The use of L-carnitine, or one of its pharmaceutically acceptable salts, is described in combination with glucose for the preparation of a medicament useful for diminishing the number of deaths caused by acute myocardial infarction, for reducing the number of days infarction patients spend in intensive care in hospital, and for reducing the number of episodes of post-infarction heart failure, in which the L-carnitine is administered intravenously within only a few hours of the onset of symptoms of acute myocardial infarction at an initial dose of 9 grams a day in combination with 1000-1500 mL of a 5% glucose solution for 5 days, after which the L-carnitine treatment is continued at a dose of 4 grams a day administered orally.