Heart & Vascular Institute Physician eNewsletter - Winter 2012
Drug therapy has always been the first line of treatment for AF, but recent studies show encouraging outcomes for an ablation-first strategy.
Ablation is currently the second line of therapy for atrial fibrillation (AF), considered only after a medicine has failed to control heart rhythm or drug therapy is not well tolerated by the patient. But recent studies touting better outcomes for an ablation-first strategy could turn this clinical guideline on its head.
So, what’s the best Plan A for managing AF: drug therapy or ablation?
This question is the center of debate in the field, says Daniel Cantillon, M.D., a staff physician in the Section of Electrophysiology and Pacing at Cleveland Clinic’s Miller Family Heart & Vascular Institute.
“There is growing evidence to support the notion that outcomes following an ablation are better among patients whose atrial fibrillation is less chronic and that, perhaps, the best time to intervene is earlier in the disease process before advanced scarring has developed in the upper chambers of the heart,” Dr. Cantillon says.
Specifically, results from an important randomized trial, MANTRA, were presented in November at the 2011 annual meeting of the American Heart Association and favor ablation-first treatment. Meanwhile, Cleveland Clinic is a center for a different ongoing study, CABANA, and currently enrolling patients to evaluate everything from treatment efficacy to cost implications and overall quality life of patients who get drug therapy vs. catheter ablation.
The Right Medical Strategy
Medical therapy remains the first line of treatment according to today’s clinical guidelines. But it’s important to note that the decision to treat AF with medication goes deeper: It’s critical to choose the right treatment strategy for drug therapy: rate control or rhythm control.
The conservative route is rate control, and it involves medicines designed to slow down the patient’s pulse. The heart is allowed to remain in AF and medicine is designed to simply slow it down. This strategy is best for patients who experience minimal symptoms—AF doesn’t interfere with their quality of life, and the main goal is to slow down AF to prevent stroke.
Rhythm control involves medicines that suppress AF and promote a normal heart rhythm using anti-arrhythmic drugs. This strategy is best for symptomatic patients who experience fatigue and/or palpitations that interfere with their daily life. “Patients typically feel tired because the heart is up to 20 percent less efficient when compared to a normal rhythm,” Dr. Cantillon explains. “For patients who are very active, that 20 percent can be sorely missed.”
Dr. Cantillon relates how the upper chambers of the heart quiver when in AF, beating up to 300 times per minute instead of contracting functionally as they do in a normal rhythm.
Quality of life is the ultimate determinant of which drug therapy is best for a patient. Meanwhile, it’s important to note that both medical strategies (rate and rhythm control) require using another medicine (usually aspirin, warfarin or dabigatran) to reduce a patient’s risk of stroke.
“A stroke is, by far, the most sinister complication resulting from atrial fibrillation,” Dr. Cantillon says, noting that the choice among these three medications depends on a patient’s risk for stroke and bleeding.
Ablation is only considered if one of these strategies fails. “For patients well-controlled on medicine, there is presently no indication for an ablation,” Dr. Cantillon says.
But drug therapy as the gold standard, first-line treatment for AF remains controversial. Anti-arrhythmic drug efficacy rates range from 40 to 60 percent (based on clinical trials going back decades). And the toxicity of drugs like amiodarone can include irreversible scarring in the lungs thyroid damage, skin changes, liver injury or ocular deposits at the rate of about 2 percent per year of treatment, Dr. Cantillon notes.
Is ablation a better way?
Ablation First: Better Results?
Growing evidence supports ablation as a successful first-line treatment for patients with less chronic AF, and that the best time to intervene is sooner to prevent scarring in the heart—not later, after medical therapy has been tried.
In the MANTRA study, 300 patients randomly received either drug therapy or catheter ablation. “The results have not yet been published or subjected to full scientific scrutiny, but the ablation-first treatment appeared to fare overall better,” Dr. Cantillon says.
This supports other smaller studies that compare drugs to ablation. In the STOP AF study, a novel “freeze” ablation system (offered at Cleveland Clinic) was compared to drugs. About 70 percent of patients treated with ablation were free from AF and off anti-arrhythmic medicines compared to 7 percent of patients treated with drugs. The lower success rate of ablation in that study was pinned to the freeze ablation technique; because it is newer, there is an operator learning curve. The advantage is the procedure takes less time to complete.
In the CABANA study’s pilot trial of 100 relatively sick patients, ablation was compared directly to drug therapy. The results, again, favored ablation: 65 percent of ablation patients were free of AF and drugs compared to the 41 percent in the medical therapy arm.
At Cleveland Clinic, the success rate of a single ablation procedure for a patient with paroxysmal atrial fibrillation is 77 percent after a single ablation procedure, and 92 percent after a second ablation. Dr. Cantillon explains that sometimes two procedures are necessary because the first ablation isolates veins that return blood from the lungs (the most common trigger of extra heart beats). But up to one-third of patients have triggers for AF outside of those veins that are not “found” until after the first ablation surgery. “The second ablation surgery will target these other ‘triggers,’ which come from other places inside the heart,” Dr. Cantillon says.
So, what’s the answer for AF: ablation or drug therapy? We hope to find a more definitive answer from the CABANA study, which has currently enrolled approximately 500 of the 3,000 patients with AF who will be randomly given ablation or drug therapy.
For now, clinical practice guidelines dictate medication first. But ablation continues to show promise as a first line of treatment before advanced scarring has developed in a patient’s heart, and possibly protecting it from further damage.