The effect of exercise training on left ventricular relaxation and diastolic suction at rest and during orthostatic stress after bed rest
The effect of exercise training on left ventricular relaxation and diastolic suction at rest and during orthostatic stress after bed rest
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DOI：
10.1113/expphysiol.2012.067488
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发表时间：
2013-02-01
影响因子：
2.7
通讯作者：
Levine, Benjamin D.
中科院分区：
文献类型：
--
作者：
Carrick-Ranson, Graeme;Hastings, Jeffrey L.;Levine, Benjamin D.
直立每搏输出量（SV）的显著减少在很大程度上有助于暴露于航天或卧床休息后的立位不耐受。目前尚不清楚是否左心室（LV）舒张和舒张期吸入减慢有助于减少SV或这些变化是否受到卧床运动训练的影响。27名健康成人完成了5周的-6度头低位卧床休息（HDBR）。在HDBR期间，9名受试者久坐不动（NOEX），而18名受试者几乎每天进行划船测力计（EX）。在仰卧位休息（两次）和降低LV负荷（下体负压; LBNP）和增加LV负荷（盐水输注）期间，收集HDBR前后的左心室质量、SV、LV舒张末期容积（LVEDV）、肺毛细血管楔压和LV功能的多普勒超声指数。HDBR后，EX组的LV质量增加，但NOEX组减少。仰卧位休息时SV和LVEDV和LBNP的降低，NOEX组大于HDBR后EX组。峰值早期二尖瓣环速度，等容舒张时间，早期传播速度，舒张早期充盈和心室舒张期吸力的非侵入性指数，以及峰值全球纵向早期应变率在仰卧位休息期间与NOEX HDBR后减慢;然而，这些变量要么不变，要么与EX减少不太明显。在两组中，HDBR后LBNP对左室卸载期间，舒张早期充盈、心室舒张和舒张期抽吸的多普勒超声测量均无显著影响。在盐水输注期间，两组的所有多普勒指数均恢复到HDBR前的水平，以使HDBR后的LV充盈压正常化。可以得出结论，HDBR后两组的动态LV充盈的多普勒指数均降低;然而，这些影响在NOEX组中更为明显。无论哪一组，在盐水输注期间，当LV充盈压增加至HDBR前水平时，HDBR后多普勒参数恢复。因此，HDBR后直立SV的减少更多地受到LV负荷条件变化的影响，即LV重塑背景下的左心房压力，而不是心室舒张和舒张期抽吸。
A marked reduction in upright stroke volume (SV) contributes substantially to orthostatic intolerance after exposure to spaceflight or bed rest. It is unclear whether slowed left ventricular (LV) relaxation and diastolic suction contribute to the reduction in SV or whether these changes are influenced by exercise training while in bed. Twenty-seven healthy adults completed 5 weeks of -6 deg head-down bed rest (HDBR). During HDBR, nine subjects were sedentary (NOEX), while 18 performed near-daily rowing ergometry (EX). Left ventricular mass, SV, LV end-diastolic volume(LVEDV), pulmonary capillary wedge pressure and Doppler ultrasound indices of LV function were collected pre- and post-HDBR during supine rest (twice) and during reduced LV loading (lower body negative pressure; LBNP) and increased LV loading (saline infusion). Post-HDBR, LV mass increased in the EX group, but decreased in the NOEX group. The reduction in SV and LVEDV during supine rest and LBNP were greater with NOEX in comparison to EX after HDBR. Peak early mitral annular velocity, isovolumic relaxation time, early propagation velocity, a non-invasive index of early diastolic filling and ventricular diastolic suction, and peak global longitudinal early strain rate were slowed during supine rest after HDBR with NOEX; however, these variables were either unaltered or the reduction was less prominent with EX. Doppler ultrasound measures of early diastolic filling, ventricular relaxation and diastolic suction were not significantly affected during LV unloading by LBNP after HDBR in either group. All Doppler indices were restored to pre-HDBR levels in both groups during saline infusion to normalize LV filling pressure after HDBR. It is concluded that Doppler indices of dynamic LV filling were reduced in both groups after HDBR; however, these effects were more pronounced in the NOEX group. Irrespective of group, post-HDBR Doppler parameters were restored when LV filling pressure was increased to pre-HDBR levels during saline infusion. Therefore, the reduction in upright SV after HDBR is more influenced by changes in LV loading conditions, namely left atrial pressure in the setting of LV remodelling, rather than ventricular relaxation and diastolic suction.