Lesion Transmurality and Continuity of Non-Occlusive Cryoballoon Ablation on Canine Ventricle.

Abstract

Background: Our understanding of lesion transmurality and continuity of non-occlusive cryoballoon ablation (NOCA) is limited. In the present study, lesion dimensions under different conditions during NOCA were assessed.

Methods: Simulated NOCA was performed on freshly harvested canine left ventricular myocardial using the cryoballoon. We conducted experiments to evaluate the effects of (1) flow rate (0, 1, and 1.5 L/min) and freezing time (120, 150, and 180 ) on lesion dimensions during segmental NOCA and (2) overlapping manners between two sequential cryoablations (overlaps of half and two-thirds the balloon area) on lesion continuity during linear NOCA. Lesion formation was assessed after 3-5 h using tetrazolium chloride staining.

Results: (1) Experiments of segmental NOCA No differences were observed in maximal lesion depths among different flow rates (0, 1, and 1.5 L/min) across cryoballoon. For ablation duration, 120-s cryotherapy was able to penetrate to a maximal lesion depth of 6.45 ± 0.80 mm, significantly smaller than those for 150 and 180-s (p < 0.001). (2) Experiments of linear NOCA: Maximal lesion depths of 2 × 120-s linear NOCA were similar between two-thirds and half-size overlaps (p = 0.192). However, non-transmural lesions were more frequently observed in half-size than two-thirds overlap (56.3% vs. 6.3%, p = 0.002).

Conclusions: When performing NOCA, lesion depths did not vary significantly with convective flow around the CB. A 120-s cryoapplication seemed to yield enough lesion depth and longer cryotherapy should be applied cautiously at a place in close anatomical contact with the esophagus. Additionally, a series of sequential applications in a half-size overlapping manner might lead to non-transmural lesions in the ablation line.