Visualization and measurement of the main bronchi by tomography as an objective indicator of thoracic situs in congenital heart disease.

When investigating complex congenital heart disease, determination of atrial situs is essential. Pathological studies have demonstrated that the best predictor of atrial situs is thoracic situs. To assess thoracic situs, bronchial tomography was performed in 92 patients with congenital heart disease. Sixty-four of these, without abnormalities of situs or cardiac position, formed 'normal' controls. The lengths of the left and right main bronchi were measured. When these were related to age, and the results analyzed statistically, linear discriminant equations resulted giving a chance of only 0.09% of misclassifying a bronchus of unknown morphology. The lowest ratio between bronchial lengths (BLR) in any individual was 1.71:1. These results were then used to assess thoracic situs in 17 patients with abnormal situs or CARDIAC POSITION. In 7 (2 with situs inversus), abdominal and thoracic situs agreed. Of 6 patients with bilateral left lung, 3 had an interrupted inferior vena cava. Of 4 patients with presumptive asplenia, 2 had bilateral right lung, but two had thoracic lateralization, one solitus and one inversus. The highest BLR in thoracic isomerism was 1.4:1. This emphasizes the complex interrelation of splenic status, thoracic, and abdominal situs, but demonstrates the value of bronchial measurement particularly in apparent situs indeterminatus.