Remote magnetic navigation to map and ablate left coronary cusp ventricular tachycardia

Remote magnetic navigation facilitates the ablations of frequent ventricular premature complexes originating from the outflow tract and the valve annulus as compared to manual control navigation

OBJECTIVE

The purpose of this study was to assess the role of remote magnetic navigation (RMN) in the ablation of ventricular premature complexes (VPCs) arising from outflow tracts (OT) and valve annuli by comparing to manual control navigation (MCN).

METHODS

A total of 152 patients with frequent VPCs were prospectively enrolled. 64 (42%) patients underwent ablation guided by RMN. Acute success rate was defined as the complete elimination and non-inducibility of clinical VPCs during the procedure.

RESULTS

Overall, acute success rate of RMN group was not different from MCN group (87.5% vs 84.1%, p = 0.56). Compared to MCN group, the fluoroscopic time of OT-VPCs ablation in the RMN group was significantly reduced by 67% (2.9 ± 2.3 min vs 8.9 ± 9.7 min, p = 0.006), and the ablation applications in successful cases were significantly reduced (11 ± 7 vs 15 ± 11, p = 0.018). Compared to MCN, RMN significantly decreased ablation applications (15 ± 9 vs 23 ± 9, p = 0.013) in the acute success rates of ablating VPCs of valve annulus, and has a trend of a higher success rate for VPCs arising from tricuspid annulus (10/11 vs 7/12, p = 0.193). No complications occurred in the RMN group. Three cases of cardiac tamponade and one case of transient atrioventricular block occurred in the MCN group (p = 0.22). After a mean follow up of 16.2 months, 2/56 and 3/74 patients had a recurrence of VPCs in the RMN group and MCN group respectively (p = 0.75).

CONCLUSIONS

When compared to MCN, RMN-guided ablation for VPCs was just as effective and safe, with the added benefit of reduced fluoroscopic time and fewer ablation applications.

Remote Navigation for Complex Arrhythmia

Magnetic navigation has been established as an alternative to conventional, manual catheter navigation for invasive electrophysiology interventions about a decade ago. Besides the obvious advantage of radiation protection for the operator who is positioned remotely from the patient, there are additional benefits of steering the tip of a very floppy catheter. This manuscript reviews the published evidence from simple arrhythmias in patients with normal cardiac anatomy to the most complex congenital heart disease. This progress was made possible by the introduction of improved catheters and most importantly irrigated-tip electrodes.

Remote magnetic navigation in atrial fibrillation

Atrial fibrillation (AF) is of profound public health importance and is largely a disease of aging and is responsible for increased morbidity- and mortality-related healthcare expenditures. Catheter ablation to isolate the pulmonary veins has become the therapy of choice for treatment of drug-refractory AF. Procedures can be very challenging and multiple difficulties must be overcome in order to achieve a successful outcome. The magnetic navigation system (MNS) has advantages in catheter maneuverability, stability and reproducibility. Due to the catheter design safety and efficacy of AF, ablation has increased. New developments are being made to allow fully remote ablation procedures in combination with the MNS. However, new technologies are still necessary to improve MNS ablation for AF.

Biophysics and clinical utility of irrigated-tip radiofrequency catheter ablation

Catheter ablation by radiofrequency (RF) energy has successfully eliminated cardiac tachyarrhythmias. RF ablation lesions are created by thermal energy. Electrode catheters with 4-mm-tips have been adequate to ablate arrhythmias located near the endocardium; however, the 4-mm-tip electrode does not readily ablate deeper tachyarrhythmia substrate. With 8- and 10-mm-tip RF electrodes, ablation lesions were larger; yet, these catheters are associated with increased risk for coagulum, char and thrombus formation, as well as myocardial steam rupture. Cooled-tip catheter technology was designed to cool the electrode tip, prevent excessive temperatures at the electrode tip-tissue interface, and thus allow continued delivery of RF current into the surrounding tissue. This ablation system creates larger and deeper ablation lesions and minimizes steam pops and thrombus formation. The purpose of this article is to review cooled-tip RF ablation biophysics and outcomes of clinical studies as well as to discuss future technological improvements.

Safety and efficacy of the remote magnetic navigation for ablation of ventricular tachycardias--a systematic review

Objective

Remote magnetic navigation (RMN) is considered to be a solution for mapping and ablation of several arrhythmias. In this systematic review we aimed to assess the safety and efficacy of RMN in ablation of ventricular tachycardia (VT).

Methods

The National Library of Medicine’s PubMed database was searched for articles containing any of a predetermined set of search terms that were published prior to November 1, 2011. Quality of evidence was rated using the GRADE system.

Results

The database search resulted in 11 relevant articles evaluating the usefulness of RMN. Three groups of VTs were studied: VT in patients with ischemic cardiomyopathy (ICMP), non-ischemic cardiomyopathy (NICMP) and structurally normal hearts (SNH). The use of RMN in patients with ICMP has been associated with success rates ranging from 71 to 80%. RMN has been shown to be a feasible and effective method for ablation of VT in NICMP and SNH patients. Success rates between 50% and 100% have been reported in NICMP populations. Rates ranging from 86% to 100% have been reported for SNH patients. The lowest rates of arrhythmia recurrence are reported for SNH patients (0–17%). In ICMP and NICMP, recurrence rates of 0–30% and 14–50%, respectively, have been reported. One patient experienced total heart block, and one patient experienced a thromboembolic event after RMN catheter ablation procedures.

