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Magnetic Remote Catheter Ablation
Abstract & Commentary
Synopsis: Remote magnetic navigation during radio-frequency ablation allows successful elimination of AV nodal re-entrant tachycardia in patients with dual AV nodal pathways.
Source: Ernst S, et al. Circulation. 2004; 109: 1472-1475.
Ernst and colleagues from St. George Hospital in Hamburg, Germany describe a new technique for positioning and manipulating ablation catheters during electrophysiologic studies. The system is a remote magnetic navigation system, which uses 2 permanent magnets to move a specially designed catheter. The magnets are computer controlled and positioned on either side of the fluoroscopy table. By creating a relatively uniform magnetic field of 0.08 Tesla, an ablation catheter with a permanent magnet at the tip can be maneuvered within the patient’s heart. By changing the orientation of the outer magnets, the magnetic field can be used to deflect the catheter tip. Since the fields are computer controlled, the magnetic field vectors can be stored and automatically re-applied to return the catheter to any prior position. A computer-controlled catheter advancement system was also used to move the catheter without the need for manual manipulation. To accomplish this, a video workstation is used with the operator manipulating the catheter using a joystick or mouse at a control station that may be outside the operating suite.
In this study, which was an early feasibility study, 42 patients underwent an ablation attempt for AV node reentrant tachycardia (AVNRT) with the use of the magnetic navigation system. Sheath insertions and placement of the diagnostic catheters were performed using standard techniques. This required a mean total of 12 ± 5 minutes with a radiation exposure of 3.4 ± 2.7 minutes. Subsequently the studies were performed with the physician-operator in a separate control room without need for lead protection. After confirming the mechanism of the arrhythmia, the right atrium close to the coronary sinus ostium was mapped for typical slow pathway potentials with the catheter manipulated solely by the magnetic navigation system. After mapping was completed, the site which gave the most favorable appearing slow pathway potential was determined and the field vectors with the best mapping result were then re-applied from the remote station to manipulate the catheter back to that site. Radio-frequency energy was then delivered and successful elimination of AV nodal reentrant tachycardia was produced in all patients. No recurrence was seen during a mean of 112 ± 48 days. No complications occurred.
Ernst et al conclude that remote magnetic navigation during radio-frequency ablation allows successful elimination of AV nodal reentrant tachycardia in patients with dual AV nodal pathways.
Comment by John DiMarco, MD, PhD
AVNRT is one of the easier arrhythmias to deal with in the electrophysiology laboratory. A successful slow pathway ablation can be achieved in more than 98% of cases and the risk of significant complication (usually atrioventricular block) should be less than 1%. The magnetic remote catheter navigation system depicted here will not be a major addition for ablation procedures in patients with AVNRT, but has the potential to be very valuable for the ablation of more complex arrhythmias.
In ablation procedures where lines are required to break arrhythmia circuits, it is often tedious and difficult to create these lines with manual catheter manipulation. Long fluoroscopy exposures may be required and this forces the operator to stand wearing lead for long periods. With a truly effective remote navigation system, the fluoroscopy exposure can be markedly reduced and the operator can sit and manipulate the catheters from outside the room. Theoretically, it should also be easier to lay truly continuous ablation lines and eliminate all "leaks" that can lead to failure.
This early report on the use of the remote magnetic navigation system is highly promising. The real test of it will come when it is applied to more complex arrhythmias such as scar related atrial tachycardias, atrial fibrillation, and ventricular tachycardia. However, the early results are encouraging and we can look forward to rapid advances in the field.
John DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville, is a member of the Editorial Board of Clinical Cardiology Alert.