[Secondary prevention after acute myocardial infarction: aspirin, warfarin or both?]

In patients suffering from acute myocardial infarction (AMI), new cardiovascular events can be prevented by aspirin or warfarin or a combination of both. Results from studies examining this issue have been published in recent years. We have evaluated the study results together with other factors that are decisive for implementation of the findings in clinical practice.

The following four studies were evaluated: the Coumadin Aspirin Reinfarction Study (CARS); the Combination Hemotherapy and Mortality Prevention (CHAMP) Study; the Warfarin, Aspirin Reinfarction Study (WARIS)-II; the Antithrombotics in the Secondary Prevention of Events in Coronary Thrombosis (ASPECT)-2 Study.

The studies had somewhat different design, particularly with regard to the intensity of anticoagulation. CARS and CHAMPS did not show any benefit with combined therapy. WARIS II concluded that warfarin had better preventive effect than aspirin; so had the two drugs in combination. ASPECT-2 suggested a benefit with the combined treatment (coumadin and aspirin) but had limited study power. In all studies, bleedings occurred most frequently in groups of patients treated with anticoagulants. In clinical practice, relatively few AMI patients would be candidates for warfarin treatment, as this drug is not recommended for the oldest patients. Adverse event profile, guidance of treatment and relation to invasive treatment procedures are factors in favour of aspirin.

Aspirin should be the antithrombotic agent of choice in secondary prevention after acute myocardial infarction. Warfarin could be used when there are specific additional indications. Combining these two agents is not recommended as a routine treatment.