The NBC Today Show aired a segment on the Stereotaxis robotic system for performing catheter ablation of atrial fibrillation using magnetically-steered ablation catheters yesterday (video here). It sure generated a lot of buzz around our hospital. While I share the reporters enthusiasm for all the gadgets and gizmos (what doctor-engineer wouldn’t like such neat toys?) the enthusiasm should be tempered with a strong dose of reality regarding this technology and any atrial fibrillation procedure.
First is the claim that the patient will be cured with “85-90%” certainty. While these success rates have been reported using this technology for the much simpler atrial flutter ablation, this level of success has not been substantiated in meta analyses of atrial fibrillation ablation studies to date:
The efficacy of AF ablation is largely influenced by a number of factors that include the following: operator experience, volume of ablations, type of cases ablated, to name a few. Nonrandomized trials document a wide variance in the efficacy of AF ablation. In the setting of paroxysmal AF, the efficacy of a single procedure ranges from 38% to 78%, with most series reporting an efficacy of 60% or more. The efficacy reported in persistent AF ranges from 22% to 45%, with most centers reporting an efficacy of 30% or less.
Certainly, patients with intermittent atrial fibrillation typically do better than those with chronic atrial fibrillation, but we are not privy to the number of procedures a patient has to undergo to achieve the success rate suggested by the physician operator in this news segment.
It is also interesting that we learn little of the limitations of robotic navigation using magnets previously reported in the literature:
Using the coordinate approach, the target location was reached in only 60% of the sites, whereas by using the wand approach 100% of the sites could be reached. After step 2 ablation, only 1 PV in 4 patients (8%) could be electrically isolated. Charring on the ablation catheter tip was seen in 15 (33%) of the cases. In 23 patients, all PVs were isolated with the conventional thermocool catheter, and in 22 patients only the right PVs were isolated with the conventional catheter. After a mean follow-up period of 11 ± 2 months, recurrence was seen in 5 patients (22%) with complete PVAI and in 20 patients (90%) with incomplete PVAI.
Admittedly, the data regarding char formation on the ablation catheter were presented before the approval of irrigated-tip ablation catheters less prone to coagulum formation that are used more recently, but few data have been published. But we recall that the reporter makes a huge claim that moving the catheter with the magnets is more “precise,” using the analogy that “it’s like trying to write on a piece of paper with a pencil using the eraser…” The above data dispute these accuracy claims. Further, she conveniently ignores the errors in catheter placement inherent to the patient’s respiration or from the movement of the heart itself. Also, we hear little of the additional time involved in moving a catheter with a magnet versus the hand.
While robotics might help the operator’s back and help reduce radiation exposure during the procedure, I am aware of no data that supports the superiority of robotics to achieve success with better safety or accuracy with atrial fibrillation ablation over more conventional manual approaches. Further, long-term data regarding success rates of this technology for catheter ablation in atrial fibrillation have yet to appear to any large extent in peer-reviewed journals.
Disclaimer: I have no industry ties with Stereotaxis or other robotic atrial fibrillation ablation systems.
Addendum 3 Feb 2009 11:30 am CST: An even more scathing review of the journalistic tactics used for this piece appear at Cardiobrief.org.Musings of a cardiologist and cardiac electrophysiologist.
*This blog post was originally published at Dr. Wes*