Abstract：
BACKGROUND: Reduced preload and thoracic blood volume accompany postural tachycardia syndrome (POTS). Head-down tilt (HDT) increases both preload and intrathoracic blood volume. The objective of this study was to assess the safety and efficacy of HDT in POTS in acute settings.
METHODS: This retrospective study evaluated POTS patients. Analyzed data included heart rate, blood pressure, cerebral blood flow velocity (CBFv) in the middle cerebral artery, and capnography. The baseline supine hemodynamic data were compared with the data obtained at the second minute of the -10° HDT. A linear mixed-effects model was used to assess the effect of HDT on hemodynamic variables.
RESULTS: The HDT was explored in seven POTS patients and an additional seven POTS patients without HDT served as controls. In the HDT arm, four POTS patients had overlapping diagnoses of myalgic encephalopathy/chronic fatigue syndrome (ME/CFS) and one patient had comorbidity of post-acute sequelae of SARS-CoV-2 infection (PASC). HDT lowered heart rate by 10% and increased end-tidal CO2 by 8%. There was no change in other cardiovascular variables.
CONCLUSIONS: In the acute setting, HDT is safe. HDT reduces the heart rate presumably by modulating baroreflex by enhancing preload and stroke volume, which in turn increases thoracic blood volume with a net effect of parasympathetic cardiovagal activation and/or sympathetic withdrawal. This pilot study provides a foundation to proceed with longitudinal studies exploring the long-term effect of repetitive HDT in conditions associated with preload failure such as POTS, ME/CSF, and PASC.
METHODS: This retrospective study evaluated POTS patients. Analyzed data included heart rate, blood pressure, cerebral blood flow velocity (CBFv) in the middle cerebral artery, and capnography. The baseline supine hemodynamic data were compared with the data obtained at the second minute of the -10° HDT. A linear mixed-effects model was used to assess the effect of HDT on hemodynamic variables.
RESULTS: The HDT was explored in seven POTS patients and an additional seven POTS patients without HDT served as controls. In the HDT arm, four POTS patients had overlapping diagnoses of myalgic encephalopathy/chronic fatigue syndrome (ME/CFS) and one patient had comorbidity of post-acute sequelae of SARS-CoV-2 infection (PASC). HDT lowered heart rate by 10% and increased end-tidal CO2 by 8%. There was no change in other cardiovascular variables.
CONCLUSIONS: In the acute setting, HDT is safe. HDT reduces the heart rate presumably by modulating baroreflex by enhancing preload and stroke volume, which in turn increases thoracic blood volume with a net effect of parasympathetic cardiovagal activation and/or sympathetic withdrawal. This pilot study provides a foundation to proceed with longitudinal studies exploring the long-term effect of repetitive HDT in conditions associated with preload failure such as POTS, ME/CSF, and PASC.
摘要：
背景：体位性心动过速综合征（POTS）伴随着前负荷和胸腔血容量的降低。头向下倾斜（HDT）会增加预负荷和胸内血容量。这项研究的目的是评估HDT在急性环境中的安全性和有效性。
方法：这项回顾性研究评估了POTS患者。分析的数据包括心率，血压,大脑中动脉的脑血流速度(CBFv),和二氧化碳描记术。将基线仰卧位血液动力学数据与在-10°HDT的第二分钟获得的数据进行比较。使用线性混合效应模型来评估HDT对血液动力学变量的影响。
结果：在7名POTS患者中研究了HDT，另外7名没有HDT的POTS患者作为对照。在HDT手臂中，4例POTS患者诊断为肌痛脑病/慢性疲劳综合征(ME/CFS),1例患者诊断为SARS-CoV-2急性后遗症(PASC).HDT将心率降低了10％，并将潮气末二氧化碳增加了8％。其他心血管变量没有变化。
结论：在急性环境中，HDT是安全的。HDT可能通过增强预负荷和每搏输出量来调节压力反射，从而降低心率。这反过来又增加胸血容量与副交感神经心迷走神经激活和/或交感神经戒断的净效应。这项初步研究为继续进行纵向研究提供了基础，探索重复HDT在与POTS等预载失效相关的条件下的长期影响，ME/CSF,PASC
方法：这项回顾性研究评估了POTS患者。分析的数据包括心率，血压,大脑中动脉的脑血流速度(CBFv),和二氧化碳描记术。将基线仰卧位血液动力学数据与在-10°HDT的第二分钟获得的数据进行比较。使用线性混合效应模型来评估HDT对血液动力学变量的影响。
结果：在7名POTS患者中研究了HDT，另外7名没有HDT的POTS患者作为对照。在HDT手臂中，4例POTS患者诊断为肌痛脑病/慢性疲劳综合征(ME/CFS),1例患者诊断为SARS-CoV-2急性后遗症(PASC).HDT将心率降低了10％，并将潮气末二氧化碳增加了8％。其他心血管变量没有变化。
结论：在急性环境中，HDT是安全的。HDT可能通过增强预负荷和每搏输出量来调节压力反射，从而降低心率。这反过来又增加胸血容量与副交感神经心迷走神经激活和/或交感神经戒断的净效应。这项初步研究为继续进行纵向研究提供了基础，探索重复HDT在与POTS等预载失效相关的条件下的长期影响，ME/CSF,PASC
