The electrocardiogram in apparently healthy men and the risk of sudden death.

The purpose of this study was to determine whether electrocardiographic abnormalities detected on a routine examination in men without clinical evidence of heart disease predicted sudden death in the absence of pre-existing clinical manifestations of heart disease. The Manitoba study consists of a cohort of 3983 men with a mean age at entry of 30.8 years who have been followed with regular examinations including electrocardiograms since 1948. During the 30 year observation period, 70 cases of sudden death have occurred in men without previous clinical manifestations of heart disease. The prevalence of electrocardiographic abnormalities before sudden death was 71.4% (50/70). The frequency of abnormalities was 31.4% (22) major ST segment and T wave abnormalities, 15.7/ (11) ventricular extrasystoles, 12.9% (nine) left ventricular hypertrophy (voltage criteria), 7.1% (five) complete left bundle-branch block, and 5.7% (four) pronounced left axis deviation. When these electrocardiographic findings in men without clinical manifestations of heart disease were related prospectively to incidence of sudden death each one except pronounced left axis deviation was a significant predictor of sudden death. Two of the variables were examined in more detail. Increased severity of primary T wave abnormalities and the association of ST segment and T wave abnormalities with increased QRS voltage further increased sudden death risk. The combination of ventricular extrasystoles with either ST-T abnormalities or left ventricular hypertrophy much increased the risk of sudden death. Thus these data indicate that electrocardiographic abnormalities detected on routine examination in men without clinical evidence of heart disease are significantly related to the occurrence of sudden death.