Recent decades have seen a dramatic reduction in short term and long term mortality after acute coronary syndromes, partly owing to the development of effective drug treatments and interventional strategies.1 Outcomes after percutaneous coronary intervention (PCI) have improved remarkably because of rapid technical developments and systematic evaluation of periprocedural antithrombotic agents—several new antiplatelet agents have been shown to be highly effective when used in conjunction with PCI. However, experts agree that anticoagulation is also a crucial component of the management of acute coronary syndromes. The anticoagulants currently available for PCI include unfractionated heparin, bivalirudin, and enoxaparin.2 The linked meta-analysis by Silvain and colleagues (doi:10.1136/bmj.e553) adds value by synthesising a large body of literature on the relative effectiveness and safety of the anticoagulant enoxaparin in PCI.3

In the 23 studies covered by the meta-analysis, most of the more than 30 000 patients had an acute coronary syndrome, and in all studies enoxaparin was compared with unfractionated heparin during PCI. Unfractionated heparin has long been considered a cornerstone of angiography and PCI, and it is widely used despite its pharmacological limitations, which include unpredictable effect and no evidence of a clear dose-effect relation. In fact, the use of unfractionated heparin in PCI still lacks strong scientific support, …