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Decreased heart rate variability has been associated with an adverse prognosis in patients after myocardial infarction. Studies carried out in the population at large show contradictory results. The authors examined the association between heart rate variability on a standard 10-second electrocardiogram and cardiac and all-cause mortality in the Rotterdam Study, a population-based cohort study of men and women aged > or =55 years, using data collected between 1990 and 1996 (mean follow-up = 4 years). Heart rate variability, taken as the standard deviation of normal R-R intervals (SDNN), was computed by means of the Modular ECG Analysis System. After exclusion of subjects with arrhythmia and those with fewer than six normal R-R intervals, the study population consisted of 2,088 men and 3,184 women. Cox's proportional hazards model was used to examine the age- and sex-adjusted risk for cardiac, noncardiac, and total mortality in relation to quartiles of SDNN, using the third quartile of SDNN as the reference category. Subjects in the lowest quartile of SDNN relative to those in the third quartile had an 80 percent age- and sex-adjusted increased risk for cardiac mortality (hazard ratio = 1.8; 95% confidence interval: 1.0, 3.2). Interestingly, for subjects in the highest quartile of SDNN, an even more pronounced risk for cardiac mortality was present (hazard ratio = 2.3; 95% confidence interval: 1.3, 4.0). Additional adjustment for possible confounders did not materially change the risk estimates. The authors conclude that heart rate variability measured on the standard 10-second electrocardiogram can be used to identify older men and women with an increased risk for cardiac mortality. In the elderly, increased heart rate variability is an even stronger indicator of cardiac mortality than decreased heart rate variability. Further studies are needed to confirm these findings and to elucidate their physiologic meaning.

Prolongation of heart rate-adjusted QT length (corrected QT interval [QTc]) is associated with elevated risk of coronary heart disease and sudden death. This may have to do with autonomic cardiac control. Because insulin is known to stimulate sympathetic activity, we studied the association of insulin level and glucose tolerance with QTc. In 1990, 383 elderly men 70–89 years of age without previous myocardial infarctions or known diabetes had a 12-lead electrocardiogram recorded and glucose tolerance determined in the frame of an ongoing follow-up study. QTc was significantly associated with fasting glucose, insulin, and C-peptide and glucose levels 60 and 120 min after an oral glucose load. For fasting C-peptide and the area under the glucose curve (AUGC), this association could not be explained by the concomitant occurrence of other risk factors of coronary heart disease. Furthermore, fasting C-peptide and the AUGC were independently additive predictors of QTc duration. The difference in QTc between men in the extreme quintiles of both variables was 22 ms. QTc prolongation seems to be part of the insulin resistance syndrome. The association may be explained by increased sympathetic activity induced by high insulin levels. An additional explanation could be an effect of high insulin, impaired glucose utilization, or both on membrane activity of myocardial cells.

Objectives. This study evaluated the predictive value of T wave amplitude and ST segment level on lead I for angina pectoris, a first myocardial infarction, sudden death and coronary heart disease death in middle-aged and elderly men. Background. Certain ST-T wave characteristics may reflect favorable autonomic cardiac control. Slight ST segment elevation has been reported to indicate a low risk of coronary heart disease mortality. Methods. A total of 876 men, born between 1900 and 1920, participated in periodic medical examinations and were followed up with respect to morbidity and mortality from 1960 to 1985. In 1985, the remaining cohort was extended to 836 elderly men from the same birth cohort who were followed up until 1990. Relative risks in categories of T wave amplitude and ST segment level were estimated by survival analysis. Results. Both middle-aged and elderly men with T wave amplitudes ≥0.15 mV had a lower risk of myocardial infarction, coronary heart disease death and sudden death than men with T wave amplitudes 0.05 to 0.15 mV. The adjusted relative risk of coronary heart disease death was 0.5 (95% confidence interval [CI] 0.2 to 1.0); in men with T wave amplitude ≤0.05 mV, relative risk was 2.0 (95% CI 1.3 to 3.1). Slight ST segment elevation was also associated with decreased risk: relative risk 0.5 (95% CI 0.3 to 1.0) compared with the isoelectric ST segment level. In men with ST segment depression, relative risk was 2.2 (95% CI 1.4 to 3.4). The associations of T wave amplitude and ST segment level were independent of each other. Conclusions. In addition to the elevated risk of coronary heart disease that is associated with ST-T wave abnormalities, we observed that normal variations in repolarization characteristics are predictive of future heart disease.