[Effects of simulated high-altitude hypobaric hypoxia on cardiac structure and function in rats].

To investigate the effects of simulated hypobaric hypoxia environment at 7 000 m above sea level on cardiac structure and function in rats.A total of 96 male SD rats were randomly divided into high-altitude hypobaric hypoxia group (hypoxia group) and normobaric normoxia group (control group). Rats of hypoxia group were placed in a large cabin simulated 7 000 m high-altitude hypobaric hypoxia environment. Operating time 23 h / d, the control circadian ratio of approximately 12 h:12 h. The rats in control group were bred under normobaric normoxia. The hypoxic group was divided into 3 d, 7 d, 14 d, 28 d groups according to hypoxic time, 12 rats in each group. Changes of structure and function of heart due to hypoxia were evaluated by echocardiography and electrocardiogram. Myocardial pathological changes were analyzed by hematoxylin-eosin staining(HE).Compared with the control group at the same time point ①With prolonged exposure to hypobaric hypoxia, the growth ratio of body mass in rats is slower. Arterial oxygen saturation was significantly lower in both 14 d and 28 d (P＜0.05). ② Left ventricular end-diastolic anterior wall thickness (LVAWD) and left ventricular end-diastolic posterior wall thickness (LVPWD) of rats in 28 d were increased significantly (P＜0.05). Left ventricular end-diastolic diameter (LVIDD) and left ventricular internal dimension systole (LVIDS) of rats in 28 d were decreased significantly (P＜0.05, P＜0.01). Left ventricular ejection fraction (EF), fractional shortening of left ventricle (FS), pulmonary vein (PV) peak velocity and PV peak gradient of rats in 7 d were decreased significantly (P＜0.05, P＜0.01). ③The QRS and QT interval period were significantly prolonged in 14 d and 28 d (P＜0.05, P＜0.01). The ST was significantly lower in 3 d and 7 d (P＜0.05, P＜0.01). The amplitude of R wave gradually shifted downward in 7 d, 14 d, 28 d (P＜0.05, P＜0.01). ④The red blood cell (RBC), hemoglobin (HGB), red blood cell distribution width (RDW) in hypoxic group were increased significantly (P＜0.01). The platelet count (PLT) count was decreased significantly in 14 d and 28 d (P＜0.01). The serum creatinine (CR) was increased significantly in 14 d and 28 d (P＜0.05). ⑤Pathological changes such as myocardial edema, sarcolemma condensate, focal degeneration and necrosis with inflammatory cell infiltration could be found at early stage of hypoxia. Myocardial compensatory repair such as myocardial fibroblasts proliferation was significant at end stage of hypoxia.Left ventricular systolic functions of rats were decreased significantly after exposure to high altitude hypoxia hypobaric. The left ventricular systolic functions would recovery compensatory after one week exposed to high altitude hypoxia hypobaric.