Cardiac nodal and cardiac autonomic functions in children with vasovagal syncope.

In the present study, cardiac nodal (sinoatrial node and atrioventricular node) and cardiac autonomic functions have been investigated in children with vasovagal syncope (VVS). Thus, the effect of existing autonomic status on the characteristics of cardiac conduction system has been demonstrated in children with VVS. The study included 51 pediatric patients (the mean age was 14.01±2.79 years, range 7 to 18 years; 30 females), who were evaluated for syncope using ECG, Holter monitoring, and echocardiography, all of which showed normal findings. All patients underwent head-up tilt testing (HUTT), and the parameters of heart rate variability (HRV) (SDNN, SDANN, SDANNi, rMSSD, pNN50, HF, LF, VLF) were evaluated with the analysis of 24-hour Holter testing. Corrected sinus node recovery time (CNRT) and Wenckebach point (WP) were measured in all patients using transesophageal atrial stimulation. The patients were divided into groups according to HUTT results and evaluated accordingly. Cardiac nodal functions were normal in all patients. HRV parameters (HF, rMSSD, pNN50) indicating parasympathetic effect were higher in patients with positive HUTT results. CNRT did not differ significantly between patients with positive HUTT results and patients with negative HUTT results. However, WP was found to be higher in patients with positive HUTT results. The studies evaluating the parameters of HRV has demonstrated increased parasympathetic tonus in children with VVS. Impairment in cardiac nodal functions may not be expected in children with VVS. However, these patients may exhibit prolonged WP due to increased autonomic tonus in favor of parasympathetic activity.