Cardiac nodal and cardiac autonomic functions in children with vasovagal syncope

Perfil Clínico, Autonômico e Escore de Calgary Modificado de Crianças e Adolescentes com Presumida Síncope Vasovagal Submetidos ao Teste de Inclinação

“…In the present study, during TT, in the entire casuistry, there was a significant increase in the LF component, the LF/HF ratio and the HF reduction, when the values were compared with those in the supine position. These data are consistent with those reported by other studies in the pediatric population 7 , 23 - 27 , 30 , 31 which have suggested hypotheses such as ineffective sympathetic tonus in the face of orthostatism, baroreceptor reflex failure after bending over, hemodynamic instability with decreased cardiac output and/or peripheral vascular resistance, factors that resulted in syncope in predisposing individuals. However, unlike previous studies with 24 to 51 children and adolescents with VVS, 23 - 25 , 27 the HRV using the ROC curve did not identify those with a positive response to TT in this study since a control group was not included (without a history of VVS), in 98.6% of the sample, the Calgary and modified Calgary scores were suggestive of VVS and the TT was positive in 74%.…”

“…These data are consistent with those reported by other studies in the pediatric population 7 , 23 - 27 , 30 , 31 which have suggested hypotheses such as ineffective sympathetic tonus in the face of orthostatism, baroreceptor reflex failure after bending over, hemodynamic instability with decreased cardiac output and/or peripheral vascular resistance, factors that resulted in syncope in predisposing individuals. However, unlike previous studies with 24 to 51 children and adolescents with VVS, 23 - 25 , 27 the HRV using the ROC curve did not identify those with a positive response to TT in this study since a control group was not included (without a history of VVS), in 98.6% of the sample, the Calgary and modified Calgary scores were suggestive of VVS and the TT was positive in 74%. Miranda et al, 32 with a selected population, also did not report a significant difference regarding the HRV components in the frequency domain between the group with a cardioinhibitory response to TT (40 patients) and the control group with a negative response to TT (24 patients) during inclination, corroborating the result of this study.…”

“… 22 Portanto, os testes autonômicos podem ser adjuvantes nesse diagnóstico 2 , uma vez que o sistema nervoso autônomo está implicado na fisiopatologia da SVV. Na população pediátrica, há alguns estudos sobre essa ferramenta com registros de curta duração para análise espectral durante o TI 7 , 23 - 27 e outros para diferenciação entre SVV e STOP, com gravações pelo sistema Holter de 24 horas. 28 , 29 …”

“… 22 Therefore, autonomic tests can help in this diagnosis 2 since the autonomic nervous system is implicated in the pathophysiology of VVS. In the pediatric population, some studies on this tool have short-term recordings for spectral analysis during TT 7 , 23 - 27 and others for differentiating between VVS and POTS, with recordings by the 24-hour Holter system. 28 , 29 …”

Prolonged QT dispersion is associated with pediatric syncope

“…Syncope is characterized with sudden loss of consciousness and tonus; it develops by insufficiency of cerebral circulation. 1 The interruption of cerebral blood flow for 6-8 seconds or 20% decrease in cerebral oxygenation can cause complete loss of consciousness. Though rarely, without decrease in cerebral blood flow, the decrease in essential matters which are necessary for brain (hypoglycemia etc.)…”