[Diagnosis of unexplained syncope in children: a multi-center study]

To examine the diagnostic value of head-up tilt test in children with unexplained syncope (UPS).

A total of 379 children (171 males, 208 females) aged 3-18 years, mean age (12 +/- 3) years with unexplained syncope from Beijing, Hunan, Hubei and Shanghai and undergoing baseline head-up tilt tests (BHUTT) or head-up tilt tests potentiated with nitroglycerine (SNHUTT) under a quiet circumstance were selected as the syncope group. Ten healthy children (5 males, 5 females) aged 9-15 years with a mean age of (11.4 +/- 2.1) years, were recruited as the control group. SPSS 10.0 software was used for data analysis.

In 379 children with unexplained syncope, 67 (17.7%) were of postural orthostatic tachycardia syndrome (POTS), 157 (41.4%) of vasovagal syncope vasoinhibitory pattern, 14 (3.7%) of vasovagal syncope cardioinhibitory pattern, 47 (12.4%) of vasovagal syncope mixed pattern, 1 (0.3%) of orthostatic hypotension (OH) and 93 children (24.5%) of UPS. In syncope group and control group, the positive rate of BHUTT was 55.9% and 0 respectively and it was 75.5% and 20.0% respectively for SNHUTT. During BHUTT, the mean time of positive response occurrence was (16 +/- 12) minutes, and the posture when positive response appeared was at a tilt angle of 60 degrees. For SNHUTT, the mean time of positive response occurrence was (6 +/- 4) minutes and the posture was at a tilt angle of 60 degrees when potentiated with nitroglycerine.

HUTT is an objective diagnostic tool of UPS. With a high diagnostic positive rate, SNHUTT can improve the diagnostic positive rate of BHUTT. Meanwhile the time of positive response occurrence during SNHUTT is markedly shorter than BHUTT.