Symposium examines latest treatments of atrial fibrillation

By Larry Haimovitch

Medical Device Daily Contributing Writer

January 26, 2010

BOSTON — The 15th annual Boston Atrial Fibrillation Symposium was recently held here. While controversy was at a minimum, there were several interesting topics that held the attention of the more than 1,000 participants, which drew attendees from EP industry clinicians, aspiring entrepreneurs and the investment community.

In recent years, there has been considerable progress in managing this disease, which afflicts 2.3% of the population over the age of 40, 6% of those over 65 and nearly 10% of those over 80. However, paraphrasing the inimitable words of Winston Churchill, from a talk he gave discussing Russia in October 1939, atrial fibrillation yet remains "... a riddle, wrapped in a mystery, inside an enigma ..."

This year's programs covered the gamut of treatment options for AF, with significant emphasis on catheter ablation. About one year ago, the first AF ablation catheter, the Navistar Thermocool, was granted FDA approval (Medical Device Daily, Feb. 9, 2009). Developed by the Biosense Webster (Diamond Bar, California) division of Johnson & Johnson (J&J; New Brunswick, New Jersey), it was cleared for the treatment of drug refractory recurrent symptomatic paroxysmal (PAF, intermittent early stage) atrial fibrillation.

Catheter ablation, which before that approval was practiced on an "off-label" basis, was now legitimized by that approval and it remains the mainstay of device-based treatment of AF.

Hugh Calkins, MD, a renowned electrophysiologist (EP) and professor of medicine at Johns Hopkins Heart & Vascular Institute (Baltimore) provided a comprehensive review of AF clinical trials in his talk titled "Current Status of Clinical Trials of AF Devices Seeking FDA Approval."

He identified 120 trials that address AF, including the following:

  1. 83 trials for catheter ablation (72 involving "new" technology) with 50 single center trials and 33 multi-center trials

  2. 50 of those trials performed outside the U.S., the rest in this country

  3. 49 trials hospital funded, 25 funded by industry and three by the National Heart, Blood & Lung Institute (Bethesda, Maryland)

According to Calkins, the next likely FDA approval will be the Arctic Front balloon catheter, originally developed by CryoCath (Montreal). This company, which was acquired by Medtronic (Minneapolis) for about $400 million (MDD, Dec. 22, 2008), was a pioneer in the development of a cryo-energy, rigid balloon catheter to perform a pulmonary vein isolation (PVI) procedure. PVI is one of the cornerstones of the treatment of AF.

The CryoCath Sustained Treatment Of Paroxysmal Atrial Fibrillation (STOP AF) pivotal clinical trial compared the cryo-balloon catheter to traditional anti-arrhythmic drug therapy. The trial enrolled 270 patients at 20 centers in the U.S. Calkins noted that the required 12-month follow-up was completed in July 2009 and that the final data will likely be presented at the upcoming mid-March annual meeting of the American College of Cardiology (Bethesda, Maryland) being held in Atlanta.

A second completed pivotal study is the Ablation Frontiers (Carlsbad, California) Tailored Treatment of Permanent AF (TTOP AF) trial, which completed its enrollment in May 2009. It employs standard radio frequency energy with some novel ablation catheters. Calkins estimated that the mandatory one-year follow-up period will be completed around mid-year 2010, with results released sometime after that.

Whereas the STOP AF trial treated patients with PAF, the TTOP AF trial enrolled patients suffering from permanent (later stage, chronic) AF, who were randomized 2:1 In favor of ablation. 24 centers enrolled a total of 210 patients.

As previously reported (MDD, Feb. 9, 2009) Ablation Frontiers was acquired by Medtronic in February 2009 for an initial payment of $225 million plus an additional payment for PMA approval, which MDD estimates at $175 million.

A third trial discussed by Calkins is being sponsored by CardioFocus (Marlborough, Massachusetts). Its technology, which also addresses PAF, features a compliant balloon that can be maneuvered easily into the pulmonary veins, ablative laser energy and direct endoscopic visualization. Thus, the slogan used at its tradeshow booth "See what you ablate, ablate what you see."

The company, which attained CE mark approval in June 2009, has now treated a total of 89 patients, including 16 in its U.S. feasibility trial. The early data, three months post-treatment, is very promising with better than 90% of the pulmonary veins chronically isolated as the result of only a single procedure.

