USAGE OF ULTRA-SHORT-TERM HEART RATE VARIABILITY ANALYSIS DURING HEAD-UP TILT TESTING IN DIAGNOSTICS OF CARDIOINHIBITORY REFLEX SYNCOPE

Background:

Participation of autonomic nervous system activity in origin of neurally mediated reflex syncope is research topic for decades but so far without consensus how to realize autonomic function evaluation during head-up tilt testing.

Purpose:
Heart rate variability analysis during head-up tilt testing in ultra-short time period closely surrounding syncope or end of testing.

Methods:
Head-up tilt testing (45 min protocol at 60 degree in standard conditions) in 48 patients with history of syncope divided in group A (REFERENCE) without syncope during testing (24 patients, 14 men, age median 33.7 years) and group B (BRADYCARDIAC) (24 patients, 13 men, median age 40.5 years) with cardioinhibitory reactions during testing, defined according to guidelines. There were no signifficant difference in age or sex between both study groups.
Heart rate variability parameters: LF (low frequency) in n.u., HF (high frequency) in n.u., LF/HF ratio were evaluated in the last 1 minute time segment with sinus rhythm in tilting position before end of tilting or syncope and in the first minute in recovery supine position. Mann-Whitney U test, Chi-square test p-value and Shapiro-Wilkov test were used for statistical data processing with p-value significance level 0.05.

Results:
The last minute of tilting: Groups A : B median values: LF 84.7 : 74.9 (p 0.018), HF 15.3 : 25.2 (p 0.018), LF/HF 6.25 : 3.4 (p 0.025)

The first minute of recovery in supine position: Groups A : B median values: LF 76.9 : 64.9 (p 0.001), HF 23.1 : 35.1 (p 0.001), LF/HF 4.4 : 1.85 (p 0.0002)

Conclusion:
Presented results revealed statistically significant changes indicating vagal predominance before cardioinhibitory syncope in comparison with reference group.