Comparative performance of open thorax epicardial linear cryoprobe ablation versus focal tip radiofrequency catheter ablation in ventricular scar

BACKGROUND: Epicardial cryoablation is increasingly utilized in open surgical procedures for treatment of ventricular arrhythmias in patients with structural heart disease when percutaneous epicardial access cannot be obtained. There are limited data regarding the effects of cryoablation within ventricular scar tissue, particularly in comparison to the performance of radiofrequency (RF) catheter ablation. This study aimed to investigate the comparative performance of ablation delivered epicardially in an open chest animal model with a linear cryoprobe versus a radiofrequency catheter. METHODS: An infarct model was created in five Yorkshire swine using microsphere injection into the left anterior descending artery. After 6-8 weeks, animals underwent median sternotomy with targeted epicardial RF ablation lesions, and linear cryoablation lesions were delivered to myocardial infarct scar regions. Specimens were pressure perfused with 10% formalin, and histological analysis was performed. RESULTS: Out of 25 epicardial RF lesions, 13 were visible and able to be analyzed. All 15 epicardial cryoablation lesions were visible. All 15 cryoablation lesions had transmural effect within scar where tissue thickness was ≤6 mm, whereas only 62% of evaluable RF lesions were transmural in scar (p = 0.01). Average cryoablation lesion depth was 4.2 ± 1.1 mm in scar and 5.6 ± 1.4 mm in border zone. CONCLUSION: Linear epicardial cryoablation is a useful tool in open surgical procedures to treat ventricular arrhythmias in structural heart disease. Cryoablation can achieve transmurality in tissue with ≤ 6 mm thickness with more technically reliable effect compared to catheter RF in the open chest.