syncope accounts for about 12% of emergency department visits , but the etiology of many patients with syncope is unclear [ 37 ] . recently , with the use of the head - up tilt test ( hut ) , the number of patients with unexplained syncope ( ups ) has been decreasing . in the elderly with syncope , the most common cause of syncope is organic heart disease . in non - elderly adults with syncope , 5066% of cases are neurally - mediated syncope ( nms ) , and less than 5% of cases there are marked differences in pathophysiology between children and adults ; however , up to now , the spectrum of underlying diseases of syncope in children has been unclear . we analyzed the distribution of etiologies of syncope in children in china through a multicenter , large sample - based study . the study population consisted of 888 children ( 417 boys , 471 girls ) aged 5 to 18 years ( mean 12.03.0 years ) with syncope , consecutively recruited from august 1999 to march 2009 in a multi - center network study of childhood syncope in beijing , shanghai , hunan province , and hubei province in china . all patients underwent an initial evaluation consisting of carefully taken history and physical examination including orthostatic and supine heart rate , blood pressure measurements and standard electrocardiogram ( ecg ) . through the initial evaluation :  some common diseases could be diagnosed definitively , for example , postural orthostatic tachycardia syndrome ( pots ) , orthostatic hypotension ( oh ) , pharmacal syncope , some severe arrhythmias , etc ;  several disorders that resemble syncope in different ways could be tentatively diagnosed ( e.g. , myocardiopathy , pulmonary hypertension , cyanotic congenital heart disease , some arrhythmias and carotid sinus hypersensitivity ) on the basis of some of the following examinations when indicated  echocardiogram , 24-hour ambulatory electrocardiography monitoring , electroencephalogram ( eeg ) , cranial or cervical computed tomography ( ct ) , cardiac catheterization or cardiac electrophysiology examination to diagnose the aforementioned diseases ;  for those whose diagnosis still could not be made exactly or suggestively through aforesaid examinations in  and  , the head - up tilt test ( hut ) was indicated to diagnose vasovagal syncope ( vvs ) , pots , oh , etc . if some patients still could not be diagnosed exactly through all these examinations , the work - up was re - appraised . patients fasted for 12 hours before testing , and for at least 3 days before testing were not allowed to have any drugs that could possibly influence the autonomic nervous system . baseline recordings of heart rate ( hr ) , electrocardiogram and blood pressure ( bp ) with a dash 2000 multileads physiological monitor ( ge , usa ) in the supine position were obtained near the end of a 10-minute resting period . the monitoring of the variation of electrocardiogram , hr and bp was carried out along with clinical monitoring of symptoms . the bhut was continued until positive response appeared , or for 45 minutes , whichever came first . if a positive response was elicited , the test was terminated by rapidly lowering the tilt table . snhut was conducted in patients with negative response in bhut using nitroglycerin ( 46 g / kg , the maximum dose 300 g ) . the monitoring of electrocardiogram , hr and bp with a dash 2000 multileads physiological monitor ( ge , usa ) was carried out along with clinical monitoring of symptoms . the tests were terminated when positive responses appeared or for 20 minutes , whichever came first . if a positive response was elicited , the test was terminated by a rapid lowering of the tilt table . informed consent was obtained from each child or their parents , and the study protocol was approved by the ethics committee of peking university first hospital . a detailed history and physical examination vvs is diagnosed if precipitating events such as fear , severe pain , emotional distress , instrumentation or prolonged standing are associated with typical prodromal symptoms . the positive standard of hut for vvs was that patients had syncope or presyncope in association with any of the following data in hut :  bp decreased ;  hr decreased ;  sinus arrest appeared ;  temple or larger than  atrioventricular block and asystole for 3 seconds . the standard of bp decrease was 80 mmhg ( 10.7 kpa , 1 mmhg=0.133kpa ) in systolic bp or 50 mmhg in diastolic bp or a 25% decrease in mean