Remote magnetic navigation: human experience in pulmonary vein ablation

The magnetic navigation system allows safety and high efficacy for ablation of arrhythmias

Aims

We aimed to evaluate the safety and long-term efficacy of the magnetic navigation system (MNS) in a large number of patients. The MNS has the potential for improving safety and efficacy based on atraumatic catheter design and superior navigation capabilities.

Methods and results

In this study, 610 consecutive patients underwent ablation. Patients were divided into two age- and sex-matched groups. Ablations were performed either using MNS (group MNS, 292) or conventional manual ablation [group manual navigation (MAN), 318]. The following parameters were analysed: acute success rate, fluoroscopy time, procedure time, complications [major: pericardial tamponade, permanent atrioventricular (AV) block, major bleeding, and death; minor: minor bleeding and temporary AV block]. Recurrence rate was assessed during follow-up (15 ± 9.5 months). Subgroup analysis was performed for the following groups: atrial fibrillation, isthmus dependent and atypical atrial flutter, atrial tachycardia, AV nodal re-entrant tachycardia, circus movement tachycardia, and ventricular tachycardia (VT). Magnetic navigation system was associated with less major complications (0.34 vs. 3.2%, P = 0.01). The total numbers of complications were lower in group MNS (4.5 vs. 10%, P = 0.005). Magnetic navigation system was equally effective as MAN in acute success rate for overall groups (92 vs. 94%, P = ns). Magnetic navigation system was more successful for VTs (93 vs. 72%, P < 0.05). Less fluoroscopy was used in group MNS (30 ± 20 vs. 35 ± 25 min, P < 0.01). There were no differences in procedure times and recurrence rates for the overall groups (168 ± 67 vs. 159 ± 75 min, P = ns; 14 vs. 11%, P = ns; respectively).

Conclusions

Our data suggest that the use of MNS improves safety without compromising efficiency of ablations. Magnetic navigation system is more effective than manual ablation for VTs.

Remote magnetic versus manual catheters: evaluation of ablation effect in atrial fibrillation by myocardial marker levels

Background

A remote magnetic navigation (MN) system is available for radiofrequency ablation of atrial fibrillation (AF), challenging the conventional manual ablation technique. The myocardial markers were measured to compare the effects of the two types of MN catheters with those of a manual-irrigated catheter in AF ablation.

Methods

AF patients underwent an ablation procedure using either a conventional manual-irrigated catheter (CIR, n = 65) or an MN system utilizing either an irrigated (RMI, n = 23) or non-irrigated catheter (RMN, n = 26). Levels of troponin T (TnT) and the cardiac isoform of creatin kinase (CKMB) were measured before and after ablation.

Results

Mean procedure times and total ablation times were longer employing the remote magnetic system. In all groups, there were pronounced increases in markers of myocardial injury after ablation, demonstrating a significant correlation between total ablation time and post-ablation levels of TnT and CKMB (CIR r = 0.61 and 0.53, p < 0.001; RMI r = 0.74 and 0.73, p < 0.001; and RMN r = 0.51 and 0.59, p < 0.01). Time-corrected release of TnT was significantly higher in the CIR group than in the other groups. Of the patients, 59.6% were free from AF at follow-up (12.2 ± 5.4 months) and there were no differences in success rate between the three groups.

Conclusions

Remote magnetic catheters may create more discrete and predictable ablation lesions measured by myocardial enzymes and may require longer total ablation time to reach the procedural endpoints. Remote magnetic non-irrigated catheters do not appear to be inferior to magnetic irrigated catheters in terms of myocardial enzyme release and clinical outcome.

Advances in imaging for atrial fibrillation ablation

Over the last fifteen years, our understanding of the pathophysiology of atrial fibrillation (AF) has paved the way for ablation to be utilized as an effective treatment option. With the aim of gaining more detailed anatomical representation, advances have been made using various imaging modalities, both before and during the ablation procedure, in planning and execution. Options have flourished from procedural fluoroscopy, electroanatomic mapping systems, preprocedural computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and combinations of these technologies. Exciting work is underway in an effort to allow the electrophysiologist to assess scar formation in real time. One advantage would be to lessen the learning curve for what are very complex procedures. The hope of these developments is to improve the likelihood of a successful ablation procedure and to allow more patients access to this treatment.

