Remote Magnetic Catheter Navigation for Cavotricuspid Isthmus Ablation in Patients With Common-Type Atrial FlutterCLINICAL PERSPECTIVE
Background— Conventional catheter ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter is a widely applied standard therapy. Remote magnetic catheter navigation (RMN) may provide benefits for different ablation procedures, but its efficacy for CTI ablation has not been evaluated in a randomized, controlled trial.
Methods and Results— Ninety patients undergoing de novo ablation of atrial flutter were randomly assigned to conventional manual (n=45) or RMN-guided (n=45) CTI ablation with an 8-mm-tip catheter. Complete bidirectional isthmus block was achieved in 84% (RMN) and 91% (conventional catheter ablation) of the cases (P=0.52). RMN was associated with shorter fluoroscopy time (median, 10.6 minutes; interquartile range [IQR], 7.6 to 19.9, versus 15.0 minutes; IQR, 11.5 to 23.1; P=0.043) but longer total radiofrequency application (17.1 minutes; IQR, 8.6 to 25, versus 7.5 minutes; IQR, 3.6 to 10.9; P<0.0001), ablation time (55 minutes; IQR, 28 to 76, versus 17 minutes; IQR, 7 to 31; P<0.0001), and procedure duration (114±35 versus 77±24 minutes, P<0.0001). Procedure duration in the RMN group did not decrease significantly with case experience. Long-term procedure success, defined as achievement of complete CTI block and freedom from atrial flutter recurrence during 6 months of follow-up, was lower in the RMN group (73% versus 89%, P=0.063). Right atrial angiography after ablation revealed no significant differences between groups in terms of right atrial diameter or CTI length, morphology, and angulation. Furthermore, none of these parameters was predictive for difficult (ablation time >20 minutes) or unsuccessful ablation.
Conclusions— RMN-guided CTI ablation is associated with reduced radiation exposure but prolonged ablation and procedure times as compared with conventional catheter navigation. Our findings suggest that ablation lesions produced with an RMN-guided 8-mm catheter are less effective irrespective of CTI anatomy.
Trial Registration— clinicaltrials.gov Identifier: NCT00560872
Received June 5, 2009; accepted September 9, 2009.
Conventional radiofrequency ablation of cavotricuspid isthmus (CTI)-dependent (“common-type”) atrial flutter (AFL) can be considered as a widely applied standard therapy with high success and low complication rates.1 It is well recognized, however, that varying anatomic properties of the CTI can complicate the procedure and may result in prolonged ablation and fluoroscopy times or even procedural failure despite the use of large-tip (8 mm) ablation catheters.2,3 Thus, efforts continue to improve the efficacy of this commonly applied procedure.4,5
Clinical Perspective on p 603
Recently, a magnetic catheter navigation system (Niobe II, Stereotaxis, Inc, St Louis, Mo) for remote mapping and ablation of cardiac arrhythmias has been introduced.6 The use of this system may reduce radiation exposure and physical stress to the operator and could theoretically enhance the safety and efficacy of the procedure due to the unrestricted and more precise catheter movement. The feasibility of remote magnetic catheter navigation (RMN) for mapping and ablation of different types of supraventricular tachycardia (SVT) has been demonstrated in nonrandomized studies.7–9 In a more recent investigation, RMN reduced fluoroscopy times and radiofrequency lesion deliveries for SVT as compared with conventional manual catheter navigation (CON).10 However, this study only included patients with SVT other than AFL, and thus the value of RMN for CTI ablation remains poorly defined.9
The aim of the present randomized, controlled trial was to evaluate the efficacy of the RMN system for mapping and ablation of CTI-dependent AFL. Furthermore, we attempted to relate ablation outcome with anatomic properties of the right atrium (RA) and the CTI as determined by right atrial angiography.
The protocol of this single-center, randomized, controlled study was approved by the Institutional Ethics Committee of the University of Göttingen.
