Cold collapse method and apparatus

Abstract

A system and method are disclosed for collapsing medical devices, such as self-expanding, drug-eluting stents for loading into delivery catheters. The collapsing apparatus may be used for crimping expandable stents and other devices onto a balloon catheter. The medical device is cooled below the austenitic phase transformation temperature of the material forming the device, such as stainless steel or nitinol, and may be cooled until the material has fully transformed to the martenstitic state. For coated medical devices, the device is warmed to a temperature just below the beginning of austenite phase transformation prior to collapsing. An apparatus having a plurality of offset blades, linear bearings, radial bearings and an actuator mechanism is provided for collapsing the medical device. The system is configured with a mandrel subassembly to push the medical device into a catheter sheath, and with a nozzle subassembly to direct cold gas to the medical device.

1 . A system for collapsing a device, comprising:
 a first cold gas source;   a second cold gas source; and   a jaws subassembly in fluid communication with the first cold gas source and the second cold gas source.   
     
     
         2 . The collapsing system of  claim 1 , further comprising a nozzle subassembly in fluid communication with the first cold gas source and the second cold gas source, the nozzle subassembly being positioned proximate the jaws subassembly. 
     
     
         3 . The collapsing system of  claim 2 , further comprising a mandrel subassembly having a mandrel slidably disposed within a portion of the jaws subassembly and a portion of the nozzle subassembly. 
     
     
         4 . The collapsing system of  claim 3 , further comprising a containment housing having a proximal wall, wherein the proximal wall is configured to slidably retain an arm connected to the mandrel. 
     
     
         5 . The collapsing system of  claim 4 , wherein the proximal wall is configured with an aperture for removably retaining a sheath holder configured to retain a sheath, wherein a proximal portion of the mandrel passes into the sheath and sheath holder when the arm of the mandrel subassembly is moved in a proximal direction, and wherein the mandrel is configured with a middle portion having a diameter larger than a diameter of the proximal portion of the mandrel. 
     
     
         6 . The collapsing system of  claim 5 , further comprising a thermocouple subassembly having a thermocouple slidably disposed within a portion of the nozzle subassembly. 
     
     
         7 . The collapsing system of  claim 1 , wherein the first cold gas source includes a first gas supply for providing gas having a temperature from minus 60° C. to minus 90° C., and the second cold gas source includes a second gas supply for providing gas having a temperature from 20° C. to minus 40° C. 
     
     
         8 . The collapsing system of  claim 7 , further comprising a third cold gas source including a-third gas supply for providing gas having a temperature from minus 90° C. to minus 150° C. 
     
     
         9 . The collapsing system of  claim 8 , wherein the third gas supply includes liquid nitrogen. 
     
     
         10 . The collapsing system of  claim 1 , wherein the first cold gas source and the second cold gas source are fed from a common gas supply so as to provide the first cold gas source with gas having a temperature from minus 60° C. to minus 150° C., and to provide the second cold gas source with gas having a temperature from 20° C. to minus 40° C. 
     
     
         11 . The collapsing system of  claim 1 , further comprising:
 a nozzle subassembly in fluid communication with the second cold gas source having a gas supply for providing gas having a temperature from 20° C. to minus 40° C., the nozzle subassembly being positioned proximate the jaws subassembly; and   a mandrel subassembly having a mandrel slidably disposed within a portion of the jaws subassembly and a portion of the nozzle subassembly, and further configured to extend into a containment housing configured for exposing a proximal portion of the mandrel to the first cold gas source having a first gas supply for providing gas having a temperature from minus 60° C. to minus 150° C.   
     
     
         12 . The collapsing system of  claim 5 , further comprising a third gas source having a third gas supply for providing gas at room temperature, wherein the third gas source is configured to circulate the room temperature gas within outer and inner walls of the containment housing. 
     
     
         13 . The collapsing system of  claim 1 , wherein the jaws subassembly includes at least two first blades each having a first end and a second end, each first blade having at least one aperture and at least one groove, and wherein the jaws subassembly includes at least two second blades each having a first end and a second end, each second blade having at least one aperture and at least one groove. 
     
     
         14 . The collapsing system of  claim 13 , wherein the jaws subassembly further includes a proximal driver and a distal driver linked together and configured to engage the first ends and the second ends of each first blade and each second blade. 
     
     
         15 . The collapsing system of  claim 14 , wherein the jaws subassembly further includes a plurality of linear bearings disposed within the apertures of the first blades and the apertures of the second blades, and wherein the grooves of the first blades are positioned to accept the linear bearings of the second blades and the grooves of the second blades are positioned to accept the linear bearings of the first blades. 
     
     
         16 . A method for collapsing a device, comprising:
 providing a device having a first diameter;   providing a jaws subassembly configured for retaining the device;   providing a first gas at a first temperature into the jaws subassembly;   providing a second gas at a second temperature into the jaws subassembly; and   actuating the jaws subassembly so as to collapse the device from the first diameter to a second diameter.   
     
     
         17 . The collapsing method of  claim 16 , further comprising:
 directing the first gas to a nozzle subassembly so as to introduce the first gas into the jaws subassembly;   directing the second gas to the nozzle subassembly so as to introduce the second gas into the jaws subassembly;   providing a mandrel subassembly having a mandrel slidably disposed within a portion of the jaws subassembly and a portion of the nozzle subassembly;   providing a containment housing having a proximal wall, wherein the proximal wall is configured to slidably retain an arm connected to the mandrel, wherein the proximal wall is configured with an aperture for removably retaining a sheath holder configured to retain a sheath, wherein a proximal portion of the mandrel passes into the sheath and sheath holder when the arm of the mandrel subassembly is moved in a proximal direction, and wherein the mandrel is configured with a middle portion having a diameter larger than a diameter of the proximal portion of the mandrel; and   prior to actuating the jaws subassembly, placing the device configured in its first diameter on the proximal portion of the mandrel.   
     
