Acute myocardial infarction: Heparin is of equivocal benefit with aspirin and thrombolysis

Clinical bottom line (level 1a)

  1. In patients with myocardial infarction treated with aspirin, heparin may improve mortality (NNT = 200 at unknown)
  2. In patients with acute myocardial infarction treated with aspirin, heparin increases rates of severe bleeding (NNH = 230 at unknown) and may increase stroke rates (NNH = 1500 at unknown)
Collins et al: BMJ 1996; 313: 652-659
Expires March 2003

The study

Systematic review of unconfounded RCTs of
  • Patients: myocardial infarction
  • Intervention: anticoagulants compared with no anticoagulants
  • Outcome: mortality; reinfarction; stroke; PE; severe bleeding (requiring a transfusion)


Articles found in not stated using not stated, not stated (search terms: 'formal computer aided search' ) and contact with investigators for further/clarified, computer aided searches, search of reference lists

Selection criteria: 'unconfounded' trials
Appraisal criteria: not stated
Articles excluded if: use of historical controls or alternate allocation, intervention other than anticoagulation confounding the treatment arm

26 trial with about 73,000 patients, 6 trials with 68,000 patients dealing with co-treatment with aspirin
no significant heterogeneity

The evidence

Outcome Time to outcome CER OR
(95% CI)		 NNT
(95% CI)
death unknown /
(%)		 0.94
(0.9 to 1.0) 		200
(120 to -)
stroke unknown /
(%)		 1.06
(0.92 to 1.2) 		-1500
(NNT = 460 to infinity;
NNH = 1150 to infinity)
severe bleeding unknown /
(%)		 1.40
(1.2 to 1.7) 		-230
(-460 to -130)

Comments

  1. There is debate over the efficiency of using heparin: do the benefits justify the effort required?
  2. Though unstated search methods, overviews from the CSTU include much unpublished and late follow-up data

Citation

  1. Collins R, MacMahon S, Flather M, et al: Clinical effects of anticoagulant therapy in suspected acute myocardial infarction: systematic overview of randomised trials. BMJ 1996; 313: 652-659
Contributor: Bob Phillips and Musab Hayatli, November 1999
Reviewer: Rowan Harwood

Clinical Question.
Patient patients with acute myocardial infarction
Intervention or Exposure heparin in addition to aspirin
Outcome mortality; stroke; bleeding