Patients were eligible for enrollment if ≥1 episode of AFL had been documented on a 12-lead surface ECG and if the atrial rate and flutter waves were suggestive of CTI dependent (common-type) AFL.11 Prior right atrial ablation and presence of an implanted device at risk for magnetic interference (eg, pacemaker, ICD) were exclusion criteria.
Eligible subjects were enrolled after written informed consent was given and were randomly assigned in blocks of 10 patients to CON- or RMN-guided CTI ablation. Enrollment started in June 2007 and ended in December 2008. Prospectively defined primary end points of this study were radiofrequency current application duration and fluoroscopy time. Prespecified secondary study end points were ablation time (defined as the time from the first to the last ablation), procedure duration (defined as the time from venous puncture until sheath withdrawal), acute success (defined as achievement of complete bidirectional CTI block), long-term success (defined as acute success and freedom from AFL recurrence during 6 months of follow-up), and the frequency of procedure-related complications.
Electrophysiological Testing and Ablation Procedure
The procedure was carried out during analgo-sedation with spontaneous respiration, using intravenous fentanyl and midazolam under continuous monitoring of blood pressure and oxygen saturation. In patients with persistent AFL, sufficient anticoagulation for >3 weeks or a transesophageal echocardiogram that excluded left atrial thrombus were prerequisites for the procedure.
Two catheters were introduced via the femoral vein: A 6F steerable decapolar catheter (Polaris X, Boston Scientific, San Jose, Calif) was positioned in the coronary sinus, and the ablation catheter was placed in the RA. In the CON group, a conventional 8-mm-tip ablation catheter (Celsius, Biosense-Webster, Diamond Bar, Calif) was introduced through a long 8F sheath (SR0 or SAFL, St Jude Medical, Minnetonka, Minn) to enhance catheter stability. In the RMN group, a magnetic 8-mm-tip ablation catheter (Celsius Navistar RMT DS, Biosense-Webster) was introduced through a short 8F sheath to allow unrestricted remote catheter navigation.
The RMN system has been described in detail elsewhere.7,8 Briefly, the magnetic ablation catheter incorporates 4 magnets in the distal portion of the catheter; the system uses 2 large permanent magnets located on either side of the procedure table to generate a magnetic field (0.08 T) within the patient for directional catheter orientation. If the operator changes the desired vector for catheter orientation on a computer screen, the system automatically alters the magnetic field accordingly. A joystick-controlled motor drive (Cardiodrive, Stereotaxis) allows catheter advancement and retraction in 1-mm steps and thereby complete remote catheter navigation for mapping and ablation.
Before ablation, entrainment maneuvers were conducted in patients with persisting AFL to confirm CTI-dependent reentry. In the case of sinus rhythm, ablation was performed during pacing from the proximal coronary sinus at a cycle length of 600 ms. Catheter navigation was performed under fluoroscopic and ECG guidance. No 3-dimensional mapping system was used in either group.
For CTI ablation, the ablation catheter was advanced through the tricuspid valve and then pulled back through the annulus at the 6 o’clock position in the left anterior oblique view until a stable atrial signal became visible at the tip electrode electrogram. After each ablation application, the catheter was withdrawn in a stepwise manner until the absence of a local atrial electrogram on the proximal electrode indicated that the catheter had reached the inferior vena cava (IVC). In the RMN group, the magnetic field vector was usually oriented inferiorly and sometimes even slightly posteriorly in the anterior and in the middle part of the CTI to optimize electrode contact and stability, whereas in the posterior CTI (close to the IVC) the vector was usually oriented more anteriorly.
Radiofrequency current was delivered in a temperature-controlled mode using a standard generator (Cordis-Stockert radiofrequency generator, Cordis-Webster, Miami, Fla) with a target temperature of 60°C, a nominal power limit of 70 W, and a maximum duration of 60 seconds.
