Ventricular size and shape by two-dimensional echocardiography

The evaluation of cardiac size and shape has been aided by the recent development of high resolution real-time two-dimensional echocardiography, which permits of dynamic cross-sectional evaluation of all or a large portion of the left ventricle throughout the cardiac cycle. This review addresses itself to the determination of left ventricular size and shape by two-dimensional echocardiography. A method is described for accurate volume determination in the intact, isolated, ejecting canine heart. By combining the two-dimensional echocardiogram with knowledge of transducer position and orientation with respect to the heart, it is possible to reconstruct a three-dimensional representation of a chamber and thereby measure volume without reliance on major geometric assumptions. Because of the unique ability of two-demensional echocardiography to produce a cross-sectional image of the beating heart in a large number of planes, it is suitable for the determination of cardiac shape and architecture. The recognition of early regional cardiac dilatation in acute myocardial infarction is described. Changes in ventricular shape brought about by the dynamic alterations lend themselves well to two-dimensional echocardiographic study. The pivotal nature of the interventricular septum renders it susceptible to changes in the functional state of both ventricles. That the interventricular septum may mediate ventricular interaction acutely is suggested by the acute effects of right ventricular loading in man using the Mueller maneuver. Leftward septal displacement and flattening of the septum during the early maximal Mueller maneuver is evidence by a substantial increase in the radius of curvature of the septal segment, without a change in the left ventricular free wall. This septal flattening occurs in diastole and persists during systole. Diastolic events thus appears to influence systolic shape. Changed septal shape may be an important mechanism of, and evidence for, ventricular interdependence in normal man.