“Masked” pulmonary venous obstruction in patients with isomerism of the right atrial appendages: an overstated association

Abstract

Isomerism of the right atrial appendages is associated with anomalies of pulmonary venous return, which may be obstructive. The associated pulmonary arterial obstruction, however, has been reported to “mask” the pulmonary venous obstruction, with resultant pulmonary edema following augmentation of the flow of blood to the lungs. We postulated that the frequency of “masked” pulmonary venous obstruction has been overreported in the literature. To ascertain the true situation, we evaluated the frequency of “masked” pulmonary venous obstruction in a large, unselected, group of patients with isomerism of the right atrial appendages. We evaluated the clinical, anatomic, and radiographic data of 65 newborns seen with this syndrome since 1970. Development of pulmonary venous obstruction, both before and after systemic-to-pulmonary shunting and/or infusion of prostaglandin E₁, was determined and correlated to clinical and radiographic findings. Of the 65 patients, 19 (29%) were ultimately diagnosed with pulmonary venous obstruction. The pulmonary veins themselves connected in infradiaphragmatic fashion in 10 patients, supracardiac in 3, to the atriums directly in 1, and in mixed fashion in the other 5. Pulmonary venous obstruction was readily apparent in 15 of the 19, as demonstrated by pulmonary edema on initial chest radiography. The remaining four cases ultimately diagnosed with pulmonary venous obstruction received augmentation of pulmonary blood flow with resultant pulmonary edema. Of these four severely cyanosed patients, pulmonary vascular markings on the initial chest radiograph had been normal in one but increased in three. Due to the presence of these clinical markers, they do not truly represent “masked” pulmonary venous obstruction. Except for two patients with minimally obstructed pulmonary arterial blood flow, 44 patients without pulmonary venous obstruction had normal or decreased pulmonary vascular markings at presentation. Of these 44, 14 received infusions of prostaglandin E₁, with none developing pulmonary edema. We conclude that pulmonary venous obstruction is usually readily apparent at time of presentation in patients with right isomerism, and that “masked” pulmonary venous is a very rare event which has been over-emphasized in the literature. Careful evaluation of clinical and radiographic findings at time of presentation can correctly identify pulmonary venous obstruction in such patients.