Effect of Sequential, Colocalized Radiofrequency and Pulsed Field Ablation on Cardiac Lesion Size and Histology

BACKGROUND: Sequential application of radiofrequency with pulsed field (PF) ablation may increase lesion depth while preserving the advantages of PF. The study’s aim was to determine lesion dimensions of sequential, colocalized radiofrequency and PF ablation. METHODS: A preclinical study using swine (n=4) performed lesions in the right/left ventricles. Ablations were performed with a force-sensing 3.5-mm irrigated-tip ablation catheter using a generator delivering both radiofrequency and PF. PF was delivered using unipolar, biphasic pulses at a standard dose (PF index, 300) with 4-mL/min irrigation. Radiofrequency was delivered at 50 W for 10 s (15 mL/min). Lesions were created by applying colocalized radiofrequency followed by sequential application of PF on the same location, PF followed by sequential application of radiofrequency on the same location, PF alone, or radiofrequency alone. Tissue was collected after 2 hours for lesion assessment. Results are mean±SD. RESULTS: Forty-five lesions were analyzed. The lesion depth of radiofrequency alone was 4.9±0.8 mm. The mean lesion depth and width for PF alone were 3.5±0.6 and 5.1±1.8 mm. Lesion depths for combined applications were significantly greater versus PF alone (6.2±1.8 mm radiofrequency followed by sequential application of PF on the same location; 5.7±1.3 mm PF followed by sequential application of radiofrequency on the same location; P <0.0001 for both). Lesion widths were also significantly greater with combined therapy versus PF alone (8.6±1.8 mm radiofrequency followed by sequential application of PF on the same location; 8.9±2.1 mm PF followed by sequential application of radiofrequency on the same location; P <0.0001 for both). Histology for both combined lesions showed central thermal necrosis surrounded by a hemorrhagic and transitional PF zone. CONCLUSIONS: Combined, colocalized radiofrequency and PF, irrespective of order, show significantly increased lesion size compared with the same dose of PF or radiofrequency alone.