Influence of the orientation of myocardial fibers on echocardiographic images.

The role of myocardial fiber orientation in recognized patterns of echocardiographic images of ventricular muscle was explored. Skeletal muscle, postmortem hearts and excised myocardium confirmed the anisotropic echocardiographic characteristics of these muscles. The short-axis ventricular views in vitro and in vivo gave a distinct pattern of echo amplitudes within the myocardium that is consistent with fiber orientation as a major factor in this pattern. A different pattern in apical long-axis views of the basal septum and free wall also is consistent with fiber orientation, but detracts from attenuation as a major cause of "dropout" in short-axis views. Choice of an optimal echocardiographic view for evaluation of wall thickness and ventricular function may be influenced by improved understanding of the factors involved in image formation.