Sakowski Chris, Starc Vito, Smith Scott M, Schlegel Todd T
University of Texas Medical Branch, Galveston, TX, USA.
Aviat Space Environ Med. 2011 Apr;82(4):416-23. doi: 10.3357/asem.2945.2011.
We studied the effects of 90 d of 6 degrees head-down bed rest (HDBR) on cardiac autonomic and advanced electrocardiographic (ECC) function, especially on repolarization heterogeneity as assessed by beat-to-beat QT interval variability (QTV), T-wave complexity, and 3-dimensional ECG. Based on prior observations of lengthening of the QTc interval during long-duration spaceflight, we hypothesized that abnormalities in ECG repolarization would also occur during long-duration HDBR.
During controlled breathing, 5-min supine high-fidelity 12-lead ECGs were obtained from 20 healthy subjects (14 men and 6 women) together with measurements of plasma volume and electrolytes at 5 points in time: within 10 d before; 28-30, 60, and 90 d into; and 3-5 d after HDBR.
By repeated measures ANOVA, 90 d of sedentary HDBR significantly increased the QTV index (from -1.87 +/- 0.33 to - 1.53 +/- 0.39 units), the index of unexplained QTV (from 0.61 +/- 0.48 to 1.21 +/- 0.40 units), the T-wave complexity intradipolar ratio (from 0.344 +/- 0.260 to 2.04 +/- 4.01%), and the spatial QRS-T angle (from 49.1 +/- 23.8 to 58.7 +/- 31.0 degrees), and significantly decreased the spatial ventricular gradient (from 91.3 +/- 26.5 to 59.1 +/- 23.0 mV x ms(-1)). These changes resolved in part by 3-5 d after resumption of ambulation, but unlike concomitant changes in the QTc interval itself and in heart rate variability, they did not significantly relate to changes in electrolytes or plasma volume.
Sedentary, long-duration HDBR reversibly increases ECG repolarization heterogeneity and by inference ventricular arrhythmic risk.
我们研究了90天6°头低位卧床休息（HDBR）对心脏自主神经和高级心电图（ECC）功能的影响，特别是对逐搏QT间期变异性（QTV）、T波复杂性和三维心电图评估的复极异质性的影响。基于先前对长期太空飞行期间QTc间期延长的观察，我们假设在长期HDBR期间也会出现心电图复极异常。
在控制呼吸期间，从20名健康受试者（14名男性和6名女性）获取5分钟仰卧位高保真12导联心电图，并在5个时间点测量血浆容量和电解质：HDBR前10天内；HDBR开始后28 - 30天、60天和90天；HDBR结束后3 - 5天。
通过重复测量方差分析，90天久坐不动的HDBR显著增加了QTV指数（从 - 1.87 ± 0.33单位增至 - 1.53 ± 0.39单位）、未解释QTV指数（从0.61 ± 0.48单位增至1.21 ± 0.40单位）、T波复杂性极间比率（从0.344 ± 0.260增至2.04 ± 4.01%）以及空间QRS - T角（从49.1 ± 23.8度增至58.7 ± 31.0度），并显著降低了空间心室梯度（从91.3 ± 26.5降至59.1 ± 23.0 mV×ms⁻¹）。这些变化在恢复活动后3 - 5天部分得到缓解，但与QTc间期本身和心率变异性的伴随变化不同，它们与电解质或血浆容量的变化无显著关联。
久坐不动的长期HDBR可逆性增加心电图复极异质性，并由此推断增加室性心律失常风险。
