Atrial Fibrillation and the Risk of Myocardial Infarction
Study Question:
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 (CHD) at baseline was enrolled from the REGARDS (Reasons for Geographic and Racial Differences in Stroke) cohort between 2003 and 2007, with follow-up through December 2009. The main outcome measures were expert-adjudicated total MI events (fatal and nonfatal).
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 approximately two-fold 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 study reported that AF was significantly associated with increased risk of incident MI independent of common CHD risk factors and potential confounders. Furthermore, the risk of MI associated with AF differed by sex and race, with women and blacks having a significantly stronger association between AF and MI than men and whites. 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 is also associated with increased risk of MI. Future studies will need to explore if more aggressive or long-term arrhythmia monitoring is useful after MI and, in turn, if standard anticoagulation for AF is sufficient to address the heightened MI risk among selected populations with AF.
