[Causes of unexplained syncope in children].

OBJECTIVE: To investigate the common causes of unexplained syncope in children. METHODS: A total of 434 children with unexplained syncope who were aged from 3.0 to 17.9 years (192 males and 242 females) and who saw the doctor between January 2006 and October 2011. were examined in order to explore the detailed histories and causes of syncope and to analyze variance in causes among different ages, genders, syncope frequencies and head-up tilt test (HUTT) results. RESULTS: (1) The causes of occasional syncope included persistent standing (30%), movement (13%), change in body position(9%), sitting(7%), and playing(6%). Persistent standing was more common as a cause in females than in males (P<0.01). Micturition syncope was mainly seen in males. Sultry weather was the main cause of syncope in females. Change in body position was a more common cause in the ≥12 years group than in the <12 years group (P<0.05), while other causes showed no significant differences among different age groups. Change in body position was a more common cause of syncope in children with negative HUTT results than in those with positive HUTT results (P<0.05). (2) All causes of occasional syncope can induce repeated syncope, and most repeated syncope (56%) had the same cause. CONCLUSIONS: The common causes of unexplained syncope include persistent standing, movement and changes of body position in children. Avoiding these causes is helpful for prevention of childhood syncope.

[Application of the head-up tilt table test in children under 6 years old].

OBJECTIVE: To study the clinical value and safety of the head-up tilt table test (HUTT) in children under 6 years old. METHODS: The HUTT results between September 2000 and August 2011 of 144 2 to 6-year-old children (81 boys and 63 girls) with syncope and dizziness of unknown causes were retrospectively studied. RESULTS: Eight children completed the based tilt table test and 136 cases completed the sublingual nitroglycerin tilt table test. No serious side effects were found in these children. Thirty-two (22.2%) of the 144 children had a positive result of HUTT, including 18 boys and 14 girls (P>0.05). When HUTT-induced syncope met positive standards, ECG record and blood pressure recovered to normal levels within 5 minutes by changing the position of the test bed, keeping the airway open, nasal oxygen inhalation and oral milk. CONCLUSIONS: The HUTT is valuable, safe and compliant in children under 6 years old.

[Arrhythmia after a positive head-up tilt table test].

OBJECTIVE: to study the characteristics of arrhythmia after a positive head-up tilt table test (HUTT). METHODS: head-up tilt table test (BHUT) or sublingual nitroglycerin-provocation head-up tilt table test (SNHUT) were performed in 1374 patients at the Second Xiangya Hospital of Central South University from March of 2001 to August of 2009. Arrhythmias were recorded in 169 patients after a positive HUTT [57 male, age 6 - 65 years, 86 children < 18 years, mean age (23.1 ± 14.8) years]. RESULTS: arrhythmias developed in 75 patients (44.38%) post a positive BHUT and in 94 patients (55.62%) post a positive SNHUT. Major types of arrhythmias were sinus bradycardia (143/169, 84.62%), junctional escape rhythm (55/169, 32.54%) and sinus arrest (26/169, 15.38%). Sinus bradycardia was more common in adult (P < 0.01). Occurrence of junctional escape rhythm and sinus arrest was not affected by age, gender and test mode. Arrhythmia and the manifestation of syncope or pre-syncope occurred simultaneously in 77 (45.56%) patients and mainly in BHUT, while arrhythmia appeared later than the syncope manifestation in 92 (54.44%) patients and mainly in SNHUT (P < 0.05). Arrhythmia and blood pressure reduction occurred simultaneously in 84 (53.50%) cases and mainly in BHUT, while arrhythmia appeared later than reduction of blood pressure in 73 (46.50%) cases and mainly in SNHUT (P < 0.01). CONCLUSIONS: (1) the common types of arrhythmia were sinus bradycardia, junctional escape rhythm and sinus arrest after a positive HUTT. Occurrence of sinus arrest was not affected by age, gender and test mode. (2) In BHUT, arrhythmia occurred mostly simultaneously with the manifestation of syncope or pre-syncope and blood pressure reduction, while arrhythmia appeared later in SNHUT.

[Clinical analysis of vasovagal syncope in children].

OBJECTIVE: To study the changes in clinical features of vasovagal syncope (VVS) in children. METHODS: From January 2000 to September 2009, 841 children with unexplained syncope or prodromata were enrolled. They were assigned to two groups according to the period of visiting hospital: group A (from January 2000 to December 2004, n=129) and group B (from January 2005 to September 2009, n=712). They were assigned to three age groups: 4-6 years old, 7-10 years old and 11-18 years old. A head-up tilt table test (HUTT) was performed on all the subjects. RESULTS: The total positive rate of HUTT was 45.3% (381/841). Compared with that in group A, the positive rate of HUTT in group B increased significantly (47.5% vs 33.3%; P<0.05). The positive rate of HUTT in female children was significantly higher than that in male children (49.3% vs 37.9%; P<0.05). The positive rate of HUTT increased with age and it was the highest in children at age of 11-18 years (49.2%), followed by in children at age of 7-10 years (44.1%) and 4-6 years (37.1%) (P<0.05). The children at age of 7-10 years and 11-18 years from group B showed significantly higher positive rate of HUTT than those from group A (46.2% vs 27.8%; 54.0% vs 32.6%, P<0.05). Vasodepressor type was the most common response type (70.9%) shown by HUTT compared with mixed type (25.5%) and cardioinhibitory type (3.6%) (P<0.05). The proportion of children with vasodepressor response type in group B was significantly higher than that in group A (72.5% vs 58.1%; P<0.05). CONCLUSIONS: There were obvious changes in the prevalence of VVS and response types before and after five years, suggesting that the development of VVS may be attributed to many factors, such as social factors, mental factor and life style.

[Efficacy of midodrine hydrochloride in the treatment of children with vasovagal syncope].

OBJECTIVE: To explore the efficacy of midodrine hydrochloride in the treatment of vasovagal syncope (VVS) in children. METHODS: Forty-eight children with unexplained syncope and prodromata (21 males, 27 females, aged 6 -17 years, mean 11 years +/- 3 years) were randomly assigned into 3 groups. They were health education group, cresol group and midodrine hydrochloride group respectively. Cresol group was comprised of children given cresol as first-line therapy in addition to health education and midodrine hydrochloride group patients given midodrine hydrochloride on the basis of cresol group. Repeated head-up tilt testing (HUTT) and follow-ups of at least 6 months were conducted to evaluate the therapeutic efficacy, side effects of midodrine hydrochloride and hemodynamic changes in treating pediatric VVS. RESULTS: (1) The HUTT-based effective rate of 3 group was 20.0% (2/10), 60.9% (14/23) and 80.0% (12/15) respectively. It was significantly higher in cases of midodrine hydrochloride group and cresol group than that of health education group (P < 0.05). However,there was no significant difference in the HUTT-based effective rate between cresol group and midodrine hydrochloride group (P > 0.05). (2) During the follow-up period, the recurrence rate of syncope was significantly lower in midodrine hydrochloride group than in other two groups (P < 0.05). However, there was no significant difference in the recurrence rate of syncope between health education and cresol groups (P > 0.05). (3) There was no statistic difference in supine hemodynamic indices (HR, SBP, DBP) between before and after treatment in 3 groups. After midodrine therapy, the effects of midodrine upon changes in systolic and diastolic pressures and heart rate, between upright beginning and supine positions, were statistically significant (P <0.05). CONCLUSION: Health education and cresol are conventional therapies for pediatric VVS. The efficacy can be enhanced by supplementing midodrine hydrochloride. Such a regimen is effective and safe in treating pediatric VVS.