Primary Percutaneous Coronary Intervention (PPCI) has traditionally been performed with the use of boluses of unfractionated heparin administered throughout the procedure.  The use of newer agents, such as enoxaparin administered intravenously throughout the procedure, has not previously been compared to this standard of therapy.

The ATOLL (Acute Myocardial Infarction Treated with Primary Angioplasty and Intravenous Enoxaparin or Unfractionated Heparin to Lower Ischemic and Bleeding Events at Short- and Long-term Follow-up) study aimed to compare these two agents; importantly, unlike in other trials, patients who received any anticoagulation before randomisation.  In this unblinded trial patients were randomly assigned (1:1) to receive a bolus of 0.5mg/kg of enoxaparin intravenously or unfractionated heparin prior to PCI.  The primary endpoint was 30-day incidence of death, complication of myocardial infarction, procedure failure, or major bleeding. The main secondary endpoint was the composite of death, recurrent acute coronary syndrome, or urgent revascularisation. Analysis was by intention to treat.

910 patients weretreated either with enoxaparin (n=450) or unfractionated heparin (n=460). The primary endpoint occurred in 126 (28%) patients given enoxaparin versus 155 (34%) patients given unfractionated heparin (p=0·06). The incidence of death (enoxaparin, 17 [4%] vs heparin, 29 [6%] patients; p=0·08), complication of myocardial infarction (20 [4%] vs 29 [6%]; p=0·21), procedure failure (100 [26%] vs 109 [28%]; p=0·61), and major bleeding (20 [5%] vs 22 [5%]; p=0·79) did not differ between groups. However, enoxaparin resulted in a significantly reduced rate of the main secondary endpoint (30 [7%] vs 52 [11%] patients; RR 0·59, 95% CI 0·38—0·91, p=0·015).

Conclusions:

In this study of patients undergoing primary PCI, the use of intravenous enoxaparin did not significantly reduce the primary endpoint compared to unfractionated heparin.  However, intravenous enoxaparin did reduce secondary endpoints of adverse ischaemic events, leading to an overall net clinical benefit.

• Montalesclot G, Zeymer U, Silvain J et al.  Intravenous enoxaparin or unfractionated heparin in primary percutaneous coronary intervention for ST-elevation myocardial infarction: the international randomised open-label ATOLL trial.  Lancet 2011; 378:693