The end point of the ablation procedure was achievement of complete bidirectional CTI block persisting for a waiting period of 30 minutes. Assessment for CTI block was performed during pacing (cycle length, 600 ms) from the proximal coronary sinus or, after repositioning of the decapolar catheter, from the low lateral RA, and was based on point-to-point activation mapping (1) along the entire ablation line and (2) at the lateral right atrium and the atrial septum. CTI block was diagnosed if the interval between the split atrial components of the isthmus electrogram was ≥110 ms or ≥90 ms with ≤15 ms variation along the line,12 and if a cranial-to-caudal activation sequence was documented at the lateral right atrium during proximal coronary sinus stimulation and at the atrial septum during pacing from the lower lateral right atrium.13
If complete CTI block was not achieved with the first ablation drag, the line was mapped for conducting gaps where local ablation was repeated.12 If conduction persisted thereafter, additional ablation lines were created just lateral and (if conduction still persisted) medial to the initial 6 o’clock line. If CTI conduction still persisted, the procedure was classified as ablation failure.
Right Atrial Angiography
RA angiography was acquired after ablation and before sheath removal by positioning a 5F pigtail catheter in the IVC, just below the RA.3 Contrast solution (50 cm3) was injected during 3 to 5 seconds, and a 25° RAO view of the RA was acquired and stored digitally. Interelectrode spaces of the ablation catheter, which was positioned perpendicular to the RAO projection along the CTI, were used as a reference for later measurements. The latest atrial diastolic frame just before the opening of the tricuspid valve was used for all measurements. RA diameter was defined as the maximum distance between the lateral atrial wall and the tricuspid valve annulus. CTI length and morphology were determined and categorized as described earlier.2,3,14 CTI length was categorized into short (≤32 mm) or long (>32 mm)14 and CTI morphology was subdivided into straight (CTI depth ≤2 mm), concave, or presence of a pouch-like recess. CTI angulation was quantified as described by others,2 measuring the angle between a line that connects the IVC and the lower hinge point of the tricuspid valve and a line parallel to the ablation catheter in the terminal IVC. A representative example for image analysis is given in Figure 1. Angiogram analysis was performed by an independent operator who was blinded for ablation outcome.
All patients were monitored in the hospital overnight. Echocardiography was performed after the procedure to rule out pericardial effusion. On the next day, the venous puncture site was inspected for significant local hemorrhage, and a 12-lead surface ECG was acquired to confirm normal sinus rhythm and rule out new cardiac conduction disturbances. Patients were then discharged and followed after 3 and 6 months. At each visit, subjects were asked for arrhythmia recurrences, ECG documentations, and current medication. An echocardiogram was acquired to assess left atrial diameter and left ventricular ejection fraction, and ambulatory Holter monitoring was performed for 7 days at each follow-up to diagnose possible arrhythmia recurrences. Long-term ablation success was defined as achievement of CTI block and absence of AFL recurrence during follow-up.
Continuous variables are expressed as mean±standard deviation or as median with interquartile range if appropriate. Normally distributed data were compared using the independent Student t test. Otherwise, comparisons between groups were performed using the Mann-Whitney U test. Categorical values are stated as absolute and relative frequencies and were compared using Fisher exact test. Time to AFL recurrence was estimated with the use of the Kaplan-Meier method and compared by the log-rank test. Estimates of treatment effect (eg, differences between means) are presented along with the 95% CI if applicable. Bonferroni correction was used to adjust α of the analysis of the 2 primary end points for multiple comparisons. All other parameters were described by exploratory data analysis. All tests are 2-tailed. P<0.05 is considered statistically significant.
We expected an average fluoroscopy time of 15±5 minutes and an average radiofrequency application duration of 600±100 seconds.15 Based on these assumptions, we calculated that a sample size of 45 patients per group would detect a 20% difference in fluoroscopy time (3 minutes) and 10% difference in radiofrequency application duration (60 seconds) with at least 80% power and a 2-tailed α of 5%.
One hundred patients were eligible; 94 subjects signed the written informed consent and were enrolled. Four patients were excluded after enrollment and random assignment to CON (n=2) and RMN (n=2) because electrophysiological testing revealed atypical atrial flutter. Baseline characteristics of the remaining 90 patients (CON n=45, RMN n=45) are given in Table 1.
