Dabigatran has been associated with greater risk of
myocardial infarction (MI) than
warfarin. It is unknown whether the increased risk is unique to
dabigatran, an adverse effect shared by other oral
direct thrombin inhibitors (DTIs), or the result of a protective effect of
warfarin against MI. To address these questions, we systematically searched MEDLINE and performed a meta-analysis on randomized trials that compared oral DTIs with
warfarin for any indication with end point of MIs after randomization. We furthermore performed a secondary meta-analysis on
atrial fibrillation stroke prevention trials with alternative
anticoagulants compared with
warfarin with end point of MIs after randomization. A total of 11 trials (39,357 patients) that compared
warfarin to DTIs (
dabigatran,
ximelagatran, and
AZD0837) were identified. In these trials, patients treated with oral DTIs were more likely to experience an MI than their counterparts treated with
warfarin (285 of 23,333 vs 133 of 16,024, odds ratio 1.35, 95% confidence interval 1.10 to 1.66, p = 0.005). For secondary analysis, 8 studies (69,615 patients) were identified that compared
warfarin with alternative
anticoagulant including
factor Xa inhibitors, DTIs,
aspirin, and
clopidogrel. There was no significant advantage in the rate of MIs with the use of
warfarin versus comparators (odds ratio 1.06, 95% confidence interval 0.85 to 1.34, p = 0.59). In conclusion, our data suggest that oral DTIs were associated with increased risk of MI. This increased risk appears to be a class effect of these agents, not a specific phenomenon unique to
dabigatran or protective effect of
warfarin. These findings support the need for enhanced postmarket surveillance of oral DTIs and other novel agents.