Isolated right ventricular hypoplasia.

Hypoplasia of the right ventricle, unassociated with severe pulmonary or tricuspid valvar malformations, is a primary congenital abnormality in which the trabeculated sinus portion of the ventricle fails to develop. An atrial septal defect or a stretched foramen ovale serves as an escape valve. The clinical, hemodynamic, and angiocardiographic features of this rare type of cyanotic heart disease are described in two children and reviewed in 13 previously reported cases. The clinical spectrum varies considerably in accordance with the degree of hypoplasia. Severe forms of hypoplasia, usually presenting in infancy, closely resemble tricuspid or pulmonary atresia. The electrocardiogram in hypoplasia, which shows right atrial enlargement and absence of right ventricular electrical forces, may be indistinguishable from an electrocardiogram in atresia. Lesser degrees of hypoplasia should be differentiated from Ebstein's malformation and anomalies of the systemic venous retum. Both our patients, who had only mild underdevelopment of the right ventricle, markedly improved after surgical closure of the atrial septal defect. It is proposed that in mild forms of hypoplasia temporary occlusion of the atrial septal defect by means of a balloon catheter should be used in the preoperative assessment of right ventricular function.