HAMBURG, GERMANY. An initial evaluation of the Stereotaxis Niobe II system for robot-assisted catheter ablation was performed at the Cleveland Clinic in 2007. The Cleveland researchers concluded that the Niobe II 4-mm tip ablation catheter was incapable of creating adequate lesions for successful atrial fibrillation (AF) ablation. They also noted frequent charring (33% of patients) at the catheter tip, which could lead to thromboembolic complications (ischemic stroke). As a result Biosense Webster, in cooperation with Stereotaxis, developed a novel open-irrigated, magnetic catheter designed to overcome the shortcomings of the prototype. This catheter, the Thermocool Navistar RMT, has now been evaluated by Dr. Karl-Heinz Kuck's group at St. Georg Hospital in Hamburg.

The evaluation included 28 patients who underwent a wide area circumferential pulmonary vein isolation (PVI) procedure using a first-generation irrigated catheter (group 1) and another 28 patients (Group 2) who underwent the same procedure using a redesigned, improved irrigated catheter. The average age of group 1 was 64 years with 79% being male, and 21 had paroxysmal AF, while the remaining 7 had the persistent variety. In group 2 the average age was 60 years with 71% being male, 18 had paroxysmal AF and 10 persistent. CARTO anatomically-guided mapping was used for all procedures and crossover to manual ablation was permitted if complete isolation had not been achieved after three hours of procedure time (necessary in 4 patients).

Follow-up included weekly telephone interviews and outpatient clinic visits at 1, 3, 6, 9, 12, 18 and 24 months after ablation. Antiarrhythmic therapy was continued for at least 3 months and discontinued if the patients were free of AF relapse. Total median procedure and fluoroscopy times declined from 370 minutes and 24 minutes in group 1 to 243 minutes and 16 minutes in group 2 indicating either a fairly steep learning curve or significant advantages of the second-generation catheter.

After a mean follow-up of 426 days (excluding a 3-month blanking period), 70% of the study participants were afib-free with or without the use of antiarrhythmics and 24% underwent a second procedure. While no complications were noted with the redesigned catheter (group 2), tip charring occurred in 61% of procedures in group 1, and one TIA was observed in group 1 prior to the design improvements. The German EPs conclude that ablation with the Stereotaxis Niobe II system and the redesigned catheter is feasible with a comparable success rate to that achieved with manual ablation.

Julian Chun, KR, et al. Remote-controlled magnetic pulmonary vein isolation using a new irrigated-tip catheter in patients with atrial fibrillation. Circulation Arrhythmia and Electrophysiology, Vol. 3, October 2010, pp. 458-64

Editor's comment: In this issue we report on two relatively small-scale evaluations of the remote controlled Stereotaxis Niobe II system for ablation of AF. It would appear that redesign of the catheter has resulted in a system that produces outcomes comparable to what is achievable via manual ablation carried out by highly experienced EPs.