Effectiveness of low-dose heparin in prevention of myocardial reinfarction

728 patients aged 50-75 years who had had Q-wave myocardial infarction 6-18 months previously were enrolled in a randomised, multicentre trial of low-dose heparin in prevention of reinfarction. The control group (365 patients) received their study centres' usual therapy; the heparin group (363 patients) also received subcutaneous calcium heparin (12,500 IU daily). Mean (SD) follow-up was 708 (265) days in the heparin group and 687 (251) in the control group. The reinfarction rate was 63% lower in the heparin than in the control group (4/303, 1.32% v 13/365, 3.56%). The difference in cumulative reinfarction rate between the groups was significant by both drug-efficacy (chi 2 = 3.99, p less than 0.05) and intention-to-treat analysis (chi 2 = 3.84, p = 0.05). Heparin treatment reduced the cumulative general mortality rates by 48% on drug-efficacy analysis (chi 2 = 3.88, p less than 0.05) and by 34% on intention-to-treat analysis (chi 2 = 2.05, not significant). Cardiovascular mortality was also reduced (33%) but not significantly. However, fatal events attributable to thromboembolism (fatal reinfarction, stroke, pulmonary embolism) were significantly less frequent in the heparin than in the control group (1 v 7, p less than 0.05). 60 patients (16.5%) discontinued heparin treatment, but only 23 patients (6.3%) stopped because of side-effects. Low-dose heparin appears to be effective, safe, well tolerated, and free from haemorrhagic risk for the prevention of myocardial reinfarction.