The left ventricle in anomalous pulmonary venous return. Morphometric analysis of 36 fatal cases in infancy.

The mass of the left ventricle is normal in infants with total anomalous pulmonary venous return, but the ventricular cavity is compromised by leftward displacement of the interventricular septum due to the combined pressure-volume overload of the right side of the heart. Severe septal displacement is associated with distorted myocardial architecture in the region of the septal attachments of the left ventricular free wall. Abnormalities of septal motion are frequently detected in echocardiograms. Left ventricular output is low, as judged by arrested development of the aortic valve circumference, and is probably compromised both by the left to right shunt and by septal displacement. Successful correction of the anomaly may depend on intervention before the changes in septal position, structure, and function have become irreversible.