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We used transoesophageal echocardiography in 4 children with either documented or suspected obstruction of the left ventricular outflow tract to determine whether this technique may provide additional morphologic information when compared to praecordial ultrasound. Transoesophageal studies defined unsuspected mitral valvar abnormalities in two patients and involvement of the subvalvar mitral apparatus in one. In one patient, the study documented a suspected fibrous ridge associated with malalignment of the outlet septum. Transoesophageal echocardiography would appear to be a new technique with definite advantages in defining the spectrum of lesions which cause obstruction to the left ventricular outflow tract in children.

Forty-one specimens with pulmonary atresia and confluent pulmonary arteries were studied to establish the frequency and the nature of anomalies of both the ductus arteriosus and the central pulmonary arteries and their possible interrelation. The specimens were divided according to the type of pulmonary atresia: valvar atresia (12 cases) versus "muscular" atresia of the pulmonary orifice (29 cases). Abnormal connexions between the duct and the adjacent great arteries, as well as stenosis of a pulmonary artery, were common in cases with atresia of the pulmonary orifice and relatively rare in cases with imperforate valve. The abnormal connexions consisted of a proximal displacement of the origin of the duct from the aorta and displacement of the entry site of the duct into the pulmonary trunk towards one of the main pulmonary arteries. A left duct thus connected to the left and a right duct to the right pulmonary artery. Pulmonary artery stenosis, exclusively occurring in those specimens with a duct connecting to a pulmonary artery, were located in the segment of pulmonary artery between the pulmonary trunk and the duct. Histological examination revealed ductal tissue in the wall of a pulmonary artery in more than half of the cases with atresia of the pulmonary orifice. Ductal tissue in a pulmonary artery and pulmonary artery stenosis frequently coexisted. It is concluded that stenoses in the central pulmonary arteries may be related to the duct. The relationship resembles that between the duct and coarctation of the aorta.

Forty-three specimens with an obstructive aortic arch anomaly, obtained from infants that had died under the age of one year, were studied to establish the relationship between the arch anomalies and the ductus arteriosus. All specimens were studied morphologically. Twenty of the 43 were also studied histologically. The morphological part of the study included measurements of all the segments of the aortic arch and establishment of the localisation of any associated coarctation. The specimens were divided according to the appearance of the isthmus. The isthmus was not present in 4, was atretic in 2, hypoplastic in 19 and had a normal diameter in 18 cases. In all cases, except 5 (2 with atresia and 3 with hypoplasia of the isthmus) there was an associated coarctation. The majority of the coarctations (28) was located preductally. All such preductal coarctations had ductal tissue in the obstructing ridge. There were 5 paraductal coarctations. Of these, two also had ductal tissue in the ridge. The distribution of the ductal tissue among the two types of coarctation suggested a spectrum of anomalies rather than two completely different entities. The patterns of the aortic arches appeared predictive for the type of coarctation present. The arches that tapered normally towards the isthmus either presented with a preductal coarctation (20 cases) or without a coarctation (3 cases). All 4 specimens in which the isthmus was lacking also had a preductal coarctation. The 5 paraductal coarctations were found in arches that showed a "reverse" pattern, tapering towards the brachiocephalic arteries. All the preductal coarctations contained ductal tissue whereas only 2 of the 5 paraductal coarctations had ductal tissue in the obstructing ridge. It is concluded that careful evaluation of all the segments of the aortic arch may be helpful in the clinical evaluation of infants with an obstructive aortic arch anomaly.

The aortic arches of 34 specimens with hypoplastic left heart syndrome were studied in order to establish the frequency, the nature and the clinical implications of aortic arch anomalies. A localized aortic coarctation was present in 23 specimens. The coarcation was located preductally in 2 and paraductally in 21 cases. The degree of obstruction caused by the coarctation varied considerably. In only 6 cases (1 preductal and 5 paraductal) was the obstruction judged to be severe. One of these cases had an additional aneurysm of the aortic wall proximal to the coarctation. An aberrant relation of the ductus arteriosus and the aortic arch was found in 2 specimens without localized coarctation. In the remaining 9 specimens the aortic arch appeared normal. The aortic arch anomalies were mostly present in specimens with a severely hypoplastic ascending aorta. Clinicians, when preparing infants with hypoplastic left heart syndrome for surgical palliation, should always suspect associated aortic arch anomalies, especially when there is severe hypoplasia of the ascending aorta. Coarctation of the aorta will require additional surgical treatment.