Low Molecular Weight Heparin and Coronary Intervention

For more than 25 years, basic experiments using cell culture and animal experimental techniques have predicted superior thrombin inhibition with use of low molecular weight heparin (LMWH) rather than unfractionated heparin (UFH). This should have application in the cardiac laboratory, where thrombin control is essential to securing a safe and optimal therapeutic angioplasty for patients with atherosclerotic heart disease. Despite much interest, few meaningful clinical studies have been completed and there are limited clinical data to establish the magnitude of benefit actually conferred through use of LMWH rather than UFH among most patients undergoing elective or urgent cardiac catheterization procedures. At this point, the available data suggest minimal clinical advantage is to be gained through the use of LMWH over UFH. Also, obtaining this modest advantage may require an extended period of drug therapy before and after intervention. Any benefit conferred is likely restricted to the period shortly after coronary intervention. On the other hand, available data suggest that serious bleeding should not be problematic despite difficulties measuring that antithrombin effect among patients receiving LMWH, even when it is combined with potent platelet inhibitor therapy. Although cell culture and animal experiments suggest that heparin compounds should be effective in limiting intimal hyperplasia (and therefore clinical restenosis) after angioplasty, randomized clinical trials have failed thus far to show any restenosis benefit for either UFH or LMWH. Ongoing studies will clarify the use of combining LMWH with potent antiplatelet agents as combined medical adjuncts to coronary intervention.