| Objective Syncope in childhood,60%-80% of which is due to vasovagal syncope (VVS), is very common. There used to be few investigations to VVS. It thus tends to generate extreme anxiety and is often extensively and inappropriately investigated. Specifying the cause of syncope is the key to prevente. Since the recent 20 years, there have been more and more studies focused on HUTT, in cluding the pathogeny of VVS, the project of the test, and the diagnosis value of the test. Now the most commonly held theory suggests the B-J reflex is the main pathogeny of VVS, and also many blood vessel active substance may play important roles. But there were few studies on the correlationship between the NO concentration in plasma, platelet 5-HT content and the pathogeny of VVS both in china and abroad. When the onset of VVS in children there is a transient cardiac output shortage caused by transient hypoxia, there is no relevant native literature reports.Therefore, our study investigates the clinical features of children with VVS and prospective measurement of NO concentration in plasma, platelet 5-HT content and the dynamic changes in oxygen saturation of 20 cases with VVS, to further clarify their relationships.Method20 children who were diagnosed as VVS because of positive HUTT in affiliated hospital of Luzhou medical college of pediatrics were enrolled HUTT positive group, while twenty healthy children as control group. NO concentration in plasma, platelet 5-HT content and oxygen saturation of the two group were measure at the beginning and the end of HUTT.8 children with VVS were treated by basic treatment, while 12 children with VVS were treated by drug treatment. Repeat HUTT and follow-up of least 6 months were conducted to evaluate the therapeutic effectiveness in treating VVS. All the date were expressed as average±standard and analysed by statistical software SPSS11.7.Result1. Clinical features:(1) In all of the 20 children with VVS, there were more girls than boys with the boys to girls ratio of 1:1.5.(2) Summer was the climax stage of attack with 15 case of all children with VVS, while winter was the lowermost with only 1 case.(3) The mean age of 20 children with VVS was (11.3±1.9) years.(4) In the study group there were 6 children had familial syncope history, which was higher than the control group.(5) There were 15 children having provocation factors before syncope in children with VVS, among which long-time standing was the most common one with the rate of 45%.(6) Presyncopal symptoms occurred in 17 patients, among which dizziness and pale had a high rate:76.5%. (7) After 2 weeks of treatment, the HUTT effective rate of basic treatment group and drug treatment grpup was respectively 25%(2/8),47.1% (5/12). And after 6 month of treatment, it was respectively 50%(4/8),83.3%(10/12).2. The changes of NO concentration in plasma during HUTT:In study group, the NO concentration in plasma at the positive performance position significantly increased, when compared with baseline level (92.36±10.42 vs 78.86±9.35μmol/L, P<0.01). In the control group, the NO consistency in plasma at the end of the test was as same as the baseline value (83.10±7.17 vs 83.85±9.82μmol/L,P>0.05).3. The changes of the platelet 5-HT content during HUTT:In study group, the platelet 5-HT content at the positive performance position significantly increased, when compared with baseline value (98.95±4.05ng/109 vs 80.15±3.47ng/109, P<0.01). In the control group, the platelet 5-HT content at the end of the test was as same as the baseline value (83.10±7.17 vs 83.85±9.82μmol/L,P>0.05).4. The changes of SpO2 during HUTT:In study group, the SpO2 at the positive performance position significantly decreased, when compared with baseline value (89%±2% vs 99%±1%, P<0.01). In the control group, the SpO2 at the end of the test was as same as the baseline value (97%±1%vs 98%±1%, P>0.05). In study group, the SpO2 after recovery of the test was as same as the baseline value (97%±1% vs 98%±1%,P>0.05), while compared with the positive performance position (89%±2% vs 97%±1%) P<0.01.Conclusion1.VVS occurs in school agechildren, there were more girls than boys. And Summer is the climax stage of attack of VVS. There often had a clear sign of presyncopal symptoms and provocation factors before the syncope, in which long-standing and dizziness, pale had the highest incidence and obviously genetic characteristics of the family.2. Midodrine hydrochloride. not only as effective as metoprolol in the treatment of children with VVS, but also much better than the general treatment and significantly reduce the recurrence of syncope in children with VVS.3. The increase of the NO concentration in plasma at head-up position is one of the pathogenies of VVS.4. Central serotonergie system may be involved in the patbogenesis of VVS.5. Maby oxygen saturation significantly decreased was the main reason and new basis of VVS.
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