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

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.

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.

(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).

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.