Analysis of Clinical Features in Children with Vasovagal Syncope Complicated by Convulsions or Incontinence

Objective: Vasovagal syncope (VVS) complicated by convulsions or incontinence (atypical VVS) has distinct manifestations prone to misdiagnosis. This study sought to investigate the clinical manifestations and contributing risk factors of atypical VVS in pediatric patients, with the goals of providing a scientific basis for early identification and improving diagnostic accuracy. Methods: We carried out a case-control study focusing on children with a diagnosis of VVS who received inpatient care in the Pediatric Department of Peking University First Hospital from January 2021 to June 2025. Patients who experienced convulsions or incontinence during syncopal episodes were assigned to the atypical VVS group, while those without these symptoms formed the control group. The clinical data of the two groups were compared, and logistic regression analysis was utilized to detect factors associated with atypical VVS. Results: A total of 393 qualified patients were recruited; there were 68 cases in the atypical VVS group and 325 cases in the control group. The age of the first syncopal episode in children with atypical VVS was significantly lower than that in the control group [9.5 (7.0, 12.0) vs. 11.0 (8.0, 13.0) years, p < 0.05]. Additionally, the atypical VVS group showed higher rates of syncope-related trauma (22.1% vs. 9.2%, χ² = 7.905, p < 0.01), positive syncope-related family history (35.3% vs. 22.8%, χ² = -4.067, p < 0.05), and syncope triggered by central factors (33.8% vs. 19.7%, χ² = 5.721, p < 0.05). The Holter monitoring results revealed that the minimum heart rate was significantly reduced in the atypical VVS group [48.0 (44.8, 52.0) vs. 50.0 (47.0, 54.0) beats/min, p < 0.01]. The analysis of heart rate variability (HRV) showed that the index of the percentage of adjacent normal-to-normal interval differences greater than 50 ms [pNN50; 23.4 (16.6, 34.2) vs. 20.1 (13.1, 28.4), p < 0.05)] and the root mean square of successive differences between adjacent normal cycles [rMSSD; 47.5 (41.0, 64.0) vs. 45.0 (36.0, 56.0), p < 0.05)] was significantly higher in the atypical VVS group than in the control group. Two independent factors associated with atypical VVS were detected with multivariate logistic regression: age at the first episode (OR = 0.874, 95% CI 0.802-0.952, p < 0.01) and minimum heart rate (OR = 0.921, 95% CI 0.879-0.965, p < 0.01). Conclusions: Pediatric patients with atypical VVS present with lower minimum heart rate and a higher incidence of syncope induced by central triggers. Compared with children with typical VVS, those with atypical VVS exhibit more pronounced autonomic nervous system imbalance, characterized by enhanced vagal tone. For children with VVS showing these clinical features, careful differential diagnosis, close follow-up, and vigilance against prolonged asystole during syncopal episodes are recommended.