LEIPZIG, GERMANY. Radiofrequency (RF) catheter ablation of common right atrial flutter (cavotricuspid isthmus-dependent – CTI) is a comparatively simple procedure with a success rate of about 95%. Because the location of the electrical circuit involved in the flutter is so well-established, this procedure lends itself particularly well to the use of electroanatomical (CARTO) mapping. German researchers now report on their evaluation of a new system combining the CART-RMT mapping system with the Stereotaxis NIOBE II remote magnetic navigation system. The Stereotaxis system makes use of two stationary magnets (one of each side of the patient) that controls the movement of a magnetically-tipped RF ablation catheter. The system is operated remotely so the operator's exposure to x-ray radiation from fluoroscopy is minimized. An earlier version of the NIOBE II system used a 4-mm catheter, but the German researchers used a new, flexible-tip, 8-mm (non-irrigated) catheter.
The clinical trial involved 26 patients (23 men, mean age of 65 years). At the time of the ablation, 20 were in flutter (19 counter-clockwise and 1 clockwise), and the remaining 6 were in sinus rhythm. In the case of one patient, a conventional ablation had to be performed because of technical difficulties with the NIOBE system. Among the remaining 25 patients, 24 were successfully ablated (acute success rate of 95%). One patient had to be ablated with a conventional catheter before complete isthmus block could be achieved. The procedure, RF application, and fluoroscopy times were 80 minutes, 31 minutes, and 11 minutes respectively in the first group of 14 patients. In the remaining patients, the corresponding times were 45 minutes, 20 minutes, and 7.2 minutes respectively indicating a steep learning curve – in other words, the new technique is relatively easy to learn.
Compared to the conventional RF flutter ablation procedure, the fluoroscopy time was reduced by 43%, but overall procedure time did not change. There were no major complications in the group of 26 patients treated with the new system; however, significant charring was observed in 19% of patients. The researchers conclude that ablation of right atrial flutter with the NIOBE II/CARTOMERGE system is safe, feasible, and effective. However, they do make the following qualifying statement, "This study was conducted to assess the acute results of RF catheter ablation using remote MNS and an 8-mm tip magnetic catheter. Therefore, no comment on the long-term outcome of this system for the ablation of AFL can be made."
Arya, A, et al. Initial clinical experience with a remote magnetic catheter navigation system for ablation of cavotricuspid isthmus-dependent right atrial flutter. PACE, Vol. 31, May 2008, pp. 597603
Editor's comment: The combined Stereotaxis/CartoMerge system has now undergone at least 9 trials that I am aware of. All, but one, have shown good safety and impressive results as far as acute success is concerned. However, somewhat curiously, I am not aware of any trials that have reported on the long-term success of the procedure. Dr. Carlo Pappone and colleagues in Milan, Italy performed the first trial of the system in atrial fibrillation patients more than 2 years ago. The acute success rate, as measured by the lack of electrical conduction between the pulmonary veins and the left atrium shortly after placing the last ablation lesion, was an impressive 95%. However, as far as I know, long-term follow-up has not yet been reported, although there has been ample time to do so. Several studies have shown that acute success does by no means guarantee long-term success. As a matter of fact, long-term success (6 months or longer) may be as low as 50% even with a 95% acute success rate. Even though the Stereotaxis/CartoMerge system certainly looks like a winner, long-term data are still required to prove its ultimate efficacy.