Initial Clinical Experience with a Remote Magnetic Catheter Navigation System for Ablation of Cavotricuspid Isthmus-Dependent Right Atrial Flutter ARASH ARYA, M.D., HANS KOTTKAMP, M.D., PH.D., CHRISTOPHER PIORKOWSKI, M.D., ANDREAS BOLLMANN, M.D., JIN-HONG GERDES-LI, M.D., SAM RIAHI, M.D., PH.D., MASAHIRO ESATO, M.D., and GERHARD HINDRICKS, M.D., PH.D. From the Department of Electrophysiology, University of Leipzig, Heart Center, Leipzig, Germany Background: A remote magnetic navigation system (MNS) is available and has been used with a 4-mm-tip magnetic catheter for radiofrequency (RF) ablation of some supraventricular and ventricular arrhythmias; however, it has not been evaluated for the ablation of cavotricuspid isthmus-dependent right atrial flutter (AFL). The present study evaluates the feasibility and efficiency of this system and the newly available 8-mm-tip magnetic catheter to perform RF ablation in patients with AFL. Methods: Twenty-six consecutive patients (23 men, mean age 64.6 ± 9.6 years) underwent RF ablation using a remote MNS. RF ablation was performed with an 8-mm-tip magnetic catheter (70◦ C, maximum power 70 W, 90 seconds). The endpoint of ablation was complete bidirectional isthmus block. To assess a possible learning curve, procedural data were compared between the first 14 (group 1) and the rest (group 2) of the patients. Results: The initial rhythm during ablation was AFL in 20 (19 counterclockwise and 1 clockwise) and sinus rhythm in six patients. Due to technical issues, the ablation in the 18th patient could not be done with the MNS, and so we switched to conventional ablation. The remote magnetic navigation and ablation procedure was successful in 24 of the 25 (96%) remaining patients with AFL. In one patient (patient 2), conventional catheter was used to complete the isthmus block after termination of AFL. The procedure, preparation, ablation, and fluoroscopy times (median [range]) were 53 (30–130) minutes, 28 (10–65) minutes, 25 (12–78) minutes, and 7.5 (3.2–20.8) minutes, respectively. Patients in group 2 had shorter procedure (45 [30–70] min vs 80 [57–130] min, P = 0.0001), preparation (25 [10–30] min vs 42 [30–65] min, P = 0.0001), ablation (20 [12–40] min vs 31 [20–78] min, P = 0.002), and fluoroscopy (7.2 [3.2–12.2] min vs 11.0 [5.4–20.8] min, P = 0.014) times. No complication occurred during the procedure. Conclusion: Using a remote MNS and an 8-mm-tip magnetic catheter, ablation of AFL is feasible, safe, and effective. Our data suggest that there is a short learning curve for this procedure. (PACE 2008; 31:597– 603) ablation, remote magnetic navigation, atrial flutter, mapping, magnetic catheter Introduction Conventional ablation of cavotricuspid isthmus (CTI)-dependent right atrial flutter (AFL) is a clinically efficacious, well-established, and widely performed procedure in electrophysiology (EP) laboratories.1–3 Recently, a magnetic catheter navigation system capable of remote cardiac mapping has been introduced.4–13 The feasibility study in animals and humans showed the continuous stability of ablation catheters using the magnetic catheter navigation system and its applicability for ablation of various supraventricular and ventricular arrhythmias excluding AFL.7–14 Here, we There are no conflicts of interest. Address for reprints: Arash Arya, M.D., Department of Electrophysiology, University of Leipzig, Heart Center, Strümpellstrasse 39, 04289 Leipzig, Germany. Fax: 0049-341865-1460; e-mail: dr.arasharya@gmail.com Received October 7, 2007; revised January 7, 2008; accepted February 11, 2008. report the first human experience on remote magnetic navigation system (MNS) in 26 consecutive patients undergoing ablation of AFL. Methods Patient Population Between May 2007 and August 2007, a total of 26 consecutive patients (23 men, mean age 64.3 ± 9.0 years) underwent catheter ablation for AFL at our EP laboratories using remote magnetic navigation NIOBE II system (Stereotaxis, Inc., St. Louis, MO, USA). In patients with sinus rhythm at the time of ablation, typical electrocardiographic (ECG) findings were used to confirm the diagnosis. In patients with AFL at the time of ablation, besides ECG morphology, activation sequence and entrainment mapping was used to confirm the diagnosis. The study protocol was approved by our local ethics committee. None of the patients received antiarrhythmic medications at the time  C 2008, The Authors. Journal compilation  C 2008, Blackwell