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Direct oral anticoagulants may increase risk for acute MI in patients with AF
Patients with atrial fibrillation had double the risk for acute MI when assigned direct oral anticoagulants compared with those assigned aspirin or vitamin K antagonists, according to findings published in the British Journal of Clinical Pharmacology.
“As regards to the possible pharmacological mechanism, it seems possible that [vitamin K antagonists] have an effect on the pathological conditions affecting angina pectoris and, as a consequence, also affect [acute] MI and have a protective effect,” Leo M. Stolk, MSc, PharmD, PhD, pharmacist, clinical pharmacologist and toxicologist at Maastricht University Medical Centre in the Netherlands, and colleagues wrote. “[Direct oral anticoagulants] (at least rivaroxaban) and also aspirin, therefore, might protect to a lesser extent against [acute] MI than [vitamin K antagonists].”
Current and past prescriptions
Researchers analyzed data from 30,146 patients from the United Kingdom aged 18 years or older with AF between March 2008 and June 2014. The patients were prescribed direct oral anticoagulants (n = 1,266; mean age, 72 years; 45% women), vitamin K antagonists (n = 13,098; mean age, 72 years; 46% women), low-dose aspirin (< 325 mg; n = 15,400; mean age, 73 years; 50% women) or a combination of treatments (n = 382; mean age, 73 years; 39% women). Direct oral anticoagulants prescribed were either rivaroxaban (Xarelto, Janssen Pharmaceuticals; 71.6%) or dabigatran (Pradaxa, Boehringer Ingelheim; 28.4%).
“This distribution of antithrombotics use is not in line with the guidances for use of antithrombotics for stroke prevention in AF,” Stolk and colleagues wrote.
Patients were excluded if they had prior acute MI. Other variables that were considered in the study included the presence of MI risk factors, sex, smoking status, BMI, alcohol use and risk for stroke using the CHA2DS2–VASc score. The primary outcome was acute MI, either STEMI or non-STEMI.
Follow-up was performed after approximately 1 year for patients who were prescribed direct oral anticoagulants vs. approximately 3 years for those assigned vitamin K antagonists or low-dose aspirin.
Among the cohort, 25% were defined as low risk for stroke (CHA2DS2-VASc score 1), 25% to 30% were high risk (CHA2DS2-VASc score 4) and the remainder were medium risk (CHA2DS2-VASc score > 1 to < 4).
Increased acute MI risk
Patients currently prescribed direct oral anticoagulants had double the risk for acute MI compared with those currently taking vitamin K antagonists (adjusted HR = 2.11; 95% CI, 1.08-4.12). Current users of low-dose aspirin also had higher acute MI risk vs. current use of vitamin K antagonists (adjusted HR = 1.91; 95% CI, 1.45-2.21). Patients who were previously prescribed low-dose aspirin had an increased risk for acute MI compared with those currently taking vitamin K antagonists.
Among those currently prescribed low-dose aspirin, both men (adjusted HR = 1.6; 95% CI, 1.1-2.33) and women (adjusted HR = 2.33; 95% CI, 1.55-3.5) had increased risk for acute MI.
Patients with high risk for stroke currently taking low-dose aspirin also had an increased risk for acute MI (adjusted HR = 2.21; 95% CI, 1.37-3.55). Those with medium risk for stroke experienced increased risk for acute MI when they were currently taking direct oral anticoagulants (adjusted HR = 2.67; 95% CI, 1.11-6.4) or low-dose aspirin (adjusted HR = 1.82; 95% CI, 1.23-2.68).
“We identified a similar increased risk of [acute] MI among current and past aspirin users in comparison with [vitamin K antagonists],” Stolk and colleagues wrote. “This is an interesting finding, as, to our knowledge, there are no earlier reports of increased [acute MI] among AF patients receiving aspirin.” – by Darlene Dobkowski
Disclosure: Stolk reports no relevant financial disclosures. One researcher reports receiving grants from EU Innovative Medicines and TI Pharma.
Perspective
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This study does not add a whole lot to the knowledge base. There has been some controversy regarding whether or not the direct oral anticoagulants increase the risk for MI or not. Some studies report an association while others do not. This is another observational study that reports there is a correlation. We still don’t have any strong evidence that there is a real risk yet.
The clinical implication of this study is that direct oral anticoagulants have correlated with an increased risk for MI in some, but not all, studies. Thus, in patients at high risk for MI, perhaps added consideration should be made for the findings in observational studies such as this. However, it is critically important to remember that correlation does not prove causation.
We need a well-designed study to answer the question once and for all: Do direct oral anticoagulants increase the risk for MI? As of right now, we really don’t know.