Heart Rate Variability in Patients with Neurocardiogenics Syncope

355-363

Abstract

Background

Bradycardia and hypotension in neurocardiogenic syncope are caused by an inadequate sympathetic and vagal stimulation during prolonged orthostatism. The aim of the study was to assess the baseline autonomic profile in patients with neurocardiogenic syncope through the analysis of heart rate variability, and to validate the reproducibility of the method in this population.

Material and method

Three groups of patients were included: 10 with NCS and positive Tilt test (group la), 9 with syncope highly suspected to be neurocardiogenic and a negative Tilt test (group Ib), and 10 healthy volunteers matched by age and sex (group II). No patient had evidence of structural heart disease, diabetes or neuropathy. Heart rate variability was analyzed during a brief period (500 seconds). Standard deviation and variance were evaluated in time do-main. The following measurements were made infrequency domain: spectral power(SP), very low frequency (VLF) (0-0.05 Hz), low frequency (LF)(0.05-0.15 Hz), high frequency (HF) (0.15-0.35 Hz), and the ratio between LF/HF areas.

Results

The mean age of the group la was 23.8 with an average of 6.8 episodes of syncope and a history of 68 months. The Tilt test responses were 7 vasovagal and 3 vasodepressive. The group Ib showed a mean age of 25.5 with an average of 6.1 episodes and a history of 26 months. The group II presented a mean age of 28.5. The analysis of heart rate variability in time domain (standard deviation and variance), and in frequency domain (SP, VLF, LF,HF and LF/HF ratio) showed no statistically significant differences between the patients with syncope (either with positive or negative Tilt test) and the control group. The analysis showed reproducible findings between both study days for all the measurements except the LF/HF ratio.

Conclusions

1) Autonomic profile assessed through baseline heart rate variability does not differ in patients with and without neurocardiogenic syncope. 2) The evaluation of heart rate variability at rest does not predict the behaviour during Tilt test. 3) Reproducibility of the method was excellent in patients with history of syncope.