CLEVELAND, OHIO. The success of a pulmonary vein isolation (PVI) ablation depends on the location and quality of the lesions (burns) imparted during the procedure. Lesion quality, in turn, depends on such factors as catheter design, duration of burn, power (wattage) applied during the burn (for RF ablations), the pressure applied to the catheter during the burn, and last, but certainly not least, the stability of the catheter during the burn. The ultimate aim of lesion creation is to form a barrier preventing the propagation of electrica l impulses throughout the entire thickness of the heart wall – without penetrating the wall in the process (tamponade) – very exacting work indeed!
The process (mapping) used in determining the location of the lesion(s) may involve the determination of electrical potentials or the location of anatomical features using electroanatomical (CARTO) mapping now increasingly associated with an overlay of a CT or MRI scan (CartoMerge). The actual ablation process is performed by the electrophysiologist (EP) who is standing next to the patient and manually directing a catheter, which extends from the femoral vein in the groin to the left atrium. Needless to say, this process takes great manual dexterity and experience and tends to produce very uneven results largely related to the skill of the EP.
Not surprisingly, a great deal of effort has been expended on coming up with ablation systems that will "level the playing field" by inserting a robot between the EP and the tip of the ablation catheter. Two such systems are now under evaluation. The Stereotaxis system uses a catheter with a magnetic head, which can be easily maneuvered to any location in the atria by controlling (remotely) the magnetic flux from 3 electromagnets placed to the right and left of the body (at heart level) and above the head. The Hansen Sensei system uses a robotic arm (placed next to the patient at groin level), which essentially guides a flexible sheath (tube) extending from the groin to the atria through the femoral vein. The ablation catheter is threaded through the sheath with only the tip (1 cm) extending from the sheath. The movement of the sheath can be very closely controlled by the robotic arm which, in turn, can be precisely controlled by the EP sitting at a remotely located console. Both systems have the great advantage of limiting radiation exposure to the operator by a factor of 10 or more.
A group of expert EPs (including Dr. Andrea Natale, Pr. Michel Haissaguerre, Pr. Pierre Jais, Dr. Walid Saliba, Dr. David Burkhart, Dr. Vivek Reddy, Dr. Luigi Di Biase, et al) report on the first full scale evaluation of the Hansen Sensei system. The study involved 40 atrial fibrillation patients of which 90% had lone atrial fibrillation. The patients were recruited at 3 centers (Bordeaux, Coburg and Prague); their average age was 57 years, and most (75%) had paroxysmal afib with the remaining 25% having persistent afib. Twenty-three patients also had typical right atrial flutter. The patients (29 men and 11 women) underwent a pulmonary vein antrum isolation using CARTO mapping, ICE guidance, and the Hansen Sensei system. The 23 patients with flutter also underwent a right atrial flutter ablation. Total average procedure time for the afib ablation was about 3 hours with an ablation time of 106 minutes and fluoroscopy time of 83 minutes. The patients were followed for 12 months at which time 34 (85%) were free of any arrhythmia without antiarrhythmics, while 13% were free of arrhythmia while taking previously ineffective antiarrhythmics. There was one (2.5%) pericardial effusion associated with the use of the Hansen Sensei system.
The EPs conclude that the use of the robotic catheter remote control system for transseptal puncture and endocardial navigation and ablation is safe and feasible, and give results similar to those obtained by EPs using manual guidance. (Editor's note: Only the very best EPs would obtain a 98% complete and partial success rate with just one ablation). NOTE: This study was supported by a grant from Hansen Medical, Inc.
Saliba, W, et al. Atrial fibrillation ablation using a robotic catheter remote control system. Journal of the American College of Cardiology, Vol. 51, June 24, 2008, pp. 2407-11
Callans, DJ. Can we improve upon human performance in the electrophysiology laboratory? Journal of the American College of Cardiology, Vol. 51, June 24, 2008, pp. 2412-13
Editor's comment: This is indeed a very exciting study which, in contrast to other studies involving robotic guidance, actually presents long-term outcome results. It would seem that the Hansen Sensei system pretty well solves all the problems involved in creating "perfect" lesions except the one that besets all robotic systems – that of pressure control. However, work is apparently underway to develop a suitable pressure sensor that will hopefully solve this problem and perfectly emulate the pressure exerted by the hands of a skilled EP.