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Interest in AF continuing to grow among clinicians


By Larry Haimovitch

Medical Device Daily Contributing Writer

May 20, 2008

SAN FRANCISCO — It was just a year ago that the Heart Rhythm Society (HRS; Washington) for the first time ever devoted a full day of its annual scientific session to atrial fibrillation (AF), With an attendance of more than 1,200 persons at the "AF Summit," it far exceeded what was expected by the society and, as a result, the event has now become a key fixture of the group's annual meeting.

"What we realized is that this is not just a one-time deal," said Hugh Calkins, MD, chairman of the society's scientific and clinical guidelines committee. Calkins, head of the EP lab at the Johns Hopkins Hospital (Baltimore), added that "atrial fibrillation remains incredibly important" to its members.

Indeed, as the most prevalent arrhythmia— with an estimated 5 million American afflicted— and the most difficult to treat, AF has risen to a place of great importance to the electrophysiology (EP) community.

In a keynote address kicking off this year's AF Summit sessions, world-renowned AF expert John Camm, MD, from St. George's Hospital Medical School (London), told the audience that "atrial fibrillation will become a prominent part of your lives."

One of the promising new drugs he cited in his talk was dronedarone, which was discussed later that day in a "Late-Breaking Clinical Trials" session. Camm described it as an analog to the widely used drug amiodarone, except that it is considerable safer.

The drug, developed by Sanofi aventis (Paris), had an excellent outcome. Known also by the brand-name Multaq, it was part of the landmark ATHENA trial, the largest single anti-arrhythmic drug trial ever conducted. According to Sanofi, it marks the first time in two decades that a clinical AF drug trial showed significant benefit.

The primary trial endpoint, which was the time to first cardiovascular hospitalization or death from any cause, was met with a statistically significant and impressive 24% benefit.

This drug does not yet have either CE-mark or FDA approval, but its potential to reduce AF-related hospitalizations is of major importance to the medical community as AF is estimated to account for about one-third of all hospital admissions arising from rhythm disturbances.

According to Christopher Cannon, MD, a cardiologist from Brigham and Women's Hospital (Boston), "this trial marks a potential paradigm change for the management of atrial fibrillation."

The other key AF treatment modalities, percutaneous catheter ablation, performed by EPs, and surgical ablation, performed by cardiac surgeons, also were prominently featured throughout the HRS sessions. With a development pace that Camm described as "fast and furious," these two approaches are increasingly successful and an excellent alternative for AF patients, the majority of whom are not successfully treated medically.

There has been and continues to be widespread disagreement of the real success rate of catheter ablation, in part because of shoddy follow-up methods. At a St Jude Medical (St. Paul, Minnesota)-sponsored satellite symposium, Doug Packer, MD, of the Mayo Clinic (Rochester, Minnesota), said that he believes the success rate for paroxysmal AF (PAF; intermittent, typically early stage) patients is about 70%. This is notably higher than the success rates for persistent and long-standing persistent patients, which he pegged at about 50%.

One of Packer's main themes was that the isolation or ablation of the pulmonary veins (PVs), which is regarded as a gold standard for PAF, will produce mediocre clinical benefit for patients with longer, or persistent-standing AF. With longer-standing AF, additional lesions, such as ablating the ganglionic plexi and the ligament of Marshall, are required to terminate the AF and return the heart to normal sinus rhythm.

Supporting Packer's comments was Mark Wood, MD, an EP specialist from VCU Pauley Heart Center (Richmond, Virginia), who said that PAF catheter ablation success rates are far higher for catheter ablation and than for persistent AF. For the latter, Wood strongly supported minimally invasive surgery over catheter ablation.

He cited several advantages of minimally invasive AF surgery, including better excision of the left atrial appendage, faster weaning off of oral anti-coagulation medication, the ability to treat certain areas that require ablation for better results and the ability to treat certain patients (morbidly obese, very elderly) that may not be amenable to catheter ablation.

At a packed Atricure (West Chester, Ohio)-sponsored breakfast meeting, a surgeon's perspective was supplied by James Edgerton, MD, from the Texas Hospital of the Southwest (Plano, Texas). He noted that his clinical success has notably improved with both an extended lesion set and better tools. In regard to the latter, he cited the new Atricure Coolrail device, which was introduced to the U.S. market in mid-March. The Coolrail, which appears to be receiving a strong reception, uses resistive heating to create full thickness lesions. Circulating internal cooling fluid in a closed-loop bi-polar radio-frequency system keeps surface temperature low and, as a result, energy is driven deeper into the tissue.

According to Ralph Damiano, MD, chief of cardiac surgery at Barnes-Jewish Hospital (St. Louis), Coolrail is a "significant addition ... for the minimally invasive treatment of persistent atrial fibrillation."

Although not exhibiting at the HRS meeting, ATS Medical (ATS; Minneapolis) is an important contender in the surgical AF ablation market. At the annual meeting of the American Association of Thoracic Surgeons (Beverly, Massachusetts), held in San Diego last week, it co-hosted an evening seminar with Intuitive Surgical (Sunnyvale, California).

ATS's surgical platform, which features the use of cryo-energy, has the strong support of its new medical director and legendary cardiac surgeon James Cox, MD, of the Washington University School of Medicine (St. Louis). Cox, who pioneered atrial fibrillation surgery, has said that "the only sure way" to achieve normal rhythm in AF patients is to cryo-ablate the coronary sinus.

Recent clinical results, presented in January with cases performed at East Carolina University (Greenville, North Carolina), are impressive. In a study of mostly persistent AF, 86% were in sinus rhythm without medication. These cases were all performed thoracoscopically using the Intuitive da Vinci robot.

Importantly, whereas Atricure's cases are being performed on a beating heart, all the ATS cases currently require full cardio-pulmonary bypass. Industry sources indicate that ATS is actively developing a beating-heart, cryo-ablation platform.

2008 Heart Rhythm Society

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