Publishing, Inc. PACE, Vol. 31 May 2008 597 ARYA, ET AL. Table I. Baseline Patients’ Characteristics Variable Age (years) Sex (male/female) Structural heart disease§ Initial rhythm Sinus rhythm CWAFL* CCWAFL† Total Group 1 Group 2 P-Value‡ 64.3 ± 9.0 22/3 17 (63%) 66.0 ± 11.5 9/1 6 (60%) 63.0 ± 7.3 13/2 11 (64.7%) 0.59 0.90 0.80 6 18 1 2 8 0 4 10 1 0.35 *Clockwise cavotricuspid isthmus-dependent right atrial flutter. † Counterclockwise cavotricuspid isthmus-dependent right atrial flutter. ‡ Comparison between groups 1 and 2. § Including coronary heart disease, hypertension and hypertensive heart disease, and left ventricular dysfunction. No patient had structural lung disease. of ablation procedure, and in cases who received them, it was discontinued at least five half-lives before the ablation procedure. Table I shows the baseline characteristics of the patients. To assess the possible effect of a learning curve on the procedure outcome, we divided the patients into two groups. Due to technical issues (failure to move the magnets from parking position), the ablation procedure in the 18th patient could not be done with remote MNS, and so, we switched to conventional ablation. This patient was excluded from the study. Remote MNS The remote MNS consists of two permanent magnets which generate a uniform magnetic field (0.08 T) and are computer-controlled and located on either side of the patient’s body.13 The MNS consists of two components: the Niobe
Stereotaxis MNS (Stereotaxis, Inc.) and an electroanatomical mapping system (CARTO-RMT; Biosense Webster, Inc., Diamond Bar, CA, USA). The CARTO-RMT system is similar to the standard CARTO system, but is able to localize the ablation catheter without interference from the magnetic field. The CARTO-RMT system sends catheter-tip location and orientation data to Stereotaxis system. It also sends target locations, points, and anatomical geometrical information from the reconstructed map to the MNS. The real-time catheter-tip location is displayed on the x-ray images, enabling continuous real-time monitoring of the catheter-tip position even without acquiring a fresh x-ray image.4,11 The operator is in a separate control room, at a distance from the x-ray beam. The details of the remote magnetic-guided navigation are described elsewhere.11–13 598 Catheter Ablation Procedure All patients gave written informed consent. The EP study and ablation procedure were performed with the patients in a fasting, nonsedated state. All the ablation procedures were performed by two authors (AA: 22 and JH-GL: 3). Before starting the ablation, the patients received fentanyl. A quadripolar steerable catheter (Inquiry; Irvine Biomedical, Inc., St. Jude Medical, Irvine, CA, USA) and a decapolar steerable catheter (Inquiry; Irvine Biomedical, Inc.) were placed in the right ventricular apex and the coronary sinus, respectively. A long 8-F sheath (SR0; St. Jude Medical, Minnetonka, MN, USA) was then placed at the juncture of the inferior vena cava and the right atrium through which an 8-mm-tip flexible magnetic catheter (NaviStar-RMT DS; Biosense Webster, Inc.) was advanced to the mid-right atrium. There are small permanent magnets in the tip and the distal portion of the catheter that enable it to be deflected in the desired direction and be guided by the MNS. The forward and backward movement of the catheter was controlled by a mechanical device (Cardiodrive
, Stereotaxis, Inc.). In addition to Cardiodrive, the navigation of the catheter was controlled by magnetic field vectors. The Stereotaxis workstation (Navigant
, Stereotaxis, Inc.) permits accurate positional changes of the catheter by 1◦ increments and advancement or retraction by 1-mm steps. Using Cardiodrive and the magnetic field presaved vectors, the catheter was initially positioned at the tricuspidal annulus in 12 o’clock position. At the second step, using the presaved magnetic field vectors, the catheter was positioned at tricuspidal annulus (6 o’clock position). To maximize the catheter contact and pressure, the magnetic May 2008 PACE, Vol. 31 REMOTE MAGNETIC ABLATION OF AFL Figure 1. The figure shows our approach to catheter positioning on isthmus. The upper panels show the fluoroscopy image and the lower ones show the corresponding magnet vectors in Stereotaxis. TA = tricuspidal annulus; CS = coronary sinus; RAO = right anterior oblique; LAO = left anterior oblique. field vector was then oriented inferiorly and posteriorly (Fig. 1). At this point, the navigation success was judged by a combination of electrogram and fluoroscopic images analysis.1–3 Stable contact was judged based on fluoroscopic image, electrogram stability, and the position of the catheter on the CARTO-RMT
