Postural tachycardia syndrome is defined by a heart rate increment of 40 beats/minute (bpm) (or a heart rate that exceeds 125 bpm) within 10 minutes of change from the supine position to an upright position in the absence of obvious orthostatic hypotension. There are multiple pathophysiological mechanisms that underlie postural tachycardia syndrome, including peripheral denervation, β-receptor supersensitivity, hypovolaemia, and impaired muscle pump. Some children afflicted with postural orthostatic tachycardia syndrome and hypovolaemic dysregulation have been found to have perturbed renin–angiotensin–aldosterone profile, disturbed vascular endothelial function, and abnormal vasodilation. The hyperadrenergic state in some postural tachycardia syndrome patients is likely a driver for orthostatic tachycardia. Other mechanisms include the presence of treatable autonomic neuropathies. An understanding of these pathophysiological mechanisms might be helpful for the effective treatment of postural tachycardia syndrome.

Background: Postural tachycardia syndrome and vasovagal syncope are common causes of orthostatic intolerance in children. The supplementation with water, or salt, or midodrine, or β-blocker was applied to children with postural tachycardia syndrome or vasovagal syncope. However, the efficacy of such medication varied and was not satisfied. This review aimed to summarise the current biomarkers in the treatment of the diseases. Data sources: Studies were collected from online electronic databases, including OVID Medline, PubMed, ISI Web of Science, and associated references. The main areas assessed in the included studies were clinical improvement, the cure rate, and the individualised treatment for postural tachycardia syndrome and vasovagal syncope in children. Results: Haemodynamic change during head-up tilt test, and detection of 24-hour urinary sodium excretion, flow-mediated vasodilation, erythrocytic H2S, and plasma pro-adrenomedullin as biological markers were the new ways that were inexpensive, non-invasive, and easy to test for finding those who would be suitable for a specific drug and treatment. Conclusion: With the help of biomarkers, the therapeutic efficacy was greatly increased for children with postural tachycardia syndrome and vasovagal syncope.