title: Temporary occlusion of the great cardiac vein and coronary sinus to facilitate radiofrequency catheter ablation of the mitral isthmus.
abstract: BACKGROUND
  Ablation of the mitral isthmus to achieve bidirectional conduction block is technically challenging, and incomplete block slows isthmus conduction and is often proarrhythmic. The presence of the blood pool in the coronary venous system may act as a heat-sink, thereby attenuating transmural RF lesion formation. This porcine study tested the hypothesis that elimination of this heat-sink effect by complete air occlusion of the coronary sinus (CS) would facilitate transmural endocardial ablation at the mitral isthmus.
  
  
  METHODS
  This study was performed in nine pigs using a 30 mm-long prototype linear CS balloon catheter able to occlude and displace the blood within the CS (the balloon was inflated with approximately 5 cc of air). Using a 3.5 mm irrigated catheter (35 W, 30 cc/min, 1 minute lesions), two sets of mitral isthmus ablation lines were placed per animal: one with the balloon deflated (CS open) and one inflated (CS Occluded). After ablation, gross pathological analysis of the linear lesions was performed.
  
  
  RESULTS
  A total of 17 ablation lines were placed: 7 with CS Occlusion, and 10 without occlusion. Despite similar biophysical characteristics of the individual lesions, lesion transmurality was consistently noted only when using the air-filled CS balloon.
  
  
  CONCLUSIONS
  Temporary displacement of the venous blood pool using an air-filled CS balloon permits transmurality of mitral isthmus ablation; this may obviate the need for ablation within the CS to achieve bidirectional mitral isthmus conduction.
authors.affiliation: Cardiac Arrhythmia Service, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA. adavila@med.miami.edu
authors.forename: Andre
authors.initials: A
authors.lastname: D'Avila
authors.forename: Aravinda
authors.initials: A
authors.lastname: Thiagalingam
authors.forename: Lori
authors.initials: L
authors.lastname: Foley
authors.forename: Melodie
authors.initials: M
authors.lastname: Fox
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Ruskin
authors.forename: Vivek Y
authors.initials: VY
authors.lastname: Reddy
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D021721:Balloon Occlusion / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D054326:Coronary Sinus / Q000503:physiopathology / Q000601:surgery*; D003331:Coronary Vessels / Q000601:surgery*; D004195:Disease Models, Animal; D004867:Equipment Design; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology / Q000601:surgery*; D007430:Intraoperative Care / Q000379:methods; D008943:Mitral Valve / Q000294:innervation* / Q000601:surgery; D013552:Swine; D016896:Treatment Outcome