Acute Ablation Efficacy
The outcome of the primary study end points is illustrated in Figure 2 and 3⇓. The procedural end point (complete bidirectional CTI block) was achieved in 41 of 45 patients (91%) in the CON group and in 38 of 45 cases (84%) in the RMN group (P=0.52). Ablation details are summarized in Table 2. Radiofrequency current application duration was significantly longer in the RMN group than in the CON group (see also Figure 2). Furthermore, RMN was associated with significantly more radiofrequency applications and longer ablation times (Table 2).
Termination of persisting AFL during ablation was observed in 40 patients 6±5 minutes (CON, n=23) and 16±14 minutes (RMN, n=17), respectively, after ablation start (difference between means, 10 minutes; 95% CI, 4 to 16; P=0.0024), and after 5±4 (CON) and 9±6 (RMN) radiofrequency applications (difference between means, 4; 95% CI, 1 to 7; P=0.012). After complete block was initially obtained, recurrent CTI conduction during the subsequent 30-minute waiting period occurred in 15% (CON) and 28% (RMN) of the cases (P=0.18) after a median of 13 (7 to 26) minutes (CON) and 2 (1 to 20) minutes (RMN) (P=0.21).
During ablation, char formation at the ablation electrode tip occurred in 91% of the cases in the RMN group as compared with 22% in the CON group (P<0.0001). Multiple charring events (>1 time) were observed in 52% (RMN) and 10% (CON) of these cases, respectively.
In cases of ablation failure (inability to achieve complete bidirectional CTI block), an alternative ablation approach was attempted, with catheter selection at the discretion of the operator. In the RMN group, conventional manual ablation with an 8-mm (n=4) or an open irrigated 4 mm (n=3) tip catheter was used as a second-line approach, and CTI block was achieved in all 7 cases. In the CON group, a manually guided, irrigated 4-mm-tip catheter was used as a secondary approach in all 4 unsuccessful cases, and CTI block was achieved in 3 of these patients.
Total procedure duration was significantly longer in the RMN group as compared with the CON group (113.5±34.8 and 77.2±24.1 minutes; difference between means, 36.3 minutes; 95% CI, 23.7 to 48.9; P<0.0001). Procedure duration in the RMN group did not decrease significantly with time (cases 1 to 22: 120.2±35.1 minutes; cases 23 to 45: 107.2±34.0 minutes; difference between means, −13.0 minutes; 95% CI, −7.8 to 33.8, P=0.21). The difference in preparation time (duration from venous puncture to first ablation) between groups was small (CON: 18.7±6.1 minutes; RMN: 21.6±7.1 minutes; difference between means, 2.9 minutes; 95% CI, 0.1 to 5.7) but statistically significant (P=0.048).
Fluoroscopy time (RMN: 10.6 [7.6 to 19.9] minutes; CON: 15.0 [11.5 to 23.1] minutes; Figure 3) and patient x-ray exposure (RMN: 3274 [2045 to 5025] μGy m2; CON: 4304 [3435 to 5862] μGy m2) were significantly lower in the RMN than in the CON group (P=0.043 and P=0.032, respectively).
Patients were followed 1 day, 91±19 days, and 189±35 days after the procedure. There was no difference in follow-up duration between groups. One patient (CON group) relocated after hospital discharge and was lost to follow-up. One patient in the CON group developed significant local hemorrhage after the ablation procedure. No other procedure-related complications were observed.
Recurrence of common-type AFL after initial achievement of CTI block occurred in 2% (CON group, 1/41) and 13% (RMN group, 5/38) of the cases (P=0.073). A second procedure that confirmed recurrence of CTI-dependent AFL was conducted in 4 of these patients. As illustrated in Figure 4, the long-term success rate of the initial ablation procedure (achievement of CTI block and no AFL recurrence during follow-up) was lower in the RMN (73%, 33/45) than in the CON (89%, 40/45) group (P=0.063).
