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Clinical value of chronotropic competence in children with vasovagal syncope

??Objective??To evaluate the chronotropic competence in children with vasovagal syncope ??VVS??. Methods??Thirty-nine patients??17 males??22 females??age ranging from 8-16 years?? with syncope were included in the study??and 28 were diagnosed with VVS??including 15 cases of vasodepressor type??9 cases of mixed type??and 4 cases of cardioinhibitory type??11 were with unexplained cause of syncope. A treadmill test was performed and heart-rate response during exercise was evaluated by the chronotropic reserve. Demographic data and change of heart rate??blood pressure during test and CRI were compared between the 2 groups and different types of VVS. Furthermore??based on CRI??patients with VVS were divided into the normal chrontropic group??n??10?? and CI group??n??17??. By following the recurrence of syncope of 2 groups??the effect of CI on the prognosis of VVS in children was observed. Results??There were no significant differences between children with VVS and with unexplained syncope in sex??age??BMI??baseline heart rate??MaxMET or baseline blood pressure. But during exercise test??peak heart rate and CRI were significantly lower in children with VVS than in unexplained syncope. The incidence of CI in children with VVS was significantly higher than that in children with unexplained syncope??64.3% vs. 27.3%??P??0.05??. The incidence of CI in VVS with vasodepressor-type in children was significantly lower than those with cardioinhibitory-type and mixed-type. During following-up period??the recurrence rate of syncope in VVS children with CI was significantly higher than that of children without CI. Patients with CI had significantly worse prognosis compared to those without CI??Log-rank??P??0.028??. Conclusion??Chrontropic competence is significantly altered in children with VVS??especially in cardioinhibitory-type and mixed-type in children. CI is the significant predictor for poor prognosis in children with VVS.