Research Activities, May 2013
Aspirin/warfarin combination reduces the risk of blood clots after aortic valve replacement surgery
Patient Safety and Quality
Following surgery to replace an aortic valve, patients have a modest risk of developing a thromboembolism (blood clot) within 90 days. To prevent blood clots, they are typically given a blood thinner, such as aspirin, warfarin, or both. While warfarin plus aspirin conferred a better reduced risk of blood clots than aspirin alone, there was an increased risk for bleeding, according to a new study.
The researchers analyzed data from a cardiac surgery database on 25,656 patients 65 years of age and older who received an aortic valve at 787 hospitals. Different anticoagulant strategies were identified, along with the 3-month incidence of death/readmission for a blood clot or bleeding event. Blood clots and death were rare in the first 3 months after surgery. Aspirin was the most popular anticoagulant used, with nearly half (49 percent) of patients receiving it compared to 23 percent who received warfarin plus aspirin and 12 percent who received warfarin alone. All three strategies had a low 3-month incidence of death: aspirin 3 percent, aspirin plus warfarin 3.1 percent, and warfarin 4.0 percent. However, adding warfarin to aspirin resulted in a 20 percent relative risk reduction for mortality after 90 days.
The 3-month incidence of blood clots was also low. Aspirin and warfarin combined resulted in a 48 percent relative reduction in the risk of both of these problems. This reduction was particularly true for patients age 75 years and older. The incidence of bleeding requiring readmission was low overall (1.6 percent). However, the 3-month incidence of rehospitalization for a bleeding event was higher among patients receiving warfarin and aspirin at discharge. The researchers recommend an aspirin-only strategy for patients at high risk for bleeding. Those with a low-risk for bleeding can benefit from receiving warfarin plus aspirin. The study was supported by AHRQ (Contract No. 290-05-0032).
See "Early anticoagulation of bioprosthetic aortic valves in older patients," by J. Matthew Brennan, M.D., M.P.H., Fred H. Edwards, M.D., Yue Zhao, Ph.D., and others in the September 11, 2012 Journal of the American College of Cardiology 60(11), pp. 971-977.