Pulmonary atresia with left ventricular-right atrial communication: basis for circular shunt.

In the usual instance of an intracardiac right-toleft shunt the blood participating in the shunt traverses a capillary bed before it returns to the chamber from which it originated. In an uncommon instance some of the shunted blood returns to the chamber of origin through intracardiac channels, yielding a phenomenon which may be termed a 'circular' shunt. This term was first used with reference to a case reported from our group by Shone, Anderson, Elliott, Amplatz, Lillehei, and Edwards (1962). In that case it was assumed that some of the right atrial blood had been shunted in a right-to-left direction into the left atrium. Some of this blood then escaped from the left ventricle through a small ventricular septal defect into the right ventricle. Then, in the presence of pulmonary stenosis and of tricuspid insufficiency, some of the blood which had originated in the right atrium returned to that chamber to complete a 'circular' shunt in which each of the four cardiac chambers had participated. We have studied two additional cases which fulfil the foregoing definition of a 'circular' shunt. In each there was pulmonary valvular atresia in association with a left ventricular-right atrial communication. In the first, the left ventricularright atrial communication was of the classical variety. In the second, this communication resulted from a combination of Ebstein's malformation of the tricuspid valve and a ventricular septal defect in which the defect opened into that part of the right ventricle which lay proximal to the attachments of the malformed tricuspid valve.