Evaluation of regional myocardial perfusion and ischemia from coronary venous blood

The usefulness of simultaneous great cardiac vein (GCV) and coronary sinus (CS) blood sampling for detecting regional differences in flow per unit weight (F/W) and metabolism has been examined in the canine left ventricle. In normally perfused ventricles, F/Ws in myocardium represented in GCV and CS drainage agreed within ±10% over a wide range (23-355 (ml/min)/100 g); GCV and CS PCO₂, pH, and percent lactate extraction differed by 0.45 ± 1.5 (SD) mmHg, 0.002 ± 0.014 units, and 0.3 ± 5.4%, respectively. GCV F/W exceeded CS F/W by >10% during selective increases in left anterior descending (LAD) inflow or reductions in left circumflex (LC) inflow; it was >10% below CS F/W during reduced LAD inflow or augmented LC inflow. GCV-CS differences in PCO₂, pH, and percent lactate extraction increased noticeably during reduced LAD inflow, averaging 5.7 ± 3.9 mmHg, -0.037 ± 0.036 units, and -25 ± 14%. Similar but directionally opposite changes occurred during reduced LC inflow (-5.8 ± 3.5 mmHg, 0.035 ± 0.032 units, and 26 ± 17%). Blood sampled near the origin of the GCV reflects perfusion in myocardium supplied virtually entirely by the LAD. GCV-CS differences that exceed normal values reflect increased heterogeneity of left ventricular perfusion and/or metabolism independently of the absolute values of the parameters measured.