Role of low-molecular-weight heparins in the management of patients with unstable angina pectoris and non-Q-wave acute myocardial infarction.

The development of effective approaches to the management of the unstable coronary syndromes has resulted from an improved understanding of interactions between the vascular wall, platelets, and coagulation factors, and of their response to pharmacologic and mechanical interventions. Furthermore, the occurrence of frequent adverse events after discharge in patients with unstable coronary artery disease (CAD) treated with these therapies alone would argue that, for many of these patients, such stabilization is not the end of the therapeutic pathway; rather, these therapies are for many a preparation for ultimate revascularization, to preserve myocardium and minimize periprocedural complications. The low-molecular-weight heparins with their unique pharmacology offer a new option in the therapy of patients with unstable CAD. There is now extensive experience in the use of several of the low-molecular-weight heparins, particularly dalteparin and enoxaparin, in the management of patients with unstable angina. Several trials have investigated the questions raised by these observations, taking advantage of the unique pharmacologic properties of the low-molecular-weight heparins for both acute inpatient use and prolonged outpatient administration. Although differences in study design preclude direct comparison between the available low-molecular-weight heparins, in these trials low-molecular-weight heparins have been shown to be effective alternatives to conventional heparin for the management of patients with unstable angina and non-Q-wave infarction. These include several small-scale trials and the larger FRagmin during InStability in Coronary artery disease (FRISC), Fragmin in Unstable Coronary Artery Disease (FRIC), Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-Wave Coronary Events (ESSENCE), FRISC II, and Thrombolysis in Myocardial Infarction (TIMI)-11B trials. Thus, the low-molecular-weight heparins appear to be a superior alternative to traditionally administered intravenous unfractionated heparin. They are more predictable in action, do not require frequent activated partial thromboplastin time (aPTT) measurements and dosage adjustments, are easier to administer, and are potentially more efficacious. With their proven efficacy, predictability of action, and convenience of administration and dosing, there are very good reasons for selecting them as first-line therapies for patients presenting with unstable angina and non-Q-wave myocardial infarction.