Cardiac Autonomic Function In Children With Vasovagal Syncope

Objective: To study the indexes of cardiac autonomic function in children with vasovagal syncope(VVS),determing the autonomic nervous function during asymptomatic period,to explore the pathophysiological mechanism of vasovagal syncope in children,auxiliary diagnosi and guide treatment.Methods: From February 2018 to January 2019,40 patients with syncope or presyncope who were admitted to the Pediatric Cardiovascular Department of the Lanzhou University Second Hosipital were selected as the study subjects.After headup tilt up test(HUTT),40 patients with VVS were diagnosed,including 31 patients with vasodepressive,1 patient with cardioinhibitory,and 8 patients with mixed type.Meawhile,20 patients with syncope or presyncope who were HUTT negative and 52 healthy children were used as controls.All children underwent Holter examination,and the indexes reflecting cardiac autonomic nervous function indexes,i.e.,time domain and frequency domain indexes of heart rate variability(HRV),QT interval and QT interval dispersion(QTd),and deceleration capacity of rate(DC)were recorded.Cardiac autonomic function measures were compared between children with VVS and healthy controls,between children with VVS and HUTT negative syncope,between children with different types of VVS,and between children with HUTT negative and healthy controls.Results: 1.The levels of rMSSD/SDNN,QTd,DC in children with VVS were higher,TP and LF smaller than those in healthy controls(P<0.05);2.The LF/HF and DC of children with VVS was higher than that of children with negative HUTT(P<0.05);3.The SDNN,SDNNi,pNN50,trigonometric index,TP,VLF,HF,and DC in children with mixed type were higher than those in vasodepressive(P<0.05);4.SDNNi decreased and DC increased in the HUTT negative group,which was significantly different from that in the healthy control group children(P<0.05);5.DC predicted vasovagal syncope with a ROC curve greater than 0.70,and DC of 5.79 ms predicted VVS with a sensitivity of 77.50% and a specificity of 69.23%;6.DC values were not significantly correlated with SDNN,rMSSD,LF,HF,LF/HF,and mean QT interval in healthy and VVS children(P>0.05).Conclusion: The autonomic nervous activity of children with VVS is weakened and dysregulated during the asymptomatic period,and the vagus nerve activity is mainly enhanced.The autonomic nervous dysfunction of VVS mixed type is more severe than that of vasodepressive and the vagus nerve activity is higher during the asymptomatic period.The change pattern of basal autonomic nerve function in children with HUTT negative syncope is different from that of VVS.There is no significant correlation between DC and some indexes of HRV and mean QT interval in children with VVS and control group;DC can be used as an indicator for predicting VVS in children,with certain sensitivity and specificity.