Patent ID: 8235977

Claim:
A cryotherapy catheter device comprising: an elongate catheter shaft extending between a proximal and distal end; an expandable body sized to deliver cryotherapy to a target tissue region when expanded to a therapeutic volume, the expandable body comprising an expandable first chamber and an expandable second chamber, the first chamber positioned proximate to the distal end of the catheter shaft and in fluid communication with a lumen for transmitting cryofluid to the first chamber, and the second chamber positioned adjacent to the first chamber such that expansion of the second chamber applies pressure on the first chamber; a source of cryofluid that is in fluid communication with the first chamber; and a source of volume displacement fluid in fluid communication with the second chamber, wherein the first chamber is positioned to deliver cryotherapy when filled with cryofluid and wherein the second chamber is configured to hold the first chamber in contact with tissue when expanded; and further wherein the second chamber when expanded occupies a non-therapeutic volume of the expandable body so as to reduce the amount of cryofluid required to expand the expandable body to the therapeutic volume.