title: Unfractionated heparin and low-molecular-weight heparin in acute coronary syndrome without ST elevation: a meta-analysis.
abstract: BACKGROUND
  In acute coronary syndrome without ST elevation, the role of unfractionated and low-molecular-weight heparin in aspirin-treated patients remains unclear, and there is conflicting evidence regarding the efficacy and safety of low-molecular-weight heparin (LMWH) relative to unfractionated heparin. We did a systematic overview of the randomised trials to assess the effect of unfractionated heparin and LMWH on death, myocardial infarction, and major bleeding.
  
  
  METHODS
  Randomised trials comparing unfractionated heparin or LMWH with placebo or untreated control, or comparing unfractionated heparin with LMWH, for the short-term and long-term management of patients with acute coronary syndrome without ST elevation, were identified by electronic and manual searches and through contact with experts and industry representatives. Odds ratios for death, myocardial infarction, and major bleeding were calculated for each trial, and results for the individual trials were combined by a modification of the Mantel-Haenszel method.
  
  
  RESULTS
  12 trials, involving a total of 17157 patients, were included. The summary odds ratio (OR) for myocardial infarction or death during short-term (up to 7 days) unfractionated heparin or LMWH compared with placebo or untreated control was 0.53 (95% CI 0.38-0.73; p=0.0001) or 29 events prevented per 1000 patients treated; during short-term LMWH compared with unfractionated heparin was 0.88 (0.69-1.12; p=0.34); and during long-term LMWH (up to 3 months) compared with placebo or untreated control was 0.98 (0.81-1.17; p=0.80). Long-term LMWH was associated with a significantly increased risk of major bleeding (OR 2.26, [95% CI 1.63-3.14], p<0.0001), which is equivalent to 12 major bleeds per 1000 patients treated.
  
  
  CONCLUSIONS
  In aspirin-treated patients with acute coronary syndrome without ST elevation, short-term unfractionated heparin or LMWH halves the risk of myocardial infarction or death. There is no convincing difference in efficacy or safety between LMWH and unfractionated heparin. Long-term LMWH has not been proven to confer benefit additional to aspirin and there is no evidence to support its use after the first 7 days.
authors.affiliation: Preventive Cardiology and Therapeutics Program, McMaster University, Hamilton, Canada.
authors.forename: J W
authors.initials: JW
authors.lastname: Eikelboom
authors.forename: S S
authors.initials: SS
authors.lastname: Anand
authors.forename: K
authors.initials: K
authors.lastname: Malmberg
authors.forename: J I
authors.initials: JI
authors.lastname: Weitz
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: S
authors.initials: S
authors.lastname: Yusuf
mesh_terms: D000208:Acute Disease; D000368:Aged; D001241:Aspirin / Q000627:therapeutic use*; D003327:Coronary Disease / Q000188:drug therapy* / Q000401:mortality; D004562:Electrocardiography; D005260:Female; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006493:Heparin / Q000627:therapeutic use*; D006495:Heparin, Low-Molecular-Weight / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic
chemical_list: D005343:Fibrinolytic Agents; D006495:Heparin, Low-Molecular-Weight; D006493:Heparin; D001241:Aspirin