Low-molecular-weight heparins in acute myocardial infarction: Rationale and results of a pilot study

Background: Antithrombotic adjuncts to fibrinolytic drugs for acute myocardial infarction increase the rate and speed of infarct artery recanalization. Hypothesis: A low-molecular-weight heparin might be preferable to unfractionated heparin for this indication, as it has been shown to be in several other thrombus-related vascular disorders. Methods: We performed a pilot study in 20 patients, all receiving aspirin and recombinant tissue plasminogen activator. Randomization was to standard dose intravenous unfractionated heparin or enoxaparin (the first dose given intravenously and followed by a subcutaneous administration). The endpoint was stability of anticoagulant effect. Results: Enoxaparin produced stable therapeutic anti-Xa levels with minimal effect on activated partial thromboplastin times. Unfractionated heparin produced wide swings of these parameters, often outside desired levels. Conclusions: Enoxaparin may be a better antithrombotic agent than conventional unfractionated heparin when used in conjunction with fibrinolytics.