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We report 2D-echocardiographic and angiocardiographic assessment of 28 cases of visceral heterotaxia with left atrial isomerism, with particular emphasis on infundibular ventricular morphology. Ventricular D-loop was present in 15 cases (52.6%), and ventricular L-loop in 13 (46.4%); 25/48 patients had concordant ventricular loop and cardiac position (89.3%). In 18 patients (64.3%) there were 2 balanced ventricles; of the other 10 patients, 9 (32.1%) presented right and 1 (3.6%) left ventricular dominance. Ventricular septal defect was present in 12 cases (42.8%). Ventriculo-arterial connections were concordant, with "normally related" great arteries in 9/15 cases with ventricular D-loop (60%). In these cases, ventricular morphology, connections and relations of the great arteries were typical of situs solitus. In the remaining 6 patients there was double-outlet right ventricle, also with normally related great arteries. In 12/13 cases (92.3%) with ventricular L-loop ventriculo-arterial connections were concordant with "mirror image normally related" great arteries. In these cases, ventricular morphology, connections and relations of the great arteries were typical of situs inversus. In one patient there was double-outlet right ventricle, also with mirror image normally related great arteries. Twelve patients (42.8%) had pulmonary stenosis and 5 had a systemic outflow obstruction (17.8%). From these observations we conclude that ventriculo-infundibular morphology, either of situs solitus-type or of situs inversus-type, is a typical anatomical feature of left atrial isomerism. These results may have important implications in the diagnosis and in the surgical management of patients with left atrial isomerism.

The patterns of pulmonary circulation were assessed by angiography in a series of 24 patients with right atrial isomerism (asplenia syndrome) and pulmonary atresia. Mean age at catheterization was 21.5 days (range 1 day-11 months). The pulmonary arteries were confluent in 22 cases (91.7%). Eighteen patients (75%) had ductus-dependent pulmonary circulation in presence of confluent pulmonary arteries, similar to cases of pulmonary atresia combined with complex congenital heart disease. The ductus appeared in continuity with the aortic arch, shaping an acute angle with the descending aorta, as in cases of pulmonary atresia with ventricular septal defect. A bilateral ductus was present in 5 cases (20.8%), 3 with confluent and 2 with nonconfluent pulmonary arteries. One patient presented multiple systemic collaterals to the lungs. All the other patients had normal arborization of the pulmonary arteries. Seven patients presented an obstructed total anomalous pulmonary venous connection: 4 in inferior vena cava and 3 in superior vena cava. These anatomical observations provide useful information for the surgical palliation of these anomalies and, probably, warrant pre-operative angiographic evaluation in all the patients with right atrial isomerism.