bp . if the child did nt achieve the standard , but the symptom of syncope or presyncope appeared , the response was also defined as positive . vasoinhibitory response was defined as an obvious decrease in bp without hr reduction and cardioinhibitory response as an abrupt decrease in hr without systolic bp decrease . when hr increased 30 bpm or the maximum of hr 120 bpm during the head - up tilt test of 10 minutes , it was defined as postural orthostatic tachycardia syndrome ( pots ) , which is often accompanied by dizziness , chest distress , headache , palpitation , pallor , etc . for the diagnosis of oh , orthostatic blood pressure measurements are recommended after 5 min of lying supine , followed by measurements taken each minute , or more often , after standing for 3 min . if the patient does not tolerate standing for this long , the lowest systolic blood pressure during the upright posture should be recorded . a decrease in systolic blood pressure 20 mmhg , or a decrease in systolic blood pressure to < 90 mmhg the positive standard of standing test or hut was as follows :  bp was normal in prostration ;  bp decreased within 3 minutes when the patient s position changed from prostration to orthostatism ; and bp decrease was 20 mmhg ( 10.7 kpa , 1 mmhg=0.133 kpa ) in systolic bp , or a decrease in systolic blood pressure to < 90 mmhg . a situational syncope is suggested if the event occurred with defecation , urination , coughing , or swallowing . the diagnosis of cardiogenic syncope mainly relies on electrocardiogram , echocardiogram and 24-hour holter monitoring , and consists primarily of cardiac ischemia and arrhythmia . cardiac ischemia - related syncope is diagnosed when symptoms are present with ecg evidence of acute ischaemia with or without myocardial infarction , independent of its mechanism . arrhythmia - related syncope is diagnosed by ecg when there is sinus bradycardia < 40 beats / min or repetitive sinoatrial blocks or sinus pauses > 3 s in the absence of negatively chronotropic medications , mobitz ii 2 or 3 degree atrioventricular block , alternating left and right bundle branch block , rapid paroxysmal supraventricular tachycardia or ventricular tachycardia and pacemaker malfunction with cardiac pauses . the study population consisted of 888 children ( 417 boys , 471 girls ) aged 5 to 18 years ( mean 12.03.0 years ) with syncope , consecutively recruited from august 1999 to march 2009 in a multi - center network study of childhood syncope in beijing , shanghai , hunan province , and hubei province in china . all patients underwent an initial evaluation consisting of carefully taken history and physical examination including orthostatic and supine heart rate , blood pressure measurements and standard electrocardiogram ( ecg ) . through the initial evaluation :  some common diseases could be diagnosed definitively , for example , postural orthostatic tachycardia syndrome ( pots ) , orthostatic hypotension ( oh ) , pharmacal syncope , some severe arrhythmias , etc ;  several disorders that resemble syncope in different ways could be tentatively diagnosed ( e.g. , myocardiopathy , pulmonary hypertension , cyanotic congenital heart disease , some arrhythmias and carotid sinus hypersensitivity ) on the basis of some of the following examinations when indicated  echocardiogram , 24-hour ambulatory electrocardiography monitoring , electroencephalogram ( eeg ) , cranial or cervical computed tomography ( ct ) , cardiac catheterization or cardiac electrophysiology examination to diagnose the aforementioned diseases ;  for those whose diagnosis still could not be made exactly or suggestively through aforesaid examinations in  and  , the head - up tilt test ( hut ) was indicated to diagnose vasovagal syncope ( vvs ) , pots , oh , etc . if some patients still could not be diagnosed exactly through all these examinations , the work - up was re - appraised . patients fasted for 12 hours before testing , and for at least 3 days before testing were not allowed to have any drugs that could possibly influence the autonomic nervous system . baseline recordings of heart rate ( hr ) , electrocardiogram and blood pressure ( bp ) with a dash 2000 multileads physiological monitor ( ge , usa ) in the supine position were obtained near the end of a 10-minute resting period . the monitoring of the variation of electrocardiogram , hr and bp was carried out along with clinical monitoring of symptoms . the bhut was