Method for 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 method of 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:
 preparing a heart valve sizer for percutaneous advancement, the valve sizer including:
 i. a proximal handle having an actuator mounted for movement thereon; 
 ii. a shaft extending distally from the actuator and housing an actuation rod axially displaceable by the actuator; 
 iii. 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, the step of preparing the sizer including ensuring the petals are in the first position; and 
 iv. 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 transition of the petals in the sizing element between the first and the second positions; 
   inserting the sizer with the petals in the first position into a catheter configured for percutaneous delivery and having a distal end;   percutaneously advancing the distal end of the catheter to a heart valve annulus;   advancing the sizer through the catheter and expelling the sizing element from the distal end of the catheter;   moving the actuator to cause displacement of the actuation rod and consequent outward radial expansion of the petals in the sizing element from the first to the second positions and into contact with the heart valve annulus; and   continuing to expand the petals outward after contacting the valve annulus until a reaction force causes the clutch mechanism to slip, 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 method 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 lengths of the first and second levers are the same. 
     
     
         3 . The method 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 sides of adjacent axial ribs. 
     
     
         4 . The method 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 method of  claim 2 , wherein the first and second levers are connected together and move outward in a scissor-like fashion. 
     
     
         6 . The method 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 the levers cross each other at midpoints thereof by a fulcrum pin. 
     
     
         7 . The method of  claim 2 , wherein the central hub comprises a generally cylindrical member having a plurality of axial recesses between axial ribs on an outer surface that receive and accommodate the first and second levers as well as the petals in the radially retracted first positions so as to form a cylinder, with outer surfaces of the petals lying flush with the ribs. 
     
     
         8 . The method 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 method 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 method 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 . A method of 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:
 preparing a heart valve sizer for percutaneous advancement, the valve sizer including:
 i. a proximal handle having an actuator mounted for movement thereon; 
 ii. a shaft extending distally from the actuator and housing an actuation rod axially displaceable by the actuator; 
 iii. 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 6 mm when the petals are in the radially retracted first positions, the step of preparing the sizer including ensuring the petals are in the first position; and 
 iv. 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 transition of the petals in the sizing element between the first and the second positions, 
   inserting the sizer with the petals in the first position into a catheter configured for percutaneous delivery and having a distal end;   percutaneously advancing the distal end of the catheter to a heart valve annulus;   advancing the sizer through the catheter and expelling the sizing element from the distal end of the catheter;   moving the actuator to cause displacement of the actuation rod and consequent outward radial expansion of the petals in the sizing element from the first to the second positions and into contact with the heart valve annulus; and   continuing to expand the petals outward after contacting the valve annulus until a reaction force causes the clutch mechanism to slip, wherein the clutch mechanism slips at a predetermined reaction force imparted by the heart valve annulus against further outward radial expansion of the petals.   
     
     
         12 . The method 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 lengths of the first and second levers are the same. 
     
     
         13 . The method 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. 
     
     
         14 . The method 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. 
     
     
         15 . The method of  claim 12 , wherein the first and second levers are connected together and move outward in a scissor-like fashion. 
     
     
         16 . The method 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 pin to a proximal section of the corresponding sizing petal, and wherein each pair of first and second levers are connected where the levers cross each other at midpoints thereof by a fulcrum pin. 
     
     
         17 . The method of  claim 12 , wherein the central hub comprises a generally cylindrical member having a plurality of axial recesses between axial ribs on an outer surface that receive and accommodate the first and second levers as well as the petals in the radially retracted first positions so as to form a cylinder, with the outer surfaces of the petals lying flush with the ribs. 
     
     
         18 . The method 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. 
     
     
         19 . The method of  claim 18 , wherein the clutch ring is coupled for rotation to the actuator via a plurality of bearings biased by springs into detents. 
     
     
         20 . The method 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.