Use of antiarrhythmic medication did not change significantly during follow-up. The proportion of patients with documented paroxysmal or persistent atrial fibrillation increased from 40% at baseline to 62% after 6 months. Five subjects underwent circumferential pulmonary vein isolation for symptomatic AF within this time period. Left atrial diameter was 47±7 mm and 47±6 mm and left ventricular ejection fraction 53±7% and 55±5% at 3 and 6 months, respectively.
Anatomic Properties of the CTI
RA angiograms were obtained from 37 (82%) and 39 (87%) of the patients in the CON and RMN group, respectively. No angiogram was acquired in cases with a history of allergic reactions against contrast medium, significantly impaired renal function, or hyperthyroidism.
RA diameter, as determined by angiographic analysis, was 64±9 mm in the total study population. Overall CTI length was 26±7 mm, with 66 (87%) classified as short (≤32 mm) and 10 (13%) as long CTI. CTI morphology was straight in 10 (13%), concave in 23 (30%), and with a pouch-like recess in 43 (57%) cases. Mean pouch depth was 8±4 mm. The average angle between CTI and VCI was 103±19°. No significant difference existed between the 2 treatment groups in terms of RA diameter or CTI length, morphology, and angulation.
Relationship Between Anatomic Properties and Ablation Efficacy
Within each treatment group, angiographic parameters were compared between ablation procedures classified as easy (ablation time ≤20 minutes) or difficult (ablation time >20 minutes) and between procedures with or without long-term success.
As illustrated in Table 3, none of the anatomic parameters was significantly predictive for difficult or unsuccessful ablation. In the RMN group, there was a nonsignificant trend of RA diameter to be larger in ablation failures.
The main finding of this prospective, randomized study is that the use of RMN for CTI ablation (8-mm-tip catheter) decreases fluoroscopy time but prolongs radiofrequency current application, ablation, and procedure times as compared with the CON approach. Although the acute success rate (achievement of CTI block) is similar with both techniques, the use of RMN is associated with a lower rate of long-term success (defined by achievement of CTI block and freedom from AFL recurrence) as compared with a CON approach.
Conventional radiofrequency ablation of the CTI in patients with common-type AFL has emerged as a standard therapy with high success and low complication rates.1 Nevertheless, recent advances in ablation technology aim to reduce x-ray exposure to patients and physicians while maintaining or improving patient safety, procedure times, and ablation success-rates.
In the present study, the use of RMN was associated with a significant reduction in fluoroscopy time and x-ray exposure. This reduction, which becomes remarkable when considering the prolonged ablation times in the RMN group, was also noted in other studies of RMN-guided ablation.9,10,16 This uniform finding can be explained by the fact that the risk of cardiac perforation appears low when the flexible magnetic catheter is navigated within the cardiac chambers. The maximal force that is exerted by the magnetic vector to the tip is limited, which makes trauma to cardiovascular structures unlikely. Thus, large catheter movements can safely be made with minimal fluoroscopy. In contrast, the stiffness of the conventional ablation catheter mandates constant visualization of the catheter tip during manipulation.
Acute CTI block was achieved in our study in 91% (CON) and 84% (RMN) of the cases. Prior investigations that used conventional 8-mm or irrigated 4-mm ablation catheters demonstrated achievement of complete CTI block in ≈90% of the cases, varying from 80% to 100% between studies and with the type of ablation catheter.11,15 Thus, our acute success rates are within the range reported in the current literature.