Steerable versus nonsteerable sheath technology in atrial fibrillation ablation: a prospective, randomized study

BACKGROUND

Steerable sheath technology is designed to facilitate catheter access, stability, and tissue contact in target sites of atrial fibrillation (AF) catheter ablation. We hypothesized that rhythm control after interventional AF treatment is more successful using a steerable as compared with a nonsteerable sheath access.

METHODS AND RESULTS

One hundred thirty patients with paroxysmal or persistent drug-refractory AF undergoing their first ablation procedure were prospectively included in a randomized fashion in 2 centers. Ablation was performed by 10 operators with different levels of clinical experience. Treatment outcome was measured with serial 7-day Holter ECGs and additional symptom-based arrhythmia documentation. Single procedure success (freedom from AF and/or atrial macroreentrant tachycardia) was significantly higher in patients ablated with a steerable sheath (78% versus 55% after 3 months, P=0.005; 76% versus 53% after 6 months, P=0.008). Rate of pulmonary vein isolation, procedure duration, and radiofrequency application time did not differ significantly, whereas fluoroscopy time was lower in the steerable sheath group (33±14 minutes versus 45±17 minutes, P<0.001). Complication rates showed no significant difference (3.2% versus 5%, P=0.608). On multivariable analysis, steerable sheath usage remained the only powerful predictor for rhythm outcome after 6 months of follow-up (hazard ratio, 2.837 [1.197 to 6.723]).

CONCLUSIONS

AF catheter ablation using a manually controlled, steerable sheath for catheter navigation resulted in a significantly higher clinical success rate, with comparable complication rates and with a reduction in periprocedural fluoroscopy time.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov. Unique identifier: NCT00469638.

Remote magnetic navigation with irrigated tip catheter for ablation of paroxysmal atrial fibrillation

BACKGROUND

The remote magnetic navigation system (MNS) has been used with a nonirrigated magnetic catheter for atrial fibrillation (AF) ablation. The objective of this study was to evaluate the feasibility and efficiency of the newly available irrigated tip magnetic catheter for index pulmonary vein isolation (PVI) in patients with paroxysmal AF (PAF).

METHODS AND RESULTS

Between January 2008 and June 2009, 30 consecutive patients with drug-resistant PAF underwent circular mapping catheter-guided PVI with MNS (MNS group). The outcomes were compared retrospectively with those of a conventional hand-controlled ablation technique during the same period in 44 consecutive patients (manual group). All 4 pulmonary veins were successfully isolated in both groups except in 4 patients in the MNS group. Radiofrequency and procedure duration were higher in the MNS group (60 ± 27 versus 43 ± 16 minutes; P = 0.0019) than in the manual group (246 ± 50 versus 153 ± 51 minutes; P < 0.0001). In the patients who underwent only PVI, total fluoroscopic time also was longer in the MNS group than in the manual group (58 ± 24 versus 40 ± 14 minutes; P = 0.0002). At 12-month follow-up after a single procedure, 69.0% of the patients in MNS group and 61.8% of patients in manual group were free of atrial tachyarrhythmia without antiarrhythmic drugs. There was no significant difference in the atrial tachyarrhythmia-free survival between the 2 groups (P = 0.961). Cardiac tamponade occurred in 1 patient in the manual group.

CONCLUSIONS

In patients with PAF, MNS-guided PVI with the newly available irrigated tip magnetic catheter backed up with manual ablation whenever required is feasible. However, it requires longer ablation, fluoroscopy, and procedural times than the conventional approach in the early experience stage.

Remote-Controlled Magnetic Pulmonary Vein Isolation Using a New Irrigated-Tip Catheter in Patients With Atrial Fibrillation

Background—

Lack of an irrigated-tip magnetic catheter has limited the role of remote-controlled magnetic navigation (Niobe II, Stereotaxis) for catheter ablation of atrial fibrillation (AF).

