A meta-analysis published in the British Medical Journal has concluded that enoxaparin appears to be superior to unfractionated heparin in reducing mortality and bleeding outcomes during percutaneous coronary intervention, particularly in patients undergoing primary percutaneous coronary intervention for ST elevation myocardial infarction.

The meta-analysis was conducted to determine the efficacy and safety of enoxaparin compared with unfractionated heparin during percutaneous coronary intervention. It included data from 23 randomised and non-randomised studies (involving a total of 30,966 patients) comparing enoxaparin with unfractionated heparin during percutaneous coronary intervention and reporting on both mortality (efficacy end point) and major bleeding (safety end point) outcomes. A total of 10,243 patients (33.1%) were undergoing primary percutaneous coronary intervention for ST elevation myocardial infarction, 8750 (28.2%) were undergoing secondary percutaneous coronary intervention after fibrinolysis, and 11,973 (38.7%) were non-ST elevation acute coronary syndrome or stable patients scheduled for percutaneous coronary intervention. A total of 13,943 patients (45.0%) received enoxaparin and 17,023 (55.0%) unfractionated heparin. The main objective of this study was to evaluate the impact of enoxaparin and unfractionated heparin on mortality (main efficacy end point) and major bleeding (main safety end point) during percutaneous coronary intervention. The following results were reported:

• In the overall cohort of patients (n=30,966), enoxaparin was associated with a 34% relative risk reduction (0.66, 95% confidence interval 0.58 to 0.77; P<0.001) and a 1.66% absolute risk reduction of mortality (NNT=60)

• In the higher risk group of patients with ST elevation myocardial infarction undergoing primary percutaneous coronary intervention (n=10,243), enoxaparin was associated with a statistically significant 48% relative risk reduction in mortality (3.12% enoxaparin v 6.03% unfractionated heparin) and a 2.91% absolute relative risk reduction (P<0.001; NNT=34).

• In the overall cohort of patients with reported major bleeding (n=30,775), enoxaparin was associated with a 20% relative risk reduction (0.80, 95% confidence interval 0.67 to 0.95; P=0.009) and an absolute risk reduction of 1.20% (NNT=83)

• Compared with unfractionated heparin, enoxaparin was associated with a 32% relative risk reduction and 2.01% absolute risk reduction of death or myocardial infarction (relative risk 0.68, 95% confidence interval 0.57 to 0.81; P<0.001, NNT=50)

The authors concluded that “during percutaneous coronary intervention, enoxaparin seems to be superior to unfractionated heparin in reducing all cause mortality and ischaemic and bleeding end points. This superiority was particularly evident in patients with ST elevation myocardial infarction undergoing primary percutaneous coronary intervention. Given the relatively low cost of enoxaparin (and its wide availability), this seems to be an attractive strategy to improve outcomes in the large number of patients undergoing percutaneous coronary intervention worldwide”.

A related editorial highlights several limitations of the meta-analysis but concludes that “the size of the benefit shown in the current large meta-analysis, the consistency of results in different subgroups, the agreement with findings from other large trials of new anticoagulants, and the low cost of enoxaparin provide sufficient evidence that enoxaparin is an attractive alternative to unfractionated heparin and should be considered for treatment of patients undergoing PCI in general, and primary PCI in particular”.