[Diagnostic values of heart rate variability on unexplained syncope in children]

To investigate the diagnostic values of heart rate varibility (HRV) on unexplained syncope (UPS) in children.

Forty-nine children with unexplained syncope underwent head-up tilt test (HUT) and Holter monitering, then the differences were analyzed between HUT positive children and HUT negative children. The receiver operating characteristic (ROC) curve was used to explore the diagnostic values of HRV.

Of the 49 patients, 32 (65.3%) were HUT positive. The diagnostic positive rate of HUT was 65.3%. The SDNNi, rMSSD, TP, ULF, VLF, LF and HF in the HUT positive group were significantly higher than those in the HUT negative group (P<0.05), respectively. There were no significant differences in SDNN, pNN50 and triangular index between the patients with different HUT outcomes (P>0.05). The ROC curve on the predictive values of SDNNi, rMSSD, TP, ULF, VLF, LF and HF showed that ULF, LF, and HF (12 947.00, 9 462.50, and 9 509.00) as cutting values produced both high sensitivity (75.0%, 68.8%, and 68.8%) and specificity (64.7%, 64.7%, and 64.7%) to predict the diagnostic values of HUT for diagnosing unexplained syncope.

ULF, LF and HF can be considered as indicators for diagnosing neurally-mediated syncope in children. ULF, LF, and HF (12 947.00, 9 462.50, and 9 509.00) taken as cutting values may produce both high sensitivity and specificity.