Methods and Results—

A novel 3.5-mm-tip irrigated magnetic catheter (group 1, Thermocool Navistar RMT, Biosense Webster) was used for 3D left atrial reconstruction (CARTO RMT) and remote-controlled magnetic pulmonary vein isolation. A redesigned catheter was used in group 2. The primary end point was wide area circumferential pulmonary vein isolation confirmed by spiral catheter recording during ablation; secondary end points included procedural data, complications, and AF recurrence. Fifty-six consecutive patients [group 1: 28 patients, 22 males, age 64 (38 to 78) years, left atrium: 47 (34 to 52) mm; paroxysmal AF: n=21, persistent AF: n=7; group 2: 28 patients, 20 males, age 60 (24 to 78) years, left atrium: 40 (35 to 53) mm; paroxysmal AF: n=18, persistent AF: n=10] were included. The primary end point was achieved in a total of 52 of 56 (93%) patients. Median procedure duration was 315 (125 to 550) minutes (group 1: 370 [230 to 550] minutes; group 2: 243 [125 to 450] minutes). Median fluoroscopy exposure to the investigator was reduced by 31%. Tip charring in 17 of 28 (61%) and complications in 3 of 28 (11%) patients in group 1 resulted in a catheter redesign. Sinus rhythm was maintained by 35 of 50 (70%) patients during a median follow-up period of 545 (100 to 683) days.

Conclusions—

Remote-controlled magnetic AF ablation with real-time verification of pulmonary vein isolation is feasible with a comparable success rate to manual ablation. Safety improved after a redesign of the catheter.

[Magnetic navigation for ablation of cardiac arrhythmias]

BACKGROUND

The first use of magnetic navigation for radiofrequency ablation of supraventricular tachycardias, was published in 2004. Subsequently, the method has been used for treatment of most types of tachyarrhythmias. This paper provides an overview of the method, with special emphasis on usefulness of a new remote-controlled magnetic navigation system.

MATERIAL AND METHODS

The paper is based on our own scientific experience and literature identified through a non-systematic search in PubMed.

RESULTS

The magnetic navigation system consists of two external electromagnets (to be placed on opposite sides of the patient), which guide an ablation catheter (with a small magnet at the tip of the catheter) to the target area in the heart. The accuracy of this procedure is higher than that with manual navigation. Personnel can be quickly trained to use remote magnetic navigation, but the procedure itself is time-consuming, particularly for patients with atrial fibrillation. The major advantage is a considerably lower radiation burden to both patient and operator, in some studies more than 50 %, and a corresponding reduction in physical strain on the operator. The incidence of procedure-related complications seems to be lower than that observed with use of manually operated ablation catheters. Work is ongoing to improve magnetic ablation catheters and methods that can simplify mapping procedures and improve efficacy of arrhythmia ablation. The basic cost for installing a complete magnetic navigation laboratory may be three times that of a conventional electrophysiological laboratory.

INTERPRETATION

The new magnetic navigation system has proved to be applicable during ablation for a variety of tachyarrhythmias, but is still under development.

Endo-epicardial ablation of ventricular arrhythmias in the left ventricle with the Remote Magnetic Navigation System and the 3.5-mm open irrigated magnetic catheter: results from a large single-center case-control series

BACKGROUND

Remote magnetic navigation (RMN) has been reported as a feasible and safe mapping and ablation system for treatment of ventricular arrhythmias (VAs). However, the reported success rates have been limited with the 4- and 8-mm catheter tips.

OBJECTIVE

This study sought to report the results in a large series of consecutive patients undergoing radiofrequency (RF) catheter ablation of VAs using the RMN with the 3.5-mm magnetic open-irrigated-tip catheter (OIC).

METHODS

A total of 110 consecutive patients with a clinical history of left VA were included in the study. In all cases, an OIC was utilized for mapping and ablation. When ablation with the RMN catheters failed, a manual OIC was used to eliminate the VA. Postablation pacing maneuvers and isoproterenol were used to verify the inducibility of the VAs. Outcomes were compared with those of a group of 92 consecutive patients undergoing manual ablation by the same operator.

RESULTS

Mapping and ablation with the magnetic OIC were performed in all 110 patients with VA. Ischemic cardiomyopathy was present in 33 (30%), nonischemic in 14 (13%), and in 63 (57%) patients no structural heart disease was present. Endocardial mapping was performed in all patients, whereas both endocardial and epicardial mapping were performed in 36 (33%) patients. Compared with manual ablation, RMN was associated with a longer procedural time (2.9 +/- 1.2 hours vs. 3.3 +/- 1.1 hours, P = 0.004) and RF time (24 +/- 12 minutes vs. 33 +/- 18 minutes, P = 0.005), whereas fluoroscopic time was significantly shorter (35 +/- 22 minutes vs. 26 +/- 14 minutes, P = 0.033). During the procedures, crossover to manual ablation was required in 15 patients (14%). At 11.7 +/- 2.1 months of follow-up in the study group and 18.7 +/- 3.7 months in the manual ablation group, 85% and 86% (P = 0.817) of patients, respectively, were free of VA.

