[Low-molecular weight heparin and acute coronary syndrome: theoretical background and its use in clinical practice]

Thrombosis is responsible for the acute manifestations of coronary artery disease. Intravenous heparin has been shown to be effective in reducing the risk of death or myocardial infarction in patients with acute coronary syndromes. Compared to standard heparin, low-molecular weight heparins (LMWHs) have improved pharmacological and pharmacokinetic properties. A number of LMWHs, such as nadroparin, dalteparin and enoxaparin, have been evaluated in patients with acute coronary syndromes. FRISC (Fragmin during Instability in Coronary Artery Disease) and FRIC (Fragmin in Unstable Coronary Artery Disease), evaluated dalteparin and found the LMWH to be more effective than aspirin alone (FRISC) and as effective as heparin in a direct comparison (FRIC). In a small trial, nadroparin was shown to significantly reduce the risk of ischemic outcomes compared with a combination of aspirin and heparin, but this effect was no longer significant in the large FRAX.I.S. trial (FRAXiparine in Ischaemic Syndrome). Enoxaparin resulted in a statistically significant reduction in the combined outcome of death, myocardial infarction and recurrent angina or of urgent revascularization when compared with heparin in the ESSENCE (Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-Wave Coronary Events) and TIMI 11B trials. Meta-analyzing of the data of these two trials revealed that even the combination of death and myocardial infarction was significantly reduced by the use of enoxaparin. There is accumulating evidence that LMWHs are safe and effective alternatives to standard heparin for the treatment of acute coronary syndromes and that they offer practical and therapeutic advantages.