Features of Clinical Manifestations and Heart Rate Variability in Children with Malignant Vasovagal Syncope.

This study aimed to identify the risk factors associated with malignant vasovagal syncope (VVS), a rare yet clinically significant subtype of VVS. This single-center case-control study enrolled children diagnosed with malignant VVS, and the malignant VVS patients were matched in a 1:4 ratio with non-asystolic VVS children as a control group through age and sex stratification. Clinical characteristics and heart rate variability (HRV) parameters were analyzed. Binary logistic regression analyses were used to identify the risk factors significantly associated with malignant VVS. A total of 10 patients in the malignant group and 40 children in the control group were included. The malignant group exhibited earlier symptom onset (7.0 ± 2.7 vs. 9.7 ± 2.7 years, < 0.05) than the control group, and children in the malignant group had a higher prevalence of central triggers (60.0% vs. 17.5%, < 0.05) and convulsive/incontinence episodes (80.0% vs. 17.5%, < 0.05) than the control group. Additionally, the malignant group demonstrated significantly elevated HRV parameters, including very low frequency (VLF), low frequency (LF), and high frequency (HF), indicating substantial autonomic dysregulation characterized by parasympathetic predominance. Central triggers (OR = 7.16, 95%CI 1.10-46.73) and convulsive/incontinence manifestations (OR = 19.02, 95%CI 2.81-128.64) were independent risk factors of malignant VVS. The age at syncope onset was significantly earlier in children with malignant VVS, and children with malignant VVS exhibited profound autonomic dysregulation characterized by significant parasympathetic predominance. Finally, children with episodes induced by central triggers and accompanied by incontinence or convulsions were at a higher risk of asystole.