system. The x-ray imaging angles were limited to approximately 38–42◦ left anterior oblique and 10–12◦ right anterior oblique. Ablation of the CTI was performed using 90second radiofrequency (RF) application with a target temperature of 70◦ C and a power limit of 70 W. Ablation lines were performed by sequentially navigating to contiguous points after termination of each RF application. The RF endpoint was complete bidirectional isthmus block. After completing the first line of lesions, we carefully remapped all the ablation lines during coronary sinus (CS) and lateral pacing to control for double potentials and conduction times. The double potentials along the ablation line should have been at least 100 ms apart. And, the activation mapping with ablation catheter should have confirmed the complete block. In cases of incomplete lesion lines, gaps were identified based on the activation times and double potentials along the ablation line, and RF energy was then, specifically, applied to the identified gaps, as previously described.1–3 The detailed method for the ablation of AFL at our laboratory is described elsewhere.3 PACE, Vol. 31 Statistical Analysis Continuous variables are expressed as median with range values and compared using the MannWhitney U-test. For categorical variables, the χ 2 test (or the exact Fisher test when applicable) was performed. Statistical tests were performed with SPSS for Windows (version 13.0, SPSS, Inc., Chicago, IL, USA). Results Remote Catheter Mapping and Ablation Twenty-five patients had counterclockwise and one patient had clockwise AFL (Table II). In the 18th patient, the ablation procedure could not be performed for technical issues (the magnets could not be moved from the parking position), and so, we switched to the conventional ablation technique. The total procedure time was 53 (30– 130) minutes. The preparation time, including puncture, catheter placement, setting up the remote navigation system, and CARTO-RMT, was 28 (10–65) minutes. The ablation phase duration was 25 (10–30) minutes. We were able to obtain an optimum contact (assessed by Navigant
Contact Bar) and stable catheter position on CTI using the remote magnetic navigation and Cardiodrive in all of our twenty-five patients (Fig. 2). The AFL was terminated during the ablation in all patients. After termination of the AFL, the line of block was May 2008 599 ARYA, ET AL. Table II. Results of the Remote-Guided Catheter Ablation Variable Tachycardia CL (ms)* Procedure time (minutes) Preparation time (minutes)† Ablation time (minutes) RF time (seconds)§ Fluoroscopy time (minutes)¶ Termination of AFL (%)‡ Successful isthmus block (%) Total Group 1 Group 2 P-Value** 230 (200–260) 53 (30–130) 28 (10–65) 25 (12–78) 614 (262–1,728) 7.5 (3.2–20.8) 100 96 230 (205–260) 80 (57–130) 42 (30–65) 31 (20–78) 628 (405–1,547) 11 (5.4–20.8) 100 90 228 (200–245) 45 (30–70) 25 (10–30) 20 (12–40) 613 (262–1,728) 7.2 (3.2–12.2) 100 100 0.84 0.0001 0.0001 0.002 0.313 0.014 – 0.92 *Cycle length. †Preparation time consist of the total time that was required for puncture, catheter placements, and preparation of magnetic navigation system and CARTO-RMT. ‡Isthmus-dependent right atrial flutter. §Radiofrequency. ¶MGycm2 /s. **Comparison between groups 1 and 2. complete in nine patients (three in group 1 and six in group 2), and further ablation was required to complete the linear block along the CTI. In group 1, we switched to conventional ablation in order to complete the isthmus block in one patient (second patient) as repeated RF energy applications were not able to complete the isthmus block. In this patient, further ablation using an irrigated-tip catheter together with a steerable sheath (Agilis
