Statins found to be protective against recurrence of atrial fibrillation after cardioversion

November 17, 2007 By Benjamin A. Olenchock, M.D. Ph.D. [mailto:bolenchock@partners.org]

 Vancouver, Canada

A new retrospective study has found that patients with atrial fibrillation who have sinus rhythm successfully restored were less likely to return to atrial fibrillation if they were prescribed a beta-blocker and a statin.

The investigators analyzed data from 625 participants in the CARAF I and CARAF II studies, both designed to observe the natural history of atrial fibrillation. Patients included in this retrospective analysis had documented atrial fibrillation and successful restoration of sinus rhythm either through pharmacologic or electrical means. Exclusion criteria included those who had recent heart surgery, patients who died within 1 year of discharge or withdrew from the study prior to the 1 year follow up. They compared patients who were discharged on statins to those with no statin therapy, and used a multivariate analysis to examine the relationship between statin use and recurrence of atrial fibrillation at one year. Confounders examined included age, enrollment period, study center, left atrial dimension, hypertension, diabetes, smoking status, and medication use.

Patients receiving statin therapy were on average 2 years older, they were more likely to have coronary artery disease, hyperlipidemia, hypertension, diabetes, kidney disease, and a smoking history. A higher percentage of patients taking statins were also prescribed beta-blockers (64% vs. 26%), calcium channel blockers (35% vs. 17%), ACE inhibitors (61% vs. 23%), and amiodarone (13% vs. 4%), while fewer were prescribed digoxin (14% vs. 33%). Fewer patients prescribed statins had a left atrial diastolic dimention less than 45 mm (69% vs. 81%). There were no differences in rate of success or method of cardioversion between groups, nor differences in incidence of mitral regurgitation.

Adjusting for the above confounders, the authors found that statin use was significantly associated with freedom from atrial fibrillation recurrence at 1 year (OR was 0.51; 95% CI 0.26-1.00). They found a significant interaction between beta-blocker use and statin therapy, so they separated the analyses based on beta-blocker use. Patients prescribed statins and beta-blockers had a significant reduction in recurrence of atrial fibrillation (OR 0.26; 95% CI 0.10-0.66) while patients prescribed statins but no beta-blocker had no benefit (OR 1.07, 95% CI 0.44-2.58).

This study adds support for the hypothesis that statins are beneficial in the management of atrial fibrillation. The authors note previous evidence which has suggested that atrial fibrillation is an inflammatory disease, and they propose that the immune-modulatory or vascular effects of statins might contribute to prevention of atrial fibrillation. The ARMYDA-3 study demonstrated a similar benefit to statins in preventing atrial fibrillation in coronary artery bypass patients. The interaction between statins and beta-blockers has not been previously reported. This trial adds to the growing literature supporting a role for statins in atrial fibrillation. Adjusting for such a large number of baseline differences in a study of 625 patients raises that possibility that confounding might influence the correlations they observe. Further testing of this hypothesis in a randomized way certainly appears to be worth-while.