Abstract: A system and method for transferring heat requires a supply tube connected in fluid communication with a capillary tube. A tip member is positioned to surround the distal end of the capillary tube to create a cryo-chamber. In operation, a liquid refrigerant is introduced into the supply tube at a working pressure (e.g. 450 psia). The pressure is then significantly reduced on the liquid refrigerant as it transits through the capillary tube. The refrigerant then exits the distal end of the capillary tube, still in its liquid state. Inside the cryo-chamber, at a pressure of less than about one atmosphere, the refrigerant transitions into its gaseous state. The resultant refrigeration causes heat to transfer into the cryo-chamber.

Abstract: A cryoablation device having a pressure monitoring system includes an elongated catheter tube that has a central lumen and is formed with a closed distal end. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube's distal end to establish an expansion chamber therebetween. A return line, which can be established between the supply line and the catheter tube or can include a return tube, is provided to exhaust expanded refrigerant from the chamber. First and second pressure sensors are respectively positioned in the supply line upstream from the expansion chamber and in the return line. Typically, both sensors are positioned to remain at extracorporeal locations throughout a cryoablation procedure. Measured pressures are used together with the supply and return line dimensions to analytically estimate the chamber pressure and allow the expansion of refrigerant in the chamber to be monitored.

Abstract: A device for cryoablating exposed tissue having a contoured contact surface includes a tube-shaped shaft and a flexible, thermally conductive enclosure that is attached to the distal end of the tube-shaped shaft. The enclosure is formed with a wall having an outer surface for contacting the target tissue and an inner surface which establishes and surrounds a cryochamber. A shapeable element is attached to the distal end of the shaft and extends into the cryochamber. The element can be permanently deformed into a pre-selected shape to cause a portion of the enclosure wall to conform to the contour of the target tissue. A high-pressure tube in the shaft passes a refrigerant through the shaft for expansion into the cryochamber. This expansion cools the wall of the enclosure, which in turn, extracts heat from the target tissue resulting in the cryoablation of the target tissue.

Abstract: Systems and methods for treating an arrhythmia originating in a pulmonary vein of a patient are described. The system includes a rigid sheath and an elongated catheter that defines an axis and has an ablating distal section. The distal section includes a plurality of conductive bands, with each band establishing an enclosed chamber. The ablating distal section is reconfigurable between a first compact configuration in which each band is positioned relatively near the axis for transit through the sheath and second expanded configuration in which each band is positioned relatively far from the axis. Once in the second configuration, a fluid refrigerant is expanded into each enclosed chamber to cool the bands and cryoablate tissue. The second configuration is particularly useful for ablating a circumferential band of tissue, for example, a band of tissue surrounding the opening (i.e. ostium) where a pulmonary vein connects with the left atrium.

Abstract: A system and method for transferring heat requires a supply tube connected in fluid communication with a capillary tube. A tip member is positioned to surround the distal end of the capillary tube to create a cryo-chamber. In operation, a liquid refrigerant is introduced into the supply tube at a working pressure (e.g. 450 psia). The pressure is then significantly reduced on the liquid refrigerant as it transits through the capillary tube. The refrigerant then exits the distal end of the capillary tube, still in its liquid state. Inside the cryo-chamber, at a pressure of less than about one atmosphere, the refrigerant transitions into its gaseous state. The resultant refrigeration causes heat to transfer into the cryo-chamber.

Abstract: A catheter for ablating internal tissue using radiofrequency (rf) or ultrasonic energy includes a mechanism to cool the catheter's distal tip. The catheter also includes either an rf electrode or an ultrasonic transducer positioned at the tip to direct energy into the internal tissue for tissue ablation. With the distal tip of the catheter positioned adjacent the target tissue, a refrigerant is introduced into the catheter and allowed to expand near the catheter's distal tip. During expansion, the fluid refrigerant transitions from a liquid state to a gaseous state. Latent heat absorbed during the phase transition cools the tip of the catheter to a temperature sufficient to prevent tissue charring and coagulum formation during ablation. In another implementation, the catheter tip is cooled to a temperature sufficient to freeze tissue and create an ice-ball at the catheter tip that stabilizes the tip relative to the target tissue.

Abstract: A cryoablation catheter having a distal portion cooled by a refrigerant is described. The catheter includes a pressure sensor in the distal portion to monitor a pressure of the refrigerant. The monitored pressure may be used to determine the integrity of the catheter, both before and during a surgical procedure, so that the supply of refrigerant is interrupted if a leak is discovered. The monitored pressure may also be used in a feedback loop to control the performance of the cryoablation catheter.

Abstract: A method of cooling an operative surface of a cryoablation device, comprises the steps of providing a primary refrigerant under pressure and pre-cooling the primary refrigerant to a temperature below a critical temperature thereof using a non-charging refrigeration system to liquify the refrigerant in combination with the steps of expanding the pre-cooled primary refrigerant in proximity to an operative surface of the cryoablation device and removing the expanded primary refrigerant from the proximity of the operative surface.

Abstract: An optimum gas mixture formulated from a group of component fluids, for use in a miniature mixed gas refrigeration system. The gas mixture has appropriate components, in appropriate concentrations, to optimize refrigeration power and heat transfer capacity, and to minimize plugging of the Joule-Thomson expansion element. The gas mixture is pressurized by a compressor to a pressure less than 750 psia, and preferably less than 420 psia, for safety reasons, and supplied to a heat exchanger. The high pressure outlet of the heat exchanger is connected to a Joule-Thomson expansion element where the high pressure gas is expanded isenthalpically to a lower temperature at least as low as 183K. This low temperature gas cools a heat transfer element mounted in the distal end of the probe, to cool an external object. Return gas flows back through the heat exchanger to pre-cool the incoming high pressure gas mixture.