Cardiac Autonomic Functions During Asymptomatic Period in Pediatric Patients with Vasovagal Syncope

Abstract

Objective: Vasovagal syncope (VVS) is the most common type of syncope in pediatric patients. One potential pathophysiological mechanism for developing VVS involves autonomic dysfunction. In this study, we evaluated autonomic functions during the asymptomatic period in patients with VVS. Methods: Patients attending to a pediatric cardiology outpatient clinic and diagnosed with VVS and control subjects consisting of healthy children were included. All subjects underwent electrocardiography, echocardiography, and Holter ECG monitoring. Then time domain index parameters in Holter ECG: SDNN, SDNNIndx, SDANN, pNN50, rMMSD and minimum, mean, and maximum heart rate were evaluated. Results: Twenty-four children (15 female, 9 male) with recurrent VVS and 27 healthy children (19 female, 8 male) were enrolled. While mean and maximum heart rates did not differ significantly between patients with syncope and healthy children, minimum heart rate was lower in syncope patients (49.3+-5.41; 44.4+-5.6 p=0.007). Statistical analysis of the results showed a significant increase in SDNN, SDNNIndx, SDANN, pNN50 and r MMSD in VVS patients compared to controls (p<0.01). Conclusion: As indicated by parameters of heart rate variability, pediatric patients with VVS exhibit chronic autonomic differences in the form of increased sympathetic and parasympathetic impulses during the asymptomatic period of their condition compared to healthy children. Although clinical history remains the most important diagnostic tool in patients with VVS, Holter ECG monitoring may provide useful diagnostic information in patients with difficult differential diagnosis.

Keywords

• vasovagal syncope
• holter ecg
• autonomic function