Patients with high stroke risk may not be getting preventive medication
Patients with atrial fibrillation (AF) who have the highest stroke risk may not be getting preventive oral anticoagulants (OACs), according to a recent US study.
Using the CHADS2 and CHA2DS2-VASc scores (clinical risk scoring systems) to calculate stroke risk, study authors found that OAC prescription (compared to aspirin-only prescription) increased with every 1-point increase in CHADS2 (adjusted odds ratio [aOR], 1.158, 95 percent CI, 1.144-1.172; p<0.001) and CHA2DS2-VASc scores (aOR, 1.163, 95 percent CI, 1.157-1.169; p<0.001). [JAMA Cardiol 2016;doi:10.1001/jamacardio.2015.0374]
However, AF patients with a higher stroke risk (CHADS2 score >3 and CHA2DS2-VASc score >4) were often not prescribed OACs, with prescription not exceeding 50 percent in this group.
“Our findings have important implications for patients with AF, particularly because annual stroke risk increases with the number of stroke risk factors measured by the CHADS2 score and the CHA2DS2-VASc score,” said the study authors.
Researchers assessed 429,417 AF patients who were enrolled in the American College of Cardiology’s National Cardiovascular Data Registry (NCDR) Practice Innovation and Clinical Excellence (PINNACLE) Registry between 2008 and 2012 who were on OAC (n=192,600; 44.9 percent), aspirin only (n=111,134; 25.9 percent), aspirin and a thienopyridine (23,454; 5.5 percent), or no antithrombotic therapy (n=102,229; 23.8 percent). As OACs such as rivaroxaban and dabigatran were only approved towards the end of the study period, warfarin was the anticoagulant prescribed in most subjects.
“Future studies will examine if the use of direct OACs increases the rate or prevalence of prescription of OACs, especially in higher risk subgroups,” said Dr. Jonathan Hsu, Assistant Clinical Professor of Medicine, Division of Cardiovascular Medicine, University of California San Diego, California, US, and lead author of the study.
According to the authors, one possible reason for the lower OAC prescription in higher risk patients is the similarity in risk factors for stroke and bleeding complications in AF patients.
“Health care professionals may be more reluctant to prescribe anticoagulation in these sicker patients due to concerns regarding bleeding risk,” they said.
“The lack of prescription of an OAC by cardiovascular specialists in more than 50 percent of patients at the highest thromboembolic risk categories suggests that US cardiovascular health care professionals, who should be well-versed in guideline-based therapy for AF, may not fully appreciate the continued increased risk of thromboembolism with accumulation of additional stroke risk factors,” said the authors.
Previous studies have demonstrated the underprescribing of OACs in AF patients at high risk of stroke with one study showing that 38 percent of AF patients with a CHADS2 score ≥2 did not receive OACs while 42.5 percent of those with lower risk (CHADS2 score of 0) were prescribed therapy. [PLoS One 2013;doi:10.1371/journal.pone.0063479]