CONCLUSION

This large series of consecutive patients demonstrates that OIC ablation using RMN is effective for the treatment of left VAs.

Remote Navigation and Electroanatomic Mapping in the Pericardial Space

Mapping and ablation in the pericardial space has been shown to be beneficial for the treatment of different supraventricular and ventricular arrhythmias. The percutaneous subxiphoid approach is the most frequently used approach to access the pericardial space. Mapping and ablation in this space may be challenging because it is an open space without obstacles where catheters can move freely, making some locations difficult to reach. Remote magnetic navigation is a modern way to overcome many of the limitations the electrophysiologist encounters during mapping and ablation of arrhythmias in the pericardial space. This article recounts the authors' experiences and reviews the limited data on this topic.

Ablation of atrial fibrillation utilizing robotic catheter navigation in comparison to manual navigation and ablation: single-center experience

BACKGROUND

Robotic catheter navigation and ablation either with magnetic catheter driving or with electromechanical guidance have emerged in the recent years for the treatment of atrial fibrillation.

OBJECTIVE

The aim of this study was to compare our center's experience of atrial fibrillation ablation using the Hansen Robotic Medical System with our current manual ablation technique in terms of acute and chronic success, as well as procedure time and radiation exposure to both the patient and the operator.

METHODS

A total of 390 consecutive patients with symptomatic and drug-resistant atrial fibrillation (289 males, 62 +/- 11 years) were prospectively enrolled in the study. All patients underwent the procedure either with conventional manual ablation (group 1, n = 197) or with the robotic navigation system (RNS) (group 2, n = 193).

RESULTS

The success rate for RNS was 85% (164 patients), while for manual ablation it was 81% (159 patients) (p = 0.264) at 14.1 +/- 1.3 months with AADs previously ineffective. Fluoroscopy time was significantly lower for RNS (48.9 +/- 24.6 minutes for RNS vs. 58.4 +/- 20.1 minutes for manual ablation, P < 0.001). Mean fluoroscopy time was statistically reduced after 50 procedures (61.8 +/- 23.2 minutes for first 50 cases vs. 44.5 +/- 23.6 minutes for subsequent procedures, P < 0.0001).

CONCLUSION

Robotic navigation and ablation of atrial fibrillation is safe and effective. Fluoroscopy time decreases with experience.

Developments and recent advances in catheter ablation of paroxysmal atrial fibrillation

The development of catheter ablation for paroxysmal atrial fibrillation (AF) has evolved rapidly over the last 10 years from an experimental unproven procedure to a commonly performed ablation therapy in many major hospitals. The pulmonary vein (PV) and left atrium were discovered to be critical in the initiation and perpetuation of AF. With a better understanding of the AF mechanisms and more experience from the ablation follow-up, we have seen the ablation technique change from PV focal ablation to empirical circumferential isolation of all four PVs. In addition, the technological aid obtained from 3D electroanatomic mapping systems has further improved the safety and long-term efficacy and minimized the procedural difficulty. Recently, the atrial substrate analysis of the high-frequency and fractionated electrograms has further afforded the improvement in the outcome of more complex arrhythmias. Therefore, in this article, we will review the recent evidence and advancements in the mechanisms of AF and catheter ablation, and highlight the unsolved issues regarding future perspectives for paroxysmal AF.

Pulmonary vein isolation for the treatment of atrial fibrillation: past, present and future

Atrial fibrillation is the most common sustained cardiac arrhythmia and is associated with impaired quality of life and an increased risk of stroke and mortality. Antiarrhythmic drugs, currently the first-line therapy for patients without permanent atrial fibrillation, fail to prevent recurrences in over 50% and are associated with significant adverse effects. In the majority of cases, atrial fibrillation arises from the repetitive firing of myocytes in muscle sleeves that extend from the left atrium into the pulmonary veins. Pulmonary vein isolation has emerged as an effective treatment in selected patients. In this paper, the past and present roles of pulmonary vein isolation are described and the future developments of this technique are explored.

