Which heparin and how much?

Acute coronary syndromes (ACS) are among the most common presentations to emergency departments in North America. An important therapeutic decision facing the clinician is whether antithrombotic therapy is justified and which type confers the lowest risk:benefit ratio. Using low molecular weight heparin (LMWH) has resulted in improved cardiovascular outcomes over unfractionated heparin in the noninvasively treated; however, its use as the antithrombotic agent in the invasive management of ACS has not always been superior. There have also been concerns about bleeding risk with LMWH, especially in the elderly and those with impaired renal function. The longer half-life of LMWH and the complexity of reversing its effect, in the context of multiple antiplatelet and fibrinolytic drugs, have also spurred debate. Finally, there is concern over unwanted thrombotic events with these agents in the cardiac catheterization laboratory.