TIME-SERIES ANALYSIS OF LONG-TERM AMBULATORY MYOCARDIAL-ISCHEMIA - EFFECTS OF BETA-ADRENERGIC AND CALCIUM-CHANNEL BLOCKADE

We have previously demonstrated the utility of time-series analysis ap plied to 72-hour ambulatory electrocardiographic data in patients with coronary artery disease, The present investigation applied time-serie s analysis to long-term (120-hour) ambulatory electrocardiographic dat a to determine the minimal period of monitoring needed (1) to detect p eriodicity of ischemia-related variables in ambulatory patients, (2) t o describe auto-correlation and cross-correlation functions for heart rate and ischemia, and (3) to describe the effects of beta-adrenergic and calcium channel blockade on circadian characteristics and coupling of heart rate and ischemia, A double-blind crossover design was used to obtain 120-hour recordings during placebo, atenolol (200 mg/day), a nd diltiazem (360 mg/day) administration, During all three treatment p eriods, distinct circadian variation of heart rate was documented by a utocorrelation and Fourier analysis, Ischemia did not exhibit clear pe riodicity as indexed by autocorrelation in any period; however, it was coupled to heart rate in all treatment periods as reflected in cross- correlation analysis. Although diltiazem did not quantitatively alter the circadian characteristics of heart rate or ischemia, atenolol prod uced a shift in the coupling between remaining ischemia and heart rate in time, Significant autocorrelation was detected for all treatment p eriods after 72 hours of monitoring, suggesting that 72 hours is the m inimum amount of time needed for analysis of ambulatory electrocardiog raphic data in patients with coronary artery disease.