Ablation strategies for atrial fibrillation

Atrial fibrillation remains the most common arrhythmia in the USA and is associated with an increased risk for stroke, congestive heart failure and overall mortality. There has been a tremendous advance in the field of catheter ablation of atrial fibrillation that has resulted in better outcomes for patients. The approach for ablation of atrial fibrillation can be different depending on patients' presentation of paroxysmal or persistent atrial fibrillation. Pulmonary vein isolation remains the cornerstone of any ablation strategy for atrial fibrillation; however, further ablation, end points of the procedure, clinical end points for successful ablation and appropriate follow-up remain controversial. We aim to discuss these different approaches and the major controversies in catheter ablation of atrial fibrillation.

Remote Magnetic Catheter Navigation for Cavotricuspid Isthmus Ablation in Patients With Common-Type Atrial Flutter

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

Ablation of atrioventricular nodal reentrant tachycardia using remote magnetic guidance (stereotaxis) requires lower temperature and power settings because of improved local contact

INTRODUCTION AND OBJECTIVES

The Stereotaxis(R) remote magnetic navigation system provides a new approach to ablation that could increase catheter stability. The aim was to determine whether improved tissue contact necessitates a change in traditional radiofrequency ablation parameters.

METHODS

The study compared ablation of atrioventricular nodal reentrant tachycardia (AVNRT) using remote navigation (4-mm catheter) in 19 patients with conventional ablation in 18 patients (4-mm catheter, temperature 60-65 degrees C, power 50 W). The radiofrequency energy needed to ensure that no more than a single nodal echo beat could be induced was measured.

RESULTS

Charring was observed with traditional parameters on the first applications of the remotely navigated catheter. Hence, the energy was subsequently reduced (to 50 degrees C and 40 W). There was no difference in the number of applications between remote navigation and conventional groups (median: 6 vs. 8.5; interquartile range [IQR]: 11 vs. 9). Applications lasting <or=5 s were usually due to catheter dislodgment. Only four patients in the remote group had applications <or=5 s compared with 11 in the conventional group (P=.041). Ablation using remote navigation was equally effective and required lower temperatures and powers (mean+/-SD temperature: 46+/-2 degrees C vs. 50+/-4 degrees C, P< .001; median [IQR] power: 29 [14] W vs. 50 [7] W, P< .001), with no difference in total energy delivered. With remote navigation, the range of impedance values between applications was less (mean+/-SD: 10.4+/-7.6 Omega vs. 19.3+/-15.4 Omega; P=.035) and the temperature variation tended to be less, suggesting greater stability between applications. There were no complications.

CONCLUSIONS

In this initial series, remote magnetic navigation was safe and effective in AVNRT ablation. Improved tissue contact reduced catheter dislodgment and necessitated a reduction in radiofrequency energy to avoid charring.

Technical advances in the ablation of atrial fibrillation

There is now a general consensus that for patients with paroxysmal atrial fibrillation, the goal of a catheter ablation procedure should be electrical isolation of the pulmonary veins (PVs). Attaining acute PV isolation has been facilitated by the advent of electronatomic mapping systems that allow real-time 3-D reconstructions of cardiac chamber anatomy, as well as integration of pre-acquired CT/MR cardiac imaging. Nevertheless, chronic PV isolation continues to remain an elusive goal. This article reviews the development of imaging and balloon technologies that may bring the field closer to permanent PV isolation with a single procedure. Particularly with regard to persistent and long-standing persistent AF, this article also reflects on the use of robotic and linear ablation technologies to facilitate ablation of the atrial "substrate".

Mapping and ablation of ventricular arrhythmias with magnetic navigation: comparison between 4- and 8-mm catheter tips

INTRODUCTION

Remote magnetic navigation (RMN) has been reported as an effective and safe tool to overcome the need for advanced operator skill in the treatment of complex arrhythmias. We report a series of patients undergoing radiofrequency catheter ablation of ventricular arrhythmias (VAs) using RMN with either a 4-mm catheter tip or an 8-mm catheter tip at four different centers.

METHODS

Sixty-five patients with clinical and symptomatic history of Vas were included. Two different magnetic catheters were used to deliver radiofrequency applications remotely. When ablation with the RMN catheters failed, a manual irrigated catheter was used to eliminate the VAs. Post-ablation pacing maneuvers were utilized to verify the inducibility of Vas.

