Head-up tilt test results in child twins with nervous mediated syncope.

Objective: To investigate the familial genetic characteristics of syncope in children.
Methods: A detailed medical history was taken from four twin pairs of children complaining of dizziness, headache, chest tightness, chest pain, prodromal symptoms of syncope or syncope, meanwhile, these patients were given routine physical examination, 12-lead ECG, echocardiography, Holter ECG, EEG, MRI of the head and other tests to exclude cardio-cerebrovascular and pulmonary diseases, with those with unknown origin for syncope undergoing head-up tilt test (HUTT) and inquiry of detailed family history.
Results: The four pairs of twins with syncope beginning at 7-12years and induced mostly by standing position (4/5), and positive family history was noted in two pairs. Vasovagal syncope (VVS)-vasoinhibitory response pattern was predominant in HUTT (4/5). The results and the response pattern in HUTT might diversify between two members within same twin pair: one appeared as vasoinhibitory response pattern and one postural orthostatic tachycardia syndrome (POTS) pattern in the first pair, one vasoinhibitory response pattern and one negative response pattern in the second pair, vasoinhibitory response pattern in the third pair and negative response pattern in the fourth pair.
Conclusions: The hereditary factors may play a more important role in younger children with syncope. Environment and psychological factors may induced syncope attack. The results and the response pattern in HUTT are diversified and which might different between two members within twin pair.
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