Characterization of Warm Saline‐Enhanced Radiofrequency Ablation Lesions in the Infarcted Porcine Ventricular Myocardium

BACKGROUND: Radiofrequency (RF) ablation of scar-mediated ventricular tachycardia is limited by the size of lesions achieved with conventional catheters. We examined the gross and histopathology characteristics of warm saline-enhanced radiofrequency (SERF) ablation delivered to left ventricular (LV) infarction scars via a novel catheter employing an extendable infusion needle electrode. METHODS AND RESULTS: Yorkshire pigs (n = 14) underwent LV infarction by left anterior descending artery balloon occlusion. After 4-6 weeks, baseline hemodynamic data were obtained and endocardial electroanatomic mapping was performed in 13 surviving animals. Following single, 40 Watt SERF ablations delivered endocardially to the center of infarctions, 4 were examined the same day (day 0). The rest underwent repeat measurements and were sacrificed at 1 week (n = 6), and at 4 weeks (n = 3). Average lesion depth and diameter were: 1.85 ± 0.7 cm and 2.33 ± 0.7 cm at day 0, 0.91 ± 0.1 cm and 1.9 ± 0.4 cm after 1 week, and 1.0 ± 0.2 cm and 1.89 ± 0.76 cm after 4 weeks, respectively. Histopathology at 1 week showed that ablation lesions covered 41 ± 10.6% of the infarct area. SERF ablation lesions extended 100%, 90%, and 68% of the total wall thickness at day 0, 1 week, and 4 weeks, respectively. Hemodynamic parameters were unchanged. There were no myocardial wall perforations or aneurysms. CONCLUSION: SERF ablation within myocardial infarct tissue produced large, near-transmural lesions, without evidence of myocardial perforation, wall thinning, or aneurysm formation. Ablations did not produce any negative hemodynamic effects in this small group of experiments.