continued until positive response appeared , or for 45 minutes , whichever came first . if a positive response was elicited , the test was terminated by rapidly lowering the tilt table . snhut was conducted in patients with negative response in bhut using nitroglycerin ( 46 g / kg , the maximum dose 300 g ) . the monitoring of electrocardiogram , hr and bp with a dash 2000 multileads physiological monitor ( ge , usa ) was carried out along with clinical monitoring of symptoms . the tests were terminated when positive responses appeared or for 20 minutes , whichever came first . if a positive response was elicited , the test was terminated by a rapid lowering of the tilt table . informed consent was obtained from each child or their parents , and the study protocol was approved by the ethics committee of peking university first hospital . a detailed history and physical examination are central to the diagnosis , which requires ruling out cardiovascular or neurologic diseases . vvs is diagnosed if precipitating events such as fear , severe pain , emotional distress , instrumentation or prolonged standing are associated with typical prodromal symptoms . the positive standard of hut for vvs was that patients had syncope or presyncope in association with any of the following data in hut :  bp decreased ;  hr decreased ;  sinus arrest appeared ;  temple or larger than  atrioventricular block and asystole for 3 seconds . the standard of bp decrease was 80 mmhg ( 10.7 kpa , 1 mmhg=0.133kpa ) in systolic bp or 50 mmhg in diastolic bp or a 25% decrease in mean bp . if the child did nt achieve the standard , but the symptom of syncope or presyncope appeared , the response was also defined as positive . vasoinhibitory response was defined as an obvious decrease in bp without hr reduction and cardioinhibitory response as an abrupt decrease in hr without systolic bp decrease . when hr increased 30 bpm or the maximum of hr 120 bpm during the head - up tilt test of 10 minutes , it was defined as postural orthostatic tachycardia syndrome ( pots ) , which is often accompanied by dizziness , chest distress , headache , palpitation , pallor , etc . for the diagnosis of oh , orthostatic blood pressure measurements are recommended after 5 min of lying supine , followed by measurements taken each minute , or more often , after standing for 3 min . if the patient does not tolerate standing for this long , the lowest systolic blood pressure during the upright posture should be recorded . a decrease in systolic blood pressure 20 mmhg , or a decrease in systolic blood pressure to < 90 mmhg , the positive standard of standing test or hut was as follows :  bp was normal in prostration ;  bp decreased within 3 minutes when the patient s position changed from prostration to orthostatism ; and bp decrease was 20 mmhg ( 10.7 kpa , 1 mmhg=0.133 kpa ) in systolic bp , or a decrease in systolic blood pressure to < 90 mmhg . a situational syncope is suggested if the event occurred with defecation , urination , coughing , or swallowing . the diagnosis of cardiogenic syncope mainly relies on electrocardiogram , echocardiogram and 24-hour holter monitoring , and consists primarily of cardiac ischemia and arrhythmia . cardiac ischemia - related syncope is diagnosed when symptoms are present with ecg evidence of acute ischaemia with or without myocardial infarction , independent of its mechanism . arrhythmia - related syncope is diagnosed by ecg when there is sinus bradycardia < 40 beats / min or repetitive sinoatrial blocks or sinus pauses > 3 s in the absence of negatively chronotropic medications , mobitz ii 2 or 3 degree atrioventricular block , alternating left and right bundle branch block , rapid paroxysmal supraventricular tachycardia or ventricular tachycardia and pacemaker malfunction with cardiac pauses . among the 888 patients aged 5 to 18 years ( mean 12.03.0 years ) with syncope , 471 ( 53.0% ) were female and 417 ( 47.0% ) male . in patients with syncope , 175 ( 19.7% ) were of vvs - vasoinhibitory pattern , 35 ( 3.9% ) vvs - cardioinhibitory pattern , 73 ( 8.2% ) vvs - mixed pattern , 286 ( 32.2% ) pots , 19 ( 2.1% ) oh , 7 ( 0.9% ) situational syncope , 13 ( 1.5% ) cardiogenic syncope , and 280 ( 31.5% ) were unexplained syncope ( ups ) ( table 1 ) . in 888 children ( 417 male and 471 female ) with syncope , their age ranged from 5 years to 18 years , and mean age was 12.03.0 years . in 595 children aged 5 to 18 years ( mean 12.32.9 