Is Cryoballoon Better for Treating Atrial Fibrillation than Drug Therapy?
Patients with intermittent atrial fibrillation appear to respond better to treatment using a freezing balloon better than to conventional anti-arrhythmic drug therapy.
Atrial fibrillation (AF) is the most common arrhythmia affecting 2.2 million Americans. The results of the STOP-AF (Sustained Treatment of Paroxysmal Atrial Fibrillation) clinical trial are being presented at the American College of Cardiology’s 59th Annual Scientific Session is meeting in Atlanta this morning.
STOP-AF was designed to evaluate Medtronic’s Arctic Front® CryoAblation Catheter System. The study involved 245 patients with paroxysmal AF and 26 medical centers in the United States and Canada who had already tried treatment with at least one anti-arrhythmic drug, but were unsuccessful. The patients were randomly assigned in a 2-to-1 ratio to cryoablation or treatment with an anti-arrhythmic medication (one the patient had not previously failed).
Not data was collected during the first 90 days, allowing each patient’s doctor to adjust drug therapy or repeat cryoablation, as needed. After that, patients were followed-up in the clinic at 1, 3, 6, 9 and 12 months. They also sent heart-rhythm tracings to their doctor over telephone lines every week and when experiencing symptoms.
Paroxysmal atrial fibrillation is a form of the arrhythmia characterized by intermittent episodes of an irregular or racing heart beat. Abnormal electrical impulses cause the upper chambers of the heart to quiver and stimulate the heart to race at a rapid rate, rather than contract with a slow, steady rhythm. Anti-arrhythmic drugs are successful in eliminating atrial fibrillation in only about half of patients and can have serious side-effects. Cryoablation is an alternative treatment in which a catheter with a balloon on its tip is threaded into the left atrium. Coolant then fills the balloon and freezes a region of heart tissue near the entrance to the pulmonary veins, where most abnormal electrical impulses originate.
Researchers found that the cryoablation procedure is nearly 10 times more effective and equally safe as conventional anti-arrhythmic drug therapy for eliminating the irregular heart rhythm.
Cryoablation was initially successful in about 98 percent of patients. After one year, nearly 70 percent of patients treated with cryoablation were free of atrial fibrillation and had not required use of a non-study drug or an interventional procedure to treat atrial fibrillation, as compared with just 7 percent of patients in the anti-arrhythmic drug group.
Just over 3 percent of patients treated with cryoablation experienced a serious complication, specifically, narrowing of the pulmonary vein (7/228), one of whom required an interventional procedure to widen the vein.
Phrenic nerve palsy (damage or irritation to the nerve that controls the diaphragm and therefore can affect breathing) was noted after 11 percent of cryoablation procedures, but none of the cases was considered serious, and approximately 98% resolved by the 12-month follow-up.
Researchers also tracked complications related to atrial fibrillation itself. During the follow-up period, nearly 97% of patients in the cryoablation group and nearly 92% of patients in the drug-therapy group avoided cardiovascular death, heart attack, stroke, or hospitalization for recurrence or ablation of atrial fibrillation, ablation of atrial flutter, complications related to unwanted blood clots, heart failure, hemorrhage, or anti-arrhythmic drug treatment.
Less than 1% of patients treated with cryoablation were hospitalized for the recurrence of atrial fibrillation, as compared with 6% in the anti-arrhythmic drug group.
Arctic Front® Cardiac CryoAblation Catheter System is the first cryoballoon catheter technology designed to treat paroxysmal atrial fibrillation.
ACC 2010 Press Release