Intravascular ventricular assist device

Abstract

One aspect of an intravascular ventricular assist device is an implantable blood pump where the pump includes a housing defining a bore having an axis, one or more rotors disposed within the bore, each rotor including a plurality of magnetic poles, and one or more stators surrounding the bore for providing a magnetic field within the bore to induce rotation of each of the one or more rotors. Another aspect of the invention includes methods of providing cardiac assistance to a mammalian subject as, for example, a human. Further aspects of the invention include rotor bodies having helical channels formed longitudinally along the length of the body of the rotor where each helical channel is formed between peripheral support surface areas facing radially outwardly and extending generally in circumferential directions around the rotational axis of the rotor.

1 . An implantable blood pump comprising:
 (a) a housing defining a bore having an axis;   (b) one or more rotors disposed within the bore, each rotor including a permanent magnet; and   (c) one or more stators disposed outside of the bore for providing a rotating magnetic field within the bore each of the one or more rotors,   the one or more rotors being constructed and arranged so that during operation of the pump the one or more rotors are suspended within the bore of the housing and out of contact with the housing solely by forces selected from the group consisting of magnetic and hydrodynamic forces on the one or more rotors, the pump having a maximum lateral dimension in any direction perpendicular to the axis of the bore of 20 mm or less and being operable to impel at least one liter per minute of blood through the bore against at a pressure difference of at least about 70 mm Hg between the inlet and outlet.   
   
   
       2 . A pump as claimed in  claim 1  wherein said maximum lateral dimension is 14 mm or less. 
   
   
       3 . A pump as claimed in  claim 2  wherein the pump is operable to impel about 1-3 liters per minute of blood through the bore against a pressure difference of about 70-90 mm Hg. 
   
   
       4 . A pump as claimed in  claim 1  wherein the pump has no moving parts which contact one another during operation. 
   
   
       5 . A pump as claimed in  claim 1  wherein the pump has no seals between parts which move during operation. 
   
   
       6 . A pump as claimed in  claim 1  further comprising a gripper adapted to engage an inner surface of an artery, the gripper being mechanically coupled to the housing and the one or more stators. 
   
   
       7 . A pump as claimed in  claim 6  further comprising an intake tube coupled to the housing, the intake tube having a bore communicating with the bore of the housing at the inlet of the housing. 
   
   
       8 . A method of providing cardiac assistance to a mammalian subject comprising the steps of:
 (a) advancing a pump including a housing having a bore, one or more rotors disposed within the bore and one or more stators disposed outside of the housing, through the vascular system of the subject until the pump is disposed at an operative position at least partially within an artery of the subject;   (b) securing the pump at the operative position;   (c) actuating the pump to spin the one or more rotors and pump blood distally within the artery solely by applying electrical currents to the one or more stators and to suspend the one or more stators within the bore solely by forces selected from the group consisting of magnetic and hydrodynamic forces applied to the one or more rotors.   
   
   
       9 . A method as claimed in  claim 8  wherein the advancing step includes advancing one or more grippers mechanically connected to the pump along with the pump and the securing step includes actuating the one or more grippers to engage a wall of the artery. 
   
   
       10 . A method as claimed in  claim 8  wherein the artery is the aorta of the subject. 
   
   
       11 . A method as claimed in  claim 10  wherein the housing has an inlet and an outlet and the advancing step is performed so as to place the inlet in fluid communication with the left ventricle of the subject's heart and place the outlet within the subject's aorta. 
   
   
       12 . A method as claimed in  claim 11  wherein the pump includes an intake tube and the advancing and securing steps are preformed so as to place the intake tube through the aortic valve of the subject and position the pump entirely within the aorta with the inlet of the housing communicating with the left ventricle through the intake tube. 
   
   
       13 . An implantable blood pump comprising:
 (a) a housing defining a bore having an inlet, an outlet and an axis extending between the ends;   (b) one or more rotors disposed within the bore substantially coaxial with the bore, each rotor including a permanent magnet;   (c) one or more stators disposed outside of the bore each substantially opposite a rotor for providing a rotating magnetic field within the bore; and   (d) a gripper mechanically connected to the housing and to the one or more stators, the gripper being adapted to engage a wall of an artery and hold the housing and stators in an operative position at least partially within the artery,   the one or more rotors being constructed and arranged so that during operation of the pump the one or more rotors are suspended within the bore of the housing and out of contact with the housing solely by forces selected from the group consisting of magnetic and hydrodynamic forces on the rotors.   
   
   
       14 . A pump as claimed in  claim 13  wherein the one or more rotors the only elements of the pump which move during operation. 
   
   
       15 . A pump as claimed in  claim 16  wherein the housing is elongated and has an inlet end and an outlet end, and wherein the gripper includes an expansible element connected to the housing adjacent the outlet end. 
   
   
       16 . A pump as claimed in  claim 15  wherein the expansible element includes a tubular stent. 
   
   
       17 . A pump as claimed in  claim 15  wherein the housing has an axis and the expansible element includes a plurality of fingers spaced circumferentially around the axis. 
   
   
       18 . A pump as claimed in  claim 15  wherein the housing has an axis and the expansible element includes a first and second spiral spring having an inner ends secured to the housing and extending in opposite circumferential directions around the axis of the housing. 
   
   
       19 . A rotor for a blood circulating pump, the rotor comprising a body having an upstream end, a downstream end and a rotational axis, the rotor body including a plurality of lobes, each of said lobes having a circumferential extent which increases in a radially outward direction away from the axis, each of said lobes having a support surface facing generally radially outwardly, the rotor being adapted to pump blood downstream upon rotation in a forward circumferential direction, each said support surface including a hydrodynamic bearing region sloping radially outwardly away from the axis in a reverse circumferential direction opposite to the forward circumferential direction. 
   
