Homocysteine and myocardial infarction.

Five (24%) subjects out of a group of 21 men, 48-58 years old (mean 54), who had suffered their first myocardial infarction (MI) before the age of 55 and with a low risk profile vis-à-vis conventional risk factors in a health screening preceding the MI, had abnormally high total plasma homocysteine values in the fasting state when investigated within 1-7 years (mean 3) after their MI. The patient group was exactly matched with 36 control subjects for sex, age, diastolic blood pressure, smoking, and serum concentrations of cholesterol and triglycerides. Total plasma homocysteine was negatively correlated to both erythrocyte folate and serum vitamin B12, and vitamin concentrations below the median of the normal distribution were found in the five with high plasma homocysteine content, indicating a possible involvement of reduced remethylation of plasma homocysteine to methionine. After methionine loading, in 3 of the patient group (14%) homocysteine levels exceeded mean +2 SD for controls, which may indicate heterozygosity for homocystinuria. Results are consistent with the hypothesis that a high plasma homocysteine content may be a risk factor for MI.