USEFULNESS OF THE ADDITION OF HEART-RATE-VARIABILITY TO HOLTER MONITORING IN PREDICTING IN-HOSPITAL CARDIAC EVENTS IN PATIENTS WITH UNSTABLE ANGINA-PECTORIS

Transient ischemia on Halter monitoring is a major determinant of outc ome in unstable angina. In this study we investigated whether analysis of heart rate variability (HRV) may further improve the prognostic yi eld of Halter monitoring in this clinical setting. We performed 24-hou r Holter monitoring in 75 patients with unstable angina (59 men, aged 62 +/- 9 years) within 12 hours of hospital admission. Number and dura tion of myocardial ischemic episodes, and both time domain and frequen cy domain HRV measures were obtained from Holter recordings. in-hospit al major cardiac events (death or myocardial infarction) occurred in 7 patients (9%). Episodes of ST-segment depression on Holter monitoring were found in 6 of 7 patients (86%) with and in 26 of 68 patients (38 %) without events (p <0.05). There were no differences between patient s with or without events in both time domain (standard deviation [SD] of all normal RR intervals in the entire 24-hour electrocardiographic recording (SDNN), SD of the mean RR intervals for all 5-minute segment s (SDANN-i), mean of SD of all RR intervals for all 5-minute segments (SDNN-i), percentage of differences between adjacent RR intervals >50 ms (pNN50), and square root of the mean squared differences of success ive RR intervals) (RMSSD), and frequency domain (ultra low, very low, low, and high frequency) HRV indexes. However, the low-frequency/high- frequency (LF/HF) ratio was significantly higher in patients with card iac events (2.12 +/- 1.4 vs 1.48 +/- 0.5, p = 0.01). Moreover, when co nsidering only the 32 patients with myocardial ischemic episodes on Ho lter monitoring, the LF/HF ratio was again higher in the 6 patients wi th than the 26 patients without major cardiac events (2.45 +/- 1.5 vs 1.31 +/- 0.3, p <0.01). Multivariate logistic regression, including cl inical and angiographic variables, showed that transient ischemia on H alter monitoring was the only independent determinant of outcome (odds ratio = 12.2, p = 0.03), with the LF/HF ratio being only slightly ove r statistical significance (adds ratio for 0.1 increments = 2.8, p = 0 .08). Our data confirm that transient ischemia on Halter monitoring is a powerful predictor of cardiac events in unstable angina and indicat es that an imbalance in cardiac autonomic tone toward a prevalence of sympathetic activity increases the risk of events in this group of pat ients. (C) 1997 by Excerpta Medica, Inc.