Comparative Effectiveness Analysis of Antithrombotics in Older Patients with Post-ACS Atrial Fibrillation

September/October 2011 Volume 4, Number 6

Chicago, IL—Similar outcomes were found with 2 different antithrombotic strategies in a comparative effec - tiveness study in patients with atrial fibrillation (AF) after a non–ST-segment elevation myocardial infarction (NSTEMI). But a trend toward more bleeding with intensified treatment was found.

Emil L. Fosbøl, MD, PhD, Fellow, Department of Cardiology, Copenhagen University Hospital Gentofte, Hellerup, Denmark, explained there are no robust data to support the recommendation of the American College of Cardiology (ACC)/American Heart Association guidelines to add warfarin (Coumadin) to dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. The study was presented at the 2012 ACC meeting.

The evidence from ongoing clini - cal trials with rivaroxaban (Xarelto), dabigatran (Pradaxa), and apixaban (Eliquis) is awaited to provide clearer answers about the best treatment strategy. The prevalence of coexisting AF and NSTEMI is 25% in this patient population, yet “we do not know how to treat these patients, and whether dual antiplatelet therapy is sufficient to prevent future events,” said Dr Fosbøl.

The investigators linked observational data from the CRUSADE Registry with Medicare data to look at longitudinal outcomes. The CRUSADE Registry—a national quality improvement initiative to promote evidencebased treatment of hospitalized patients with NSTEMI acute coronary syndromes (ACS)—included data from 200,000 patients from 500 hospitals across the United States from 2001 to 2006.

In this comparative effectiveness analysis, the registry of patients with AF who received coronary stenting and were discharged on either DAPT (N = 1200) or DAPT plus warfarin (N = 448) were included. The in-hospital major bleeding rate was 16.3% in the DAPT group and 13.5% in the DAPT plus warfarin group, and the inhospital stroke rate was similar at 0.4% and 0.5%, respectively.

The median age was 78 and 77 years, respectively. Although this analysis included patients aged ≥65 years only, based on Medicare data, it reflects the typical population with AF. “This is the patient most commonly seen,” said Dr Fosbøl, “but physicians are hesitant about antithrombotic treatment, because of their age and frailty.”

At 1 year after discharge, there was a similarly high rate of the composite end point of myocardial infarction (MI), ischemic stroke, and death, at 20.6% in the DAPT group and 19.4% in the DAPT plus warfarin group. These rates remained similar after adjusting for confounders and clinical characteristics.

The incidences of bleeding requiring hospitalization at 1 year were 11.9% and 14.4%, respectively. The difference between the groups did not reach significance, but there was a trend toward more bleeding with DAPT plus warfarin.

“Their predictive risk for ischemic events and bleeding was similar, and we feel fairly confident that the 2 groups are similar,” in this analysis, said Dr Fosbøl. The median scores for CHADS2 (approximately 2.0) and Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA; nearly 6) were similar in the DAPT and DAPT plus warfarin patients. CHADS2 predicts the risk of a thromboembolic event, and ATRIA, a fairly new score, assesses longitudinal bleeding. The ATRIA score includes previous hospitalization for bleeding, sex, and age, among other factors, and ranges from 0 to 10. The strongest predictor for long-term bleeding is a previous bleeding incident.

The use of drug-eluting stents (DES) was similar in both groups at 80%. The type of stent did not influence the bleeding risk in the 2 groups, but more MIs, strokes, and deaths were reported in the patients with a DES compared with a bare-metal stent.

Although efficacy was similar with the 2 treatment strategies, the trend toward higher rates of bleeding with DAPT plus warfarin is a concern. However, Dr Fosbøl noted that clinical trial data are needed to determine the best treatment strategies for these patients.

For now, physicians must individualize the treatment to the patient and include the patient in the discussion to select the treatment strategy.

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