CardioFocus demonstrates notable progress for AF

By Larry Haimovitch

Medical Device Daily Contributing Writer

May 10, 2011

SAN FRANCISCO — As discussed in Tuesday's issue of Medical Device Daily, there has been considerable progress in treating atrial fibrillation (AF) with catheter-based technologies in recent years. However, the rate of success, estimated at 57% for a single procedure, is far from satisfactory. Thus, the quest for better methods to perform AF catheter ablation continues at a strong pace. One company, which is demonstrating impressive progress, is privately-owned, venture capital-backed CardioFocus (Marlborough, Massachusetts). Two important abstracts that were presented here last week's at the annual scientific sessions of the Heart Rhythm Society (HRS; Washington) demonstrated that the company's technology could be a force to be reckoned with in the coming years.

CardioFocus has developed an approach, a visually guided laser balloon (VGLB), primarily addresses paroxysmal (intermittent) AF. It features a 12 Fr deflectable sheath, 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 in the past, the company's two key attributes are the direct visualization and its compliant balloon. The compliant balloon allows the physician to achieve optimal contact with the oft irregularly-sized pulmonary veins.

Direct visualization is very important because other ablation technologies (mainly radiofrequency) have used indirect X-ray guidance, which can be technically challenging and often results in incomplete isolation (ablation) of the PVs, leading to mediocre success in eliminating the AF.

Vivek Reddy, MD, from Mount Sinai School of Medicine (New York) presented the results of the first 200 patients treated in a multicenter clinical setting. A second important study, presented by one of Reddy's colleagues at Mount Sinai, Srinivas Dukkipati, MD, addressed the durability of pulmonary vein isolation.

Reddy presented the results of 200 patients treated at nine clinical sites with 33 operators, showing 78.4% of the PVs isolated on the first attempt, with 98.8% of the PVs isolated with a second ablation. Reddy also reported that the results improved substantially with more operator experience. For example, total procedure time dipped 16% after 15 cases, while fluoroscopy time decreased nearly by half.

Most importantly, after a six-month follow-up for over half the 200 patients enrolled in the study, the single procedure, drug-free rate of freedom from AF was 65%. This compares favorably to the single procedure success rate of 57% from a meta analysis of numerous randomized clinical trials and the less than 50% success rate reported in the PMA trials by both the BIosense Webster's (Diamond Bar, California) Thermocool catheter and the Medtronic (Minneapolis) Arctic Front cryoablation catheter.

Reddy concluded his presentation commenting that "this favorable experience sets the stage for truly comparative long-term efficacy and safety studies (versus radiofrequency ablation)." Indeed, CardioFocus hopes to initiate a randomized, multicenter trial comparing radiofrequency (RF) to VGLB in the United States in the second half of 2011.

Dukkipati also reported very positive results. This trial, conducted at both domestic and international sites with 56 patients, revealed that 86% of the patients' pulmonary veins were persistently isolated at three months, compared with previous rates of 38% to 57% with the "gold standard," traditional RF ablation.

Additionally, Dukkipati reported in a post-presentation interview that limited 12-month follow-up data on 35 patients showed that 71% were free of atrial fibrillation and are not taking anti-arrhythmic drugs.

Addressing the issue of a short learning curve, in the three centers in the study, seven operators performed fewer than 10 procedures, while two performed more than 10. "Even for the less experienced operators, more than three out of four pulmonary veins were isolated at the time of remapping," he said.

Regarding the safety profile, no patients experienced atrial esophageal fistula, stroke, transient ischemic attack or death, while one patient experienced cardiac tamponade and one had phrenic nerve palsy. There also were no cases of significant pulmonary vein stenosis.

Dukkipati concluded that the "visually-guided laser balloon can achieve high rates of acute and durable pulmonary vein isolation safely, even with limited operator experience."

Another company showing substantial progress in the field of AF ablation is Endosense (Geneva, Switzerland). The company's flagship product is the TactiCath, the first force-sensing ablation catheter designed to give physicians a real-time, objective measure of contact force during the catheter ablation procedure.

Numerous pre-clinical and human studies in the past couple of years have shown that insufficient force may lead to subpar results (low efficacy, longer procedure times) while excessive force can cause various adverse events (tamponade, esophageal injury).

Endosense recently reported (Medical Device Daily, May 5, 2011) that its TactiCath contact-force sensing ablation catheter has been used to perform more than 1,000 AF patient cases in Europe. Its distributor, Biotronik (Berlin, Germany) has built and is continuing to grow the market for the TactiCath as its exclusive distributor in Europe as well as Latin America, Canada, Africa and the Middle East.

In addition, Endosense recently said (Medical Device Daily, May 9, 2011) that it has engaged with Rhythmia Medical (Burlington, Massachusetts) and in a joint development project to integrate the contact-force data into Rhythmia's advanced three-dimensional cardiac mapping, visualization and navigation system.

Finally, Endosense and Siemens Healthcare reported the completion of prototype software integrating the contact-force data with Siemens' electrophysiology solutions. The new application, which was created under a joint development agreement originally announced in January, was designed to allow electrophysiologists to view catheter tip-to-tissue contact force within a fluoroscopically enabled, three-dimensional anatomic heart model during catheter ablation procedures.

A host of new clinical results were presented at HRS, with favorable early data from the company's EFFICAS I post-market clinical trial that shed new insights into the relationship between catheter tip-to-tissue contact force and early pulmonary vein isolation line reconduction.

EFFICAS I is a 45-patient, single-arm, prospective, multi-center European clinical trial that was designed to demonstrate the correlation between contact forces applied during pulmonary vein isolation and atrial fibrillation treatment efficacy at three months. While investigators performed the procedure with the TactiCath, they were blinded to contact force measurements; however, the contact forces applied were recorded. Patients were re-assessed with a mapping catheter at three months to identify potential gaps in the PVI lines. Contact force parameters from initial procedures were then analyzed to determine the relationship with lesion formation.

Karl-Heinz Kuck, MD, Asklepios Klinik St. Georg (Hamburg, Germany), a veteran in the field of electrophsiology, said that "EFFICAS I shows for the first time a direct correlation between low contact force and post-operative PV isolation line reconduction at three month follow-up. " The EFFICAS I data showed this to be particularly true when low contact forces were applied at the first ablation site.

Full results from EFFICAS I will be applied to EFFICAS II, in which investigators will take full advantage of the real-time, objective TactiCath contact-force control features to improve their ablation technique during lesion creation. Now enrolling patients, the EFFICAS II study will measure reduction in PVI gaps as well as procedural improvements as compared to EFFICAS I.

Vivek Reddy, a widely respected EP practitioner is also very enthused about this technology, saying that "contact force is the last missing piece of information needed to improve the treatment of AF."

2011 Heart Rhythm Society

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