The Organization to Assess Strategies for Ischemic Syndromes (OASIS) Pilot Study: evaluation of acute and long-term therapies for patients with acute coronary syndromes without ST elevation.

The objectives of the Organization to Assess Strategies for Ischemic Syndromes (OASIS) Pilot Study (phase 2) were (1) to compare the efficacy, safety, and feasibility of recombinant hirudin versus unfractionated heparin as short-term therapy in patients with acute coronary syndromes without ST elevation and (2) to compare the efficacy and safety of long-term therapy with warfarin and aspirin versus standard therapy with aspirin alone in the same patient population. Investigators at 31 Canadian centers randomized 909 patients to receive either medium-dose hirudin, low-dose hirudin, or unfractionated heparin. The incidence of the 7-day primary composite outcome of cardiovascular death, new myocardial infarction (MI), or refractory angina was significantly lower among patients who received hirudin than among those assigned to unfractionated heparin. A subset of these patients was subsequently randomized to long-term, low-intensity (international normalized ratio [INR] < 1.5) or moderate-intensity (INR 2-2.5) anticoagulant treatment with warfarin or to standard therapy. In this substudy, promising results were observed in favor of moderate-intensity warfarin. These findings provided the rationale for the design and conduct of the large-scale, phase III OASIS-2 trial.