Cardiovascular disease continues to reign as the leading health-related killer of Canadians. Survivors of myocardial infarction (MI) run a high risk of suffering a subsequent attack, thus necessitating a thorough investigation into potential therapies for secondary prevention.
While the antiplatelet action of Aspirin is currently favoured for the prevention of recurrent cardiac complications, the role of the coagulation cascade in causing thrombosis implicates oral anticoagulants, such as warfarin, as agents of potentially similar or superior therapeutic benefit. The results of the recent Warfarin, Aspirin, Reinfarction Study (WARIS II) suggest that the use of warfarin on its own, or in combination with Aspirin, may be more effective than Aspirin alone in reducing the incidence of reinfarction or thromboembolic stroke following an initial event of MI.
In this randomized, multicentre study, 3,630 MI survivors were assigned to treatment with either Aspirin (160mg daily), warfarin, or Aspirin (75mg daily) in combination with warfarin for a mean duration of four years. Primary outcome was a composite of death, nonfatal reinfarction or thromboembolic cerebral stroke.
The primary outcome was observed in 241 of 1,206 patients on the Aspirin-only regiment (20%), 203 of 1,216 patients receiving warfarin only (16.7%), and 181 of 1,208 patients receiving the combination treatment (15%). These results indicate the superiority of warfarin alone and in combination with Aspirin over Aspirin alone in the prevention of nonfatal reinfarction and nonfatal thromboembolic stroke. However, the data failed to show significant statistical difference in effect on mortality.
Despite the apparent benefits of warfarin in the WARIS II study, the two groups receiving warfarin experienced approximately four times as many major bleeding events as the Aspirin-only group. Given this observation, anticoagulant therapy may be considered in patients especially at risk for thromboembolic events or who demonstrate resistance to Aspirin treatment.
Source
- Hurlen M, Abdelnoor MPH, Smith P, et al. Warfarin, aspirin, or both after myocardial infarction. N Engl J Med 2002;347:969-74.
