The Role of MR Imaging in Determination of Atrial Situs in Congenital Heart Disease with Situs Ambiguus

ABSTRACT

PURPOSE: to assess the role of MR imaging in determining of the atrial situs in complicated congenital heart disease with situs ambiguus. MATERIALS AND METHODS: In order to classify the situs, the morphology of atrial appendages, on bronchial length ratio, the superior-inferior relation of the pulmonary artery (PA) and main bronchi on each side, and splenic abnormality were evaluated by MR imaging in 22 patients (12 boys and 10 girls), and the results were compared. RESULTS: In all patients, the superior-inferior relation of the PA and main bronchi tended to lateralize, and in one, bronchial length ratio was not consistent with the relation between the PA and bronchus. Bronchial and atrial situs, as determined by appendage morphology, were consistent in ten of 13 right isomerism patients, and in only three of nine of these with left isomerism. All 13 right isomerism patients, classified by the relation of the PA and main bronchi, showed asplenia, whereas eight of nine of these with left isomerism had polysplenia. CONCLUSION: In the assessment of atrial situs by MR imaging, the positional relation of a bronchus and the PA, bronchial length ratio, and splenic abnormality are constant and reliable. The accuracy of classification of situs on the basis of atrial appendage morphology is, however, limited.