Origin of great cardiac vein and coronary sinus drainage within the left ventricle

The relative contributions of left anterior descending (LAD) and left circumflex (LC) arterial inflow to blood sampled at various points within the great cardiac vein (GCV) and coronary sinus (CS) have been investigated in open-chest dogs. Dissolved helium (He) and hydrogen (H2) were infused into external circuits perfusing the LAD and LC, respectively, and their steady-state concentrations were measured chromatographically at various points within the GCV and CS. Under basal conditions GCV H2 averaged only 5% of mid-CS H2 and did not change greatly during alterations of preload and afterload or during selective LAD or LC obstruction and vasodilation. The relationship of mid-CS He to GCV. He was more variable under basal conditions and changed noticeably during selective changes in LAD or LC inflow. Appreciable amounts of He were present consistently in left marginal vein drainage. We conclude that: 1) GCV blood is remarkably free of LC inflow in both normal and abnormal physiological states; 2) the origin of mid-CS blood is more variable, both from animal to animal and in individual animals before and after interventions; 3) a portion of LAD drainage normally reaches the CS through circumflex venous branches rather than the GCV.