HEART-RATE DYNAMICS IN PATIENTS WITH STABLE ANGINA-PECTORIS AND UTILITY OF FRACTAL AND COMPLEXITY-MEASURES

Dynamic analysis techniques may uncover abnormalities in heart rate (H R) behavior that are not easily detectable with conventional statistic al measures. However, the applicability of these new methods for detec ting possible abnormalities in HR behavior in various cardiovascular d isorders is not well established. Conventional measures of HR variabil ity were compared with short-term (less than or equal to 11 beats, alp ha(1)) and long-term (>11 beats, alpha(2)) fractal correlation propert ies and with approximate entropy of RR interval data in 38 patients wi th stable angina pectoris without previous myocardial infarction or ca rdiac medication at the time of the study and 38 age-matched healthy c ontrols. The short- and long-term fractal scaling exponents (alpha(1), alpha(2)) were significantly higher in the coronary patients than in the healthy controls (1.34 +/- 0.15 vs 1.11 +/- 0.12 [p <0.001] and 1. 10 +/- 0.08 vs 1.04 +/- 0.06 [p <0.01], respectively), and they also h ad lower approximate entropy (p <0.05), standard deviation of all RR i ntervals (p <0.01), and high-frequency spectral component of HR variab ility (p <0.05). The short-term fractal scaling exponent performed bet ter than other heart rate variability parameters in differentiating pa tients with coronary artery disease from healthy subjects, but it was not related to the clinical or angiographic severity of coronary arter y disease or any single nonspectral or spectral measure of HR variabil ity in this retrospective study. Patients with stable angina pectoris have altered fractal properties and reduced complexity in their RR int erval dynamics relative to age-matched healthy subjects. Dynamic analy sis may complement traditional analyses in detecting altered HR behavi or in patients with stable angina pectoris. (C) 1998 by Excerpta Medic a, Inc.