Effect of coronary artery occlusion on regional arterial and venous O2 saturation, O2 extraction, blood flow, and O2 consumption in the dog heart.

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Abstract
The effects of coronary artery ligation on regional arterial and venous O2 saturation, O2 extraction, blood flow and O2 consumption were studied in occluded and unoccluded areas of the hearts of 14 anesthetized open-chest dogs. In 7 animals, a coronary artery was occluded for 10 min and in 7 others a vessel was ligated for 2 h. Microspectrophotometric observations of small regional arteries and veins in quick-frozen hearts to determine regional O2 extraction were combined with regional blood flow measurements with radioactive microspheres to determine regional myocardial O2 consumption by the Fick principle. Flow was significantly lower in the occluded compared to the control area at both times. The subendocardial:subepicardial flow ratio was reversed at 2 h in the occluded area. O2 extraction was greater in the occluded areas. O2 consumption was lower in the occluded area. At 2 h the subendocardial:subepicardial consumption ratio was reversed in the occluded area, indicating a greater decrement in consumption in the subendocardium. Measurements of arterial saturation indicate an increasing number of blood vessels with O2 saturations < 80% with coronary artery occlusion. These vessels were found in all occluded areas, indicating a marked heterogeneity of blood flow within the area of occlusion. Some vessels may have normal flow and others, low or no flow. There was heterogeneity of flow and O2 extraction which led to areas with relatively normal O2 consumption in the core of the infarct.