Surgical Ablation of Cardiac Tissue with Nanosecond Pulsed Electric Fields in Swine

Background: Myocardial tissue can be ablated by the application nanosecond pulsed fields (nsPEFs). The applied electric fields irreversibly permeabilize cell membranes and thereby kill myocytes while leaving the extracellular matrix intact. Methods: In domestic pigs (n = 10), hearts were exposed via sternotomy and either ablated in vivo (n = 5) or in excised, Langendorff-perfused hearts (n = 5). The nsPEFs consisted of 6–36 pulses of 300 ns each, delivered at 3–6 Hz; the voltage applied varied from 10 to 12 kV. Atrial lesions were either created after inserting the bottom jaw of the bipolar clamp into the atrium via a purse string incision (2–3 lesions per atrium) or by clamping a double layer of tissue at the appendages (one lesion per atrium). Ventricular lesions were created after an incision at the apex. The transmurality of each lesion was determined at three points along the lesion using a triphenyl tetrazolium chloride (TTC) stain. Results: All 27 atrial lesions were transmural. This includes 13/13 purse string lesions (39/39 sections, tissue thickness 2.5–4.5 mm) and 14/14 appendage lesions (42/42 sections, tissue thickness 8–12 mm). All 3 right ventricular lesions were transmural (9/9 sections, 18 pulses per lesion). Left ventricular lesions were always transmural for 36 pulses (3/3 lesions, 9/9 sections). All lesions have highly consistent width across the wall. There were no pulse-induced arrhythmias or other complications during the procedure. Conclusions: nsPEF ablation reliably created acute lesions in porcine atrial and ventricular myocardium. It has far better penetration and is faster than both radiofrequency ablation and cryoablation and it is free from thermal side effects.