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Background: During catheter ablation, delivery of radiofrequency (RF) energy to a target site is sometimes interrupted by catheter instability and clinical factors. The impact of interruption of RF delivery on lesion characteristics has not been characterized., Objective: The purpose of this study was to determine the impact of interruption of RF application on lesion size., Methods: Forty-two RF ablation lesions (21 left ventricle, 21 right ventricle) were created in the ventricles of 6 swine using power control mode (30 W; target contact force 15g) with 1 of 3 conditions: 15-second ablation (15s), 30-second ablation (30s), or two 15-second ablations (15s×2) at the same site separated by a 2-minute pause., Results: Lesion volume was significantly larger for 30s lesions (501 ± 146 mm 3 ) compared to both 15s×2 (314 ± 98 mm 3 ) and 15s (242 ± 104 mm 3 ) lesions (P <.001 for both pairwise comparisons). Compared to 15s lesions, lesion volume was numerically greater for 15s×2 lesions, but this did not reach statistical significance (P = .087). Differences in lesion volume between 30s and 15s×2 lesions were driven mainly by differences in lesion width (10.7 ± 1.1 mm vs 9.1 ± 1.7 mm; P = .04) rather than depth (9 ± 1.2 mm vs 8.4 ± 1.2 mm; P = .29). There were no differences in mean contact force by group. There was no difference in total force-time integral for the 30s and 15s×2 lesion groups [median 444 (interquartile range 312) g∙s vs 380 (164) g∙s; P = 1]., Conclusion: Compared to lesions resulting from continuous RF ablation, lesions resulting from interrupted ablation have a smaller overall lesion volume, predominantly due to smaller lesion width. These data suggest that if disruption in energy delivery occurs, lesions may need closer spacing to avoid gaps., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)