Analysis of heart rate variability during head-up tilt testing in a patient with idiopathic postural orthostatic tachycardia syndrome (POTS)

A 16-year-old boy was diagnosed with idiopathic postural orthostatic tachyc ardia syndrome (POTS) during head-up tilt testing. During a passive tilt, t he patient's heart rate (HR) increased by 30 beats/min within 5 min. After 25 min of tilting, his HR further increased to 133 beats/min and he began t o complain of lightheadedness and weakness without hypotension. Power spect ral analysis of HR variability during the tilt test revealed that the ratio of low and high frequency powers increased with the onset of orthostatic i ntolerance. Propranolol (10 mg every morning) dramatically alleviated his c linical symptoms, and he has been asymptomatic with gaining weight after di scontinuing his crowded train commuting.