Skoog Johan, Zachrisson Helene, Länne Toste, Lindenberger Marcus
Department of Medical and Health Sciences, Linköping University Linköping, Sweden.
Department of Clinical Physiology and Department of Medical and Health Sciences, Linköping University Linköping, Sweden.
Front Physiol. 2016 Jun 14;7:232. doi: 10.3389/fphys.2016.00232. eCollection 2016.
Slower lower limb blood pooling and associated blunted sympathetic activation has been detected in healthy women prone to orthostatic syncope. Whether these findings are true also for patients with vasovagal syncope (VVS) is unknown. The aim was to investigate initial blood pooling time (poolingtime, time to 50% of total blood pooling) together with hemodynamic responses and orthostatic tolerance during lower body negative pressure (LBNP) in VVS and healthy controls.
Fourteen VVS women (25.7 ± 1.3 years) and 15 healthy women (22.8 ± 0.8 years) were subjected to single-step and graded LBNP to pre-syncope. Lower limb blood pooling (ml · 100 ml(-1)), poolingtime (s), hemodynamic responses and LBNP-tolerance were evaluated. LBNP induced comparable lower limb blood pooling in both groups (controls, 3.1 ± 0.3; VVS, 2.9 ± 0.3 ml · 100 ml(-1), P = 0.70). In controls, shorter poolingtime correlated to higher LBNP-tolerance (r = -0.550, P < 0.05) as well as better maintained stroke volume (r = -0.698, P < 0.01) and cardiac output (r = -0.563, P < 0.05). In contrast, shorter poolingtime correlated to lower LBNP-tolerance in VVS (r = 0.821, P < 0.001) and larger decline in stroke volume (r = 0.611, P < 0.05). Furthermore, in controls, shorter poolingtime correlated to baroreflex-mediated hemodynamic changes during LBNP, e.g., increased vasoconstriction (P < 0.001). In VVS, poolingtime was not correlated with LBNP-induced baroreceptor unloading, but rather highly correlated to resting calf blood flow (P < 0.001).
Shorter poolingtime seems to elicit greater sympathetic activation with a concomitant higher orthostatic tolerance in healthy women. The contrasting findings in VVS indicate a deteriorated vascular sympathetic control suggesting well-defined differences already in the initial responses during orthostatic stress.
在易发生直立性晕厥的健康女性中，已检测到下肢血液淤积减缓以及相关的交感神经激活减弱。这些发现对于血管迷走性晕厥（VVS）患者是否同样成立尚不清楚。本研究旨在调查VVS患者和健康对照者在下肢负压（LBNP）期间的初始血液淤积时间（淤积时间，即达到总血液淤积量50%的时间）、血流动力学反应和直立耐力。
14名VVS女性（25.7±1.3岁）和15名健康女性（22.8±0.8岁）接受单步和分级LBNP直至接近晕厥。评估下肢血液淤积量（ml·100 ml⁻¹）、淤积时间（s）、血流动力学反应和LBNP耐力。LBNP在两组中引起的下肢血液淤积量相当（对照组，3.1±0.3；VVS组，2.9±0.3 ml·100 ml⁻¹，P = 0.70）。在对照组中，较短的淤积时间与较高的LBNP耐力相关（r = -0.550，P < 0.05），以及更好地维持每搏输出量（r = -0.698，P < 0.01）和心输出量（r = -0.563，P < 0.05）。相反，在VVS患者中，较短的淤积时间与较低的LBNP耐力相关（r = 0.821，P < 0.001）以及每搏输出量的更大下降（r = 0.611，P < 0.05）。此外，在对照组中，较短的淤积时间与LBNP期间压力反射介导的血流动力学变化相关，例如血管收缩增加（P < 0.001）。在VVS患者中，淤积时间与LBNP引起的压力感受器卸载无关，而是与静息小腿血流量高度相关（P < 0.001）。
在健康女性中，较短的淤积时间似乎会引发更大的交感神经激活，同时具有更高的直立耐力。VVS患者的对比结果表明血管交感神经控制恶化，提示在直立应激的初始反应中就已存在明确差异。
