Bidirectional Association Between Atrial Fibrillation and Myocardial Infarction, and Relation to Mortality in the Framingham Heart Study

Background Individuals with both atrial fibrillation (AF) and myocardial infarction (MI) have higher mortality compared with individuals with only 1 condition. Whether mortality differs according to the temporal order of AF and MI is unclear. Methods and Results We included participants from the FHS (Framingham Heart Study) from 1960 and onwards. We assessed the hazard ratio (HR) of new‐onset AF and MI, and mortality according to MI and AF status (prevalent and interim) using multivariable‐adjusted Cox proportional hazards models. Interim diseases were modeled as time‐varying variables. For the analysis of new‐onset AF, 10 923 participants (55% women; mean±SD age, 54±8 years) were included. For new‐onset MI, 10 804 participants (55% women; mean±SD age, 54±8 years) were included. Compared with no MI, the hazard of new‐onset AF was higher in participants with prevalent (HR, 1.60 [95% CI, 1.32–1.94]) and interim MI (HR, 3.96 [95% CI, 3.18–4.91]). Both ST‐segment–elevation MI and non–ST‐segment–elevation MI were associated with new‐onset AF. Interim AF, not prevalent AF, was associated with higher hazard rate of new‐onset MI (HR, 2.21 [95% CI, 1.67–2.92]). Interim AF was associated with both ST‐segment–elevation MI and non–ST‐segment–elevation MI. Mortality was significantly greater among participants with AF and MI compared with participants with 1 of the 2, regardless of temporal order. Conclusions We report a bidirectional association between AF and MI, which was observed for both non–ST‐segment–elevation MI and ST‐segment–elevation MI. Participants with both AF and MI had considerably higher mortality compared with participants with only 1 of the 2 conditions, regardless of order.