Conclusions

RMN has been shown to be an effective and safe method for ablation of VT in various patient populations with low recurrence and complication rates. However, more comparative and randomized studies are necessary, and therefore the true value of RMN for VT ablation remains still unknown.

Role of catheter ablation of ventricular tachycardia associated with structural heart disease

In patients with structural heart disease, ventricular tachycardia (VT) worsens the clinical condition and may severely affect the short- and long-term prognosis. Several therapeutic options can be considered for the management of this arrhythmia. Among others, catheter ablation, a closed-chest therapy, can prevent arrhythmia recurrences by abolishing the arrhythmogenic substrate. Over the last two decades, different techniques have been developed for an effective approach to both tolerated and untolerated VTs. The clinical outcome of patients undergoing ablation has been evaluated in multiple studies. This editorial gives an overview of the role, methodology, clinical outcome and innovative approaches in catheter ablation of VT.

[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.

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.

[Magnetic navigation in invasive electrophysiological diagnostic and therapy]

Electrophysiological stimulation and ablation is currently performed with manually deflectable catheters of different lengths and curves. Disadvantages of conventional therapy are catheter stiffness, limited local stability, risk of dislocation or perforation, and reduced tissue contact in regions with difficult access. Fluoroscopy to control catheter movement and position may require substantial radiation times. Magnetic navigation was first applied for right heart catherization in congenital heart disease in 1991; the first electrophysiological application took place in 2003. Today, an ablation electrode with small magnets is aligned in the patient's heart by two external magnets positioned at both sides of the thorax. Antegrade and retrograde movement of the distal catheter tip are performed via an external device on the patient's thigh. Three-dimensional MRI scans acquired before intervention can be merged with electroanatomical reconstruction, leading to further reductions of radiation burden. During treatment of supraventricular tachyarrhythmias high local precision of magnetically guided catheters, good local stability, and a substantially reduced radiation time have been reported. First applications in ventricular tachyarrhythmias and complex congenital cardiac defects indicate a comparable effect. Limitations of this therapy are the application in left atrial procedures (open irrigated ablation catheters not yet available), difficult transaortic retrograde approach (high lead flexibility), and the considerable costs. Magnet-assisted navigation is feasible during percutaneous coronary interventions of tortuous coronary arteries and in positioning guidewires in coronary sinus side branches for resynchronisation therapy. Future applications will be complex left atrial procedures, magnetically guided cardiac stem cell therapy, local drug application, and extracardiac vessel therapy.

Remote magnetic navigation: human experience in pulmonary vein ablation

OBJECTIVES

We aimed at assessing the feasibility and efficacy of remote magnetic navigation (MN) and ablation in patients with atrial fibrillation (AF).

BACKGROUND

This novel MN system could facilitate standardization of the procedures, reducing the importance of the operator skill.

METHODS

After becoming familiar with the system in 48 previous patients, 45 consecutive patients with AF were considered for ablation using the Niobe II remote magnetic system (Stereotaxis, St. Louis, Missouri) in a stepwise approach: circumferential pulmonary vein ablation (CPVA), pulmonary vein antrum isolation (PVAI), and, if failed, PVAI using the conventional approach. Remote navigation was done using the coordinate or the wand approach. Ablation end point was electrical disconnection of the pulmonary veins (PVs).

RESULTS

Using the coordinate approach, the target location was reached in only 60% of the sites, whereas by using the wand approach 100% of the sites could be reached. After step 2 ablation, only 1 PV in 4 patients (8%) could be electrically isolated. Charring on the ablation catheter tip was seen in 15 (33%) of the cases. In 23 patients, all PVs were isolated with the conventional thermocool catheter, and in 22 patients only the right PVs were isolated with the conventional catheter. After a mean follow-up period of 11 +/- 2 months, recurrence was seen in 5 patients (22%) with complete PVAI and in 20 patients (90%) with incomplete PVAI.

CONCLUSIONS

Remote navigation using a magnetic system is a feasible technique. With the present catheter technology, effective lesions cannot be achieved in most cases. This appears to impact the cure rate of AF patients.

Remote magnetic catheter mapping and ablation of permanent junctional reciprocating tachycardia in a seven-year-old child

BACKGROUND

Mapping and catheter ablation of permanent junctional reciprocating tachycardia (PJRT) in children can be challenging. Remote magnetic navigation may improve precise mapping and catheter stability during ablation, as well as reduce fluoroscopy time, especially in conjunction with a non-fluoroscopic mapping system.

OBJECTIVE

We report a case of PJRT ablation in a 7-year-old child using remote magnetic navigation.

METHODS AND RESULTS

Mapping of the right atrium (RA) and the coronary sinus (CS) and catheter ablation were performed using remote magnetic navigation in conjunction with a non-fluoroscopic mapping system (NavX). We observed excellent catheter steering abilities and constant wall contact during ablation, allowing a short and safe procedure.

CONCLUSIONS

Remote magnetic navigation may be used for mapping and ablation of PJRT in children.