Balloon-based AF catheter ablation technologies show excellent results

By Larry Haimovitch

Medical Device Daily Contributing Writer

May 23, 2015

BOSTON — The 35th annual scientific sessions of the Heart Rhythm Society (HRS; Washington), which was held here late last week, covered myriad topics relevant to the electrophysiology (EP) community and the industry that serves their needs.

The diagnosis and treatment of atrial fibrillation (AF) has long been a key topic at HRS and continued to be here in Boston. And, while there has been considerable progress in improving catheter ablation technology, an important therapeutic approach, there remains considerable opportunity for better safety and efficacy.

To wit, a recent report from the Agency for Healthcare Research and Quality (AHRQ; Medical Device Daily, May 5, 2015) comparing catheter ablation to medical management for the treatment of AF opined that “there was insufficient evidence to draw conclusions regarding the efficacy, effectiveness and safety of this procedure for Medicare beneficiaries,” although the procedure is already covered by CMS. The AHRQ authors recommended additional research into several questions, including the question of which patients should receive ablation as a first-line therapy for AF. In addition, the authors concluded that “large, methodologically sound studies are needed” to establish the value of ablation on a number of outcomes, including stroke and mortality.

Despite nagging concerns about its rates of success, AF catheter ablation has grown at a rapid pace in the last several years. At this year’s annual St. Jude Medical analyst meeting held in February in New York, management provided some excellent catheter ablation market data, which is provided below.

Catheter Ablation Market Data

  1. The global catheter ablation market approximates $1.1 billion and is growing at a low double-digit rate. 

  2. U.S. procedures are estimated to be about 250K in 2015, growing at about a 15% annual rate.

  3. AF ablations comprise the largest share of the domestic ablation market (over 50% in 2015) and are growing at a 17% annual rate.

  4. Global ablation procedures are estimated to be about 990K in 2015, growing at a 13% annual rate.

Source: St. Jude Medical Annual Analyst Meeting February 2015

Without doubt, radiofrequency (RF) energy has been the dominant AF catheter technology in the past decade, with the Biosense Webster (Diamond Bar, California) division of Johnson & Johnson (New Brunswick, New Jersey) owning the lion’s share of the market. Its Thermocool brand obtained the first to PMA approval for an AF-labeled catheter in early 2009.

The acquisition of CryoCath by Medtronic (MDT; Minneapolis) nearly five years ago marked a gradual shift in the competitive landscape, as MDT’s marketing prowess, the ease of use of a balloon-based approach to PV isolation, (rather than “hunt & peck” approach of RF) and its perceived safety have enabled MDT to garner significant share in recent years.  Its domestic market share gains have accelerated markedly since it launched the second generation Arctic Front Advance Cardiac CryoAblation Catheter about two years ago. While there is no generally accepted AF catheter ablation market share information, MDD “guesstimates” that MDT has captured 15% or more.

Its second generation system, which advances the original cryoballoon system, provides improved cooling uniformity and is designed to reduce the effort needed to treat a broad range of pulmonary vein anatomies and to provide a more continuous lesion.

An investigator-initiated, single-center study called FreezeAF, was presented here at a Late Breaking Clinical Trial session. The study compared the Arctic Front Advance to conventional radiofrequency ablation. According to the lead investigator Armin Luik, MD, from Städtisches Klinikum (Karlsruhe, Germany) the aim of the study was to determine whether the Arctic Front Advance catheter is non-inferior to the open-irrigated radiofrequency pulmonary-vein isolation in patients with paroxysmal (intermittent or sporadic) atrial fibrillation.

Freedom from AF at six and 12 months was 63% and 68% among patients respectively treated with the cryoballoon ablation catheter compared with success rates of 64% and 65%, respectively, among patients treated with conventional radiofrequency ablation. Thus, the cryoballoon was statistically non-inferior to radiofrequency ablation, meeting its primary end point of non-inferiority.

In FreezeAF, 156 patients with paroxysmal AF were randomized to cryoballoon ablation and 159 randomized to radiofrequency ablation. All patients in the trial had failed at least one antiarrhythmic medication, and the primary end point in the study defined treatment as a failure if paroxysmal AF events greater than 30 seconds reoccurred. Redo procedures were not permitted within the first 6 months following the ablation, and ablations using only the original energy source were permitted between six and 12 months.

In addition to reporting that the cryoballoon was non-inferior to radiofrequency ablation, Luik said there were no cardiovascular deaths or stroke/transient ischemic attacks. Complication rates, however, were significantly higher among patients treated with the cryoballoon. Adverse events were driven by an increase in phrenic-nerve palsy, which occurred in 5.1% of patients who were treated with the cryoballoon.

Another promising balloon-based ablation technology that prominently in the limelight here was the CardioFocus (Marlborough, Massachusetts) visually guided laser balloon (VGLB) catheter, which is tradenamed the HeartLight Endoscopic Ablation System.

The VGLB, like the cryoballoon, has been tested mostly for paroxysmal AF. Its key features are a compliant and adjustable balloon that can be maneuvered easily into the pulmonary veins, ablative laser energy and direct endoscopic visualization. According to several industry experts that have been spoken to MDD, the two key attributes are its direct visualization and compliant balloon. The compliant balloon allows the physician to reliably achieve optimal contact with the oft irregularly-sized pulmonary veins.

The results of its multi-center, randomized pivotal clinical trial, which compared the HeartLight to the “gold standard” Thermocool irrigated RF ablation catheter, were reported at a Late Breaking Clinical Trial session by the lead investigator Vivek Reddy from the Icahn School of Medicine at Mount Sinai (New York). These data will support the company’s upcoming PMA application to the FDA.

In discussing the VGLB, Reddy noted that the most interesting aspect of the technology is the fact that it is a balloon with a camera.

“You're looking at the tissue and then identifying where one lesion is and how much overlap [there is] with the next lesion. At least in theory, you should be able to get continuous lesions all the way around in the pulmonary-vein isolation."

The “bottom line” of this trial is that a single HeartLight ablation procedure was found to be as safe and effective as standard radiofrequency ablation if used as approved, meeting the primary end point for non-inferiority. Specifically, 61.1% of patients treated with the HeartLight and 61.7% of patients treated with standard ablation were free from AF or atrial flutter/tachycardia. Single-procedure success and single-procedure success plus the use of antiarrhythmic-drug therapy were similar in both treatments.  Although the HeartLight cohort had fewer adverse events, both arms of the trial attained approximately the same statistical level of safety.

The major difference in the two arms of the trial is that overall procedure, ablation, and fluoroscopy times were significantly longer for the VGLB cohort. Reddy spent considerable time at various junctures during the several day conference explaining this difference.

"All of the operators were quite experienced with RF ablation," he said during the Late Breaking Clinical Trial session, “whereas very few of the laser ablation doctors had significant experience with this technology.” He specifically noted that only 23% of the operators performed more than five cases and only 7% performed more than 10 cases before the trial began. By the end of the pivotal study, only 17% of the operators performed more than 15 cases.

Reddy believes that the VGLB has the potential to be an upgrade over the technically demanding point-by-point ablation procedures operators perform in the majority of patients.

At a standing room only session later in the conference, Reddy further stated that “when you consider that the RF investigators may have performed more than a thousand procedures similar to the control arm and that the safety and efficacy endpoints were satisfied with investigators having performed a total of less than six HeartLight procedures on average, the results are truly remarkable.”

2015 Heart Rhythm Society

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