 Anticoagulation with heparin is indicated in several situations, such as acute coronary disease in combination with antiplatelet therapy for the prevention and treatment of venous thromboembolism and situations with high risk of thromboembolism. Recently, the latest trials on anticoagulation for stroke prevention on atrial fibrillation have shown an increased risk for acute mycardial infarction on patients submitted to new oral anticoagulants, such as dabigatran. The mechanism is still unclear, however, in this context, some previous studies about interaction between anticoagulants mainly heparin and platelet aggregation have shown conflicting results: while some suggest an inhibitory effect of heparin on platelet function, others suggest that heparin could promote an increase in platelet activation. The present study aims to assess the effects of the LMWH Enoxaparin and direct thrombin inhibitor, Dabigatran, on platelet aggregation, studied and compared by different methods in patients with chronic coronary artery disease CAD. 