Non‐Uniform Blood Flow in the Left Ventricular Wall of Dogs Measured by the Xe‐133 Wash‐out Technique

Intra‐myocardial injections of Xe‐133 into the left ventricular wall revealed time‐activity curves which indicate that blood flow in the subepicardial layers is 30 % greater than in the subendocardial layers. A two‐compartment model of the ventricular wall was therefore considered, and a good correlation was found between this model and the results of graphical and computer analyses of time‐activity curves obtained by injections of Xe‐133 into the left coronary artery. The flows of these two compartments and flows after superficial and deep intra‐myocardiai injections were not identical. Thus the myocardial two‐compartment model must be abandoned. A gradual decrease of flow from the subepicardial to the subendocardial surface is suggested. If this is true then the wash‐out curve after intra‐coronary injection of Xe‐133 is multi‐exponential and thereby inaccessible to graphical analysis.