; St. Jude Medical, Inc.) resulted in complete isthmus block. No major complication occurred during the procedure. Significant charring on the ablation catheter was observed in five (19.2%) patients. Effect of Learning Curve Figure 2. Projection of the anatomical location of the ablation line reconstructed in CARTO-RMT on fluoroscopy images. The red dots show the projection of ablation lesions imported from CARTO-RMT on the fluoroscopy image in Stereotaxis workstation. The white arrow shows the position of the tip of the ablation catheter projected from CARTO-RMT on fluoroscopy image. The yellow and the green arrows show the system and the desired magnetic vectors, respectively. RAO = right anterior oblique; LAO = left anterior oblique; ABL = Ablation catheter; CS = coronary sinus. 600 In order to compare the possible effect of learning curve on the procedure outcome, we compared the procedure data between the first 10 and the last 15 patients (Table II). Compared to the first group, patients in group 2 had shorter procedure (45 [30–70] min vs 80 [57–130] min, P = 0.0001), preparation (25 [10–30] min vs 42 [30–65] min, P = 0.0001), ablation (20 [12–40] min vs 31 [20– 78] min, P = 0.002), and fluoroscopy (7.2 [3.2–12.2] min vs 11.0 [5.4–20.8] min, P = 0.014) times. With respect to RF ablation time, there was no significant difference between the two groups (Table II). Comparison with Historical Control Group Although our study was not randomized, to assess the possible effect of the remote magnetic May 2008 PACE, Vol. 31 REMOTE MAGNETIC ABLATION OF AFL navigation on the procedure and the fluoroscopy times, we compared these times between procedures performed by remote magnetic navigation and 40 CTI-dependent AFL ablation performed directly before (n = 20) and after (n = 20) the study period with comparable baseline characteristics to our patients. With respect to the fluoroscopy time, there was no difference in the first and second parts of the control group (P = 0.45). The fluoroscopy times in the study and the historical control group were 7.5 (3.2–28.0) and 14.3 (4.0–45.3) minutes, respectively (P < 0.0001). However, the total procedure time was not different between the two groups (45 [30–110] min vs 53 [30–130] min, P = 0.12). Discussion Main Findings To the best of our knowledge, this is the first study of a remote magnetic catheter navigation system with the use of the new 8-mm-tip magnetic catheter for ablation of AFL in humans. Our results indicate that (1) the remote magnetic catheter navigation is able to obtain an optimum contact and stable catheter position on CTI (Fig. 2); (2) using the 8-mm-tip catheter remote magnetic catheter, navigation and ablation of AFL is feasible, safe, and effective; and (3) there is a short learning curve for using this system for the ablation of AFL, and therefore, operating the system would be easy to learn. Previous Studies To the best of our knowledge, there are no published data on the remote magnetic catheter navigation for the ablation of AFL using the 8-mmtip magnetic catheter in humans. Previous studies assess the efficacy of this remote MNS for the ablation of various arrhythmias using a 4-mm-tip catheter.4–15 Ernst et al. performed RF catheter ablation using the remote MNS in 42 consecutive patients with atrioventricular nodal reentrant tachycardia.13 Using a 4-mm-tip magnetic catheter (55◦ C, maximum power 40 W, 60 seconds), the ablation procedure was successful in all patients. Slow pathway ablation and modification were achieved in 15 and 27 patients, respectively. There were no complications. Pappone et al. assessed the feasibility of remote magnetic catheter navigation in patients with atrial fibrillation undergoing circumferential pulmonary vein ablation.11 Ablation was done with a 4-mm-tip magnetic catheter (65◦ C, maximum power 50 W, 15 seconds) and the remote ablation was successful in 38 of 40 patients without complications. Di Biase et al. have recently assessed PACE, Vol. 31 the efficacy of remote magnetic navigation in 45 consecutive patients with atrial fibrillation.15 The ablation endpoint was complete electrical isolation of all pulmonary veins. During the ablation, using MNS, the pulmonary veins were isolated in only 8% of the patients. After switching to the conventional approach with thermocool ablation catheter, the authors were able to isolate all the pulmonary veins in 22 (49%) patients. In 23 (51%) patients, only the right pulmonary veins were isolated. They reported significant charring on the catheter in 33% of the patients. After a mean follow-up of 11 ± 2 months, 25 patients (56%) had atrial fibrillation recurrence. Aryana et al. reported the results of ablation of ischemic ventricular tachycardia in 24 consecutive patients with 77 inducible ventricular tachycardias. Among 21 tachycardias that were targeted with MNS (4-mm-tip catheter), 81% were successfully ablated, and in the