Background: Despite the use of heparin and aspirin, 5-10% of patients with unstable angina develop myocardial infarction or refractory angina in hospital. We tested the hypothesis that recombinant hirudin (lepirudin), a direct thrombin inhibitor, would be superior to heparin, an indirect thrombin inhibitor, in patients with acute ischaemic syndromes who were receiving aspirin.
Methods: 10,141 patients with unstable angina or suspected acute myocardial infarction without ST elevation were randomly assigned heparin (5000 units bolus then 15 units kg(-1) h(-1); n=5058) or hirudin (0.4 mg/kg bolus then 0.15 mg kg(-1) h(-1) infusion; n=5083) for 72 h in a double-blind trial. The primary outcome measure was cardiovascular death or new myocardial infarction at 7 days. Analysis was by intention to treat.
Findings: At 7 days, 213 (4.2%) patients in the heparin group and 182 (3.6%) in the hirudin group had experienced cardiovascular death or new myocardial infarction (relative risk 0.84 [95% CI 0.69-1.02]; p=0.077). The numbers with cardiovascular death, new myocardial infarction, or refractory angina at 7 days were 340 (6.7%) with heparin and 284 (5.6%) with hirudin (0.82 [0.70-0.96]; p=0.0125). These differences were primarily observed during the 72 h treatment period (cardiovascular death or myocardial infarction relative risk 0.76 [0.59-0.99], p=0.039: cardiovascular death, myocardial infarction, or refractory angina 0.78 [0.63-0.96], p=0.019). Although there was an excess of major bleeding requiring transfusion with hirudin (59 [1.2%] vs 34 [0.7%] with heparin; p=0.01), there was no excess in life-threatening episodes (20 in each group) or strokes (14 in each group).
Interpretation: The data from OASIS-2 suggest that recombinant hirudin is superior to heparin in preventing cardiovascular death, myocardial infarction, and refractory angina with an acceptable safety profile in patients with unstable angina or acute myocardial infarction without ST elevation. Thus, a direct thrombin inhibitor is more effective than an indirect thrombin inhibitor.