Unfractionated heparin and low molecular weight heparin in acute coronary syndrome without ST elevation: a meta analysis

Overview—Acute coronary syndrome without ST elevation is attributed to unstable angina and non-Q-wave myocardial infarction. The role of unfractionated and low molecular weight heparin (LMWH) in the management of aspirin treated patients with acute coronary syndrome without ST elevation has not been determined satisfactorily by any single large study. This meta-analysis investigates this issue.

Design—Meta-analysis of 12 randomised trials, involving a total of 17 157 patients.

Main outcome measures—The primary efficacy outcome measures were death and non-fatal myocardial infarction. The primary safety outcome measure was the occurrence of a major bleed. Secondary outcome measures of interest were recurrent angina and the need for re-vascularisation.

Main results—In aspirin treated patients, short-term (up to seven days) treatment with unfractionated heparin or LMWH was associated with significant reductions in death and non-fatal myocardial infarction (summary odds ratio 0.53; 95% CI 0.38, 0.73, p=0.0001), equivalent to 29 events prevented per 1000 patients. No significant difference was found between unfractionated heparin and LMWH during short-term treatment. Long term LMWH conferred no reduction in deaths or non-fatal infarcts, but was associated with a significantly increased risk of major bleeding (odds ratio 2.26, (95% CI 1.63, 3.14), p<0.0001), equivalent to 12 major bleeds per 1000 patients treated.

Conclusion—The authors conclude that there are benefits of using unfractionated heparin or LMWH in aspirin treated patients presenting with acute coronary syndrome without ST elevation in the short-term, but cannot find evidence to support its use beyond the first seven days.

Critique—Acute coronary syndrome without ST elevation (unstable angina and non-Q wave myocardial infarction) is a common presentation to accident and emergency. Patients who present in this way are at significant risk of developing recurrent ischaemic events. Previous randomised trials, while sizeable, have been …