During follow-up, however, the rate of AFL recurrences in the RMN group (13%) tended to be higher than in our control (CON) group (2%) and possibly higher than the rate reported for conventional CTI ablation in prior reports (≈10%, ranging from 2% to 13% with the mode and duration of follow-up11,15). Limited data exist to date on the use of RMN for ablation of SVT,7–10,16–18 and, in particular, of common-type AFL.9 Of note, only 1 of these investigations was a randomized controlled trial.10 This study by Wood et al10 compared RMN and conventional catheter navigation for slow pathway, accessory pathway, or AV junctional ablation. As in our study, the use of RMN was associated with reduced fluoroscopy time and similar acute success rates as compared with the conventional approach. Contrary to our findings, however, Wood et al observed a lower number of radiofrequency lesions and comparable procedure times in the RMN group. Arya et al9 recently reported their experience with RMN-guided CTI ablation in 26 patients with common-type AFL. In this study, complete CTI block was achieved with a magnetic 8-mm-tip ablation catheter in 96% of the cases. The median ablation time was 25 (12 to 78) minutes, procedure duration was 53 (30 to 130) minutes, and fluoroscopy time was 7.2 (3.2 to 12.2) minutes. The comparability of these findings to our results, however, is limited by the fact that Arya et al used a 3D mapping system (CARTO) that has been shown to affect procedural parameters.5,19 In recent preliminary reports from other groups,20–22 RMN-guided CTI ablation with an 8-mm magnetic tip catheter resulted in complete CTI block in only 89% (8/9),20 59% (10/17),21 and 54% (15/28)22 of the cases. Of note, these investigations also noted prolonged ablation and procedure times,20,21 a high incidence of char formation at the catheter tip,22 and an elevated rate of AFL recurrences (12%) during follow-up.21
The observation that RMN-guided CTI ablation requires more radiofrequency current application and results in lower overall success rates suggests that lesions produced with an 8-mm magnetic catheter are less effective than those applied conventionally. Other studies evaluated RMN for slow pathway or accessory pathway ablation and found lesions produced with a 4-mm magnetic tip catheter equally or even more effective than with the conventional approach.10,23 In contrast, Di Biase et al16 were unable to produce effective lesions with the same catheter and the RMN system in their study of circumferential pulmonary vein isolation. Thus, the ability to achieve effective ablation lesions with the RMN system appears to vary with the anatomic region, the ablation electrode, and the type of desired lesion (focal versus linear, subendocardial versus transmural).
Successful CTI ablation requires a continuous transmural linear lesion. Specific anatomic characteristics, such as a long or concave CTI, prominent pectinate muscles, existence of a sub-Eustachian pouch, or presence of a rectangular orientation of the CTI with respect to the IVC may hamper the application of effective ablation lesions.2,3,24,25 In the present study, the distribution of these anatomic properties did not differ significantly between the 2 treatment groups. Furthermore, we were not able to relate specific anatomic characteristics to ablation outcome in either of the 2 groups, although the sample size may have been not sufficiently sized for this subanalysis. Prior studies showed that use of an 8-mm-tip catheter can overcome some of the ablation difficulties related to CTI morphology.15 It is well appreciated, however, that adequate lesion formation with large ablation electrodes requires a sufficient electrode to tissue surface area of contact.26 In consideration of the anatomic complexity of the CTI, significant force often must be exerted to the catheter tip to embed the ablation electrode parallel oriented within the tissue and to thereby increase the area of contact for energy transfer. Earlier studies demonstrated that the maximal endocardial force that is exerted by the RMN-assisted magnetic catheter is generally lower than that applied by CON-controlled ablation catheters.6 Furthermore, 3 of the 4 magnetic components of the Navistar RMT DS 8-mm ablation catheter are located proximal to the electrode ring, away from the tip. This distribution may further reduce the force exerted to the electrode tip if the catheter is advanced over a convex contour, as is the case when passing from the VCI onto the CTI.
In the present study, we found that significantly more power was delivered during RMN- than during CON-guided ablation to reach comparable target temperatures. This finding suggests that a larger proportion of the magnetic catheter electrode tip surface was exposed to the blood flow, resulting in enhanced electrode cooling and dissipation of ablation energy into the circulating blood pool. This also supports the hypothesis that a smaller area of electrode to tissue contact accounts for insufficient CTI ablation lesions in the RMN group.