     
         18 . The collapsing method of  claim 17 , further comprising moving the arm in a proximal direction so as to move the device in its second diameter into the sheath. 
     
     
         19 . The collapsing method of  claim 16 , wherein providing a first gas includes providing the first gas at a temperature from minus 60° C. to minus 90° C., and wherein providing a second gas includes providing the second gas at a temperature from 20° C. to minus 40° C. 
     
     
         20 . The collapsing method of  claim 19 , further comprising, prior to providing a first gas at a first temperature, exposing the device in its first diameter to a third gas at a temperature from minus 90° C. to minus 150° C. 
     
     
         21 . The collapsing method of  claim 16 , wherein providing a first gas includes providing the first gas at a temperature from minus 90° C. to minus 150° C., and wherein providing a second gas includes providing the second gas at a temperature from 20° C. to minus 40° C. 
     
     
         22 . An assembly for collapsing a device, comprising:
 at least two first blades each having a proximal end having a slot and a distal end having a slot, each first blade having a proximal aperture, a distal aperture, a proximal groove and a distal groove, wherein the proximal aperture is positioned proximal the proximal groove and the distal aperture is positioned distal the distal groove; and   at least two second blades each having a proximal end having a slot and a distal end having a slot, each second blade having a proximal aperture, a distal aperture, a proximal groove and a distal groove, wherein the proximal aperture of the second blade is positioned distal the proximal groove and the distal aperture of the second blade is positioned proximal the distal groove.   
     
     
         23 . The collapsing assembly of  claim 22 , further comprising a plurality of linear bearings disposed within the apertures of the first blades and the apertures of the second blades, wherein the grooves of the first blades are positioned and configured to accept the linear bearings of the second blades and the grooves of the second blades are positioned and configured to accept the linear bearings of the first blades. 
     
     
         24 . The collapsing assembly of  claim 23 , further comprising:
 a housing having a proximal end having a proximal radial bearing and a distal end having a distal radial bearing, the housing further having a plurality of apertures configured to retain the linear bearings;   a proximal cam assembly configured to be rotatably secured within the proximal radial bearing and configured to engage the proximal end slots of each first blade and each second blade;   a distal cam assembly configured to be rotatably secured within the distal radial bearing and configured to engage the distal end slots of each first blade and each second blade;   a proximal driver operatively connected to the proximal cam assembly;   a distal driver operatively connected to the distal cam assembly; and   a linking mechanism connected to the proximal driver and the distal driver.   
     
     
         25 . The collapsing assembly of  claim 24 , wherein each first blade is configured with a beveled edge having a first side and a second side joining at a first tip, wherein each second blade is configured with a beveled edge, having a first side and a second side joining at a second tip, and wherein each first blade and each second blade are positioned within the housing to move relative to each other from a first position with the first and second tips offset from each other by a first distance, to a second position with the first and second tips offset from each other by a second distance different than the first distance, such that radial motion of the linking mechanism causes the first and second tips to move from the first position that forms a lumen within the housing having a first diameter to the second position that causes first and second tips to form a lumen having a second diameter. 
     
     
         26 . The collapsing assembly of  claim 25 , wherein each blade is formed from stainless steel, plated with nickel and polished to a substantially defect free surface. 
     
     
         27 . A method for collapsing a device, comprising:
 providing at least two first blades each having a proximal end having a slot and a distal end having a slot, each first blade having a proximal aperture, a distal aperture, a proximal groove and a distal groove, wherein the proximal aperture is positioned proximal the proximal groove and the distal aperture is positioned distal the distal groove;   providing at least two second blades each having a proximal end having a slot and a distal end having a slot, each second blade having a proximal aperture, a distal aperture, a proximal groove and a distal groove, wherein the proximal aperture of the second blade is positioned distal the proximal groove and the distal aperture of the second blade is positioned proximal the distal groove;   providing a plurality of linear bearings disposed within the apertures of the first blades and the apertures of the second blades, wherein the grooves of the first blades are positioned and configured to accept the linear bearings of the second blades and the grooves of the second blades are positioned and configured to accept the linear bearings of the first blades;   providing a housing having a proximal end having a proximal radial bearing and a distal end having a distal radial bearing, the housing further having a plurality of apertures configured to retain the linear bearings;   providing a proximal cam assembly configured to be rotatably secured within the proximal radial bearing and configured to engage the proximal end slots of each first blade and each second blade;   providing a distal cam assembly configured to be rotatably secured within the distal radial bearing and configured to engage the distal end slots of each first blade and each second blade;   providing a proximal driver operatively connected to the proximal cam assembly;   providing a distal driver operatively connected to the distal cam assembly;   providing a linking mechanism connected to the proximal driver and the distal driver;   wherein each first blade is configured with a beveled edge having a first side and a second side joining at a first tip, wherein each second blade is configured with a beveled edge having a first side and a second side joining at a second tip, and wherein each first blade and each second blade are positioned within the housing to move relative to each other from a first position with the first and second tips offset from each other by a first distance, to a second position with the first and second tips offset from each other by a second distance different than the first distance, such that radial motion of the linking mechanism causes the first and second tips to move from the first position that forms a lumen within the housing having a first diameter to the second position that causes first and second tips to form a lumen having a second diameter;   placing a device having an expanded diameter into the housing having a lumen at a first diameter; and   rotating the linking mechanism so that the first and second blades form a lumen of a second diameter, wherein the device is collapsed from the expanded diameter to substantially the second diameter.