Changes of plasma intermedin during head-up tilt test in children with postural tachycardia syndrome and its significance

Abstract

To explore possible mechanisms of postural tachycardia syndrome (POTS) by comparing plasma intermedin (IMD) during head-up tilt test (HUTT) in children with POTS. The study subjects were divided into two groups: POTS group and control group. The POTS group consisted of twenty-nine children (male 14, female 15) with POTS, the mean age (12.4 ±3.1) years old, admitted into Peking University First Hospital from November 2013 to June 2014. The control group consisted of 32 healthy children (male 17, female 15). Their mean age was (11.6±2.2) years old, who were confirmed as healthy by physical examination and HUTT. Finapres Medical System was used to continuously monitor heart rate and blood pressure during HUTT, and electrocadiogram was performed. Supine systolic and diastolic blood pressure, mean arterial pressure (MAP), ΔMAP (standing mean arterial pressure-supine MAP), supine heart rate and ΔHR (standing HR-supine HR) were compared between POTS group and control group. Sandwich immunoluminescence assay was used to test plasma IMD. The plasma IMD level was compared in supine between POTS and control group. The plasma IMD level in supine was compared with HUTT in POTS group. No significant differences were found in age, height, weight, supine systolic and diastolic blood pressure, MAP, ΔMAP and supine heart rate between POTS group and control group (P>0.05). ΔHR in POTS group was significantly higher than that of control group ((48±10) vs. (22±7) beats /min, t=9.797, P<0.05). The plasma IMD level in POTS group was lower than that of control group in supine position ((497±61)×10(-6) vs. (529±58)×10(-6) mg/L, t=2.117, P<0.05). But, it was higher during HUTT than supine IMD in POTS group ((537±57) ×10(-6) vs. (497±61)×10(-6) mg/L, t=-2.464, P<0.05). The plasma delta IMD level (HUTT vs. supine) was positively correlated with delta HR in POTS group (r=0.435, P<0.05). The excessively high heart rate during HUTT have a positive correlation with plasma IMD, which may play a role in the pathogenesis of POTS in children.