AF still at the heart of annual HRS meeting

By Larry Haimovitch

Medical Device Daily Contributing Writer

May 10, 2011

SAN FRANCISCO — As has been the case in recent years, the 32nd annual scientific sessions of the Heart Rhythm Society (HRS; Washington) sponsored an AF Summit, focusing attention on atrial fibrillation (AF) with a full day of presentations.

The atrial fibrillation device market is a significant one. At its February investor conference, St. Jude Medical (Saint Paul, Minnesota) pegged the 2011 global AF device market at about $2.2 billion. Moreover, it is one of the fastest growing device markets, with St. Jude forecasting that the market will grow at 11% to 13% this year. The company believes that catheters used to ablate cardiac arrhythmias account for the largest individual category at about $640 million, or 29% of the total AF device market. St. Jude expects that in 2011 the global catheter ablation market will grow roughly 10% over 2010 levels.

According to Hugh Calkins, MD, an electrophysiologist (EP) and professor of medicine at Johns Hopkins Heart & Vascular Institute (Baltimore) who was one of the key featured speakers at this symposia, "the pace of progress in catheter ablation is very impressive." He said the understanding of AF, an extraordinarily complex disease and the most common arrhythmia in the U.S., has clearly been increasing at a rapid clip.

He cited the steady improvements in the success rate of catheter ablation, pointing to the results of six randomized clinical trials that yielded a 77% success rate for catheter ablation versus a paltry 29% for medical management. The 77% rate is for multiple ablation procedures (the single procedure rate is estimated at 57%) and includes drugs to supplement catheter ablation but nevertheless these results are encouraging and are far better than for drugs.

Yet, Calkins cautioned that "there is much we still do not know." For example, the long term safety, efficacy and survival rates for patients treated with catheter ablation. He said that the EP community is eagerly awaiting the results from the multicenter international Catheter Ablation Versus Anti-arrhythmic Drug Therapy for Atrial Fibrillation Trial (CABANA) trial. Funded by the National Heart, Lung, and Blood Institute (Bethesda. Maryland), this landmark 3,000 patient trial was designed to test the hypothesis that the treatment strategy of left atrial catheter ablation will be superior to medical management.

CABANA has an estimated duration of five years, with the primary end point of total mortality and secondary end points including a host of cardiovascular end points such as hospitalizations, bleeding, and stroke. According to the ClinicalTrials.gov website, the final data from this trial is not due for at least another four years.

One of the most intriguing AF topics at HRS was discussed at the Late Breaking Abstract Session, when the results of the Conventional Ablation for Atrial Fibrillation With Or Without Focal Impulse and Rotor Modulation (CONFIRM) trial were reported by Sanjiv Narayan, MD, from the University of California San Diego (UCSD). According to Dr. Narayan, who has spent about a decade working on this diagnostic technology with grants from the National Institutes of Health (Bethesda), this approach looks at the "basic ways that the heart responds to arrhythmias, with patient tailored physiological mapping."

The CONFIRM trial tested the hypotheses that: (1) AF is caused by localized electrical rotors or focal beats. These rotors – or, as Narayan described them, "localized areas of electrical activity" that can be found all over the atria –can be visualized for the first time using a physiological mapping system that utilizes a conventional basket, mapping catheter as part of the approach; (2) Localized ablation, called focal impulse and rotor modulation or FIRM, will acutely terminate or slow AF and improve efficacy when added to conventional AF ablation techniques.

Narayan's scientific collaborator, Ruchir Sehra, MD, provided Medical Device Daily with an analogy of the concept of localized electrical rotors. Ruchir Sehra, MD, during a post-HRS interview with Medical Device Daily. Ruchir, who has been intimately involved in this project, likened AF to a fire, which requires both a spark or match plus kindling to cause the fire to start. Conventional ablation or isolation of the pulmonary veins, now described in the EP world as "the cornerstone of AF catheter ablation, eliminates the matches or sparks. The role of FIRM is to identify where the kindling is and then to remove it.

The CONFIRM trial, which began enrolling in October 2005, ultimately enrolled a total of 103 patients, with about two-thirds of the patients with persistent or long standing AF.

The data is very promising, with the 32 FIRM guided patients achieving an 84% success rate, compared to only 51% for the 63 conventionally treated patients. The results are even more impressive for several reasons: (1) 84% of the FIRM patients were monitored by implantable loop monitors, which is a very precise means to accurately detect episodes of AF; (2) this data described two year outcomes, which speaks to the durability of the approach; (3) this data was accomplished with a single procedure and is considerably better than the conventional method. (4) the success in treating patients in the trial with persistent AF is remarkable; typically this patient subset achieves the poorest outcomes with catheter ablation and often require a second or third catheter ablation to overcome their AF and return to normal sinus rhythm; (5) FIRM rapidly terminated AF predominantly to normal sinus rhythm in less than 10 minutes prior to conventional ablation.

"Our current AF ablation procedures are very time consuming and shortening them would be a huge benefit," said Doug Packer, MD, and EP from the Mayo Clinic (Rochester, Minnesota), commenting on the CONFIRM trial at an HRS sponsored press conference. "This technology could usher in a paradigm shift in AF ablation, where we would move from anatomic ablation to a physiological-based approach."

This technology was licensed three years to privately-owned, angel funded Topera Medical (Lexington, Massachusetts). The company filed a 510(k) application in March and plans a limited U.S. commercial launch of the diagnostic system under the tradename RhythmView in the first half of 2012. The company said it hopes to launch in Europe at the end of 2012.

2011 Heart Rhythm Society

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