Background-Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation. Methods and Results-Of 170 patients referred for ablation of common atrial flutter, conventional ablation of the cavotricuspid isthmus with Ͼ21 applications failed to create a

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... ectional block in 13 (7.6%). An irrigated-tip catheter ablation was performed on identified gaps in the ablation line according to a protocol found to be safe in animals: a moderate flow rate of 17 mL/min and temperature-controlled (target, 50°C) RF delivery with a power limit of 50 W. Bidirectional isthmus block was achieved in 12 patients by use of a mean delivered power of 40Ϯ6 W with a single application in 6 patients and 2 to 6 applications in the other 6. No side effects occurred during or after the procedure. Conclusions-Irrigated-tip catheter ablation is safe and effective for achieving cavotricuspid isthmus block when conventional RF energy has failed. (Circulation. 1998;98:835-838.)