RESULTS

Twenty-eight patients (43%) had ischemic cardiomyopathy [coronary artery disease (CAD)], 16 patients (25%) had non-ischemic cardiomyopathy [idiopathic dilated cardiomyopathy (IDC)], and 21 patients (32%) had structurally normal hearts (SNH) or right ventricle outflow tract tachycardia (RVOT). In patients with structural heart disease (CAD, IDC), success was achieved in 22% with the 4-mm catheter tip and in 59% with the 8-mm catheter tip (p = 0.014). In patients with SNH/RVOT, success was achieved in 85% with the 4-mm catheter tip and in 87% with the 8-mm catheter tip (p = 1.00).

CONCLUSIONS

Our findings showed that, with RMN, there is an increased success related to the catheter tip utilized. However, in patients with right ventricular outflow origin, the standard 4-mm tip provided adequate lesions for successful ablation in most patients.

Early experience with robotic navigation for catheter ablation of paroxysmal atrial fibrillation

INTRODUCTION

Pulmonary venous antra isolation (PVAI) is the cornerstone of catheter ablation procedure for drug refractory paroxysmal atrial fibrillation (AF). However, the procedure is technically challenging. Robotic navigation has a potential to expedite and facilitate the procedure.

METHODS

A robotic catheter control system was used for remote navigation-supported PVAI in 22 patients (mean age = 55 +/- 9 years, 16 males, study group). An irrigated-tip catheter with estimate of catheter force on the tissue was used. This was compared in nonrandomized fashion with conventional hand-controlled catheter ablation in 16 patients (mean age = 55 +/- 9 years, 13 males, control group). The procedures were performed under guidance of Ensite NavX navigation system (St. Jude Medical, St. Paul, MN, USA) and intracardiac echocardiography.

RESULTS

Robotic navigation was associated with significantly shorter overall duration of radiofrequency delivery (1,641 +/- 609 vs 2,188 +/- 865 seconds, P < 0.01), shorter total procedural time (207 +/- 29 vs 250 +/- 62 minutes, P = 0.007), fluoroscopy exposure (15 +/- 5 vs 27 +/- 9 minutes, P < 0.001), and lower radiation dose (1,119 +/- 596 vs 3,048 +/- 2,029 mGy/m(2), P < 0.001). No complication was observed in either the study or the control group. During the 5 +/- 1 months follow-up in the study group and 9 +/- 3 months in the control group, 91% and 81% of patients, respectively, were AF free.

CONCLUSIONS

In our early clinical experience, PVAI using a remote robotic catheter navigation was effective, safe, and associated with shorter procedural and fluoroscopic times than conventional PVAI.

[Update on arrhythmias and cardiac electrophysiology]

This article contains a review of the most important developments in clinical arrhythmology and interventional cardiac electrophysiology that have been reported during the past year. Special emphasis has been placed on clinical conditions that are most prevalent in the general population as well as on progress that has been achieved using the main therapeutic approaches, whether pharmacologic or interventional.

Recurrence of atrial fibrillation correlates with the extent of post-procedural late gadolinium enhancement: a pilot study

OBJECTIVES

We sought to evaluate radiofrequency (RF) ablation lesions in atrial fibrillation (AF) patients using cardiac magnetic resonance (CMR), and to correlate the ablation patterns with treatment success.

BACKGROUND

RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium and pulmonary veins (PV) would correlate with moderate-term procedural success.

METHODS

Thirty-five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bidirectional conduction block around each PV ostium. AF recurrence was documented using a 7-day event monitor at multiple intervals during the first year. High spatial resolution 3-dimensional LGE CMR was performed 46 +/- 28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1: minimal, 3: extensive and circumferential) assessed.

RESULTS

Thirteen (37%) patients had recurrent AF during the 6.7 +/- 3.6-month observation period. Paroxysmal AF was a strong predictor of nonrecurrent AF (15% with recurrence vs. 68% without, p = 0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior pulmonary vein (RIPV) (82% vs. 31%, p = 0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p < or = 0.05) and was a univariate predictor of recurrence using Cox regression (p = 0.049, Bonferroni corrected).

CONCLUSIONS

Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and left atrial scarring on 3-dimensional LGE CMR. This finding was significant for RIPV scar and may have implications for the procedural technique used in PV isolation.

