Tricuspid atresia. Morphology of the outlet chamber with special emphasis on surgical implications.

An anatomic study of 28 heart specimens with tricuspid atresia showed 15 hearts with ventriculoarterial concordance and a right-sided anterior outlet chamber. Of these 15 hearts, 12 showed evidence of restricted pulmonary blood flow. In eight of these 12 specimens, an anterior deviation of the outlet septum, relative to the primary septum, was present. This deviation caused a narrowing inside the outlet chamber and functioned as infundibular pulmonary stenosis. The outlet chambers of the 15 hearts with ventriculoarterial concordance were compared with those of 13 hearts with tricuspid atresia and ventriculoarterial discordance and also a right-sided anterior outlet chamber. In the latter group of 13 hearts, five showed evidence of restricted pulmonary blood flow, at least partially caused by posterior deviation of the outlet septum relative to the primary septum. A clear difference in outlet chamber morphology was found without exception between specimens with and without ventriculoarterial concordance. Clinical data in three long-term survivors of the Fontan procedure demonstrate that the special morphology of the outlet chamber can pose surgical problems. Especially in patients with ventriculoarterial concordance, when the outlet chamber is incorporated into the pulmonary circuit, the surgeon must give special attention to the specific morphology to prevent undesirable sequelae.