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Atrial Fibrillation and Types of Myocardial Infarction | Journal Scan
Study Questions:
What is the association between atrial fibrillation (AF) and myocardial infarction (MI), overall and by type, in the ARIC (Atherosclerosis Risk in Communities) study?
Methods:
This was a post hoc analysis of the ARIC study, a community-based population study designed to investigate the causes of atherosclerosis and its clinical outcomes. The analysis included 14,462 participants. AF cases were identified from study visit ECGs and by review of hospital discharge records. MIs were identified by contacting participants annually, identifying hospitalizations during the previous year, and by review of discharge records. Incident MI was the first occurrence of a fatal or nonfatal MI in a participant without evidence of prior MI. MI events were classified as ST-segment elevation MI (STEMI) or non-STEMI (NSTEMI) by an independent adjudication committee.
Results:
Over a median follow-up of 21.6 years, 1,374 MI events occurred. In an adjusted analysis and with AF as a time-varying variable, there was a significant association between AF and risk of MI (hazard ratio [HR], 1.63; 95% confidence interval [CI], 1.32-2.02). However, AF was associated with NSTEMI (HR, 1.80; 95% CI, 1.39-2.31), but not STEMI (HR, 0.49; 95% CI, 0.18-1.34). The association between AF and risk of MI was stronger in women than in men (interaction p < 0.001); the risk of MI associated with AF was stronger in blacks than in whites, but the interaction did not reach statistical significance.
Conclusions:
The association between AF and MI is limited to NSTEMI, after adjustment for cardiovascular and other risk factors, and the association is stronger in women than in men.
Perspective:
This is a valuable study that clarifies the association between AF and MI. The authors demonstrate that the association is limited to NSTEMI (i.e., not STEMI). Certainly, these findings suggest that direct coronary thromboembolization (as may lead to totally occlusive thrombus) is less likely the mechanism through which AF leads to MI; demand infarction may be a more plausible mechanism. Furthermore, the authors contribute to the growing evidence of gender and racial differences in cardiovascular disease outcomes; indeed the association between AF and MI was stronger in women than in men. Such observations may lend themselves to efforts to increase detection and treatment of AF in particular populations.
Keywords: Acute Coronary Syndrome, Atherosclerosis, Atrial Fibrillation, Electrocardiography, Epidemiology, Follow-Up Studies, Hospitalization, Infarction, Myocardial Infarction, Risk, Risk Factors, Thrombosis
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