INFLUENCE OF ORAL MAGNESIUM SUPPLEMENTATION ON CARDIAC EVENTS AMONG SURVIVORS OF AN ACUTE MYOCARDIAL-INFARCTION

Objective-To investigate the effect of long term oral magnesium treatm ent on incidence of cardiac events among survivors of an acute myocard ial infarction. Design-Double blind, placebo controlled parallel study in which patients were randomised to treatment or placebo. Setting-Tw o coronary care units and corresponding outpatient clinics. Subjects-4 68 survivors of an acute myocardial infarction (289 men and 178 women) aged 31-92. Interventions-One tablet of 15 mmol magnesium hydroxide o r placebo daily for one year. Main outcome measures-Incidences of rein farction, sudden death, and coronary artery bypass grafting in one yea r. Results-There was no significant difference between treatment and p lacebo groups in the incidence of each of the three cardiac events, bu t when the events were combined and drop outs were excluded from calcu lations there was a significantly higher incidence of events in the tr eatment group (56/167 v 33/153; relative risk 1.55 (95% confidence int erval 1.07 to 2.25); p = 0.02). When the timing of events was incorpor ated by means of a Kaplan-Meier plot the treatment group showed a sign ificantly higher incidence of events whether drop outs were included o r excluded (p < 0.025). Conclusion-Long term oral treatment with 15 mm ol magnesium daily does not reduce the incidence of cardiac events in survivors of an acute myocardial infarction and, indeed, seems to incr ease the risk of developing a cardiac event. Consequently, this treatm ent cannot be recommended as secondary prophylaxis for such patients.