235: Heart rate variability in the first five minutes of the tilt test to predict syncope?

Abstract

Vasovagal syncope mechanisms, diagnostic tools and treatments are currently strongly explored and debated. The aim of this study is to specify the early cardiac autonomic adaptations to tilt test in negative and positive (cardio-inhibitory and vasodepressor) subjects. Healthy men (n=81) from 18 to 35 years old underwent a 45 min 80° tilt test after a 15 min rest. Three clinicians independently classified each test results according to the VASIS classification: negative (NEG), mixed, cardio-inhibitor (CI) or vasodepressive (VD) syncope. Only three groups were studied: the NEG (n=13), CI (n=11) and VD (n=8). ECG recorded during 5 min of resting (Rest5) and the first 5 min of the tilt test (Early5) were compared within and between groups. ECG signals were analysed with the validated algorithm Segmenta (LTSI, Rennes) to calculate usual HRV parameters: Ptot, LF, HF, LFnu, HFnu. First , within group comparisons showed that in NEG subjects from Rest5 to Early5, HF and HFnu decreased (p<0,01) and LF (p<0,05) and LFnu (p<0,01) increased. VD subjects showed similar responses (p<0,05), except for HF indices (NS). In CI subjects LF and HF indices weren’t significantly different between Rest5 and Early5. Second , between groups comparisons of the relative adaptations (%) from Rest5 to Early5 showed that the increase in LFnu was higher in NEG (+180±80%) than in CI (+66±50%) (p<0,01). HFnu decrease was also higher in NEG (-66±5%) than in CI (-38±9%) (p<0,05). Our results suggest a lack of sympatho-vagal balance activation in the first 5 min of tilt test in subjects with vasovagal syncope. CI and VD syncope groups show a lower decrease of HF indices in the Early5. Moreover, CI group shows a lower increase of LF indices. A perspective of this work is the set of cut-off values from data recorded over the first 5 min of tilt test to estimate the risk and the type of vasovagal reaction, based on a bigger population. Figure (abstract 235) – LFnu and HFnu variations (%) in NEG and CI