Cross-sectional echocardiographic examination of the interatrial septum.

The interatrial septum has not been readily appreciated by M-mode echocardiography. Cross-sectional echocardiography has the capability of recording the shape and location of the interatrial septum. Real-time cross-sectional echograms using a mechanically oscillating transducer were obtained on 100 consecutive patients. Echocardiographic examination of the left atrium and aorta was obtained in a plane perpendicular to the long axis of the atria. In 15 normal patients and 17 patients with atrial septal defects (ASD) and 51 patients with other forms of heart disease, the interatrial septum was recorded as a linear echo from the aorta to the posterior wall of the left atrium. In six patients who had ostium primum ASDs, the echoes from the interatrial septum disappeared near its expected junction with the interventricular septum. Drop out of echoes in the mid portion of the septum was noted in those patients who had ostium secundum atrial septal defects but this could not be differentiated from normal. These preliminary data indicate that examination of the interatrial septum is feasible and may be specific in those few patients examined so far with ostium primum atrial septal defect. The ability to locate and record the shape of the interatrial septum could have many investigate and clinical uses.