Approaches to the treatment of unstable angina and non-Q wave myocardial infarction.

Multiple clinical trials have been undertaken to understand better the events leading to unstable angina and non-Q wave myocardial infarction. Some of these studies focused on evaluating the role of antithrombotic therapy; others evaluated the role of more aggressive invasive treatment versus medical therapy. In the 1980s and 1990s, studies revealed that antithrombotic therapy with either acetylsalicyclic acid alone or heparin alone was more effective than placebo. The Thrombosis in Myocardial Infarction (TIMI) IIIB study attempted to compare medical therapy with early surgical intervention, reporting that early intervention did not result in any significant improvement in patient outcome over medical therapy. In the mid- to late 1990s, the thrombin hypothesis was introduced, suggesting that thrombin antagonists would arrest the coagulation and thrombotic cascade. The Global Use of Strategies To Open Occluded Coronary Arteries (GUSTO) IIb study put the thrombin hypothesis to the test, and it found that there was no significant difference between hirudin and unfractionated heparin treatments after 30 days. Glycoprotein IIb/IIIa receptor antagonists were then researched in the Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC), the c7E3 Fab Antiplatelet Therapy in Unstable Refractory angina (CAPTURE), the Platelet IIb/IIIa Antagonism for the Reduction of Acute coronary syndrome events in a Global Organization Network (PARAGON) and the Platelet Receptor Inhibition of Ischemic Syndrome Management in Patients Limited to Unstable Angina Signs and Symptoms (PRISM-PLUS) studies, shifting the attention to the platelet. These studies gave contrasting results, bringing to the foreground the issues of optimal use of antithrombotic agents and proper timing of surgical intervention. Medical therapy for unstable angina and non-Q wave myocardial infarction was addressed in the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events (ESSENCE) study, which compared a low molecular weight heparin, enoxaparin, with unfractionated heparin. A significant difference in outcomes was found in favour of enoxaparin.