Partial anomalous pulmonary venous drainage and intact atrial septum with mitral stenosis: the paradox of a small shunt

Clinical, hemodynamic, and angiographic features of 10 patients with partial anomalous pulmonary venous drainage, intact atrial septum, and rheumatic mitral stenosis have been presented. Seventeen patients with this combination of anomalies reported in the literature have also been reviewed. The clinical diagnosis of mitral stenosis was possible in each of our 10 cases. Partial anomalous pulmonary venous drainage and intact atrial septum in addition to mitral stenosis was clinically suspected in only four patients. The findings suggesting additional presence of partial anomalous pulmonary venous drainage and intact atrial septum in a patient with mitral stenosis include: wide variable splitting of the second sound, pulmonary ejection systolic murmur with or without a thrill, and radiological evidence of unilateral increase in pulmonary vascularity or unilateral hilar pulsations. Hemodynamic findings were characterized by a relatively modest left to right shunt (Qp/Qs:2.2±1.4). Elevated pulmonary vascular resistance was found in the anomalously draining as well as the normally draining lung segments (9.1 ±4.9 and 6.5±3.4 units, respectively, t=1.32;NS). The mechanism of the unexpected high resistance in the anomalously draining lung segments permitting only a small left to right shunt is discussed.