remaining patients, conventional ablation with an irrigated-tip catheter was required to complete the ablation procedure. In the conventional ablation arm of the study, the success rate of the ablation was 97% (irrigatedtip catheter). Although the success rate of the ablation in this study was lower than the conventional group, it is worth mentioning that different catheter types have been used in these two groups.4 The cumulative success rate in our patients was 95% (Table II), which is comparable to other published studies.3,16–19 Kottkamp et al. studied 50 patients with AFL and assessed the efficacy of RF catheter ablation. Overall, complete bidirectional isthmus block was achieved in 47 of 50 patients (94%).3 Sacher et al. have recently in a prospective, randomized study compared the clinical efficacy of an 8-mm gold-tip, externally irrigated-tip, and an 8-mm platinum-iridium-tip catheters. The complete bidirectional isthmus block was achieved equally with the three different catheters (95% for both 8-mm-tip catheters, 100% for irrigated-tip catheter, P = NS).16 Safety No major complication occurred in our patients. One patient experienced a hematoma in the left groin. Echocardiography after the ablation was done in all patients and showed no pericardial effusion. Previous studies have also confirmed the safety of the remote MNS, and to the best of our knowledge, no perforation and tamponade has been reported using this system so far.4–13 Learning Curve Our data suggested that there is a learning curve using the MNS (Fig. 3). Previous studies have also showed the presence of such a learning May 2008 601 ARYA, ET AL. Figure 3. Panels A through D show the procedure, preparation, fluoroscopy, and ablation times of our patients (see text for detailed discussion). curve using this system for ablation of other arrhythmias.11 Our data showed that although the ablation phase duration was shorter in group 2, the RF ablation time was not statistically different between the two groups. It shows that by doing more procedures the operators needed less time to achieve optimum contact and stable catheter position on CTI (Fig. 2). Limitations This study was conducted to assess the acute results of RF catheter ablation using remote MNS and an 8-mm-tip magnetic catheter. Therefore, no comment on the long-term outcome of this system for the ablation of AFL can be made. No randomized control group is included in our study; however, the aim of our study was just to assess the feasibility and efficacy of the remote MNS for the ablation of AFL using the newly available 8-mmtip magnetic catheter. However, comparison with matched historical controls at our EP laboratory suggested that the remote magnetic navigation and ablation might reduce the fluoroscopy time; however, this finding should be verified in a randomized study. We did not define the anatomy of the CTI before the ablation procedure; therefore, we cannot comment on the potential applicability of 602 this system in such difficult cases. Finally, we did not use Hallo catheter to confirm the bidirectional isthmus block and this might have overestimated our success rate.20 However, our long-term success in these patients ablated at our center is 93%, which is comparable to the published series. Conclusion In conclusion, our study showed that when using the remote MNS and the 8-mm-tip catheter, the ablation procedure of AFL is safe, feasible, and effective. The bidirectional isthmus block was achieved in 96% of the patients, which is comparable with the recently published patient series using conventional approaches for the ablation of AFL.3,16–19 Considering the effect of learning curve on the fluoroscopy times and its comparison with the abovementioned published studies and our historical control group, this system could reduce the radiation exposure to the patients, and especially, operators, while the efficacy of the ablation procedure is comparable to other conventional methods. Acknowledgment: The authors want to thank the nursing and technical staff at our department. Without their dedicated work, this study would not have been possible in the presented way. May 2008 PACE, Vol. 31 REMOTE MAGNETIC ABLATION OF AFL References 1. Poty H, Saoudi N, Abdel Aziz A, Nair M, Letac B. Radiofrequency catheter ablation of type one atrial flutter: Prediction of late success by electrophysiological criteria. Circulation 1995; 92:1389– 1392. 