Introduction: Postural tachycardia syndrome (POTS) is a suspected dysautonomia with symptoms of orthostatic intolerance and abnormally increased heart rate while standing. We aimed to study cardiac autonomic nervous system functioning in head-up tilt (HUT) in adolescents with POTS to find out if parasympathetic tone is attenuated in the upright position. Methods: We compared characteristics of a group of 25 (females 14/25; 56%) adolescents with POTS and 12 (females 4/12; 34%) without POTS aged 9–17 years. We compared heart rate variability with high- and low-frequency oscillations, and their temporal changes in HUT. Results: The high-frequency oscillations, i.e., HF, attenuated in both groups during HUT (p < 0.05), but the attenuation was bigger in POTS (p = 0.04). In the beginning of HUT, low-frequency oscillations, i.e., LF, increased more in POTS (p = 0.01), but in the end of HUT, an attenuation in LF was seen in the POTS group (p < 0.05), but not in the subjects without POTS. There were no associations of previous infections or vaccinations with POTS. Subjects with POTS were sleepier and their overall quality of life was very low. Conclusion: The results imply to an impaired autonomic regulation while standing in POTS, presenting as a lower HF and higher LF in the beginning of HUT and an attenuated LF in the prolonged standing position.

中文翻译：

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青少年姿势性心动过速综合征患者平视倾斜试验的心率变异性

简介：姿势性心动过速综合征 (POTS) 是一种疑似自主神经功能障碍，具有直立不耐受症状和站立时心率异常增加。我们的目的是研究 POTS 青少年抬头倾斜 (HUT) 时心脏自主神经系统的功能，以了解直立位置的副交感神经张力是否减弱。方法：我们比较了一组 25 名（女性 14/25；56%）患有 POTS 的青少年和 12 名（女性 4/12；34%）没有 POTS 的 9-17 岁青少年的特征。我们比较了心率变异性与高频和低频振荡，以及它们在 HUT 中的时间变化。结果：HUT 期间两组的高频振荡，即 HF 均减弱（p < 0.05），但 POTS 中的衰减更大（p = 0.04）。在 HUT 开始时，低频振荡，即 LF，POTS 中增加更多（p = 0.01），但在 HUT 结束时，在 POTS 组中观察到 LF 衰减（p < 0.05），但在没有 POTS 的受试者中没有。以前的感染或疫苗接种与 POTS 没有关联。患有 POTS 的受试者更困倦，他们的整体生活质量非常低。结论：结果表明在 POTS 中站立时自主神经调节受损，表现为在 HUT 开始时较低的 HF 和较高的 LF 以及在长时间站立时减弱的 LF。