Medical Device Daily Washington Editor

The concept of "one size fits all" is falling more out of favor every day in modern medicine, and one of the presentations at the 87th annual meeting of the American Association of Thoracic Surgeons (Beverly, Massachusetts) dumped yet more dirt into the grave of medicine for the masses.

Fred Morady, MD, a professor of cardiovascular disease at the University of Michigan Health Systems (UMHS; Ann Arbor) titled his discussion "Catheter Ablation for Atrial Fibrillation: Does One Size Fit All Our Patients?"

Morady said that the "answer is obviously no," at least not for paroxysmal atrial fibrillation (PAF), which is "clearly a different arrhythmia" from chronic AF. Morady's discussion was on circumferential ablation, an approach that eliminates the need for the long and winding percutaneous approach and gets around the need to stop the heart, a requirement of the Maze procedure.

However, Morady also does not rely on a standardized set of lesions to do the job, but induces AF, ablating only after seeing where the heart's electrical system is malfunctioning. The idea is to ablate only the areas that need ablating and no more.

"There are multiple mechanisms that contribute to AF," Morady said, including nerve tissue located in the pulmonary veins and various other musculatures in the area of the atria. He said that AF can be very mechanism-specific, describing the case of a 60-year-old man who demonstrated no rapid pulmonary vein (PV) activity, but had right atrium fibrillation, nonetheless. "So instead of doing a left-side procedure, all we did was circle" the source of the AF at the right atrium and ablate the external surface of the heart with a Lasso catheter, made by Biosense Webster (Diamond Bar, California).

However, Morady said that circumferential ablation had limits when applied to the PV, including flutters in 3%-30% of patients, some instances of left atrial dysfunction, and the fact that this procedure will be less than adequate in some patients and more than needed in others.

Morady said that the Maze procedure offered long-term freedom from AF in 90% of patients, a gold standard that catheter ablation might never match. The Maze procedure was developed by Jim Cox, MD, formerly a professor of surgery at the Washington University School of Medicine (St. Louis) and now the chairman/CEO of the World Heart Foundation (Geneva). This procedure, which Cox first performed in 1987, involves a series of incisions made in the right and left atria to interrupt the abnormal conduction of impulses, thus restoring a more normal rhythm and reducing AF. However, the procedure requires that the heart be stopped and some Maze patients experience fluid retention. Thus, ablation came into being as an alternative.

Morady said that in order to isolate the source of the AF, "we challenge the patient with very high doses of isoproterenol," a beta adrenergic receptor agonist that induces irregular rhythm by enhancing the polarization that immediately precedes a contraction in the affected muscle, thus inducing AF. "We believe it's more specific than pacing" the heart with an external source of electricity.

"Our goal is to try to eliminate the AF with the least amount of ablation" for several reasons. One of these is that too many ablations can impair the function of the left atrium. "The more ablations you do, the more atrial flutters you get," Morady said, and a small number of ablations equals a lower risk of collateral damage.

Morady uses orally ingested barium in his practice to visualize the esophagus, which is somewhat prone to shifting about when the patient is only sedated. This is typically not a problem with patients who are under general anesthesia.

Morady discussed a study that was published in the April 18, 2006, edition of Circulation describing the outcome of a non-randomized, non-controlled study involving the treatment of 153 consecutive patients with PAF. Of that number, 15 were "encircled" with the Lasso catheter on the right-side pulmonary veins, five only on the left-side pulmonary veins, and both sides in another 50 patients. The remaining needed treatment that did not fully encircle any pulmonary veins.

Twenty-eight patients needed a repeat procedure for AF or flutter, but in the 12-month follow-up, 118 of the 153 patients were free of AF or flutter; there was a success rate of 77%. The physicians performed a total of 180 left atrial procedures in that 153-patient group, and two developed pericardial tamponade. The team treated this with percutaneous drainage in one of the two, and by surgery in the other.

The case for this approach in the treatment of chronic AF was likewise compelling. Morady described a controlled, randomized study, also conducted at UMHS, in which each of 145 patients received amiodarone, an anti-arrhythmic agent, and two treatments of cardioversion. The study subjects were treated with circumferential pulmonary vein ablation, and all patients "reported" their cardiac rhythms via telephone for a year.

This study, which appeared in the April 18, 2006, edition of the New England Journal of Medicine, resulted in 74% of ablated patients being free of recurrent AF at one year vs. less than 5% of the controls who had the same outcome. However, the authors stated in the article that "an intent-to-treat analysis showed that 74% of patients in the ablation group and 58% of those in the control group were free of recurrent atrial fibrillation or flutter without antiarrhythmic-drug therapy at one year."