A new catheter-based cryosurgery system is proving its potential as a valuable tool for electrophysiologic (EP) applications inside the heart. The long, narrow, flexible catheter evaporates room-temperature liquid refrigerant within its tip to produce localized cryogenic temperatures. The catheter provides a `less invasive' percutaneous approach to the inner walls of the heart to confirm and ablate arrhythmogenic sites with cryosurgical benefits-- preservation of tissue integrity, absence of thrombus formation. The system's primary engineering challenges are safe refrigerant handling and catheter temperature performance. Surgical results in the animal model demonstrate the system has sufficient cooling power and temperature range to alter EP response, both temporarily and permanently. With tip temperatures between -20 degree(s)C and -35 degree(s)C at the atrioventricular (AV) junction, reversible conduction block is produced in the AV node with minimal damage to heart structures. Taking the tip below -50 degree(s)C creates permanent block in the AV node through formation of a necrotic lesion. Summing these results leads to the conclusion that the technology has the potential to identify arrhythmogenic sites without damage, to verify the site, and to ablate it--within the same procedure, without moving the catheter.
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