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Heart Pathology Associated with Exposure to High Sustained +G sub Z
SCHOOL OF AEROSPACE MEDICINE BROOKS AFB TX
Pagination or Media Count:
The pathology of Gz acceleration was examined using unanesthetized adult miniature and immature farm-type swine, with and without anti-G Suit inflation. Following single exposures of 8 or 9 Gz for 45 to 90s--acceleration exposures that have been shown tolerable to man--swine were sacrificed and a detailed necropsy performed. Considering only the adult miniature swine, the endocardial area of the left ventricles showed evidence grossly of recent hemorrhage of varying severity involving both the wall and papillary muscles. The degree and location of the subendocardial hemorrhage was quantitated by grading the area of ventricle involved--1 slight to 4 extensive. Of the 23 adult miniature pigs autopsied, the scores for papillary muscle hemorrhage, after 1 exposure to 9Gz 45 to 90s ranged from a mean of 2.3 to 3.3 and the extent of ventricular wall involvement was 2.5 to 3.3. Histologically, heart hemorrhage was limited to the subendocardial area, primarily involving the space between heart muscle and the endocardium and was particularly evident surrounding Purkinje fibers. Similar studies using immature farm-type swine not miniature pigs found these younger swine 4 to 5 months of age to be less susceptable to such endocardial hemorrhage. Heart tissue recovery in these pigs following 1 exposure to 9Gz for 45 s, required approximately 14 days. It appears that this lesion is similar although less severe than heart muscle lesions associated with low blood volume hemorrhagic shock studies and may have similar physiologic bases. It was concluded that particular attention should be made of the endocardium of victims of high performance aircraft accidents. Author
APPROVED FOR PUBLIC RELEASE