Ventricular assist device

Abstract

Apparatus and methods are described including an elongate tube configured to traverse an aortic valve of a subject, such that a proximal end of the tube is disposed within an aorta of the subject and a distal end of the tube is disposed within a left ventricle of the subject, the elongate tube comprising a blood-impermeable material, and a radially-expandable frame disposed within at least a portion of the tube. An impeller is disposed inside the radially-expandable frame, the impeller being configured to rotate such as to pump blood from the left ventricle to the aorta. A protective structure is disposed around the impeller, in addition to the radially-expandable frame of the elongate tube. Other applications are also described.

1 . An apparatus comprising:
 an elongate tube configured to traverse an aortic valve of a subject, such that a proximal end of the tube is disposed within an aorta of the subject and a distal end of the tube is disposed within a left ventricle of the subject, the elongate tube comprising a blood-impermeable material, and a radially-expandable frame disposed within at least a portion of the tube;   an impeller disposed inside the radially-expandable frame, the impeller being configured to rotate such as to pump blood from the left ventricle to the aorta; and   a protective structure disposed around the impeller, in addition to the radially-expandable frame of the elongate tube.   
     
     
         2 . The apparatus according to  claim 1 , wherein the impeller is configured to be placed within the subject's left ventricle. 
     
     
         3 . The apparatus according to  claim 1 , wherein the impeller is configured to be placed within the subject's aorta. 
     
     
         4 . The apparatus according to  claim 1 , wherein the protective structure comprises a cage. 
     
     
         5 . The apparatus according to  claim 4 , wherein the protective structure comprises a radially-expandable cage. 
     
     
         6 . The apparatus according to  claim 4 , wherein the cage is integrally formed with the radially-expandable frame of the elongate tube. 
     
     
         7 . The apparatus according to  claim 4 , wherein the cage is disposed inside the radially-expandable frame. 
     
     
         8 . The apparatus according to  claim 4 , wherein the cage is configured to align a longitudinal axis of the impeller with a longitudinal axis of the tube. 
     
     
         9 . The apparatus according to  claim 4 , wherein the cage and the radially-expandable frame of the elongate tube are cut from a single piece of a shape memory material. 
     
     
         10 . The apparatus according to  claim 1 , wherein the impeller comprises at least one impeller blade comprising:
 at least one helical elongate element; and   a film of material supported at least partially by the helical elongate element.   
     
     
         11 . The apparatus according to  claim 10 , wherein the impeller further comprises a spring disposed inside of the helical elongate element, wherein the film of material is supported between the helical elongate element and the spring. 
     
     
         12 . The apparatus according to  claim 11 , wherein the impeller comprises a plurality of helical elongate elements, and the film of material is supported between the plurality of helical elongate elements and the spring, such that the impeller defines a plurality of blades. 
     
     
         13 . The apparatus according to  claim 11 , wherein the impeller is configured to be radially constrained by the helical elongate element and the spring being axially elongated, and wherein in response to the axial elongation of the helical elongate element and the spring, the film is configured to change shape without the film of material breaking. 
     
     
         14 . The apparatus according to  claim 11 , wherein the spring, when disposed in a non-radially-constrained configuration thereof, is configured by virtue of its rigidity, to stabilize the impeller with respect to the tube, during rotation of the impeller, such that a gap between the outer edge of the impeller and the inner surface of the tube is maintained. 
     
     
         15 . The apparatus according to  claim 11 , wherein:
 the spring defines a lumen therethrough,   the impeller further comprises proximal and distal bushings; and   the apparatus comprises a rigid shaft configured to extend from the proximal bushing to the distal bushing via the lumen defined by the spring, the rigid shaft being configured to stabilize the impeller with respect to the tube, during rotation of the impeller, such that a gap between the outer edge of the impeller and the inner surface of the tube is maintained.   
     
     
         16 . The apparatus according to  claim 11 , wherein the spring, when disposed in a non-radially-constrained configuration thereof, is configured such that there are substantially no gaps between windings of the spring and adjacent windings thereto. 
     
     
         17 . The apparatus according to  claim 1 , wherein the impeller and the tube are configured such that, when the impeller and the tube are deployed within the subject, a gap between an outer edge of the impeller and an inner surface of the tube is less than 1 mm. 
     
     
         18 . The apparatus according to  claim 17 , wherein the impeller and the tube are configured such that, when the impeller and the tube are deployed within the subject, the gap between the outer edge of the impeller and the inner surface of the tube is less than 0.4 mm. 
     
     
         19 . The apparatus according to  claim 17 , wherein the impeller is configured to be stabilized with respect to the tube, such that, during rotation of the impeller, the gap between the outer edge of the impeller and the inner surface of the cage is maintained. 
     
     
         20 . A method comprising:
 placing a tube into a body of the subject, such that the tube traverses an aortic valve of the subject, such that a proximal end of the tube is disposed within an aorta of the subject and a distal end of the tube is disposed within a left ventricle of the subject,
 the tube including a blood impermeable material, and a radially-expandable frame disposed within at least a portion of the tube, 
 an impeller being disposed inside the frame, a protective structure in addition to the frame being disposed around the impeller; and 
   rotating the impeller, such as to pump blood from the subject's left ventricle to the subject's aorta.   
     
     
         21 . The method according to  claim 20 , wherein the protective structure comprises a cage.