Heart Rate Variability in Patients with Neurocardiogenic Syncope or Presyncope

ABSTRACT

BACKGROUND AND OBJECTIVES: Neurocardiogenic syncope is believed to be caused by a transient imbalance of autonomic nervous system. Actually, there were significant differences in heart rate variability (HRV) indices during head-up tilt test between patients with neurocardiogenic syncope and normal controls. But there was no definite evidence for it during daily activity. So, we tried to evaluate HRV during daily activity with 24-hour ambulatory electrocardiography monitoring. MATERIALS AND METHODS: 27 patients with neurocardiogenic syncope or presyncope (mean age 45+/-3) and 25 normal volunteers (mean age 47+/-2) comparable for age and sex underwent 24-hour ambulatory electrocardiography. Head-up tilt test was used to diagnose neurocardiogenic syncope or presyncope in patients group. HRV was analysed over the whole 24 hours, using time and frequency domain parameters. Student's t-test was applied. ResultsThere were no significant differences in HRV measures between two groups, over 24-hour period and day-time and night-time period. But the hourly HRV measures showed a transient decrease of LF, LFnorm and LF/HF ratio in patients group compared to normal control group. CONCLUSIONS: These results indicate that patients with neurocardiogenic syncope or presyncope suffer from temporarily decreased sympathetic tone with normal parasympathetic tone. So, transient additive change of autonomic nervous tone may cause syncope or presyncope in these patients. (Korean Circulation J 2000;30 (6)716-723)