To enhance tissue contact, a long sheath is routinely used for CTI ablation at our institution and was therefore used in the CON group of the present study. We limited the use of a long sheath to the CON group because its use in the RMN group would have significantly restricted the process of remote navigation. We cannot exclude that this discrepancy between the study groups influenced our results, although others demonstrated that CTI ablation with a conventional 8-mm-tip catheter is highly effective even without the use of a long sheath.3,14
Last, it appears notable that char formation at the ablation electrode tip was observed in 91% of the cases in the RMN group (compared with 22% in the CON group). It remains speculative whether a reduced tip to tissue surface area of contact may underlie the high incidence of char formation in the RMN group. Of note, other investigators have also expressed concern about a higher incidence of char formation during RMN-guided ablation.16 Irrigated magnetic catheters have recently become available and may reduce the risk of char formation but also increase lesion efficacy during RMN-guided ablation.20
RMN-guided CTI-ablation is associated with reduced radiation exposure but prolonged ablation and procedure times as compared with conventional catheter navigation. Furthermore, the use of the RMN system resulted in a lower overall success rate (achievement of CTI block and freedom from AFL recurrence during follow-up).
Our findings suggest that ablation lesions produced with an RMN-guided 8-mm catheter are less effective, irrespective of the CTI anatomy, and potentially related to a reduced tip to tissue surface area of contact.
Sources of Funding
This investigator-initiated study was supported by a research grant from Stereotaxis, Inc.
Drs Vollmann and Zabel received research grants from Stereotaxis, Inc.
Blomstrom-Lundqvist C, Scheinman MM, Aliot EM, Alpert JS, Calkins H, Camm AJ, Campbell WB, Haines DE, Kuck KH, Lerman BB, Miller DD, Shaeffer CW Jr, Stevenson WG, Tomaselli GF, Antman EM, Smith SC Jr, Faxon DP, Fuster V, Gibbons RJ, Gregoratos G, Hiratzka LF, Hunt SA, Jacobs AK, Russell RO Jr, Priori SG, Blanc JJ, Budaj A, Burgos EF, Cowie M, Deckers JW, Garcia MA, Klein WW, Lekakis J, Lindahl B, Mazzotta G, Morais JC, Oto A, Smiseth O, Trappe HJ. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Supraventricular Arrhythmias). Circulation. 2003; 108: 1871–1909.
Heidbuchel H, Willems R, van Rensburg H, Adams J, Ector H, Van de Werf F. Right atrial angiographic evaluation of the posterior isthmus: relevance for ablation of typical atrial flutter. Circulation. 2000; 101: 2178–2184.
Da Costa A, Faure E, Thevenin J, Messier M, Bernard S, Abdel K, Robin C, Romeyer C, Isaaz K. Effect of isthmus anatomy and ablation catheter on radiofrequency catheter ablation of the cavotricuspid isthmus. Circulation. 2004; 110: 1030–1035.
Steven D, Rostock T, Servatius H, Hoffmann B, Drewitz I, Mullerleile K, Meinertz T, Willems S. Robotic versus conventional ablation for common-type atrial flutter: a prospective randomized trial to evaluate the effectiveness of remote catheter navigation. Heart Rhythm. 2008; 5: 1556–1560.
Faddis MN, Blume W, Finney J, Hall A, Rauch J, Sell J, Bae KT, Talcott M, Lindsay B. Novel, magnetically guided catheter for endocardial mapping and radiofrequency catheter ablation. Circulation. 2002; 106: 2980–2985.
Ernst S, Ouyang F, Linder C, Hertting K, Stahl F, Chun J, Hachiya H, Bansch D, Antz M, Kuck KH. Initial experience with remote catheter ablation using a novel magnetic navigation system: magnetic remote catheter ablation. Circulation. 2004; 109: 1472–1475.
Arya A, Kottkamp H, Piorkowski C, Bollmann A, Gerdes-Li JH, Riahi S, Esato M, Hindricks G. Initial clinical experience with a remote magnetic catheter navigation system for ablation of cavotricuspid isthmus-dependent right atrial flutter. Pacing Clin Electrophysiol. 2008; 31: 597–603.
