Padrões de disautonomia por meio da variabilidade da frequência cardíaca durante o teste de inclinação em crianças e adolescentes com história de síncope

Abstract

In the pediatric population, 15% have had at least one episode of syncope up to 18 years of age, whose main etiology is vasovagal (SVV). Although this condition is frequent, there are few studies on this sign, its characterization by the tilt test (TT) and the analysis of the autonomic nervous system, which is part of its pathophysiology. Objectives: to analyze the clinical profile, the Calgary score and the modified Calgary score, its association with the responses to TT and the heart rate variability (HRV) of children and adolescents with syncope. Methods: this is a cohort, observational, cross-sectional and prospective study, carried out with 73 participants from January 2016 to March 2020, at Hospital das Clínicas, Universidade Federal de Minas Gerais. Participants underwent clinical evaluation, calculation of scores and TT. It was performed at an angle of 70º, with monitoring for HRV through spectral analysis, to register the components of low frequency (LF), high frequency (HF) and the LF/HF ratio, in the supine position and in the 10th min of TT. Statistical analysis was performed with Student's t test, Mann-Whitney test for continuous variables; chi-square and Fisher tests for qualitative variables and Wilcoxon test for paired analysis. Results: the median age was 14.0 years (38 females). Prodromes occurred in 59 patients, recurrence in 50 and trauma in 19. The mean Calgary and modified Calgary scores were 1.80 and 1.38, respectively. The average evolution time was 37, 3 months; the last episode had occurred 109.2 days, with a median of 4 episodes. There was an association between sex and age (median of 15 in females and 13 in males, p = 0.02). In 54 patients, the response was positive, with vasovagal in 49 (39 vasodepressor, 7 cardioinhibitory and 3 mixed), postural hypotension in 3 and orthostatic tachycardia in 2, with an average time of 13.9 minutes. During TT, there was a decrease in HF and an increase in LF in normalized units (nu) and in the LF/HF ratio (p <0.0001). There was an inverse association between age and positive response to TT (p=0.01). In the supine position, BF was 33.6 and 47.4 units, in females and males, respectively (p = 0.02). Despite this, applying receiver operating characteristic curve, there was no statistical significance for LF and the scores. Conclusions: there was a large proportion of prodromes and recurrence and the predominant response was vasodepressor. The male sex presented greater sympathetic activation in the supine position. The Calgary scores and the LF component did not allow predicting the response to TT.