Low molecular weight heparins in acute ischaemic syndromes

Thrombus formation and ongoing generation play a major role in the pathogenesis of unstable angina and myocardial infarction (MI). Unfractionated heparin is widely used as an adjunctive therapy in the management of acute ischaemic syndromes, but it has a number of limitations including inter-patient variability, need for monitoring, and the fact that its use may be associated with thrombocytopenia. Low molecular weight heparins have pharmacological and pharmacokinetic properties that may result in better clinical outcomes and safety. They are easy to administer and do not require monitoring. Low molecular weight heparins have been shown to reduce mortality and the incidence of MI and recurrent ischaemia compared with placebo in patients with unstable angina and non-Q-wave MI, and have a more predictable anticoagulant effect than standard unfractionated heparin. They also can be used long term in the outpatient setting, in the form of self-administered subcutaneous injections. The clinical relevance of these new developments is still being defined in ongoing clinical trials and cost-effectiveness analyses.