INFERIOR VENA CAVAL POSITION IN THE DIFFERENTIAL DIAGNOSIS OF ATRIAL AND VENTRICULAR SEPTAL DEFECTS.

Abstract

The dominant features of congenital heart lesions with left-to-right shunts observed by conventional roentgen examination are increase of pulmonary vascularity and enlargement of the heart. Of particular importance is the differential diagnosis of atrial and ventricular septal defects. Increased size of the left atrium indicates a shunt distal to the atrioventricular valve, while no enlargement of the left atrium is found in atrial septal defects (2). In ventricular septal defects clinical signs of enlargement of the left ventricle are usually present. In cases of secundum atrial septal defect the left ventricle is presumably of normal size. Assessment of the size and configuration of the left ventricle on the basis of conventional roentgenography is generally considered difficult since available criteria are hard to apply in practice. In the determination of left ventricular dilatation, however, the topographical relationship of the inferior vena cava to the posterior surface of the heart in the lateral projection of the chest is a valuable diagnostic aid. It occurred to us that since left ventricular dilatation does not occur in atrial secundum septal defects but is the rule in ventricular septal defects with significant shunts, such altered relationship of the left ventricle to the inferior vena cava might be useful in differentiating these lesions. This report concerns our experience with the utilization of this sign. Methods To test the validity of this concept, all cases of ventricular and atrial secundum septal defects at the Children's Clinic of the Karolinska Hospital were reviewed. Each case was proved by cardiac catheterization and angiography. The series included some adults who were brought to the Children's Clinic for angiocardiography. All patients under four years of age were eliminated from the group because of the recognized difficulties in obtaining chest roentgenograms in full inspiration at this age. Also excluded from the series were patients in whom the degree of inspiration was so shallow as to prevent visualization of the inferior vena cava in the lateral projection. Of the patients with ventricular septal defect, only significant shunts were considered, as small shunts characteristically produce no significant alteration in cardiac contour and therefore do not constitute a problem in differential diagnosis from the atrial septal defect. It was felt that a significant shunt was present in the included cases of ventricular septal defect if cardiac enlargement and definite increase in prominence of the pulmonary vasculature were evident. Since patients with atrial septal defects typically have large shunts and radiologically detectable alterations in heart size and pulmonary vascularity, there was no necessity to eliminate any of these on the basis of size of the shunt.