AUSTIN, TEXAS. Success rates for catheter ablations aimed at curing atrial fibrillation vary widely and depend almost entirely on the skill and experience of the electrophysiologist (EP) performing the procedure. The main limitations in achieving a successful result involve precision of catheter movement, stability and contact with atrial tissue, especially the pressure between the tip of the catheter and the atrial wall. An additional problem with catheter ablations is that they involve fluoroscopy imaging thus exposing both the EP and the patient to a significant amount of x-ray radiation.
Robotic guidance of the mapping and ablation catheters has evolved in an attempt to deal with some of the problems inherent in manual ablation. Two main systems are now available – the Hansen Robotic Medical system and the Stereotaxis system. Both share the feature of allowing the EP to perform an ablation procedure well away from the patient and thus reduces the radiation exposure to the EP by 90% or more. Both systems also feature a computer screen displaying a real-time image of the heart and a joystick used to maneuver the mapping and/or ablation catheters inside the atrium with great precision. However, while the Stereotaxis system employs large external magnets to orient the catheter tip in 3-dimensional space, the Hansen system uses a robot arm (similar to the da Vinci system used for radical prostatectomy) to guide the ablation catheter. Recently developed technology (Intellisense) measures the contact force between the catheter tip and the atrial wall, thus significantly reducing the risk of perforation.
Although both systems have been under development for at least 5 years, no large scale clinical trials have reported on their long-term efficacy in curing AF until now. In the December 2009 issue of the Journal of Cardiovascular Electrophysiology, Dr. Andrea Natale and colleagues report on their evaluation of the Hansen system. The study involved 390 afibbers (74% male with an average age of 62 years) of whom about 80% had lone afib (no underlying heart disease). Most of the patients (67%) had paroxysmal AF, 28% had persistent, and 5% had permanent (long-standing persistent) AF. Consecutive patients undergoing catheter ablation between September 2007 and February 2008 were assigned to undergo pulmonary vein antrum isolation (PVAI) + the creation of other lesions as necessary either using a manual procedure (197 patients) or a robot-assisted (RNS) procedure (193 patients) using the Hansen system. All procedures, both manual and RNS, were carried out by two EPs who performed about the same number of each type.
All patients underwent a standard PVAI which resulted in complete electrical isolation of the pulmonary veins in 100% of cases. Patients with persistent and permanent AF had additional lesions as deemed necessary. Average fluoroscopy time was significantly lower in the RNS group (49 minutes) than in the manual group (58 minutes). After the procedure patients were given an event recorder for 5 months and asked to transmit 4 times a week even if asymptomatic. A 7-day Holter monitor was obtained at 3, 6, 9 and 12 months post-ablation. After an average follow-up of 14 months (minimum 12 months), 72% of patients in the RNS group and 70% of those in the manual group were in normal sinus rhythm (NSR) without the use of antiarrhythmics. An additional 13% of RNS patients and 11% of manual patients were in NSR with the aid of previously ineffective antiarrhythmics (partial success).
- Paroxysmal AF - Success Rate* - Manual 85%; RNS 90%
- Persistent AF - Success Rate* - Manual 73%; RNS 71%
- Permanent AF - Success Rate* - Manual 68%; RNS 100%
- All AF - Manual 81%; RNS 85%
* Afib-free with or without the use of previously ineffective antiarrhythmics
Two patients in the manual group (1.0%) experienced complications (1 tamponade and 1 hematoma) as compared to 3 patients (2 tamponades and 1 hematoma) in the RNS group.
The research team concludes that, "Our results indicate that robotic navigation and ablation of atrial fibrillation is as safe and effective as manual ablation. In addition, with robotic navigation fluoroscopy time decrease with experience and complication rates are consistent with those reported for manual ablation". Di Biase, L, et al. Ablation of atrial fibrillation utilizing robotic catheter navigation in comparison to manual navigation and ablation. Journal of Cardiovascular Electrophysiology, Vol. 20, December 2009, pp. 1328-35