Prediction of sudden cardiac death by fractal analysis of heart rate variability in elderly subjects

OBJECTIVES The aim of this study was to test the hypothesis that abnormal s caling characteristics of heart rate (HR) predict sudden cardiac death in a random population of elderly subjects. BACKGROUND An abnormality in the short-term fractal scaling properties of H R has been observed to be related to a risk of life-threatening arrhythmias among patients with advanced heart diseases. The predictive power of alter ed short-term scaling properties of HR in general populations is unknown. METHODS A random sample of 325 subjects, age 65 years or older, who had a c omprehensive risk profiling from clinical evaluation, laboratory tests and 24-h Holter recordings were followed up for 10 years. Heart rate dynamics, including conventional and fractal scaling measures of HR variability, were analyzed. RESULTS At 10 years of follow-up, 164 subjects had died. Seventy-one subjec ts had died of a cardiac cause, and 29 deaths were defined as sudden cardia c deaths. By univariate analysis, a reduced short-term fractal scaling expo nent predicted the occurrence of cardiac death (relative risk [RR] 2.5, 95% confidence interval [CI], 1.9 to 3.2, p < 0.001) and provided even stronge r prediction of sudden cardiac death (RR 4.1, 95% CI, 2.5 to 6.6, p < 0.001 ). After adjusting for other predictive variables in a multivariate analysi s, reduced exponent value remained as an independent predictor of sudden ca rdiac death (RR 4.3, 95% CI, 2.0 to 9.2, p < 0.001). CONCLUSIONS Altered short-term fractal scaling properties of HR indicate an increased risk for cardiac mortality, particularly sudden cardiac death, i n the random population of elderly subjects. (J Am Coll Cardiol 2001;37:139 5-302) (C) 2001 by the American College of Cardiology.