Oral anticoagulation in the secondary prevention of myocardial infarction

Evidence in favour of oral anticoagulant therapy (OAT) in patients suffering from an acute myocardial infarction has been published in 1977 by Chalmers and co-workers (New Engl. J. Med. 297, 1091). For OAT after discharge an International Review Group (IRG) concluded in 1970 that "anticoagulant therapy probably prolongs survival at least over two years, but that benefit is as a rule restricted to patients with a history of angina or previous infarction" (The Lancet, 1, 203). Since the IRG finished their analysis, favourable results of four additional comparative studies have been published, three of which were double-blind and performed in the Netherlands. These four studies demonstrated a beneficial effect of adequate oral anticoagulation. The latest study was performed to assess benefits and untoward reactions of long-term OAT in the elderly. Results were published in November 1980 (The Lancet, 2,989). Mortality in the 738 patients who entered the trial, all of whom older than sixty years, having survived a transmural infarction, and having been on OAT for at least six months (mean: six years), was lower in patients on active treatment (p = 0.016), due to the important difference in recurrent myocardial infarction (RMI). Fifty-eight RMI's occurred in the placebo group as compared to only twenty in the AC group (p less than 0.01). Fatal cerebrovascular accidents were evenly distributed over the two groups, with a preponderance of haemorrhage in patients on active treatment. No fatal extracranial haemorrhage occurred. Incidence and severity of bleeding complications were in agreement with good patient compliance. No significant relationship was found between the recurrence of infarction and either the age of the patient or the length of treatment before entering trial. The steadiness of the widening gap between the mortality and RMI's observed in the two groups indicates that the efficacy of OAT persisted throughout the entire observation period of two years.