood flow impeller, and wherein the first disk portion defines a first disk portion central aperture configured for transit of a blood flow received through a blood flow inlet into the blood flow impeller for impelling radially outwardly between the first disk portion and the second disk portion via the vanes for output from a blood flow outlet; and
generating a stator drive signal indicative of a magnitude of the drive currents supplied to the stator coils by the motor drive circuit or a magnitude of a drive power supplied to the stator coils via the drive currents.
18 . The method of claim 17 , wherein:
the centrifugal ventricular assist device comprises a housing that defines a central hub;
the second disk portion defines a second disk portion central aperture; and
the central hub extends at least partially through the second disk portion central aperture.
19 . The method of claim 18 , wherein the housing defines a volute region that extends circumferentially and is configured to receive the blood flow from the blood flow impeller and redirect the blood flow to the blood flow outlet.
20 . The method of claim 17 , wherein:
the blood flow impeller has a rotation axis; and
the blood flow impeller is magnetically suspended parallel to the rotation axis during operation of the centrifugal ventricular assist device via the embedded magnetic segments.