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Aviat Space Environ Med. 1975 Apr;46(4 Sec 1):413-8.

Coronary hemodynamics during positive (+G-z) acceleration.


Left circumflex (LC) and left anterior descending (LAD) coronary flows, coronary perfusion pressure (P-ca), and arterial O-2 content (Cao-2) were determined in five dogs, lightly anesthetized with chloralose, during exposures to +2.0 and +3.0 G-Z stress; and for three of these dogs at +3.5-G-Z. At +2.0 G-Z, except for one dog with the most marked decrease in P-ca, KC and LAD flows increased above control by 15 s and thereafter gradually returned toward control; coronary resistances were significantly below control at 15 and 30 s (p smaller then 0.05). At +3.0 G-Z, LC and LAD flows were significantly greater than control (p smaller 0.05) from 30 to 60 s, while resistances were below control (p smaller than 0.05). At +3.5 G-Z, LC flow was maintained above control by a much reduced resistance, with P-ca below control; LAD flow increased in one dog, remained unchanged in one, and decreased slightly in one, although resistance always decreased. Cao-2 did not change significantly at any +G-Z level, and myocardial O-2 transport paralleled the changes in coronary flow.

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