Introduction:In radiofrequency ablation procedures for cardiac arrhythmia, the efficacy of creating repeated lesions at the same location ("insurance lesions") remains poorly studied. We assessed the effect of type of tissue, power, and time on the resulting lesion geometry during such multiple ablation procedures.Methods: A custom ex vivo ablation model was used to assess lesion formation. An ablation catheter was oriented perpendicular to the tissue and used to create lesions that varied by type of tissue (atrial or ventricular free wall), power (30 or 50 W), and time (30, 40, or 50 s for standard ablations and 5, 10, or 15 s for high-power, shortduration [HPSD] ablations). Lesion dimensions were recorded and then analyzed.Radiofrequency ablations were performed on 57 atrial tissue samples (28 HPSD, 29 standard) and 28 ventricular tissue samples (all standard).Results: With ablation parameters held constant, performing multiple ablations significantly increased lesion depth in ventricular tissue when ablations were performed at 30 W for 50 s. No other set of ablation parameters was shown to