Robotic magnetic navigation for ablation of human arrhythmias: initial experience

BACKGROUND

Magnetic navigation system (MNS) (Niobe, Stereotaxis, Saint-Louis, Missouri, USA) allows remote control of a radiofrequency ablation catheter using a steerable magnetic field and a catheter advancement system.

AIMS

We report our initial experience of ablation of human arrhythmias using the MNS.

METHODS

Eighty-four patients (mean age 54+/-17years; 39 women) had an electrophysiologic study followed by ablation with the MNS using non-irrigated 4, 8 and 3.5mm-tip catheters with three distal magnets. All patients were symptomatic, with commonly-accepted indications for ablation: atrioventricular nodal re-entrant tachycardia (AVNRT; n=37); typical atrial flutter (n=15); accessory pathway (n=12); atypical atrial flutter (n=7); ventricular tachycardia (n=7); atrial tachycardia (n=3); paroxysmal atrial fibrillation (n=3). Electroanatomical mapping was used for atrial flutter, atrial fibrillation, atrial tachycardia and ventricular tachycardia procedures (29 patients, 34%).

RESULTS

Ablation was performed successfully in 69 (82%) patients. In 15 patients (18%), MNS technique was unsuccessful: seven typical atrial flutters, four accessory pathways, two left atrial flutters after atrial fibrillation ablation, one ventricular tachycardia and one AVNRT; in all these cases except one typical atrial flutter and two left atrial flutters, success was obtained by switching to the manual technique by means of an irrigated catheter. Total fluoroscopy time was 14+/-11minutes; operator exposure fluoroscopy time was 1.5+/-0.6minutes; procedure time was 169+/-72minutes.

CONCLUSION

MNS ablation is a feasible treatment for various human arrhythmias, with a high success rate. Mapping with a magnetic catheter is safe. However, magnetic ablation of typical atrial flutter remains challenging, probably because of insufficient pressure for cavotricuspid isthmus ablation.

Atrial fibrillation: unanswered questions and future directions

The seminal demonstration of the role of pulmonary vein triggers in the pathogenesis of atrial fibrillation (AF) and the potential therapeutic role of catheter ablation to treat patients who have paroxysmal AF was provided just over a decade ago. This initial observation ushered in the modern era of catheter ablation to treat patients who have AF, and tremendous progress has been made in understanding its pathogenesis and the catheter approaches to treating this rhythm. This article reflects on some of the major unanswered questions about AF management, and the future technologic and investigational directions being explored in the nonpharmacologic management of AF.

Recurrence of atrial fibrillation correlates with the extent of post-procedural late gadolinium enhancement: a pilot study

OBJECTIVES

We sought to evaluate radiofrequency (RF) ablation lesions in atrial fibrillation (AF) patients using cardiac magnetic resonance (CMR), and to correlate the ablation patterns with treatment success.

BACKGROUND

RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium and pulmonary veins (PV) would correlate with moderate-term procedural success.

METHODS

Thirty-five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bidirectional conduction block around each PV ostium. AF recurrence was documented using a 7-day event monitor at multiple intervals during the first year. High spatial resolution 3-dimensional LGE CMR was performed 46 +/- 28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1: minimal, 3: extensive and circumferential) assessed.

RESULTS

Thirteen (37%) patients had recurrent AF during the 6.7 +/- 3.6-month observation period. Paroxysmal AF was a strong predictor of nonrecurrent AF (15% with recurrence vs. 68% without, p = 0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior pulmonary vein (RIPV) (82% vs. 31%, p = 0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p < or = 0.05) and was a univariate predictor of recurrence using Cox regression (p = 0.049, Bonferroni corrected).

CONCLUSIONS

Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and left atrial scarring on 3-dimensional LGE CMR. This finding was significant for RIPV scar and may have implications for the procedural technique used in PV isolation.

