Focal and linear endocardial and epicardial catheter-based cryoablation of normal and infarcted ventricular tissue

Background: This study of a chronic porcine postinfarction model examined whether linear epicardial cryoablation was capable of creating large, homogenous lesions in regions of the myocardium including scarred ventricle. Endocardial and epicardial focal cryolesions were also compared to determine if there were significant differences in lesion characteristics. Methods: Eighty focal endocardial and 28 focal epicardial cryoapplications were delivered to eight normal caprine and four normal porcine ventricular myocardium, and 21 linear cryolesions were applied along the border of infarcted epicardial tissue in a chronic porcine infarct model in six swines. Results: Focal endocardial cryolesions in normal animals measured 9.7 ± 0.4 mm (length) by 7.3 ± 1.4 mm (width) by 4.8 ± 0.2 mm (depth), while epicardial lesions measured 10.2 ± 1.4 mm (length) by 7.7 ± 2 mm (width) by 4.6 ± 0.9 mm (depth); P > 0.05. Linear epicardial cryolesions in the chronic porcine infarct model measured 36.5 ± 7.8 mm (length) by 8.2 ± 1.3 mm (width) by 6.0 ± 1.2 mm (depth). The mean depth of linear cryolesions applied to the border of the infarct scar was 7 ± 0.7 mm, as measured by magnetic resonance imaging. Conclusions: Cryoablation can create deep lesions when delivered to the ventricular epicardium. Endocardial and epicardial cryolesions created by a focal cryoablation catheter are similar in size and depth. The ability to rapidly create deep linear cryolesions may prove to be beneficial in substrate-based catheter ablation of ventricular arrhythmias.