Rotational atherectomy systems and methods with shock absorbing element

Abstract

A rotational atherectomy system may include a drive shaft, a motor, and a clutch with a threshold torque where the clutch may include a motor plate rotationally connected to the motor, a drive shaft plate rotationally connected to the drive shaft, and a biasing clutch configured to rotationally engage the motor plate and the drive shaft plate, wherein torques less than the threshold torque are transmitted completely between the motor plate and the drive shaft plate, which remain rotationally coupled by static friction, and wherein torques greater than the threshold torque cause the motor plate and the drive shaft plate to rotate relative to one another and cause a residual torque to be transmitted between the motor and the drive shaft, the residual torque being less than the threshold torque and being determined by a kinetic coefficient of friction.

What is claimed is: 
     
         1 . A rotational atherectomy system comprising:
 a motor;   a drive shaft in operative connection with the motor, the motor capable of rotating the drive shaft; and   a shock absorbing element in operative connection with the motor and the drive shaft and comprising a resilient element capable of elastic deformation.   
     
     
         2 . The rotational atherectomy system of  claim 1 , wherein the shock absorbing element comprises:
 a drive gear operatively connected with the motor and comprising:
 a drive gear hub; 
 a peripheral ring having a plurality of teeth; and 
 a plurality of resilient radially extending elements operatively connected to the drive gear hub and extending radially to the peripheral ring and capable of deflection under load to allow the drive gear hub to rotate relative to the peripheral ring; and 
 a take-off gear in operative communication with the drive gear and with the drive shaft. 
   
     
     
         3 . The rotational atherectomy system of  claim 2 , the plurality of resilient radially extending elements comprising:
 a base connected with the drive gear hub and having an axis extending substantially directly radially outward from the drive gear hub;   an opposing base connected to the peripheral ring and substantially radially aligned with the base; and   a substantially S-shaped portion connected between the base and the opposing base.   
     
     
         4 . The rotational atherectomy system of  claim 2 , the plurality of resilient radially extending elements comprising a series of spokes or struts connected with the base and with the opposing base. 
     
     
         5 . The rotational atherectomy system of  claim 2 , the plurality of resilient radially extending elements comprising a substantially flat diaphragm connected with the base and with the opposing base. 
     
     
         6 . The rotational atherectomy system of  claim 2 , further comprising the take-off gear being keyed to the drive shaft. 
     
     
         7 . The rotational atherectomy system of  claim 2 , further comprising the take-off gear being not keyed to the drive shaft and wherein the shock absorbing element further comprises:
 a resilient member operatively engaged with the take-off gear and operatively engaged with the drive shaft.   
     
     
         8 . The rotational atherectomy system of  claim 7 , the resilient member comprising opposing ends and wherein a first end is operatively connected with the take-off gear and the opposing end is operatively connected with the drive shaft. 
     
     
         9 . The rotational atherectomy system of  claim 7 , the resilient member comprising a coil or spring. 
     
     
         10 . The rotational atherectomy system of  claim 7 , the resilient member comprising a resilient cylindrical bushing. 
     
     
         11 . The rotational atherectomy system of  claim 1 , wherein the shock absorbing element comprises:
 a drive pulley operatively connected with the motor;   a take-off pulley in operative communication with the drive pulley and with the drive shaft; and   a resilient, stretchable belt in operative engagement with the drive pulley and the take-off pulley.   
     
     
         12 . The rotational atherectomy system of  claim 1 , wherein the shock absorbing element comprises:
 a drive pulley operatively connected with the motor;   a take-off pulley in operative communication with the drive pulley and with the drive shaft;   a belt or chain in operative engagement with the drive pulley and the take-off pulley; and   at least one idler pulley disposed between the drive pulley and take-off pulley, the at least one idler pulley having an inner surface, the inner surface in operative engagement with the non-resilient belt or chain, the at least one idler pulley positioned on a resiliently secured shaft and arranged to be drawn outwardly out of position with increased belt or chain tension.   
     
     
         13 . The rotational atherectomy system of  claim 12 , further comprising the drive pulley having an outer surface and two idler pulleys, each idler pulley arranged substantially along a tangent line connected the drive pulley's outer surface and the inner surface of the idler pulley, wherein the shape of the non-resilient belt or chain comprises an inverted tear shape. 
     
     
         14 . A method for reducing torque experienced at the distal end of a rotational atherectomy drive shaft during blockage of the drive shaft, comprising:
 providing a motor;   providing a drive shaft in operative communication with the motor and capable of being rotated at high rotational speeds by the motor; and   providing a shock absorbing element in operative connection with the motor and the drive shaft and comprising a resilient element capable of elastic deformation.   
     
     
         15 . The method of  claim 14 , further comprising providing a clutch in operative engagement with the shock absorbing element.