Some like it hot; some like it cold. Whether by radio frequency (RF) or cryoballoon, ablation interventions have been edging out medical therapy as an efficacious treatment for atrial fibrillation in some patients. But that doesn’t always translate into success, either clinically or financially. Costs, recurrences and lack of proof that the procedures offer a stroke benefit pose challenges.
“From observational studies, we really don’t have evidence that ablation reduces stroke risk,” says Douglas L. Packer, MD, a cardiologist at the Mayo Clinic in Rochester, Minn. “We have great evidence that it reduces symptoms, increases quality of life and eliminates atrial fibrillation in many but not all patients. We need (large clinical trials) to know whether ablation is of substantial stroke benefit.”
Principal investigator of STOP AF and the ongoing CABANA trial, Packer straddles both the now known and the still unknown. STOP AF, a randomized, controlled clinical trial, evaluated the effectiveness and safety of Medtronic’s Arctic Front cryoballoon in patients with symptomatic paroxysmal atrial fibrillation who had failed on at least one antiarrythmic drug (J Am Coll Cardiol 2013;61:1713-1723). But its follow-up was only one year with a patient cohort of 245. CABANA (Catheter Ablation Versus Antiarrhythmic Drug Therapy for Atrial Fibrillation) will randomize 2,200 patients with atrial fibrillation to ablation or drug therapy for a five-year follow-up.
CABANA’s completion date is still years away, though. In the meantime, technologies continue to evolve amid a changing fiscal landscape.
Putting it in practice
Atrial fibrillation statistics
Source: J Am Coll Cardiol online March 28, 2014
Results from recent ablation trials have given electrophysiologists more confidence to move forward with ablation programs. In the Medtronic-sponsored STOP AF trial, for instance, physicians achieved pulmonary vein isolation using the cryoballoon alone in 83 percent of patients. Patients treated with cryoablation had a 12-month treatment success rate of 70 percent compared with 7 percent of the patients treated with antiarrhythmic drugs.
The overall serious adverse event rates at 12 months were similar in the two groups, but researchers noted that ablation-related complications such as pulmonary vein stenosis and phrenic nerve injury were possible.
“STOP AF was looking at patients who have paroxysmal atrial fibrillation in the absence of underlying disease, so it is very representative of patients with relatively early atrial fibrillation,” Packer says. “If you look at a typical practice, the most common variety of atrial fibrillation is paroxysmal.”
Trials evaluating catheter ablation have reported rates on par with STOP AF. The ThermoCool AF Trial enrolled a patient population somewhat similar to STOP AF and randomized them to either ablation treatment with Biosense Webster’s ThermoCool catheter or antiarrhythmic drug therapy (JAMA 2010;303:333-340). At nine months, 66 percent of the ablation group was atrial fibrillation-free compared with 16 percent of the drug group with a 30-day treatment-related adverse event rate of 9 percent vs. 5 percent. Biosense Webster sponsored the trial.
Guidelines in the U.S. and Europe recommend catheter ablation performed by a trained electrophysiologist as a treatment for patients with paroxysmal atrial fibrillation who have failed or can’t tolerate at least one antiarrhythmic drug. More recently, the 2014 Guideline for the Management of Patients with Atrial Fibrillation in the U.S. called for an additional role for RF ablation. With several RF catheters and the Arctic Front cryoballoon and catheter system FDA-approved for paroxysmal atrial fibrillation, operators now have options in their treatment decisions. Some physicians welcome the efficiency of the cryoballoon, which doesn’t require point-by-point delivery in several applications to isolate the pulmonary vein. Others favor the versatility of RF catheter ablation, which also can be performed efficiently in the hands of a proficient operator.
“Some labs find they can get through an isolation procedure more quickly with cryo,” says Matthew R. Reynolds, MD, MSc, a cardiologist at