The Influence of Vein Size, Cryoballoon Diameter and Balloon-Vein Angulation on Tissue Temperature: An In-Vitro Study

Background: Cryoballoon (CB) ablation (CB-A) is effective in achieving pulmonary vein (PV) isolation for treatment of atrial fibrillation. The factors affecting CB-A efficacy are poorly understood. We examined the effects of the ratio of CB to vein size and CB to vein angulation, in an in-vitro model. Methods: PV phantoms were constructed from bovine muscle mounted onto vinyl tubes with internal long axes (mm) of 16, 19 and 25. Two micro-thermistors were mounted at the CB-PV antrum at 1mm tissue depth. Six 4-minute freezes were performed with 23 and 28mm CBs in a 370C saline bath. Tissue temperatures were assessed at co-axial CB-PV occlusion and 300 angulation, producing an area of greater contact (zone 1) and one of lesser contact (zone 2), at opposing poles. Results: (table †Between-group differences) Conclusion: Increased ratio of PV-CB size was associated with colder CB and tissue temperatures. Non-coaxial PV-CB alignment was associated with warmer temperatures. Tissue temperatures in the area of lesser contact (zone 2) were warmer for the smaller balloon, but not the larger. These data indicate that PV-CB size and alignment influence the effectiveness of CB-A.Tabled 1Vein diameter (mm)Balloon temperature (0C)p-value†Tissue temperature (0C)p-value†28mm balloon, coaxial CB-PV16-44.5±0.7<0.001-33.7±0.3<0.00119-47.2±0.6-35.0±0.025-52.2±1.0-38.8±2.523mm balloon, coaxial CB-PV16-42.2±2.90.02-26.5±2.60.00119-44.8±2.8-27.5±2.725-46.7±0.8-32.5±1.228mm balloon, angulated (zone1/zone2)16-35±1.70.001-30.5±-2.1/-19.0±2.80.001/0.0125-40.0±0.6-36.0±-3.2/-20.5±1.623mm balloon, angulated (zone1/zone2)16-42.2±3.40.01-33.3±-1.2/-23.3±5.4<0.001/0.625-48.5±3.1-39.0±-1.9/-24.7±4.7 Open table in a new tab