The latest article in our Clinical Therapeutics series begins with a 59-year-old man who presents with a recurrent episode of symptomatic atrial fibrillation despite attempts to maintain sinus rhythm with antiarrhythmic drugs. Catheter ablation can be effective in such patients, but more than one procedure may be necessary.
Atrial fibrillation affects up to 5 million people in the United States, and data suggest that, as the population ages, the incidence will continue to rise. The rate of ischemic stroke among patients with nonvalvular atrial fibrillation averages 5% per year. The mortality rate of patients with atrial fibrillation is about double that of patients in normal sinus rhythm.
• What is the natural history of atrial fibrillation?
Atrial fibrillation is usually a progressive disease. The natural history often begins with infrequent episodes of limited duration, termed “paroxysmal atrial fibrillation.” Such episodes then tend to become more frequent and longer in duration, progressing to persistent atrial fibrillation (which fails to terminate spontaneously within seven days and may require cardioversion) or permanent atrial fibrillation (if the arrhythmia lasts for more than one year and cardioversion either has not been attempted or has failed).
• What is the comparative efficacy of radiofrequency catheter ablation and antiarrhythmic therapy for the treatment of atrial fibrillation?
Several randomized trials have demonstrated superior outcomes of radiofrequency ablation compared to antiarrhythmic drug therapy. In one trial, 198 patients with paroxysmal atrial fibrillation who had previously failed antiarrhythmic drug therapy were randomly assigned to either radiofrequency ablation or antiarrhythmic drug therapy with other agents. At 1 year, 86% of patients assigned to catheter ablation and 22% of patients assigned to antiarrhythmic drug therapy had not had a recurrent atrial tachyarrhythmia (P<0.001). Cardiovascular hospitalizations were also less frequent in the ablation arm.
Morning Report Questions
Q: What are the indications for catheter ablation for atrial fibrillation?
A: Catheter ablation is indicated to prevent recurrence of symptomatic atrial fibrillation in patients in whom medical therapy has been ineffective. Ablation is most effective in patients with paroxysmal atrial fibrillation and less effective in patients with persistent atrial fibrillation, heart failure, or valvular disease. The desire to stop oral anticoagulation alone is not a valid indication to refer a patient for atrial fibrillation ablation.
Q: What are potential complications of catheter ablation?
A: Cardiac tamponade due to perforation is a potentially life threatening complication occurring in approximately 1.3% of patients. Direct injury can also occur to the phrenic nerve as a result of ablation near the right superior pulmonary vein and superior vena cava. Such injury can cause diaphragmatic paralysis. Esophageal injury has been reported in approximately 10% of patients; atrioesophageal fistulae are rare (0.04%) but can be devastating and even lethal. Cerebrovascular thromboembolism has been reported to occur in up to 2% of patients. Pulmonary vein stenosis is a late complication of ablation caused by injury to the pulmonary vein musculature. The reported incidence varies from 0 to 10%.