Affiliation:
1. Cardiology Branch, National Heart Institute and the Clinical Endocrinology Branch, National Institute of Arthritis and Metabolic Diseases Bethesda, Maryland
Abstract
The effect of varying CBF and myocardial O
2
delivery on MV
O
O2
was studied in 23 experiments. In 14 of the experiments an isolated dog heart was perfused, while in the others the heart of a dog, whose systemic circulation was maintained on cardiopulmonary bypass, was studied. The ventricles were kept empty, developed no pressure and performed no external work, while their temperature was held constant. CBF and myocardial O
2
delivery were controlled by pumping blood into the coronary arteries, total coronary venous return was collected from the right side of the heart and MV
O
O2
, was calculated during a steady state by the Fick principle. Myocardial anoxia was avoided by maintaining the coronary venous O
2
content above 4 vol % and myocardial O
2
extraction below 78%.
A comparison of MV
O
O2
at two levels of CBF (and O
2
delivery) was made in 42 instances, and in 32 of them 11 MV increased substantially as CBF was elevated, or vice versa. The ten exceptions all occurred when O
2
delivery greatly exceeded MV
O
O2
with O
2
extraction ratios below 35%. The fundamental mechanisms responsible for these findings are not clear, but a number of possible explanations are discussed.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
69 articles.
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