Transmural coronary venous O2 saturations in normal and isolated hearts.
Blood O2 saturations were measured by microscopic oximetry in the small coronary veins of wither open-chest or isolated and blood-perfused dog hearts. Subendocardial saturations (average 34%) were significantly lower than subepicardial (average 52%) in isolated hearts contracting isovolumically at systolic and coronary perfusion pressures of 100 mmHg. Saturations of botb regions fell and were not significantly different from each other (both averaged 16%) with partial coronary occlusion. When MVo2 was increased by calcium infusion, subendocardial saturations fell sharply to about 2% and were significantly, lower than subepicardial (average 10%). Conversely, when MVo2 was decreased by ventricular decompression, saturations rose equally in subendocardium (average 40%) and subepicardium (average 45%) (not significant). These data illustrate the efficacy of cascular autoregulation in isolated hearts. In open-chest dogs, as in isolated hearts with partial coronary occlusion, subendocardial (average 20%) saturations were not significantly diffenent from each other and ranged from 0 to 70%, suggesting the possibility of significant differences either in regional coronary flow or MVo2, or both, in closely adjacent areas throughout the myocardium.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D003326:Coronary Circulation; D003331:Coronary Vessels; D004285:Dogs; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010313:Partial Pressure; D010477:Perfusion; D011312:Pressure; D012039:Regional Blood Flow; D014680:Veins
D001285:Atropine; D010100:Oxygen; D002118:Calcium