Direct measurement using epicardial echocardiography in open-chest dogs showed that the inner, middle, and outer thirds of the myocardial wall contribute 58%, 25%, and 17% to total wall thickening.
Direct epicardial echocardiographic measurements in dogs confirm that a gradient of thickening exists across the myocardial wall, with the inner portion contributing the largest fraction (58%) to total systolic thickening.
Simple geometric models of the left ventricle and indirect experimental measurements suggest that the inner myocardial wall contributes the largest fraction to total wall thickening. We measured transmural differences in regional wall thickening directly, using an epicardial M mode echocardiographic transducer (6 mm diameter, 5 MHz) placed on the anterior free wall of the left ventricle. Wall thickness was partitioned into inner and outer regions by inserting a waxed, 3-0 suture at different depths within the wall. The suture was used as an intramural echo target that was imaged simultaneously with the endocardium to determine inner and outer fractional contribution to total wall thickness. Data were collected in open-chest dogs at rest, during inotropic stimulation with isoproterenol, and during right heart bypass, which was used to vary cardiac output and preload. Results obtained with this method demonstrated that systolic wall thickness was nonuniform at rest and during each intervention. The fractional contributions to total wall thickening of the inner, middle, and outer thirds of the myocardial wall were estimated from the data to be 58%, 25%, and 17%, respectively. The experimental findings corresponded closely to theoretical predictions, supporting the conclusion that a gradient of thickening exists across the myocardial wall, with the inner portion of the wall contributing the largest fraction to total systolic thickening.
Myers et al. (1986) studied None (animal study). Epicardial M mode echocardiography was evaluated on Fractional contribution to total wall thickness. Direct measurement using epicardial echocardiography in open-chest dogs showed that the inner, middle, and outer thirds of the myocardial wall contribute 58%, 25%, and 17% to total wall thickening.