AF implicated in sudden cardiac death

By Caroline Price, Senior medwireNews Reporter

People who develop atrial fibrillation (AF) are at more than twice the usual risk for sudden cardiac death (SCD), reveal US study findings published in JAMA Internal Medicine.

A meta-analysis of the Atherosclerosis Risk in Communities (ARIC) Study and the Cardiovascular Health Study (CHS) shows that AF was associated with a 2.5-fold increased risk for SCD (defined as death from a sudden, pulseless condition presumed to be due to ventricular arrhythmia) in the general population.

Authors Lin Chen (University of Minnesota, Minneapolis) and team say that, if confirmed, the research "adds to our evolving understanding that AF is not a benign condition."

"Not only does AF predispose to stroke, heart failure, and death, but the arrhythmia per se may increase the risk of death from ventricular tachyarrhythmias," they add.

The team's analysis was based on data for 15,439 participants (aged 45-64 years at baseline) in the ARIC Study from 1987-1989 through December 31, 2001, and for 5479 participants (aged ≥65 years at baseline) in the CHS from 1989-1990 (n=4857) or 1992-1993 (n=622) through December 31, 2006.

The median follow-up was 13.1 years for both studies. Crude incidence rates of SCD in the ARIC Study were 2.89 per 1000 person-years among people who developed AF, compared with 1.30 per 1000 person-years among those who did not; in the CHS, the corresponding rates were 12.00 versus 3.82 per 1000 person-years.

Hazard ratios for SCD and non-SCD (defined as death from coronary heart disease [CHD] not meeting SCD criteria) in meta-analysis of the two studies were 2.47 and 2.98, respectively, after adjusting for age, gender, and race, as well as a raft of risk factors and other potential confounders including body mass index, smoking, diabetes, CHD, left ventricular hypertrophy, and antiarrhythmic drug use.

In a separate analysis of the ARIC study, the researchers found that, although somewhat attenuated, the risk for SCD remained elevated after updating for shared risk factors for non-SCD, such as heart failure and CHD, over the course of follow up. "This observation suggests that the association between AF and SCD is only partially explained by the measured shared risk factors," the authors write.

However, Kyndaron Reinier and Sumeet Chugh (Cedars-Sinai Medical Center, Los Angeles, California) caution in a related editorial:"Until such time that a causal association is confirmed between AF and SCD, it is difficult for these results to influence clinical management of AF or SCD.

"Whether it is control of the heart rate, control of the rhythm, or stroke prophylaxis, present management of the patient with AF should be governed largely by current evidence-based guidelines aimed at reduction of AF symptoms and hospitalization and the need to minimize risk of future cerebrovascular accidents."

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