A prospective study of excessive postural heart rate change on head-up tilt.

Abstract

Healthy subjects with asymptomatic postural tachycardia (≥30bpm) at baseline were evaluated over a 1-year period to determine whether they developed orthostatic symptoms. Subjects were evaluated at baseline and at 1year using the autonomic reflex screen and autonomic symptom profile (ASP). Heart rate increment on HUT did not differ at baseline (40.6±7.5bpm) or at 1year (37.1±11.1bpm; n=26; p>0.05). Orthostatic symptoms measured by the ASP did not reveal significant orthostatic dysfunction throughout follow-up (baseline, 7.88±7.61; 1year, 9.04±6.64; n=26; p>0.05). The ten autonomic domains of the ASP did not reveal a change in autonomic symptoms from baseline (13.56±13.66) to 1-year follow-up (15.12±11.62; n=26; p>0.05). Cardiovagal function was unchanged between baseline and follow-up for both heart rate variability to deep breathing (baseline, 23.9±11.6bpm; 1year, 23.0±9.3bpm; n=26; p>0.05) and Valsalva ratio (baseline, 2.16±0.39; 1year, 2.15±0.33; n=26; p>0.05). These findings further argue that heart rate criteria (≥30bpm) for Postural Tachycardia Syndrome (POTS) are not appropriate in younger individuals and higher postural heart rates do not predispose individuals to the development of POTS.