Low-frequency oscillation of sympathetic nerve activity decreases during development of tilt-induced syncope preceding sympathetic withdrawal and bradycardia
Low-frequency oscillation of sympathetic nerve activity decreases during development of tilt-induced syncope preceding sympathetic withdrawal and bradycardia
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DOI：
10.1152/ajpheart.01027.2004
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发表时间：
2005-10-01
影响因子：
4.8
通讯作者：
Sugimachi, M
中科院分区：
文献类型：
--
作者：
Kamiya, A;Hayano, J;Sugimachi, M
当动脉压（AP）维持良好时，直立应激期间的交感神经激活伴随着交感神经活动（SNA）的低频（LF，类似于0.1 Hz）振荡的显著增加。然而，在直立性神经介导的晕厥的发展过程中SNA的LF振荡仍然未知。研究了10名健康受试者，他们发生了直立倾斜（HUT）诱发的晕厥，10名年龄匹配的非晕厥对照。使用复合解调法评估了15分钟60度HUT试验期间小腿肌肉SNA（MSNA，显微神经描记术）、R-R间期和AP（手指光电体积描记术）变异性的非平稳时间依赖性变化。在两组中，HUT在前5分钟内增加心率、MSNA幅度、MSNA变异性的LF和呼吸高频（HF）幅度以及AP变异性的LF和HF幅度，但降低R-R间期变异性（心脏迷走神经活动指数）的HF幅度。在非晕厥组中，这些变化在整个HUT中持续。在晕厥组中，收缩期AP在晕厥发作前100 ~ 60 s降低; MSNA变异性的LF振幅降低，而MSNA的幅度和AP变异性的LF振幅保持升高。从晕厥发生前60 s开始，MSNA和心率下降，心迷走神经活动指数增加，AP进一步下降至晕厥时水平。LF振荡的MSNA变异性下降，在直立性神经介导的晕厥的发展，之前交感神经撤回，心动过缓，和严重的低血压，晕厥的水平。
Sympathetic activation during orthostatic stress is accompanied by a marked increase in low-frequency (LF, similar to 0.1-Hz) oscillation of sympathetic nerve activity (SNA) when arterial pressure (AP) is well maintained. However, LF oscillation of SNA during development of orthostatic neurally mediated syncope remains unknown. Ten healthy subjects who developed head-up tilt (HUT)-induced syncope and 10 age-matched nonsyncopal controls were studied. Nonstationary time-dependent changes in calf muscle SNA (MSNA, microneurography), R-R interval, and AP ( finger photoplethysmography) variability during a 15-min 60 degrees HUT test were assessed using complex demodulation. In both groups, HUT during the first 5 min increased heart rate, magnitude of MSNA, LF and respiratory high-frequency (HF) amplitudes of MSNA variability, and LF and HF amplitudes of AP variability but decreased HF amplitude of R-R interval variability ( index of cardiac vagal nerve activity). In the nonsyncopal group, these changes were sustained throughout HUT. In the syncopal group, systolic AP decreased from 100 to 60 s before onset of syncope; LF amplitude of MSNA variability decreased, whereas magnitude of MSNA and LF amplitude of AP variability remained elevated. From 60 s before onset of syncope, MSNA and heart rate decreased, index of cardiac vagal nerve activity increased, and AP further decreased to the level at syncope. LF oscillation of MSNA variability decreased during development of orthostatic neurally mediated syncope, preceding sympathetic withdrawal, bradycardia, and severe hypotension, to the level at syncope.