Its excellent results are fostered by the direct visualization from the built-in endoscope and the advantage of a compliant balloon in making contact with the well-documented anatomical variation of the pulmonary veins. Its results are particularly impressive because only a single balloon catheter was used to treat these patients, with no touch-up with other devices permitted during the procedure.

In the U.S., a ten-center feasibility trial is now underway, with a total of 100 patients to be enrolled. The company could launch its pivotal trial in late-2010.

In a talk titled "Balloon-Based Systems for AF Ablation: Outcomes and Complications," Vivek Reddy. MD, from Mount Sinai Medical Center (New York) noted that balloon-based approaches to the treatment of PAF are "very promising" and are eagerly awaited by the EP community.

There were several papers and an evening symposium discussing the Endosense (Geneva, Switzerland) TactiCath RF ablation irrigated catheter, which Reddy described as the "first force sensing ablation catheter."

Virtually every speaker discussing this device noted that today's catheters lack force control against the wall of the heart, often resulting in either insufficient or excessive tissue contact. Many EPs believe that inadequate tissue contact is the main culprit in a high (30%-40%) ablation procedural failure rate, while also being a major contributor to oft-very lengthy procedures. Meanwhile, excessive force is clearly the cause of two major risks of catheter ablation: tamponade, or fluid accumulation in the sac of the heart and esophageal perforation, a potentially disastrous event.

The TactiCath addresses these drawbacks, providing a highly sensitive sensor to evaluate in real-time the force of the catheter against the heart's tissue.

The superlatives flowing at the company's dinner symposium were impressive. Noted EP physician Karl Heinz Kuck, MD, of St. George Hospital (Hamburg, Germany) said that this technology is "the last missing piece of information that we need to improve our ability to treat AF."

Kuck has been working closely with the company and was the principal investigator of its TOCCATA (TOuCh+ for CATheter Ablation) trial, which enabled the company to gain its CE mark approval.

His ebullience for this technology was absolutely evident by his statement that "there is no doubt in my mind that force sensing catheters will eventually become a standard of care".

Reddy closed his talk with his own emphatic comment that "force sensing is here to stay!"

In the U.S., Endosense plans to initiate the TOCCASTAR AF trial in 2010, enrolling symptomatic PAF patients in both the U.S. and Europe. Now that J&J has FDA approval for Its Navistar Thermocool catheter, it is likely that the trial will be randomized 1:1 between TactiCath and Thermocool.

There are also interesting developments in the realm of surgical treatment of AF. At an evening symposium sponsored by surgical ablation market leader Atricure (Cincinnati), several noted AF experts participated in an FDA clinical trial development and site recruitment meeting.

The purpose of this gathering was to kick off the DEEP AF (Dual Epicardial/Endocardial Ablation for Persistent AF Patients) trial, which will begin this year as a feasibility study at five U.S centers and treat 30 patients. If successful, it will be broadened into a full scale pivotal trial that could lead to a PMA approval.

The concept of DEEP AF is that patients with persistent AF are by far the most challenging to treat and cure, that the success rates with catheter ablation (endocardial) or surgery (epicardial) have been mediocre and that perhaps a combined hybrid approach might be more successful.

The world's expert in performing hybrid procedures, Mark La Meir, MD, a cardiac surgeon at the Centre for Heart Disease, University Hospital (Brussels, Belgium) spoke at this gathering and rhetorically asked the audience: "Why not combine endo and epicardial ablation and take the advantages of both procedures and eliminate the disadvantages of each of the procedures through collaboration?"

La Meir and his EP colleague Laurent Pison, MD, have been doing precisely that, performing a hybrid procedure on longstanding or persistent AF patients. While they only treated 29 patients to date (half of which had persistent AF), and have data on 19 patients six-months post-procedure, 17/19 or 89% are in sinus rhythm and cured of their AF. This success rate is considerably better than has been seen for either catheter ablation or surgery on their own.

In an interview with MDD, both physicians were extremely pleased with their early results and expressed confidence in the future potential of hybrid procedures.

"I think that this a fantastic procedure for patients with persistent atrial fibrillation," said La Meir. "We expect that we will be doing many more of these procedures in the future."

Another hybrid approach to treating AF is being explored by nContact Surgical (Morrisville, North Carolina), which recently reported the initiation of a feasibility clinical trial designed to evaluate the safety and efficacy of a combined surgical and catheter procedure, a so-called convergent procedure. Whereas Atricure is targeting persistent AF, the nContact trial will treat patients with symptomatic paroxysmal AF.


2010 Boston Atrial Fibrillation Symposium

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