# US 6,237,355 B1 · Precooled cryogenic ablation system

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- Number: US 6,237,355 B1
- Document ID: US6237355B1
- Status: Granted
- Kind: B1
- Application number: 09/344,423
- Filed: 1999-06-25
- Granted: 2001-05-29
- Earliest claimed: 1999-06-25
- Assignees: CryoGen, Inc.
- Inventors: Hong Li
- Web page: https://patentgrep.com/patent/US6237355B1

## CPC

- F25D 3/10: using liquefied gases, e.g. liquid air {(for cooling semiconductor devices H10W40/305)}
- A61B 18/02: by cooling, e.g. cryogenic techniques
- A61B 2018/0212: {using an instrument inserted into a body lumen, e.g. catheter}
- A61B 2018/0262: {using a circulating cryogenic fluid}
- F25D: REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR (refrigerated showcases A47F3/04; thermally-insulated vessels for domestic use A47J41/00; refrigerated vehicles, see the appropriate subclasses of classes B60 - B64; containers with thermal insulation in general B65D81/38; heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants, or materials for the production of heat or cold by chemical reactions other than by combustion C09K5/00; thermally-insulated vessels for liquefied or solidified gases F17C; air-conditioning or air-humidification F24F; refrigeration machines, plants, or systems F25B; cooling of instruments or comparable apparatus without refrigeration G12B)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A method and apparatus for using a secondary refrigerant to precool and liquefy a primary refrigerant, then vaporizing and expanding the primary refrigerant to cool a cold tip of a cryosurgical instrument for ablation of biological tissue, such as cardiovascular tissue, in particular endocardiac tissue and tissue inside a cardiac blood vessel. The secondary refrigerant has a critical temperature above the critical temperature of the primary refrigerant, and a cooling temperature below the critical temperature of the primary refrigerant, thereby facilitating the use of the precooling step to provide liquid primary refrigerant in an operating room environment in which the primary refrigerant could not otherwise be provided in the liquid phase.

## Claims

### Claim 1

A cryosurgical instrument for ablation of endocardiac tissue, comprising:
a source of a gaseous primary refrigerant said source providing said primary refrigerant at a temperature above the critical temperature of said primary refrigerant;
a source of a liquid secondary refrigerant, said secondary refrigerant having a critical temperature higher than said critical temperature of said primary refrigerant;
a secondary expansion element connected to receive said liquid secondary refrigerant, said secondary expansion element being constructed to vaporize and expand said secondary refrigerant to a temperature below said critical temperature of said primary refrigerant;
a primary-to-secondary heat exchanger having a primary refrigerant flow path connected to receive said gaseous primary refrigerant, and a secondary refrigerant flow path connected to receive said vaporized and expanded secondary refrigerant from said secondary expansion element, said heat exchanger being constructed to cool and liquefy said primary refrigerant;
a primary expansion element connected to receive said liquid primary refrigerant from said heat exchanger, said primary expansion element being constructed to vaporize and expand said primary refrigerant to a selected cryogenic temperature; and
a cryoablation heat transfer element connected to receive said vaporized and expanded primary refrigerant;
wherein said primary refrigerant comprises SUVA-95, and said secondary refrigerant comprises AZ-20.