Feld GK, Srivatsa U, Hoppe B. Ablation of Isthmus-Dependent Atrial Flutters. In: Huang SKS, Wood MA, ed. Catheter Ablation of Cardiac Arrhythmias. Philadelphia, PA: Saunders Elsevier; 2006.
Cauchemez B, Haissaguerre M, Fischer B, Thomas O, Clementy J, Coumel P. Electrophysiological effects of catheter ablation of inferior vena cava-tricuspid annulus isthmus in common atrial flutter. Circulation. 1996; 93: 284–294.
Da Costa A, Romeyer-Bouchard C, Dauphinot V, Lipp D, Abdellaoui L, Messier M, Thevenin J, Barthelemy JC, Isaaz K. Cavotricuspid isthmus angiography predicts atrial flutter ablation efficacy in 281 patients randomized between 8 mm- and externally irrigated-tip catheter. Eur Heart J. 2006; 27: 1833–1840.
Di Biase L, Fahmy TS, Patel D, Bai R, Civello K, Wazni OM, Kanj M, Elayi CS, Ching CK, Khan M, Popova L, Schweikert RA, Cummings JE, Burkhardt JD, Martin DO, Bhargava M, Dresing T, Saliba W, Arruda M, Natale A. Remote magnetic navigation: human experience in pulmonary vein ablation. J Am Coll Cardiol. 2007; 50: 868–874.
Chun JK, Ernst S, Matthews S, Schmidt B, Bansch D, Boczor S, Ujeyl A, Antz M, Ouyang F, Kuck KH. Remote-controlled catheter ablation of accessory pathways: results from the magnetic laboratory. Eur Heart J. 2007; 28: 190–195.
Koektuerk B, Chun JKR, Schmidt B, Metzner A, Tilz R, Ernst S, Koester I, Ouyang F, Kuck KH. Remote controlled catheter ablation of typical atrial flutter: A preliminary comparison of the magnetic 8 mm tip catheter versus the novel 3.5 mm irrigated tip magnetic catheter (Abstract). Europace. 2008; 10: i176.
Anne W, Janse P, Schwagten B, Van Belle Y, Valk S, Jordaens L, Szili-Torok T. Ablation of atrial flutter by he maximum voltage-guided technique: The role of magnetic navigation. Heart Rhythm. 2009; 6: S276.
Preminger M, Kamath GS, Sichrovsky T, Arshad A, Mittal S, Steinberg JS. Early experience with remote magnetic navigation ablation of cavo-tricuspid isthmus: Potential limitations (Abstract). Heart Rhythm. 2009; 6: S61.
Kirchhof P, Ozgun M, Zellerhoff S, Monnig G, Eckardt L, Wasmer K, Heindel W, Breithardt G, Maintz D. Diastolic isthmus length and ‘vertical’ isthmus angulation identify patients with difficult catheter ablation of typical atrial flutter: a pre-procedural MRI study. Europace. 2009; 11: 42–47.
Radiofrequency ablation of the cavotricuspid isthmus (CTI) is a commonly applied standard therapy for CTI-dependent atrial flutter. A remote magnetic catheter navigation (RMN) system for mapping and ablation of cardiac arrhythmias has recently been introduced that may reduce radiation exposure and physical stress to the operator and that could theoretically enhance the procedure safety and efficacy by facilitating precise catheter manipulation. The present randomized, controlled trial was designed to evaluate the efficacy of the RMN system as compared with the usual manual catheter manipulation approach for mapping and ablation of CTI-dependent atrial flutter. Both groups used 8-mm ablation electrodes. In addition, we attempted to relate ablation outcome to CTI anatomy as determined by right atrial angiography. RMN-guided ablation of the CTI did reduce radiation exposure, but procedure times were longed as compared with the conventional, manual approach. Furthermore, the ablation lesions produced with the RMN-guided 8-mm catheter appeared to be less effective, irrespective of the anatomic properties of the CTI, possibly related to reduced catheter tip–to–tissue contact. These findings do not support routine use of the current RMN system with an 8-mm-tip electrode for ablation of common right atrial flutter.