Both decreased and increased heart rate variability on the standard 10-second electrocardiogram predict cardiac mortality in the elderly - The Rotterdam Study

Decreased heart rate variability has been associated with an adverse progno sis in patients after myocardial infarction. Studies carried out in the pop ulation at large show contradictory results. The authors examined the assoc iation between heart rate variability on a standard 10-second electrocardio gram and cardiac and all-cause mortality in the Rotterdam Study, a populati on-based cohort study of men and women aged greater than or equal to 55 yea rs, using data collected between 1990 and 1996 (mean follow-up = 4 years). Heart rate variability, taken as the standard deviation of normal R-R inter vals (SDNN), was computed by means of the Modular ECG Analysis System. Afte r exclusion of subjects with arrhythmia and those with fewer than six norma l R-R intervals, the study population consisted of 2,088 men and 3,184 wome n, cox's proportional hazards model was used to examine the age- and sex-ad justed risk for cardiac, noncardiac, and total mortality in relation to qua rtiles 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 qua rtile had an 80 percent age- and sex-adjusted increased risk for cardiac mo rtality (hazard ratio = 1.8; 95% confidence interval: 1.0, 3.2). Interestin gly, 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 us ed to identify older men and women with an increased risk for cardiac morta lity. In the elderly, increased heart rate variability is an even stronger indicator of cardiac mortality than decreased heart rate variability. Furth er studies are needed to confirm these findings and to elucidate their phys iologic meaning.