Catheter-based clutched heart valve sizer

Abstract

A valve sizer for determining an appropriate replacement valve size when performing a heart valve replacement procedure is provided. In one version the valve sizer has a hollow shaft with proximal and distal ends. A movable sizing element couples to the distal end of the shaft and is radially expandable between first, contracted and second, expanded positions. An actuator assembly on a handle includes an actuator coupled to a clutch member via a ball-spring-detent clutch. A rod extends through the shaft and maintains a fixed distance between the handle and a distal hub in the sizing element. Movement of the actuator causes axial movement of the shaft, thereby causing radial expansion of sizing petals relative to the hub. The clutch slips when a predetermined reaction force from the surrounding valve annulus is met by the petals.

We claim: 
     
         1 . A percutaneously delivered heart valve sizer for determining an appropriate replacement prosthetic heart valve size when performing a valve replacement procedure, the replacement prosthetic heart valves having a range of specific sizes, comprising:
 a proximal handle having an actuator mounted for movement thereon;   a shaft extending distally from the actuator and housing an actuation rod axially displaceable by the actuator;   a sizing element coupled to a distal end of the shaft, the sizing element having a central hub with a central bore along a central axis that receives the actuation rod and a plurality of petals each radially movable between a radially retracted first position and a radially expanded second position, the petals being connected to transition between the first and second positions upon displacement of the actuation rod in the shaft, wherein the petals remain parallel to the axis of the hub while being displaced between the first and second positions;   a catheter configured for percutaneous delivery that receives the sizer with the petals in their first position and through which the sizer may be advanced to a heart valve annulus and expelled for sizing a surrounding heart valve annulus; and   a clutch mechanism connected between the actuator and the actuation rod in the shaft so as to transmit movement forces therebetween, wherein movement of the actuator causes displacement of the actuation rod and consequently outward radial expansion of the petals in the sizing element from their first to their second positions and into contact with the heart valve annulus, wherein the clutch mechanism slips at a predetermined reaction force imparted by the heart valve annulus against further outward radial expansion of the petals.   
     
     
         2 . The valve sizer of  claim 1 , wherein the actuation rod acts on a plurality of first levers pivotally connected to the central hub that move outward in conjunction with a plurality of second levers pivotally connected to the central hub to radially displace the petals, and the lengths of the first and second levers are the same. 
     
     
         3 . The valve sizer of  claim 2 , wherein the central hub comprises a generally cylindrical body having a series of radially-projecting axial ribs, and the first and second levers rotate about pins journaled in the sides of adjacent axial ribs. 
     
     
         4 . The valve sizer of  claim 2 , wherein the actuation rod acts on small fingers on both the first and second levers so as to produce an outward force on both levers. 
     
     
         5 . The valve sizer of  claim 2 , wherein the first and second levers are connected together and move outward in a scissor-like fashion. 
     
     
         6 . The valve sizer of  claim 5 , wherein the actuation rod has a plurality of movement tabs projecting outward through axial slots in the central hub to which a proximal end of each of the first levers connects via a pivot pin, and a distal end of each of the first levers connects via a pivot pin to a distal end of a sizing petal, and wherein a distal end of each of the second levers connects via a pivot pin to a fixed point at a distal end of the central hub, while a proximal end of each of the second levers connects via a pivot to a proximal section of the corresponding sizing petal, and wherein each pair of first and second levers are connected where they cross each other at their midpoints by a fulcrum pin. 
     
     
         7 . The valve sizer of  claim 2 , wherein the central hub comprises a generally cylindrical member having a plurality of axial recesses between axial ribs on its outer surface that receive and accommodate the first and second levers as well as the petals in their radially retracted first positions so as to form a cylinder, with the outer surfaces of the petals lying flush with the ribs. 
     
     
         8 . The valve sizer of  claim 1 , wherein the actuator comprises an actuator ring mounted for rotation on the handle, and the actuation rod is fixed with respect to a clutch ring that is coupled for rotation to the actuator ring via the clutch mechanism, and wherein the clutch ring is connected via a screw thread to the handle so that rotation of the clutch ring causes axial movement of the actuation rod. 
     
     
         9 . The valve sizer of  claim 8 , wherein the clutch ring is coupled for rotation to the actuator via a plurality of bearings biased by springs into detents. 
     
     
         10 . The valve sizer of  claim 1 , wherein the actuator comprises an actuator ring mounted for rotation on the handle, and the actuation rod is fixed with respect to a clutch ring that is coupled for rotation to the actuator ring via the clutch mechanism, and wherein the handle also includes a window at one circumferential location and the clutch ring has a number of numerical markings thereon indicating different sizes of replacement prosthetic heart valves, the numerical markings being sized and aligned to show one at a time through the window on the handle upon rotation of the clutch ring relative to the handle such that a desired valve size shows through the window when the clutch mechanism slips. 
     
