Atrial Fibrillation and the Risk of Myocardial Infarction

Study Questions:

What is the risk of incident myocardial infarction (MI) associated with atrial fibrillation (AF)?

Methods:

A prospective cohort of 23,928 participants residing in the continental United States and without coronary heart disease at baseline were enrolled from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort between 2003 and 2007, with follow-up through December 2009. The main outcome measures were expert-adjudicated total MI events (fatal and nonfatal). Cox proportional hazards analysis was used to examine the association between baseline AF with incident MI in a series of models with incremental adjustments.

Results:

Over 6.9 years of follow-up (median 4.5 years), 648 incident MI events occurred. In a sociodemographic-adjusted model, AF was associated with about twofold increased risk of MI (hazard ratio [HR], 1.96; 95% confidence interval [CI], 1.52-2.52). This association remained significant (HR, 1.70; 95% CI, 1.26-2.30) after further adjustment for total cholesterol, high-density lipoprotein cholesterol, smoking status, systolic blood pressure, blood pressure–lowering drugs, body mass index, diabetes, warfarin use, aspirin use, statin use, history of stroke and vascular disease, estimated glomerular filtration rate, albumin-to-creatinine ratio, and C-reactive protein level. In subgroup analysis, the risk of MI associated with AF was significantly higher in women (HR, 2.16; 95% CI, 1.41-3.31) than in men (HR, 1.39; 95% CI, 0.91-2.10) and in blacks (HR, 2.53; 95% CI, 1.67-3.86) than in whites (HR, 1.26; 95% CI, 0.83-1.93); for interactions, p = 0.03 and p = 0.02, respectively. On the other hand, there were no significant differences in the risk of MI associated with AF in older (≥75 years) versus younger (<75 years) participants (HR, 2.00; 95% CI, 1.16-3.35 and HR, 1.60; 95% CI, 1.11-2.30, respectively); for interaction, p = 0.44.

Conclusions:

The authors concluded that AF is independently associated with an increased risk of incident MI, especially in women and blacks.

Perspective:

This analysis suggests that AF was significantly associated with increased risk of incident MI independent of common coronary heart disease risk factors and potential confounders. This risk was stronger in women and blacks than in men and whites. The excess risk of MI, coupled with the tendency to undertreat AF, may further magnify the risk of poor outcomes in these two groups. These findings add to the growing concerns of the seriousness of AF as a public health burden; in addition to being a well-known risk factor for stroke, it appears to be also associated with increased risk of MI.

Clinical Topics: Anticoagulation Management, Diabetes and Cardiometabolic Disease, Dyslipidemia, Lipid Metabolism, Nonstatins

Keywords: Cholesterol, Myocardial Infarction, Stroke, C-Reactive Protein, Body Mass Index, Warfarin, Cholesterol, HDL


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