CHICAGO, IL – An analysis of a Canadian registry of patients with atrial fibrillation reveals that one in five treated with oral anticoagulants were also treated with antiplatelet medication. Investigators point out that a "substantial proportion" of patients treated with the dual therapy did not have a compelling reason for adding the antiplatelet, however.
"Although 60% of patients did have some indication for aspirin, such as coronary or peripheral arterial disease, or even diabetes, which you could argue is no longer an indication for aspirin, 40% of the atrial-fibrillation patients had absolutely no reason for being on aspirin," lead investigator Dr Milan Gupta (McMaster University, Hamilton, ON) told heartwire.
The analysis of the Stroke Prevention and Rhythm Intervention in Atrial Fibrillation (SPRINT-AF) registry was presented last week at the American Heart Association (AHA) 2014 Scientific Sessions. The registry was designed to determine how physicians assess stroke risk in adults with atrial fibrillation and make their decisions about anticoagulation. The study was a retrospective, cross-sectional analysis of 1091 Canadian practices of cardiologists, internists, and family physicians.
In total, 936 patients with nonvalvular AF were enrolled in phase 1 of the SPRINT-AF registry, and of those, 782 (87.7%) were treated with oral anticoagulants. Of treated patients, 53.2% received warfarin and 46.8% received one of the newer oral anticoagulants.
Among the group who received oral anticoagulation, 18.2% were also treated with an antiplatelet. Breaking it down by oral anticoagulation type, 21.9% of warfarin-treated patients received antiplatelet therapy compared with 14.2% of those treated with a novel oral anticoagulant. As noted, 60% of patients in the registry who received antiplatelet therapy had a clinical indication for treatment, such as a history of coronary, cerebrovascular, or peripheral arterial disease. The remaining 40% did not have a valid indication for aspirin.
The MI Patient Who Develops AF
To heartwire, Gupta said the challenge is that there are many indications, soft and hard, for antiplatelet therapy in patients with and without atrial fibrillation. For patients with established vascular disease, there is no doubt that there is an important role for antiplatelet therapy, he said. In these patients, such as a stable patient with a previous MI or stroke, the big unknown is how to treat them if they develop atrial fibrillation and require oral anticoagulation. "The question is do we still need the aspirin now that we've started an anticoagulant?" asked Gupta.
He explained that clinical studies, mostly European trials dating back to the 1980s, that compared warfarin and aspirin in patients with coronary disease or prior MI (but without atrial fibrillation) showed warfarin to be at least as cardioprotective as aspirin. Theoretically, if a patient with coronary disease and atrial fibrillation is treated with warfarin, aspirin might not be needed if warfarin protects against stroke and lowers cardiovascular risk.
"What we do know, beyond a shadow of a doubt, is that when you combine low-dose aspirin with other anticoagulants, the risk of major or life-threatening bleeding rises substantially, often at least twofold. Aspirin is not a benign therapy," said Gupta. For physicians, as well as patients, he believes there is an underappreciated risk of bleeding with low-dose aspirin.
Gupta said that there is a need for a clinical trial in patients with atrial fibrillation and coronary artery disease, one that would randomize individuals to treatment with oral anticoagulation alone or anticoagulation and antiplatelet therapy. Given the current lack of evidence, Gupta said physicians are likely reluctant to withdraw an antiplatelet without knowing if the anticoagulant alone is good enough.
"The heartening thing in our registry is that aspirin use was only at about 18%," said Gupta. "If we look at some of the big atrial-fibrillation trials that have been done recently, the use of antiplatelet therapy was substantially higher, in the 30% to 40% range."
In the SPRINT-AF registry, patients treated with antiplatelet therapy had a higher burden of vascular disease compared with those who received oral anticoagulants alone. In a multivariable regression analysis, a history of coronary artery disease was associated with a significantly greater likelihood of receiving anticoagulation plus antiplatelet therapy. Men were also more likely than women to receive antiplatelet therapy.
"From a clinical-practice standpoint, this makes sense," said Gupta. "We know that if patients have coronary disease, one of the first things we do is place them on aspirin. Men are more likely to have coronary disease than women and generally have more risk factors than women. Studies have shown that men with multiple risk factors will receive aspirin for primary prevention."
Heartwire from Medscape © 2014 Medscape, LLC
Cite this: Many AF Patients Needlessly Treated With Antiplatelets on Top of OACs: SPRINT-AF Registry - Medscape - Nov 27, 2014.