Is Coronary Sinus Blood Oxygen Tension Behavior Determined by Myocardial Oxygen Tension Variation during Cardiac Reperfusion?

The relationship between coronary sinus blood oxygen tension (CSPO2) and myocardial oxygen tension (MPO2) variations during cardiac ischemia and reperfusion was studied in anesthetized open-chest dogs. Oxygen tension was measured by a polarographic method. Ischemia resulted in a slightly decreased CSPO2 and a more pronounced reduction of MPO2. After reperfusion the CSPO2 rose rapidly and transiently before it returned gradually to the control level. By contrast, during the recovery period, the MPO2 increased slowly, with recovery occurring long after the peak of CSPO2. These data suggest that during the reperfusion phase, the CSPO2 variation is probably due to opening of the myocardial arteriovenous shunts instead of an increase of flow through the myocardial capillary bed.