Disruption of phase synchronization between blood pressure and muscle sympathetic nerve activity in postural vasovagal syncope
Disruption of phase synchronization between blood pressure and muscle sympathetic nerve activity in postural vasovagal syncope
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DOI：
10.1152/ajpheart.00415.2013
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发表时间：
2013-10-01
影响因子：
4.8
通讯作者：
Stewart, Julian M.
中科院分区：
文献类型：
--
作者：
Schwartz, Christopher E.;Lambert, Elisabeth;Stewart, Julian M.
在血管迷走性晕厥（VVS）期间，肌肉交感神经活动（MSNA）的撤回可能不是外周动脉阻力和动脉压（AP）急剧下降的必要条件。我们测试的假设，MSNA-AP压力反射夹带被破坏之前VVS不管MSNA撤回使用血压和MSNA之间的相位同步在头向上倾斜（HUT）测量反射耦合。我们研究了8名VVS受试者和8名健康对照受试者。在仰卧位基线和HUT的早期、中期、晚期和晕厥阶段测量心率、AP和MSNA。计算了测量MSNA和AP相位之间随时间变化的差异的相位同步指数。计算了AP对MSNA（神经弧）和MSNA对AP（外周弧）的影响的方向性指数。在HUT的早期、中期和晚期，VVS组的心率高于对照组，晕厥时心率显著下降（P = 0.04）。AP显着下降，在中期，晚期和晕厥阶段的倾斜VVS的受试者（P = 0.001）。在HUT期间，两组之间的MSNA无显著差异（P = 0.700）。然而，VVS受试者的相位同步指数在中期和晚期显著降低，而对照受试者则无此现象（P <0.001）。此外，晕厥前神经弧比外周弧受到的影响更大。总之，VVS伴随着同步AP-MSNA关系的丢失，在微弱时MSNA丢失或不丢失。这提供了深入了解在血管迷走性昏厥时不依赖于MSNA的血管收缩损失和AP下降背后的机制。
Withdrawal of muscle sympathetic nerve activity (MSNA) may not be necessary for the precipitous fall of peripheral arterial resistance and arterial pressure (AP) during vasovagal syncope (VVS). We tested the hypothesis that the MSNA-AP baroreflex entrainment is disrupted before VVS regardless of MSNA withdrawal using the phase synchronization between blood pressure and MSNA during head-up tilt (HUT) to measure reflex coupling. We studied eight VVS subjects and eight healthy control subjects. Heart rate, AP, and MSNA were measured during supine baseline and at early, mid, late, and syncope stages of HUT. Phase synchronization indexes, measuring time-dependent differences between MSNA and AP phases, were computed. Directionality indexes, indicating the influence of AP on MSNA (neural arc) and MSNA on AP (peripheral arc), were computed. Heart rate was greater in VVS compared with control subjects during early, mid, and late stages of HUT and significantly declined at syncope (P = 0.04). AP significantly decreased during mid, late, and syncope stages of tilt in VVS subjects only (P = 0.001). MSNA was not significantly different between groups during HUT (P = 0.700). However, the phase synchronization index significantly decreased during mid and late stages in VVS subjects but not in control subjects (P < .001). In addition, the neural arc was significantly affected more than the peripheral arc before syncope. In conclusion, VVS is accompanied by a loss of the synchronous AP-MSNA relationship with or without a loss in MSNA at faint. This provides insight into the mechanisms behind the loss of vasoconstriction and drop in AP independent of MSNA at the time of vasovagal faint.