years ) with nms vvs - vasoinhibitory pattern accounted for 175 cases ( 19.7% ) , whose ages ranged from 5 to 18 years ( mean 13.03.0 years ) ; 77 ( 44.0% ) were male and 98 ( 56.0% ) were female . there were 35 ( 3.9% ) cases with vvs - cardioinhibitory pattern , with an age range from 6 to 18 years ( mean 12.32.7 years old ) , of whom 17 ( 48.6% ) were males and 18 ( 51.4% ) were females ; 73 ( 8.2% ) cases had vvs - mixed pattern , including 26 ( 35.6% ) males and 47 ( 64.4% ) females , age range from 5 to 17 years , with a mean of 12.72.6 years ( table 1 , figure 1 ) . there were 286 ( 32.2% ) ( 133 males , 153 females ) children with pots , with an age range from 5 to 18 years ( mean 11.82.7 years old ) ( table 1 , figure 1 ) . nineteen ( 2.1% ) children had oh , including 12 ( 63.2% ) males and 7 ( 36.8% ) females . their age range was from 5 to 15 years , with a mean of 10.02.9 years old ( table 1 , figure 1 ) . there were 7 ( 0.9% ) children with situational syncope , with an age range of 8 to 18 years ( mean 15.13.6 years ) . six cases were males and one was female ( table 1 , figure 1 ) . there were 13 children ( 4 male and 9 female ) aged 7 to 18 years ( mean 12.53.2 years ) with cardiogenic syncope ( table 1 , figure 1 ) . in 280 children aged 5 to 18 years ( mean 11.53.3 years ) with ups , 142 ( 50.7% ) were males and 138 ( 49.3% ) females ( table 1 , figure 1 ) . among the 888 patients aged 5 to 18 years ( mean 12.03.0 years ) with syncope , 471 ( 53.0% ) were female and 417 ( 47.0% ) male . in patients with syncope , 175 ( 19.7% ) were of vvs - vasoinhibitory pattern , 35 ( 3.9% ) vvs - cardioinhibitory pattern , 73 ( 8.2% ) vvs - mixed pattern , 286 ( 32.2% ) pots , 19 ( 2.1% ) oh , 7 ( 0.9% ) situational syncope , 13 ( 1.5% ) cardiogenic syncope , and 280 ( 31.5% ) were unexplained syncope ( ups ) ( table 1 ) . in 888 children ( 417 male and 471 female ) with syncope , their age ranged from 5 years to 18 years , and mean age was 12.03.0 years . in 595 children aged 5 to 18 years ( mean 12.32.9 years ) with nms , vvs - vasoinhibitory pattern accounted for 175 cases ( 19.7% ) , whose ages ranged from 5 to 18 years ( mean 13.03.0 years ) ; 77 ( 44.0% ) were male and 98 ( 56.0% ) were female . there were 35 ( 3.9% ) cases with vvs - cardioinhibitory pattern , with an age range from 6 to 18 years ( mean 12.32.7 years old ) , of whom 17 ( 48.6% ) were males and 18 ( 51.4% ) were females ; 73 ( 8.2% ) cases had vvs - mixed pattern , including 26 ( 35.6% ) males and 47 ( 64.4% ) females , age range from 5 to 17 years , with a mean of 12.72.6 years ( table 1 , figure 1 ) . there were 286 ( 32.2% ) ( 133 males , 153 females ) children with pots , with an age range from 5 to 18 years ( mean 11.82.7 years old ) ( table 1 , figure 1 ) . nineteen ( 2.1% ) children had oh , including 12 ( 63.2% ) males and 7 ( 36.8% ) females . their age range was from 5 to 15 years , with a mean of 10.02.9 years old ( table 1 , figure 1 ) . there were 7 ( 0.9% ) children with situational syncope , with an age range of 8 to 18 years ( mean 15.13.6 years ) . six cases were males and one was female ( table 1 , figure 1 ) . there were 13 children ( 4 male and 9 female ) aged 7 to 18 years ( mean 12.53.2 years ) with cardiogenic syncope ( table 1 , figure 1 ) . in 280 children aged 5 to 18 years ( mean 11.53.3 years ) with ups , 142 ( 50.7% ) were males and 138 ( 49.3% ) females ( table 1 , figure 1 ) . it is defined as  a sudden and brief loss of consciousness associated with a loss of postural tone , from which recovery is spontaneous  with a variety of causes . it usually accounts for about 12%   of emergency department visits . in clinical practice , more and more costly investigations typically yield fewer and fewer diagnoses , and the causes of syncope in many patients are unclear [ 37 ] . children with syncope always are diagnosed as ups in clinical service . recently , with the use of hut , most children with ups can be precisely diagnosed ; however , there are still some cases of ups . some reported that in elderly people with syncope , the most common cause of disease was organic heart disease , and the next was pulmonary artery thrombus and syncope subsequent to taking medicine . in 1986 , lipsitz reported that in adults with syncope , 5066% of patients had neurally - mediated syncope ( nms ) , 1020% had psychogenic disease , and less than 5% of patients had syncope attributed to supraventricular tachycardia . other studies have discovered that various of etiologies of syncope were correlated with age . however , there are many differences in physiological functions between children and adults . however , there have been few recent studies on the disease spectrum of children with syncope . in 2004 , liu et al .   