Association of clinical features with different hemodynamic patterns in head-up tilt test in children with unexplained syncope

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To explore the different hemodynamic patterns during the course of head-up tilt tests in children with unexplained syncope and the association of clinical features with different hemodynamic patterns in head-up tilt test in children with unexplained syncope. 100 pediatric patients with unexplained syncope, aged 11 +/- 2 (6-16), 36 male and 64 female, with the mean course of 10 +/- 16 months (2 d-5 y), underwent head-up tilt tests or head-up tilt tests potentiated with nitroglycerine under quiet circumstance. Blood pressure and heart rate were monitored simultaneously. According to their different hemodynamic patterns, they were divided into vasovagal response pattern, postural orthostatic tachycardia syndrome (POTS) response pattern, orthostatic hypotension (OH) response pattern and normal response pattern. The vasovagal response was divided into vasodepressor, cardioinhibitory and mixed patterns. The distribution and different clinical features of different response patterns in the unexplained syncope were also studied. Fifty (50%) of the 100 children with unexplained syncope displayed the hemodynamic pattern of vasovagal response, among which 31 (31%) displayed the pattern of vasodepressor response, 7 (7%) cardioinhibitory response, and 12 (12%) mixed response. Thirty-three patients (33%) displayed POTS response, 2 (2%) OH response, and 15 (15%) the normal hemodynamic response. Patterns of dysautonomic response and chronotropic incompetence were not observed in these children with unexplained syncope. The age of the children with normal response during HUT was 10 +/- 3 years, significantly younger than that of the children with vasovagal response and POTS response (12 +/- 2 and 12 +/- 2, both P < 0.01). There were no differences in sex ratio and duration of syncope among the vasovagal response, POTS and normal response. But the syncopal spells in the children with POTS response was less frequent and the baseline heart rate of the children with POTS response was 81 +/- 7, significantly faster than that of the children with vasovagal response and normal response (71 +/- 9 and 74 +/- 7, both P < 0.01). There was no significant difference in the baseline blood pressure among the children with vasovagal response, POTS and normal response. There were also no significant differences in the age, sex ratio, and duration of syncope, number of syncopal spells, baseline heart rate, and baseline blood pressure among the children with vasodepressor response, cardioinhibitory response and mixed response. There are different hemodynamic response patterns in head-up tilt testing in children with unexplained syncope, and there was some association between hemodynamic response patterns and their clinical features.