Abstract: In order to determine the changes of the myocardial structure at the acute high altitude exposure in rats, the rats were took from lower to higher altitudes, the observation was aimed in the study of rat myocardial specimen under light and electronic microscopes. It was found that there were severe lesions in left and right ventricle and interventricular septum, such as cloud swelling, hydropic degeneration, lytic necrosis and interstitial edema under light microscope. The chondriosomes swelling, sarcoplasmic reticula dilatation, myofibrillae solution and edema of inside and outside of the celles were shown under electronic microscope. The lesions above were more severe in the right ventricle than those in the left(P< 0.01). The results revealed that the cardiac lesions of rats were pancardiac disribution obviously and the lesions of the right ventricle was more severe than those of the left ventricle. It′s also suggested that the protection of whole heart should be paid attention to when move to high altitude in short time.

Key words: high altitude, myocardium, acute anoxia