Linear epicardial cryoablation effects in a porcine model: Lesion characteristics and vascular risk

INTRODUCTION: Cryoablation in open-chest surgical interventions for ventricular arrhythmias has been reported with reasonable procedural outcomes. However, the characteristics of cryoablation lesions on the ventricular myocardium are not well defined. The purpose of the present study was to determine the tissue and vascular effects of a linear epicardial cryoablation probe in a porcine animal model. METHODS: Five adult Yorkshire swine underwent median sternotomy and application of linear cryoablation lesions using a malleable aluminum linear cryoablation probe of varying duration (2, 3, 4, and 5 min), including one lesion placed intentionally over the left anterior descending coronary (LAD) artery. Histological analysis was performed. RESULTS: Maximum lesion depth was approximately 1.0 cm with 3 min freezes, with no significant increase in depth achieved with longer lesions. No transmural lesions were achieved. No large vessel epicardial coronary artery injuries were seen to the LAD; however, surprisingly, remote isolated interventricular septal injury was seen in all animals, suggestive of possible compromise of smaller coronary arterial vessels. CONCLUSION: Single application freezes with an aluminum linear cryoablation probe can create homogeneous ablative lesions over the ventricular myocardium with a maximum depth of approximately 1.0 cm. No large vessel injury occurred with direct lesion application of the LAD; however, small coronary vessels may be at risk.