Nanosecond pulsed field ablation: Feasibility of creating the Cox-maze lesion set on the beating heart

Objective: This study examined the feasibility of creating Cox-maze IV lesions, including the ablation of the left posterior wall (box) and the isthmus lines, using nanosecond pulsed-field ablation (nsPFA) in a beating heart porcine model. Methods: Nine pigs underwent surgical nsPFA. Lesions included the right atrial appendage, left atrial appendage, left atrial posterior wall (the box), and isthmus lines, as replicated by ablating across the mitral and tricuspid annuli. Each ablation lasted 2.5 to 5 seconds. At 30 days, the cardiac tissue was examined histologically. Ablation lines were sectioned at 5-mm intervals and stained with 10% triphenyl tetrazolium chloride and Gomori trichrome. Exit block testing and echocardiography were performed before, after, and 30 days postablation. Valvular and coronary tissues were assessed by a blinded pathologist. Results: Seven pigs survived for an average of 26 ± 8 days. Two pigs died acutely from refractory ventricular fibrillation immediately after transvalvular ablations. Transmurality was confirmed for 99.6% (251/252) of histologic cross-sections and 97% (32/33) of lesions. The mean ablated tissue thickness was 6.7 ± 3.3 mm. At 30 days, exit block was confirmed at 94% of available testing sites (16/17). There was no evidence of progression of baseline valvular regurgitation. Histologic assessment did not find significant differences between ablated and nonablated valves or coronary arteries. Conclusions: An nsPFA clamp device effectively created transmural lesions, including the box and isthmus lesions. This nonthermal energy source may shorten procedural time and enable surgical ablation in the beating heart. However, the relationship between nsPFA and ventricular arrhythmias warrants additional study.