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 Holter monitoring is a major determinant of outcome in unstable angina. In this study we investigated whether analysis of heart rate variability (HRV) may further improve the prognostic yield of Holter monitoring in this clinical setting. We performed 24-hour Holter monitoring in 75 patients with unstable angina (59 men, aged 62 ±9 years) within 12 hours of hospital admission. Number and duration of myocardial ischemic episodes, and bath time domain and frequency domain HRV measures were obtained from Holter recordings. In-hospital 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 50 ms (pNN50), and square root of the mean squared differences of successive 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 cardiac events (2.12 ± 1.4 vs 1.48 ±0.5, p = 0.01). Moreover, when considering only the 32 patients with myocardial ischemic episodes on Holter monitoring, the LF/HF ratio was again higher in the 6 patients with than the 26 patients WithOut major cardiac events (2.45 ± 1.5 vs 1.31 ± 0.3, p