   
       20 . A rotor for a blood circulating pump, the rotor comprising a body having an upstream end, a downstream end and a rotational axis, the rotor body including a helix region and a support region axially offset from the helix region, the helix region defining a plurality of generally helical channels, the support region defining one or more support surfaces facing substantially radially outwardly and extending generally in circumferential directions around the axis, the support region defining one or more passages connected to said helical channels so that the one or more passages and said helical channels cooperatively define one or more continuous flow paths extending between the upstream and downstream ends, the channels having greater aggregate cross-sectional area than the one or more passages. 
   
   
       21 . A rotor for a blood circulating pump, the rotor comprising a body having an upstream end, a downstream end and a rotational axis, the rotor body including a helix region and a support region axially offset from the helix region, the helix region of the body defining a plurality of generally helical channels, the support region defining one or more support surfaces facing substantially radially outwardly and extending generally in circumferential directions around the axis, the support region defining one or more passages connected to the channels so that the one or more passages and the channels cooperatively define one or more continuous flow paths extending between the upstream and downstream ends, the support region having greater solidity than the helix region. 
   
   
       22 . A rotor for a blood circulating pump, the rotor comprising a body having an upstream end, a downstream end and a rotational axis, the rotor body including a helix region and a support region axially offset from the helix region, the helix region defining a plurality of generally helical channels and having peripheral surfaces facing outwardly away from said axis, the support region including a plurality of lobes projecting outwardly away from said axis and passages between the lobes, the passages being continuous with the channels, the lobes defining one or more support surfaces facing outwardly away from the axis, the support surfaces having an aggregate extent in a circumferential direction around the axis greater than an aggregate extent of said peripheral surfaces in the circumferential direction. 
   
   
       23 . A rotor as claimed in  claim 22  wherein the helix region is disposed upstream of the support region, the channels of the helix region being open at the upstream end of the body and the grooves of the support region being open at the downstream end of the body. 
   
   
       24 . A rotor as claimed in  claim 23  wherein, over at least a portion of the axial extent of the support region, each said lobe has a circumferential extent which increases in a radially outward direction away from the axis toward said support surfaces. 
   
   
       25 . A rotor as claimed in  claim 23  wherein the walls of said helical channels have a pitch in a forward circumferential direction toward the upstream end of said body and the support surfaces include hydrodynamic bearing regions sloping outwardly away from the axis in a reverse circumferential direction opposite to the forward circumferential direction. 
   
   
       26 . A rotor as claimed in  claim 25  wherein each of the lobes includes a first hydrodynamic bearing region, a second hydrodynamic bearing region disposed downstream of the first hydrodynamic bearing region, and a land between the first and second hydrodynamic bearing regions, the land extending radially outwardly from the hydrodynamic bearing regions over at least a portion of the circumferential extent of the hydrodynamic bearing regions. 
   
   
       27 . A rotor as claimed in  claim 24  wherein said support region includes a ferromagnetic material. 
   
   
       28 . A rotor as claimed in  claim 27  wherein said support region is a unitary mass of a ferromagnetic material. 
   
   
       29 . A rotor as claimed in  claim 28  wherein the entire rotor body is a unitary mass of a ferromagnetic material. 
   
   
       30 . A rotor as claimed in  claim 27  wherein said ferromagnetic material has permanent magnetization and said support surfaces constitute poles of a permanent magnet. 
   
   
       31 . An implantable blood pump comprising a housing defining a bore having an axis, a first rotor as claimed in  claim 30  disposed within the bore substantially coaxial with the bore, and a first stator disposed outside of the bore for providing a rotating magnetic field within the bore at the first rotor. 
   
   
       32 . A pump as claimed in  claim 31  wherein the stator has a maximum dimension transverse to the axis of the bore of 13 mm or less. 
   
   
       33 . A pump as claimed in  claim 31  wherein the plurality of lobes consists of two lobes. 
   
   
       34 . A pump as claimed in  claim 31  wherein the housing includes a ceramic material at the surface defining the bore. 
   
   
       35 . A pump as claimed in  claim 31  wherein the bore includes an inflow section upstream from the upstream end of the rotor, the inflow section being substantially free of obstructions to rotational flow of blood about the axis of the bore. 
   
   
       36 . A pump as claimed in  claim 31  further comprising a second rotor disposed in the bore, the second rotor comprising a body having an upstream end, a downstream end and an axis extending between said ends, the second rotor being coaxial with the first rotor, the body of the second rotor including a permanent magnet and defining a plurality of generally helical channels and one or more support surfaces facing substantially radially outwardly and extending generally in circumferential directions around the axis, the pump further comprising a second stator axially offset from the first stator for providing a rotating magnetic field at the second rotor. 
   
   
       37 . A pump as claimed in  claim 37  wherein the channels of the first rotor have a pitch in a first direction and the channels of the second rotor have a pitch in a second direction opposite to the first direction. 
   
   
       38 . A pump as claimed in  claim 37  wherein the first rotor is disposed upstream of the second rotor. 
   
   
       39 . A pump as claimed in  claim 38  wherein the channels of the second rotor have a pitch angle greater than the channels of the first rotor. 
   
   
       40 . A pump as claimed in  claim 39  wherein a portion of the bore between the first and second rotors is substantially in the form of a surface of revolution about the axis of the bore and substantially free of obstructions to rotational flow of blood about the axis of the bore.