analyzed the cause of syncope in 30 children , finding that in 20 cases ( 66.7% ) , etiology of syncope was as follows : neurological disorders in 12 cases ( 40.0% ) , including ischemic of intracranialis artery in 7 cases , seizure in 1 case , hysteria in 2 cases , concussion of the brain in 1 case , and episodic dizziness accompanied by elbow pain in 1 case . cardiovascular disorders were found in 7 cases ( 23.3% ) , including supraventricular tachycardia in 3 cases , long q - t syndrome leading to ventricular tachycardia in 1 case , and tetralogy of fallot in 3 cases . the other 10 cases ( 33.3% ) were found to be of uncertain etiologies , and 2 of them occurred post - exercise or following a long period of standing . however , because the diagnostic measures were limited and the number of patients was quite small , the outcome of the study could not reveal the constituent ratio of syncope in children . in 2008 , we analyzed the etiology of syncope in 474 children ; however , this was a single center study instead of a multi - center study in china and the number of patients evaluated was small . there have not been any multi - center - based studies on the spectrum of underlying disease in children with syncope . therefore , it would be very important to conduct a multi - center study with a large sample size on the disease spectrum in children with syncope . in 2009 , noizet - yverneau , et al reported the frequency of syncope and pre - syncope in a pediatric emergency care unit . in their study , 159 children ( mean age , 114 years ) were included , accounting for 0.8% of the pecu s visits . it was shown that 48% of patients had syncope and 52% had pre - syncope . neither cardiac arrhythmia nor obstructive cardiomyopathy was diagnosed . in our multicenter , large sample study , we found that in 888 children with syncope , 175 ( 19.7% ) were vvs - vasoinhibitory pattern , 35 ( 3.9% ) were vvs - cardioinhibitory pattern , 73 ( 8.2% ) were vvs - mixed pattern , 286 ( 32.2% ) were pots , 19 ( 2.1% ) were oh , 7 ( 0.9% ) were situational syncope and 13 ( 1.5% ) were cardiogenic syncope , and there were 280 ( 31.5% ) remaining unexplained cases of syncope . we discovered that nms was the most common cause of syncope in children , accounting for 67.0% of cases . identifying the disease spectrum in children with syncope would be of great help in clinical practice . our study is limited by its relatively small sample size . in spite of this limitation , we report that nms was the most common cause of syncope in children . in the future , we will investigate the syncope spectrum in children through a larger multi - center study .
summarybackgroundsyncope accounts for about 12% of emergency department visits , but the etiology in many patients with syncope is unclear . 
 recently , with the use of the head - up tilt test ( hut ) , the number of patients with unexplained syncope ( ups ) has been decreasing ; however , the spectrum of underlying diseases of syncope in children is unclear . this retrospective study aimed to analyze the spectrum of underlying diseases in children with syncope.material/methodsthis multi - center clinical study consisted of 888 children ( 417 males , 471 females , aged 518 yrs , median age 12.03.0 yrs ) with syncope who came from beijing city , hunan province , hubei province and shanghai from august 1999 to march 2009 . 
 the clinical and laboratory data of children were studied and the spectrum of underlying diseases in children with syncope was analyzed.resultsin 888 children with syncope , 175 ( 19.7% ) had vasovagal syncope ( vvs ) with vasoinhibitory response , 35 ( 3.9% ) had vvs with cardioinhibitory response , 73 ( 8.2% ) had vvs with mixed response , 286 ( 32.2% ) had postural orthostatic tachycardia syndrome ( pots ) , 19 ( 2.1% ) had orthostatic hypotension , 7 ( 0.9% ) had situational syncope , 13 ( 1.5% ) had cardiogenic syncope , and 280 ( 31.5% ) had unexplained syncope.conclusionsthe data suggest that neurally - mediated syncope was the most common cause in children with syncope . 
 pots and vvs were the most common hemodynamic patterns of neurally - mediated syncope .