Two dimensional echocardiographic diagnosis of situs

Abstract

At present there is no reliable method of recognising atrial isomerism by two dimensional echocardiography. The authors therefore used two dimensional echocardiography to examine 158 patients including 25 with atrial isomerism and 4 with situs inversus. Particular attention was paid to the short and long axis subcostal scans of the abdomen. Using the position of the inferior vena cava and the aorta with respect to the spine it was possible to separate those with situs solitus for the others. Two false positives for abnormal situs had exomphalos. In situs solitus the aorta lay to the left of the spine and the inferior vena cava lay to the right. One patient with situs solitus and azygos continuation of the inferior vena cava also had inferior vena cava to right atrial connection. In the 4 patients with situs inversus the mirror image of the normal pattern was present. In 9 patients with right isomerism the inferior vena cava and aorta ran together on one or other side of the spine. The inferior vena cava, anterior to the aorta at the level of the diaphragm, received at least the right hepatic veins (normal or partial anomalous hepatic venous connection). Of the 16 patients with left isomerism, 14 had azygos continuation of the inferior vena cava which was visualised posterior to the aorta in all but 2. All patients with left isomerism had total anomalous hepatic venous connection to 1 or both atria via 1 or 2 separate veins. Two dimensional echocardiography therefore provides the means of detecting abnormal atrial situs and of diagnosing right or left isomerism in the great majority of patients, if not all.