A large, retrospective study suggests patients with atrial fibrillation may have a lower risk of acute myocardial infarction (AMI) if they receive vitamin K antagonists (VKAs) rather than other anticoagulants.
Investigators found that patients taking direct oral anticoagulants (DOACs, rivaroxaban or dabigatran) had more than twice the AMI risk of patients taking VKAs.
And the AMI risk for patients taking low-dose aspirin was nearly double that of those taking VKAs.
Leo M. Stolk, PharmD, PhD, of Maastricht University Medical Centre in the Netherlands, and his colleagues reported these results in the British Journal of Clinical Pharmacology.
The investigators analyzed data on 30,146 adults with atrial fibrillation who were new users of DOACs (n=1266), VKAs (n=13,098), low-dose aspirin (n=15,400), or mixed anticoagulants (n=382). Most DOAC users were taking rivaroxaban (71.6%), but some were taking dabigatran (28.4%).
The mean follow-up was 0.95 years for DOAC users, 2.72 years for VKA users, 2.86 years for low-dose aspirin users, and 2.99 years for mixed medication users.
The investigators estimated the hazard ratio (HR) of AMI for users of DOACs, aspirin, or mixed medications versus VKAs. The team adjusted their analysis for age, sex, lifestyle, risk factors, comorbidities, and use of other medications.
Compared to VKA users, the risk of AMI was significantly higher for DOAC users (HR=2.11; 95% CI 1.08 – 4.12, P<0.05) and aspirin users (HR=1.91; 95% CI 1.45-2.51, P<0.05). The risk was not significantly higher for mixed medication users (HR=1.69; 95% CI 0.69, 4.16).
When patients were stratified by gender, there was a significantly increased risk of AMI for aspirin users who were male (HR=1.60; 95% CI 1.10, 2.33, P<0.05) or female (HR=2.33; 95% CI 1.55, 3.50, P<0.05), when compared to VKA users. Neither DOACs nor mixed medications were associated with a significantly increased risk of AMI in this analysis.
The investigators also stratified patients according to their CHA2DS2-VASc score at the index date.
Among patients with a high score (≥4), there was a significantly increased risk of AMI for aspirin users compared to VKA users (HR=2.21; 95% CI 1.37,3.55, P<0.05).
Among patients with a medium score (>1 and <4), the risk of AMI was significantly higher for DOAC users (HR=2.67; 95% CI 1.11, 6.40, P<0.05) and aspirin users (HR=1.82; 95% CI 1.23, 2.68, P<0.05) compared to VKA users.
The investigators said this study suggests VKAs probably have greater beneficial effects on AMI than DOACs, and ongoing research is needed as the use of DOACs increases.
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