Objective:To investigate the changes in heart rate deceleration capacity(DC) and heart rate va-riability(HRV) parameters in children with vasovagal syncope(VVS), to assess the basic autonomic function of children with VVS, and to explore the reference value of DC for the diagnosis of VVS in children.

Methods:VVS group included 62 patients diagnosed with VVS in the Cardiovascular Department of Children′s Hospital Affiliated to Capital Institute of Pediatrics from June 2015 to December 2017, 56 outpatients undergoing physical examination were selected as the healthy control group, and the changes in DC and HRV matched to age and gender were analyzed respectively.Indexes of DC and HRV of both groups of children in health control group and children with VVS were compared among different age groups or different genders.

Results:(1)Analysis of DC and HRV based on age or gender: whether in healthy children or in children with VVS, DC and HRV parameters varied significantly in the range of different ages, while they were the same in children with different genders.(2)Comparison of DC and HRV in school-age and puberty children between VVS group and healthy control group: in school-aged children, DC of VVS group was significantly higher than that of healthy control group [(6.8±1.0) ms vs.(6.0±0.7) ms, t=-2.412, P<0.01]. Mean square root rates of succe-ssive normal sinus RR interval differences(rMSSD) increased, and the difference was significant (P<0.05). In children at puberty, DC in children of VVS group was significantly higher than that in the healthy control group [(7.4±1.2) ms vs.(6.6±1.1) ms, t=-2.742, P<0.01], rMSSD, LF and HF value were significantly higher compared with those of the healthy control group (all P<0.05). (3)Predictive value of DC on VVS: the binary Logistic regression analysis found that only DC was associated with VVS in different age groups.By using receiver operating characteristic curve to analyze the predictive value of DC on VVS, it was found that when making DC 6.5 ms for school age and 7.0 ms at puberty as the threshold, a better prediction of VVS could be achieved with good sensitivity and specificity.

Conclusions:Children′s autonomic nervous function changes with age, and DC and HRV parameters change significantly during adolescence and at school age.Children with VVS may have abnormally increased vagal tone.When DC ≥6.5 ms at school age or DC≥7.0 ms at puberty, it may have a reference value for the diagnosis of VVS.