     
         11 . The surgical sizer of  claim 1 , wherein the sizing element has a diameter of less than about 6 mm when the petals are in their radially retracted first positions, and the sizing element has a diameter of about 29 mm when the petals are in their radially expanded second positions. 
     
     
         12 . A percutaneously delivered heart valve sizer for determining an appropriate replacement prosthetic heart valve size when performing a valve replacement procedure, the replacement prosthetic heart valves having a range of specific sizes, comprising:
 a proximal handle having an actuator mounted for movement thereon;   a shaft extending distally from the actuator and housing an actuation rod axially displaceable by the actuator;   a sizing element coupled to a distal end of the shaft, the sizing element having a plurality of petals each radially movable between a radially retracted first position and a radially expanded second position upon displacement of the actuation rod in the shaft, wherein the sizing element has a diameter of less than about 6 mm when the petals are in their radially retracted first positions;   a catheter configured for percutaneous delivery that receives the sizer with the petals in their first position and through which the sizer may be advanced to a heart valve annulus and expelled for sizing a surrounding heart valve annulus; and   a clutch mechanism connected between the actuator and the actuation rod in the shaft so as to transmit movement forces therebetween, wherein movement of the actuator causes displacement of the actuation rod and consequently outward radial expansion of the petals in the sizing element from their first to their second positions and into contact with the heart valve annulus, wherein the clutch mechanism slips at a predetermined reaction force imparted by the heart valve annulus against further outward radial expansion of the petals.   
     
     
         13 . The valve sizer of  claim 11 , wherein the sizing element has a central hub with a central bore along a central axis that receives the actuation rod, and the actuation rod acts on a plurality of first levers pivotally connected to the central hub that move outward in conjunction with a plurality of second levers pivotally connected to the central hub to radially displace the petals, and the lengths of the first and second levers are the same. 
     
     
         14 . The valve sizer of  claim 12 , wherein the central hub comprises a generally cylindrical body having a series of radially-projecting axial ribs, and the first and second levers rotate about pins journaled in the sides of adjacent axial ribs. 
     
     
         15 . The valve sizer of  claim 12 , wherein the actuation rod acts on small fingers on both the first and second levers so as to produce an outward force on both levers. 
     
     
         16 . The valve sizer of  claim 12 , wherein the first and second levers are connected together and move outward in a scissor-like fashion. 
     
     
         17 . The valve sizer of  claim 15 , wherein the actuation rod has a plurality of movement tabs projecting outward through axial slots in the central hub to which a proximal end of each of the first levers connects via a pivot pin, and a distal end of each of the first levers connects via a pivot pin to a distal end of a sizing petal, and wherein a distal end of each of the second levers connects via a pivot pin to a fixed point at a distal end of the central hub, while a proximal end of each of the second levers connects via a pivot to a proximal section of the corresponding sizing petal, and wherein each pair of first and second levers are connected where they cross each other at their midpoints by a fulcrum pin. 
     
     
         18 . The valve sizer of  claim 12 , wherein the central hub comprises a generally cylindrical member having a plurality of axial recesses between axial ribs on its outer surface that receive and accommodate the first and second levers as well as the petals in their radially retracted first positions so as to form a cylinder, with the outer surfaces of the petals lying flush with the ribs. 
     
     
         19 . The valve sizer of  claim 11 , wherein the actuator comprises an actuator ring mounted for rotation on the handle, and the actuation rod is fixed with respect to a clutch ring that is coupled for rotation to the actuator ring via the clutch mechanism, and wherein the clutch ring is connected via a screw thread to the handle so that rotation of the clutch ring causes axial movement of the actuation rod. 
     
     
         20 . The valve sizer of  claim 18 , wherein the clutch ring is coupled for rotation to the actuator via a plurality of bearings biased by springs into detents. 
     
     
         21 . The valve sizer of  claim 11 , wherein the actuator comprises an actuator ring mounted for rotation on the handle, and the actuation rod is fixed with respect to a clutch ring that is coupled for rotation to the actuator ring via the clutch mechanism, and wherein the handle also includes a window at one circumferential location and the clutch ring has a number of numerical markings thereon indicating different sizes of replacement prosthetic heart valves, the numerical markings being sized and aligned to show one at a time through the window on the handle upon rotation of the clutch ring relative to the handle such that a desired valve size shows through the window when the clutch mechanism slips. 
     
     
         22 . The surgical sizer of  claim 11 , wherein the sizing element has a diameter of about 29 mm when the petals are in their radially expanded second positions.