2. Shah DC, Hässaguerre M, Jais P, Fischer B, Takahashi A, Hocini M, Clementy J. Simplified electrophysiologically directed catheter ablation of recurrent common atrial flutter. Circulation 1997; 96:2505– 2508. 3. Kottkamp H, Hugl B, Krauss B, Wetzel U, Fleck A, Schuler G, Hindricks G. Electromagnetic versus fluoroscopic mapping of the inferior isthmus for ablation of typical atrial flutter: A prospective randomized study. Circulation 2000; 102:2082–2086. 4. Aryana A, d’Avila A, Heist EK, Mela T, Singh JP, Ruskin JN, Reddy VY. Remote magnetic navigation to guide endocardial and epicardial catheter mapping of scar-related ventricular tachycardia. Circulation 2007; 115:1191–1200. 5. Thornton AS, Rivero-Ayerza M, Knops P, Jordaens LJ. Magnetic navigation in left-sided AV reentrant tachycardias: Preliminary results of a retrograde approach. J Cardiovasc Electrophysiol 2007; 18:467– 472. 6. Ray IB, Dukkipati S, Houghtaling C, McPherson CD, Kastelein N, Ruskin JN, Reddy VY. Initial experience with a novel remote-guided magnetic catheter navigation system for left ventricular scar mapping and ablation in a porcine model of healed myocardial infarction. J Cardiovasc Electrophysiol 2007; 18:520–525. 7. Chun JK, Ernst S, Matthews S, Schmidt B, Bansch D, Boczor S, Ujeyl A, et al. Remote-controlled catheter ablation of accessory pathways: Results from the magnetic laboratory. Eur Heart J 2007; 28:190– 195. 8. Thornton AS, Jordaens LJ. Remote magnetic navigation for mapping and ablating right ventricular outflow tract tachycardia. Heart Rhythm 2006; 3:691–696. 9. Davis DR, Tang AS, Birnie DH, Gollob MH. Successful ablation of a concealed parahisian accessory pathway using a remote magnetic navigation system following failure by conventional methods. J Interv Card Electrophysiol 2006; 16:149–151. 10. Thornton AS, Janse P, Theuns DA, Scholten MF, Jordaens LJ. Magnetic navigation in AV nodal re-entrant tachycardia study: Early results of ablation with one- and three-magnet catheters. Europace 2006; 8:225–230. PACE, Vol. 31 11. Pappone C, Vicedomini G, Manguso F, Gugliotta F, Mazzone P, Gulletta S, Sora N, et al. Robotic magnetic navigation for atrial fibrillation ablation. J Am Coll Cardiol 2006; 47:1390–1400. 12. Ernst S, Hachiya H, Chun JK, Ouyang F. Remote catheter ablation of parahisian accessory pathways using a novel magnetic navigation system—a report of two cases. J Cardiovasc Electrophysiol 2005; 16:659–662. 13. Ernst S, Ouyang F, Linder C, Hertting K, Stahl F, Chun J, Hachiya H, et al. Initial experience with remote catheter ablation using a novel magnetic navigation system: Magnetic remote catheter ablation. Circulation 2004; 109:1472–1475. 14. Faddis MN, Blume W, Finney J, Hall A, Rauch J, Sell J, Bae KT, et al. Novel, magnetically guided catheter for endocardial mapping and radiofrequency catheter ablation. Circulation 2002; 106:2980–2985. 15. Di Biase L, Fahmy TS, Patel D, Bai R, Civello K, Wazni OM, Kanj M, et al. Remote magnetic navigation: Human experience in pulmonary vein ablation. J Am Coll Cardiol 2007; 50:868–874. 16. Sacher F, O’Neill MD, Jais P, Huffer LL, Laborderie J, Derval N, Deplagne A, et al. Prospective randomized comparison of 8-mm gold-tip, externally irrigated-tip and 8-mm platinum-iridium tip catheters for cavotricuspid isthmus ablation. J Cardiovasc Electrophysiol 2007; 18:709–713. 17. Subbiah RN, Gula LJ, Krahn AD, Posan E, Yee R, Klein GJ, Skanes AC. Rapid ablation for atrial flutter by targeting maximum voltage-factors associated with short ablation times. J Cardiovasc Electrophysiol 2007; 18:612–616. 18. Chang SL, Tai CT, Lin YJ, Ong MG, Wongcharoen W, Lo LW, Chang SH, et al. The electroanatomic characteristics of the cavotricuspid isthmus: Implications for the catheter ablation of atrial flutter. J Cardiovasc Electrophysiol 2007; 18:18–22. 19. Da Costa A, Thévenin J, Roche F, Romeyer-Bouchard C, Abdellaoui L, Messier M, Denis L, et al., for the Loire-Ardèche-Drôme-Isère-Puyde-Dôme Trial of Atrial Flutter Investigators. Results from the LoireArdèche-Drôme-Isère-Puy-de-Dôme (LADIP) Trial on atrial flutter, a multicentric prospective randomized study comparing amiodarone and radiofrequency ablation after the first episode of symptomatic atrial flutter. Circulation 2006; 114:1676–1681. 20. Anselme F, Savouré A, Cribier A, Saoudi N. Catheter ablation of typical atrial flutter: A randomized comparison of 2 methods for determining complete bidirectional isthmus block. Circulation 2001; 103:1434–1439. May 2008 603