Feasibility and safety of remote-controlled magnetic navigation for ablation of atrial fibrillation

Radiofrequency ablation for atrial fibrillation (AF) involves complex catheter manipulation resulting in prolonged procedure time and fluoroscopy exposure. Remote magnetic navigation (RMN) represents a novel approach toward improving the ability to perform complex ablation. Forty patients underwent ablation for AF, 20 using RMN (NIOBE II, Stereotaxis, Inc) with a 4-mm-tip magnetic catheter (Celsius, Biosense Webster) and 20 using a conventional 8-mm-tip bidirectional ablation catheter (Blazer, Boston Scientific). All patients underwent a combined wide area circumferential ablation and segmental pulmonary vein (PV) isolation using a circular mapping catheter and cavotricuspid isthmus ablation for right atrial flutter. The procedural end point was PV entrance block. There was no difference in atrial size, left ventricular systolic function, or type of AF between groups. PV entrance block was achieved in all patients. Mean procedure time was 279 +/- 60 minutes in the conventional group versus 209 +/- 56 minutes in the RMN group (p <0.001). Mean fluoroscopy time in the conventional group was 58.6 +/- 21 minutes versus 19.5 +/- 9.8 in the RMN group (p <0.001). At 1 year there were 15 patients in the conventional group and 16 in the RMN group free from clinical AF and off antiarrhythmic drugs (p = NS). There were 2 additional ablations performed for atypical atrial flutter in the conventional group and 3 in the RMN group (p = ns). Ablation catheter char formation was not observed. There were no procedural complications. In conclusion, radiofrequency ablation of AF performed with RMN is safe and feasible. Compared with conventional hand-navigated ablation, RMN ablation results in similar clinical outcomes with decreased fluoroscopy and procedure times.

Robotic versus conventional ablation for common-type atrial flutter: a prospective randomized trial to evaluate the effectiveness of remote catheter navigation

BACKGROUND

Conventional catheter ablation for common-type atrial flutter (AFL) is a widely established therapy but has not been compared with the use of a robotic navigation system (RNS) thus far.

OBJECTIVES

The purpose of this study was to investigate the feasibility of a new, nonmagnetic RNS with regard to safety, efficacy, and X-ray exposure to investigator and patient compared with the conventional ablation approach in patients with AFL.

METHODS

Fifty patients (65.7 +/- 9.3 years, 40 male) undergoing de novo catheter ablation for AFL were randomly assigned to conventional or RNS-guided cavotricuspid isthmus (CTI) ablation.

RESULTS

Complete bidirectional isthmus block was achieved for all patients without occurrence of procedure-related complications. The fluoroscopy time and the investigator X-ray exposure (8.2 +/- 4.6 vs. 5.8 +/- 3.6, P = .038; and 8.2 +/- 4.6 vs. 1.9 +/- 1.1 minutes, P<.001) as well as the mean radiofrequency (RF) duration and the energy delivered were significantly higher in the conventional than in the RNS group (321.7 +/- 214.6 vs. 496.4 +/- 213.9 seconds, P = .006; 8279 +/- 5767 vs. 16,308 +/- 6870 J, P<.001, respectively). The overall procedure time in the RNS group was significantly longer than in the conventional group (79.2 +/- 30.6 vs. 58.4 +/- 17.7 minutes; P = .04) but significantly decreased comparing the first 10 with the last 10 patients in the RNS group (105.3 +/- 34.8 vs. 60.6 +/- 6.3 minutes; P = .003). Starting ablation during AFL, bidirectional block instantly after termination was observed in 90% of the RNS and 50% of the conventionally treated patients (P = .03).

CONCLUSION

The present study demonstrates the safety and feasibility of RNS for performing CTI ablation in patients with common-type AFL for use in the clinical routine. As a result of the remote navigation, X-ray exposure and RF duration to achieve bidirectional block were significantly decreased and occurred more often immediately after AFL termination. These findings are consistent with increased catheter stability and RF application efficacy using RNS compared with conventional catheter manipulation.

New techniques of mapping and ablation for tachyarrhythmias in children

Advancement in mapping and ablation technologies in the past decade has made arrhythmia treatment in children safer and more effective. Electroanatomical mapping systems with features of nonfluoroscopic navigation, 3D-geometry construction and color-coded arrhythmia mapping have been extensively used to map and ablate tachycardias in children. In addition, a variety of cooled radiofrequency ablation systems have been used in selected patients to create larger and deeper lesions. Cryoenergy ablation, with its reversible nature of tissue injury during the cooling phase, is emerging as the energy of choice for ablating perinodal arrhythmias to minimize the risk of inadvertent conduction block. Other evolving ablation systems, including cryoballoon, high-intensity focused ultrasound balloon and a hybrid catheter capable of delivering both radiofrequency and cryoenergy, are also under investigation. Finally, a remote navigation system that minimizes radiation exposure and will enable physicians of all skill levels to reach difficult target sites in children is on the horizon.