title: Epicardial beating heart cryoablation using a novel argon-based cryoclamp and linear probe.
abstract: OBJECTIVE
  Epicardial, beating heart cryoablation for the treatment of atrial fibrillation may be limited by heat from intracardiac blood flow. We therefore evaluated the ability to create cryolesions using an argon-based cryoclamp device, which temporarily occludes blood flow and facilitates transmurality.
  
  
  METHODS
  Six mongrel dogs underwent sternotomy. A clamp employing a 10-cm argon-based linear cryoablation device was used epicardially to isolate the pulmonary veins and left atrial appendage. After clamping of lesions, the probe was removed from the cryoclamp device, and the remaining linear lesions, analogous to the Cox maze III, were performed. Pulmonary vein stenosis was evaluated with the use of magnetic resonance imaging. Left atrial function and pulmonary venous flow velocities were assessed with transesophageal echocardiography. Transmurality was confirmed both electrically and histologically. Animals were then put to death at 30 days.
  
  
  RESULTS
  All acute and chronic cryoclamp lesions produced conduction block. There was no change in right (RPV) or left pulmonary vein (LPV) diameter on the basis of magnetic resonance imaging at baseline and at planned death (RPV-1, 19.6 +/- 2.9 mm vs 16.9 +/- 2.8 mm, P = .22; RPV-2, 13.2 +/- 2.0 mm vs 11.8 +/- 1.6 mm, P = .22; and LPV, 12.2 +/- 2.4 mm vs 11.2 +/- 1.9 mm, P = .30). Left atrial function and pulmonary venous flow velocities were unchanged. Tissue sections determined transmurality in 93% of cryoclamp lesions and 84% of linear ablations performed with the 10-cm malleable probe.
  
  
  CONCLUSIONS
  Epicardial application of this cryoclamp device on the beating heart produced transmural lesions, which persisted 30 days. Linear epicardial cryoablation was not as effective as the cryoclamp device at producing consistent transmural lesions. This novel, versatile device may be useful in treating patients with atrial fibrillation on the beating heart without cardiopulmonary bypass.
authors.affiliation: New York Presbyterian Hospital-Weill Cornell Medical Center, Department of Cardiothoracic Surgery, New York, NY, USA.
authors.forename: Federico
authors.initials: F
authors.lastname: Milla
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Skubas
authors.forename: William M
authors.initials: WM
authors.lastname: Briggs
authors.forename: Leonard N
authors.initials: LN
authors.lastname: Girardi
authors.forename: Leonard Y
authors.initials: LY
authors.lastname: Lee
authors.forename: Wilson
authors.initials: W
authors.lastname: Ko
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Tortolani
authors.forename: Karl H
authors.initials: KH
authors.lastname: Krieger
authors.forename: O Wayne
authors.initials: OW
authors.lastname: Isom
authors.forename: Charles A
authors.initials: CA
authors.lastname: Mack
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D002304:Cardiac Pacing, Artificial; D003250:Constriction; D003452:Cryosurgery / Q000295:instrumentation* / Q000379:methods; D004285:Dogs; D017548:Echocardiography, Transesophageal; D008279:Magnetic Resonance Imaging; D009206:Myocardium / Q000473:pathology; D011667:Pulmonary Veins