Linear Ablation with Duty-Cycled Radiofrequency Energy at the Cavotricuspid Isthmus STEFANIE BOLL, LAM DANG, M.Sc., PH.D., and CHRISTOPH SCHARF, M.D. From the Cardiovascular Center, Clinic im Park, Zurich, Switzerland Background: Multielectrode catheters using duty-cycled radiofrequency (RF) have been developed to treat atrial fibrillation (AF). Many of these patients also have atrial flutter. Therefore, a linear multielec- trode has been developed using the same RF energy. Objective: The concept and acute results of linear ablation using duty-cycled RF were tested in the cavotricuspid isthmus (CTI). Methods: The CTI was targeted in 75 patients, in 68 (90%) among them as an adjunct to AF ablation with the same technology. A linear electrode catheter with a 4-mm tip and five 2-mm ring electrodes was connected to a generator titrating duty-cycled RF at 20–45 W up to a target temperature of 70 ◦ C in 1:1 unipolar/bipolar mode. Results: During a mean procedure time of 20 ± 12 minutes, complete CTI block was achieved by 4 ± 3 applications of duty-cycled RF in 69 (92%) patients. No more than three RF applications were necessary in 60% of patients. During the initial learning curve, standard RF had to be used in five (7%) patients. Complete block was not achieved in one patient with frequent episodes of AF. Char was observed in five (7%) patients with poor electrode cooling; consequently, the temperature ramp-up was slowed and manually turned off in the event of low-power delivery. Two groin hematomas occurred; otherwise, no clinical complications were observed. Conclusion: Multielectrode catheters delivering duty-cycled RF can effectively ablate the CTI with few RF applications with promising acute results. Further modifications are necessary to improve catheter steering and prevent char formation. (PACE 2010; 33:444–450) ablation, atrial fibrillation Background Duty-cycled bipolar/unipolar radiofrequency (RF) has recently become available for ablation therapy of atrial fibrillation (AF). One advantage of this approach is simultaneous application of RF energy across an electrode array, intended to cre- ate contiguous lesions near an anatomical struc- ture, that is, the pulmonary vein antrum. Initial re- sults show 80% success in paroxysmal 1 and 66% in persistent AF. 4 The electrodes used in these studies are designed for circular lesions around the pulmonary veins or point-by-point ablation of fractionated electrograms, but not for linear le- sions. However, many investigators prefer com- plete linear ablation in persistent AF. 7 In addition, This study was supported by an unrestricted grant from the Car- diovascular Research Foundation, Seestrasse 220,8027 Zurich. Disclosures: Christoph Scharf has served in a user advisory group for Ablation Frontiers and has received research grants, speaker fees and has held stock options. In addition, he is an advisor to Biotronik and received grant support and speaker fees from Medtronic and St. Jude. Address for reprints: Christoph Scharf, M.D., Cardiovascular Center, Clinic im Park, Seestrasse 220, 8027 Zurich, Switzer- land. Fax: 41 44 209 2017; e-mail: christoph.scharf@gmail.com Received July 16, 2009; revised August 21, 2009; accepted October 26, 2009. doi: 10.1111/j.1540-8159.2009.02658.x linear ablation at the cavotricuspid isthmus (CTI) is a reasonable adjunct to AF ablation, even in pa- tients without a history of atrial flutter, if flutter is induced during the procedure. 11 As a consequence a novel linear catheter has been developed, which uses the same multichan- nel RF generator. The purpose of this study was to test the feasibility and safety of this catheter de- sign in creating continuous linear lesions in a well- defined macroreentrant arrhythmia such as typical right atrial flutter. 3,5 Patients undergoing atrial fib- rillation ablation with duty-cycled RF were chosen preferably, because the duty-cycled RF generator system was already installed. Methods Patients The subjects of this study were 75 patients undergoing RF ablation of the CTI from November 2007 to May 2009 (Table I). Most of the patients underwent duty-cycled left atrial RF ablation for paroxysmal AF (n = 55, 73%) and persistent AF (n = 13, 18%) during the same procedure using the same technology (Ablation Frontiers, Carls- bad, CA, USA). A previous ablation procedure for AF had been performed in six (8%) patients. One patient had undergone a previous CTI ablation at another institution and presented with typical flutter. Antiarrhythmic drug therapy (amiodarone C 2009, The Authors. Journal compilation C 2009 Wiley Periodicals, Inc. 444 April 2010 PACE, Vol. 33