Organization to Assess Strategies for Ischemic Syndromes - OASIS-1


Hirudin vs. heparin for death/MI/revascularization in non-Q wave MI.


To evaluate hirudin compared with heparin in patients with acute myocardial ischemia without ST elevation.

Study Design

Study Design:

Patients Screened: Not given
Patients Enrolled: 909
Mean Follow Up: 180 days
Mean Patient Age: 64
Female: 33.5

Patient Populations:

Patients admitted to hospital within 12 hours of chest pain suspicious for unstable angina or MI.


ST elevation
Contraindications to hirudin or heparin
Stroke in previous year
Renal impairment
PTCA within previous 6 months
Need for long-term anticoagulation
Planned thrombolysis
Age < 21 or > 85 years
Estimated body weight > 110 kg
Cardiogenic shock
Unrelated diseases with life expectancy < 6 months

Primary Endpoints:

Cardiovascular death, new MI, or refractory angina at 7 days

Secondary Endpoints:

Cardiovascular death, new MI, or severe angina

Drug/Procedures Used:

Heparin (5000 unit bolus with 1000-1200 units/hr) vs hirudin (low dose, 0.2 mg/kg bolus + 0.10 mg/kg/hr infusion; medium dose 0.4 mg/kg bolus + 0.15 mg/kg/hr infusion)

Concomitant Medications:


Principal Findings:

A total of 371 patients were randomized to heparin, 271 patients to low-dose hirudin, and 267 patients to medium dose hirudin.

At 7 days, 6.5% of patients in the heparin group, 4.4% in the low dose group, and 3.0% in the medium dose group (P=.267 heparin versus low-dose hirudin; P=.047 heparin versus medium-dose hirudin) suffered cardiovascular death, new MI, or refractory angina.

Fewer patients underwent coronary artery bypass graft surgery in the two hirudin groups (3.7% low-dose, 1.1% medium-dose group) compared with heparin (4.0%) (P=.028 for heparin versus Medium dose).

At day 8 or 9, the group treated with medium-dose hirudin experienced a sharp increase in events, so that the difference compared with heparin decreased.

At 35 and 180 days, both doses of hirudin had lower rates of ischemic events compared to heparin.

Rates of minor bleeding were significantly higher for the two hirudin doses comapred to heparin.


The OASIS trial suggested that the medium hirudin dose was superior to heparin, and provided pilot information for dosing in the larger OASIS-2 trial. Direct thrombin inhibitors continue to be promising alternatives to heparin for anticoagulation in acute coronary syndromes.


1. Circulation 1997;96:769-77. Final results

Clinical Topics: Acute Coronary Syndromes, Anticoagulation Management, Cardiac Surgery, Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Anticoagulation Management and ACS, Lipid Metabolism, Novel Agents, Interventions and ACS

Keywords: Myocardial Infarction, Acute Coronary Syndrome, Thrombin, Heparin, Coronary Artery Bypass, Hirudins

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