Many patients with AF lack indication for aspirin use

In recently published findings, investigators with the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) registry have indicated that the benefit of adding aspirin therapy to oral anticoagulation (OAC) in patients with atrial fibrillation (AF) is unclear.

The registry enrolled 10,126 AF patients from 176 U.S. practices from June 2010 through August 2011. The study was limited to patients taking OAC (n=7,347).

Primary outcomes were 6-month bleeding, hospitalization, ischemic events, and mortality. Overall, 35% of AF patients on OAC also received aspirin (OAC+ASA). Patients receiving OAC+ASA were more frequently male and had more comorbid illness than those on OAC alone. Over one-third (39%) of OAC+ASA had no history of atherosclerotic disease, yet 17% had elevated ATRIA bleeding risk scores (≥5). Major bleeding and bleeding hospitalizations were significantly higher in those on OAC+ASA vs. those taking OAC alone. Rates of ischemic events were low.

The authors could find no explanation for the variation in aspirin use based on concomitant illnesses or bleeding risk. They suggested that, in light of the risks of OAC+ASA, physicians carefully assess the presence of an indication for combination therapy.

Source: Steinberg BA, Kim S, Piccini JP, et al. Use and associated risks of concomitant aspirin therapy with oral anticoagulation in patients with atrial fibrillation: Insights from the ORBIT-AF registry. Available at http://bit.ly/AFoacASA. Accessed July 27, 2013.

Dabigatran and MI risk questioned again

Dabigatran is in the news again. Two new analyses have raised questions once again about the risk of MI in dabigatran treatment. Both studies showed an increased risk of MI, ranging from 38% to 70%, compared to treatment with comparator drugs and placebo.

In the first study, researchers looked at all randomized, controlled studies, including data from the RE-LY trial, on the use of dabigatran in patients with venous thromboembolism and acute coronary syndrome, as well as data presented to the Food and Drug Administration. The review showed a statistically significant 48% increased risk of MI compared with controls.

The risk of MI with dabigatran also was highlighted at the recent 2013 Congress of the International Society on Thrombosis and Haemostasis meeting in Amsterdam, the Netherlands. A meta-analysis of 10 studies that included 23,839 dabigatran-treated patients showed an overall 32% increase in the risk of MI. Compared with warfarin, the risk of MI was increased 38%, while the risk of MI was 70% higher among dabigatran-treated patients compared with placebo-treated patients.

The data connected with this issue have been conflicting and consensus is lacking in the cardiology community. Other studies have found no increased risk, so the debate is likely to continue. The newer target-specific agents, rivaroxaban and apixaban, have not been reported to have an association with increased risk of coronary events and thus offer an alternative to dabigatran if physicians so choose.

Source: O’Riordan M. Two new analyses link dabigatran to MI. July 10, 2013. Available at http://bit.ly/MIdabig. Accessed July 27, 2013.

Aspirin shows benefit for extended VTE prophylaxis after total hip arthroplasty

The role of aspirin in thromboprophylaxis after total hip arthroplasty (THA) is controversial. A recent study compared aspirin with dalteparin for prevention of venous thromboembolism after hip replacement surgery. The study included 778 patients who had elective unilateral THA between 2007 and 2010.

After an initial 10 days of dalteparin prophylaxis following elective THA, patients were randomly assigned to receive 28 days of dalteparin or aspirin. The primary efficacy outcome was symptomatic VTE confirmed by objective testing and bleeding.

Five of 398 patients (1.3%) assigned to dalteparin and 1 of 380 (0.3%) assigned to aspirin developed VTE.  Aspirin was noninferior but not superior to dalteparin. Clinically significant bleeding occurred in 5 patients (1.3%) receiving dalteparin and 2 (0.5%) receiving aspirin.

The authors concluded that considering the low cost and greater convenience, aspirin may be considered a reasonable alternative for extended thromboprophylaxis after THA.

Source: Anderson DR, Dunbar MJ, Bohm ER et al. Aspirin versus low-molecular-weight heparin for extended venous thromboembolism prophylaxis after total hip arthroplasty: A randomized trial. Ann Intern Med. 2013;158(11):800–806.