Nanosecond vs Microsecond Pulsed Field Ablation Lesion Durability and Muscle Contraction in a Canine Model

BACKGROUND A nanosecond pulsed field generator and a circular multielectrode catheter have been introduced. OBJECTIVES The aim of this study was to compare the durability, safety, and muscle contraction of ablation via microsecond or nanosecond pulsed field ablation (PFA) in canines. METHODS Under general anesthesia without muscle relaxants, 24 canines were subjected to isolation of the superior vena cava (SVC) and pulmonary veins (PVs) using nanosecond or microsecond PFA. Repeat mapping was performed and the animals were sacrificed acutely (7 days, n = 9), subacutely (30 days, n = 9), or chronically (3 months, n = 6). RESULTS All SVCs were isolated with durable isolation. A total of 161 sections from the SVC revealed transmural lesions in all sections, with a mean depth of 1.3 f 0.7 mm. Similarly, all the PVs were isolated. Durable isolation was achieved in 23 (95.8%) of 24 PVs in nanosecond PFA and 22 (91.7%) of 24 PVs in microsecond PFA. Nanosecond PFA resulted in transmural lesions in 148 (97.4%) of 152 sections and a median lesion depth of 2.7 f 1.2 mm. Microsecond PFA created transmural lesions in 155 (96.9%) of 160 sections with a median depth of 2.6 f 1.0 mm. There were no significant differences in depth or transmurality between groups. Nanosecond PFA caused no, slight, and severe muscle contraction in 70.8%, 12.5%, and 16.7% PVs, respectively, and microsecond PFA resulted in no and severe muscle contraction in 29.2% and 70.8% PVs, respectively. Nanosecond PFA demonstrated a significantly lower incidence of severe muscle contraction (P < 0.001). CONCLUSIONS Nanosecond PFA yields comparable lesion durability, safety, and significantly reduced muscle contractions to microsecond PFA, which may help enable PV isolation without general anesthesia. (JACC Clin Electrophysiol. 2025;11:1218-1230) (c) 2025 by the American College of Cardiology Foundation.