Vasovagal syncope and postural orthostatic tachycardia syndrome in adolescents: transcranial doppler versus autonomic function test results.

Background: Syncope is a temporary loss of consciousness due to cerebral hypoperfusion associated with autonomic dysfunction. Vasovagal syncope (VVS) and postural orthostatic tachycardia syndrome (POTS) are the most common causes of syncope in adolescents.

Purpose: Here we conducted a comparative analysis of VVS and POTS in adolescents using transcranial doppler (TCD) and autonomic function tests to identify the mechanisms underlying the occurrence of each.

Methods: From August 2014 to July 2024, a tilt-table test was conducted on patients who presented with syncope or presyncope as the main symptom. Based on the head-up tilt test results, the patients were classified into the VVS or POTS groups and their medical records retrospectively analyzed.

Results: The study included 137 patients: 100 (73%) in the VVS group and 37 (27%) in the POTS group. There were no significant intergroup differences in patient characteristics. In the TCD, the diastolic blood flow velocity during symptom onset was significantly lower in the VVS versus POTS group (18.40±7.14 cm/sec vs. 22.32±8.48 cm/sec, P=0.008). Additionally, the pulsatility index was higher in the VVS group (1.51±0.41 vs 1.22±0.37, P<0.005). There were no intergroup differences in autonomic function tests results or composite autonomic severity scores.

Conclusion: The cerebral blood flow velocity during diastole differs between VVS and POTS, suggesting that it may be a determining factor in the pathogenesis of each.