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Two companies reported progress in mid-September toward their goal of FDA approval for a cryotherapeutic treatment for atrial fibrillation (AF), the most prevalent form of cardiac arrhythmia in the world.

CryoCath Technologies (Montreal, Quebec) received conditional approval from the FDA to initiate an investigational device exemption (IDE) study to treat AF. In another report issued the same day, CryoCor (San Diego, California) a development-stage company, said it had completed U.S. patient enrollment of the first phase of its feasibility trial for paroxysmal AF and had begun additional enrollment in the feasibility trial for atrial flutter at Arizona Heart Hospital (Phoenix, Arizona) and Iowa Heart Center (Des Moines, Iowa), two of the 10 centers involved in this study.

During cryotherapeutic treatment of AF, energy is delivered via a minimally invasive catheter procedure, with temperatures of minus 80o Celsius or lower applied to the cells implicated in the arrhythmia. The therapeutic impact of freezing cells comes in the thawing process. As they thaw, the cells break open and die, the area of dead cells creating an insulating barrier to the unwanted electrical activity, while at the same time keeping other structures intact.

The CryoCath study will involve what the company called a "toolbox" approach to treat AF with up to three different CryoCath catheters Arctic Circler Linear, Freezor Xtra and Freezor MAX. The Arctic Circler is uniquely configured to treat AF originating in the pulmonary veins and has the ability to create curvilinear lesions rapidly within the ostia (openings) of the four pulmonary veins (PV). Freezor Xtra will touch up gaps resulting from unique PV anatomy and to destroy certain foci that often trigger AF. Freezor MAX will be used to create a Flutter line in all AF patients regardless if atrial flutter is present or not.

"We are very excited to initiate our AF regulatory path on the heels of our recently successful U.S. launch of Freezor," said Steven Arless, president and CEO of CryoCath. "Our enthusiasm is further bolstered given our belief that cryotherapy is best suited to treat AF."

The study is designed to take place in two phases. The first phase will enroll up to 30 patients in as many as three U.S. centers. Based on safety and acute success rates, the company expects to continue enrolling patients necessary to generate the information required to submit a premarket approval application (PMA). The final protocol for the second phase will be determined later in the year after the FDA has issued its AF trial guidance document. CryoCath currently has three cardiac ablation products approved in the U.S., Freezor, Freezor Xtra and SurgiFrost, but none of these are for AF.

Vivek Reddy, MD, of Massachusetts General Hospital (Boston, Massachusetts), the principal investigator of this new study, said, "Cryoablation, given its growing track record of not invoking PV stenosis, represents a potential paradigm-shifting therapy in the treatment of AF."

For its part, CryoCor reported that in the U.S., 31 patients had been treated, and enrollment is complete for the feasibility trial with use of the CryoCor System for the treatment of paroxysmal AF, which was first initiated in May 2002. As per the feasibility trial protocol, up to six-month patient follow-up for safety and efficacy is currently being conducted with these patients. Additionally, the company said it expects to file for FDA approval to expand enrollment in the U.S. paroxysmal AF feasibility trial using its second-generation cryoablation catheter.

Gregory Ayers, MD, PhD, CryoCor's president and CEO, said, "Our progress in the clinic has allowed us to secure financing, to strengthen our management team and begin to build overall physician confidence that the CryoCor System provides a promising minimally invasive therapy to serve the arrhythmia ablation market." The company also said it has had progress under a study for the use of cryotherapy for the treatment of atrial flutter, the second most commonly occurring cardiac arrhythmia that often progresses to (or coexists with) AF.

At Arizona Heart Hospital, a new study center, David Riggio, MD, assistant director of electrophysiology with Arizona Arrhythmia Consultants, treated the first patient under the Phase II feasibility trial for atrial flutter with CryoCor's Cardiac Cryoablation System. Robert Hoyt, MD, also treated one patient under the same protocol at the Iowa Heart Center. Earlier this year, CryoCor completed enrollment of 30 patients under the Phase I U.S. feasibility trial. The company said it expects to complete the 20-patient enrollment for the Phase II atrial flutter feasibility trial by 4Q03, followed by a pivotal trial necessary to support a PMA application to the FDA.

CryoCor also reported publication in the Journal of the American College of Cardiology of an article demonstrating over long-term follow-up that the use of the CryoCor System in the electrical isolation of pulmonary veins is feasible and may prevent arrhythmia recurrence in AF patients without the occurrence of pulmonary vein stenosis. The article reported that the safety profile of the CryoCor system was better than voluntarily reported complication rates in non-controlled trials using radiofrequency (RF) energy 7.7% with use of the CryoCor System as compared to 8% to 35% using RF energy. No pulmonary vein stenosis was reported after 12-month patient follow-up.

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