[Relationship between unexplained palpitation in 
children and head-up tilt test].

To explore the relationship between unexplained palpitation in children and head-up tilt test (HUTT).
 Methods: A total of 142 children with the main symptom of unexplained palpitation were admitted to the Specialist Out-Patient Clinic of Children's Cardiovascular Disease from Sept. 2008 to Feb. 2017 in the Second Xiangya Hospital, Central South University. Among them, 63 cases were male, 79 cases were female, with the mean age of (10.12±2.88) years old. The detailed history, physical examinations, conventional 12 electrocardiogram, chest X-ray, echocardiography, myocardial enzymes and thyroid function were all examined. The disorders of heart disease, systemic disease and drug effect were ruled out. The HUTT inspection was then given to them.
 Results: Among the 142 palpitation cases, 79 cases were HUTT positive (55.6%) and 63 cases were HUTT negative (44.4%). The age in HUTT positive patients was older than that in HUTT negative patients (P<0.05), with no significant difference in gender (P>0.05). There were three types of hemodynamic changes in HUTT positive patients. Among them, 38 cases were postural orthostatic tachycardia syndrome (48.1%), 36 cases were the vasovagal syncope vasodepressive type (45.6%) and 5 cases were the vasovagal syncope mixed type (6.3%). There were no hemodynamic types for vasovagal syncope cardioinhibitory type, orthostatic hypotension and orthostatic hypertension.
 Conclusion: Among the clinically unexplained palpitations children, more than half are caused by unbalanced autonomic nervous function. HUTT can help clear the cause of unexplained palpitations.