Hoffmann Bradley, Dehkordi Parastoo, Khosrow-Khavar Farzad, Goswami Nandu, Blaber Andrew P, Tavakolian Kouhyar
University of North Dakota School of Electrical Engineering & Computer Science, Grand Forks, ND, USA.
Heart Force Medical Inc, Vancouver, Canada.
NPJ Microgravity. 2022 Jul 12;8(1):25. doi: 10.1038/s41526-022-00206-7.
During head-down tilt bed rest (HDT) the cardiovascular system is subject to headward fluid shifts. The fluid shift phenomenon is analogous to weightlessness experienced during spaceflight microgravity. The purpose of this study was to investigate the effect of prolonged 60-day bed rest on the mechanical performance of the heart using the morphology of seismocardiography (SCG). Three-lead electrocardiogram (ECG), SCG and blood pressure recordings were collected simultaneously from 20 males in a 60-day HDT study (MEDES, Toulouse, France). The study was divided into two campaigns of ten participants. The first commenced in January, and the second in September. Signals were recorded in the supine position during the baseline data collection (BDC) before bed rest, during 6° HDT bed rest and during recovery (R), post-bed rest. Using SCG and blood pressure at the finger, the following were determined: Pulse Transit Time (PTT); and left-ventricular ejection time (LVET). SCG morphology was analyzed using functional data analysis (FDA). The coefficients of the model were estimated over 20 cycles of SCG recordings of BDC12 and HDT52. SCG fiducial morphology AO (aortic valve opening) and AC (aortic valve closing) amplitudes showed significant decrease between BDC12 and HDT52 (p < 0.03). PTT and LVET were also found to decrease through HDT bed rest (p < 0.01). Furthermore, PTT and LVET magnitude of response to bed rest was found to be different between campaigns (p < 0.001) possibly due to seasonal effects on of the cardiovascular system. Correlations between FDA and cardiac timing intervals PTT and LVET using SCG suggests decreases in mechanical strength of the heart and increased arterial stiffness due to fluid shifts associated with the prolonged bed rest.
在头低位卧床休息（HDT）期间，心血管系统会出现体液向上转移。这种体液转移现象类似于太空飞行微重力期间所经历的失重状态。本研究的目的是利用心震图（SCG）的形态来研究为期60天的长期卧床休息对心脏机械性能的影响。在一项为期60天的HDT研究（法国图卢兹的MEDES）中，同时收集了20名男性的三导联心电图（ECG）、SCG和血压记录。该研究分为两个阶段，每个阶段有10名参与者。第一阶段于1月开始，第二阶段于9月开始。在卧床休息前的基线数据收集（BDC）期间、6°HDT卧床休息期间以及卧床休息后的恢复（R）期间，均在仰卧位记录信号。利用SCG和手指处的血压，测定了以下指标：脉搏传输时间（PTT）和左心室射血时间（LVET）。使用功能数据分析（FDA）对SCG形态进行分析。在BDC12和HDT52的SCG记录的20个周期内估计模型系数。SCG基准形态AO（主动脉瓣开放）和AC（主动脉瓣关闭）振幅在BDC12和HDT52之间显著降低（p<0.03）。还发现PTT和LVET在HDT卧床休息期间降低（p<0.01）。此外，发现两个阶段之间卧床休息的PTT和LVET反应幅度不同（p<0.001），这可能是由于心血管系统的季节效应。使用SCG的FDA与心脏定时间隔PTT和LVET之间的相关性表明，由于长期卧床休息相关的体液转移，心脏机械强度降低，动脉僵硬度增加。
