[Effects of 7 d head-down bed rest on human vectorcardiogram (VCG)]

To study the effects of short-term simulated weightlessness on human vectorcardiogram (VCG).Seven d -6 degrees head-down bed rest (HDBR) was used to simulate weightlessness. Eight healthy males, aged 19-21, served as the subjects. VCG was recorded before and on day 1, 3, 7 of HDBR.QRS loop in the horizontal plane rotated counterclockwise, while QRS loop in the right sagittal plane rotated clockwise during HDBR (P0.05 or P0.01). QRS-T angle in the horizontal and right sagittal plane increased significantly during HDBR.Seven d HDBR leads to changes of VCG parameters, which were all in normal ranges and in accordance with the volume changes of atrium and ventricle, but obviously different from those resulted from pathological ventricular thickening and myocardial ischemia.