Distribution of Myocardial Glucose Consumption Under Normal Conditions and During Isoprenaline and Dobutamine Infusion

Abstract

Tracer microsphere studies on regional myocardial blood flow revealed an inhomogeneous distribution within the left ventricular wall under various experimental conditions. In the normal and the anesthetized closed chest dog as well as in isolated heart preparations blood flow to the subendocardial layers exceeds that to the subepicardial layers; ratios, calculated from subendocardial and subepicardial flow ranged from 1.1 to 1.8 (Flohr et al., 1973; Ypintsoi et al., 1973; Domenech et al., 1980) depending largely on the size of the particles applied. While it is a matter of discussion, which particle size can delineate nutritional blood flow in the myocardium, it is commonly accepted that under normal conditions a blood flow gradient between the subepi- and subendocardial layer exists. This blood flow pattern may be induced by a comparable pattern of myocardial metabolic rate. Measurements of sarcomere length in diastole and in systole (Sonnenblick et al., 1967), calculations of tension developed (Streeter et al., 1970) and the analysis of tissue oxygen clearance in acute ischemia (Winbury et al., 1981) in different layers of the left ventricular wall seem to support this hypothesis. By measuring local capillary oxygen saturation and local blood flow, Holtz et al. (1977) calculated peak values of oxygen consumption in the subendocardial region.