Patients with atrial fibrillation undergoing vitamin K antagonist monotherapy have a lower risk for first-time MI and stroke than those undergoing acetylsalicylic acid monotherapy, according to findings published in the Journal of the American College of Cardiology.
Additionally, the study showed that acetylsalicylic acid monotherapy and vitamin K antagonist combination therapy was not associated with a lower risk for MI but was linked to increased bleeding risk.
“For the prevention of CAD, acetylsalicylic acid therapy is standard of care, but in patients with AF, anticoagulation with vitamin K antagonists has been shown to be more beneficial than [acetylsalicylic acid] in preventing ischemic stroke,” Christina J.Y. Lee, MD, from the department of health science and technology at Aalborg University and the department of clinical epidemiology and cardiology, Aalborg University Hospital in Aalborg, Denmark, and colleagues wrote. “Most of the previous studies of MI risk in patients with AF have investigated the risk of recurrent MI, whereas data for the effectiveness of [acetylsalicylic acid] and [vitamin K antagonists] in primary prevention of MI is lacking.”
Researchers conducted a nationwide study with 71,959 patients to estimate the risk for stroke and bleeding according to antithrombotic treatment in patients with AF who experienced first-time MI.
Danish nationwide administrative registries were used to identify patients with first-time AF who were diagnosed between 1997 and 2012 who had no history of CAD.
Patients were put into time-varying exposure cohorts based on antithrombotic treatment, and outcomes for RR were estimated by Poisson regression models.
Fifty-two percent (n = 37,539) of patients were treated with vitamin K antagonist monotherapy, 35% (n = 25,458) with acetylsalicylic acid monotherapy and 13% (n = 8,962) with dual therapy at baseline.
During the study period, first-time MI occurred in 3% of patients (n = 2,275).
The associated risk for MI was significantly higher for acetylsalicylic acid (incidence rate ratio [IRR] = 1.54; 95% CI, 1.4-1.68) and dual therapy (IRR = 1.22; 95% CI, 1.06-1.4) compared with the vitamin K antagonist-treated cohort.
There was a significantly increased risk for bleeding for patients undergoing dual therapy (IRR = 1.93; 95% CI, 1.81-2.07).
Compared with the vitamin K antagonist therapy group, there was a significantly higher risk for stroke in the acetylsalicylic acid group (IRR = 2; 95% CI, 1.88-2.12) and the dual therapy group (IRR = 1.3; 95% CI, 1.18-1.43).
In a related editorial, Jonathan L. Halperin, MD, from the Cardiovascular Institute at the Icahn School of Medicine at Mount Sinai, wrote that the results of the study should prompt clinicians to rethink the approach to antithrombotic therapy for patients with AF; however, further study is needed to answer important questions.
“The work of Lee et al adds important information that can be applied clinically in managing the risk of both stroke and MI in patients with AF, and should reduce the tendency to add aspirin to an anticoagulant for those without known coronary disease and perhaps even for those with stable ischemic heart disease,” Halpern wrote. “Important questions remain about optimal antithrombotic strategies for patients in more acute situations, such as those who have recently sustained MI or undergone revascularization, and ongoing trials are likely to shed more light on these as well.” – by Dave Quaile
: The study was supported by Bristol-Myers Squibb and Pfizer. Halperin and Lee report no relevant financial disclosures. See the study for all other researchers’ relevant financial disclosures.