Prenatal role of the ductus arteriosus in absent pulmonary valve syndrome

Absent pulmonary valve with ventricular septal defect is associated with ductal agenesis and markedly dilated main and branch pulmonary arteries. The less common variant with intact ventricular septum generally exhibits a patent ductus and smaller branch pulmonary arteries, and may be associated with tricuspid atresia. We identified 7 patients with the prenatal diagnosis of absent pulmonary valve, 5 with ventricular septal defect (Group 1) and 2 with an intact ventricular septum (Group 2). Imaging, color Doppler, and pulsed-Doppler recordings were analyzed. The branch and main pulmonary arteries were measured and expressed as a ratio with the descending aorta. Pulmonary regurgitation time (PRT) and diastolic acceleration time (DAT) were derived, and DAT/PRT was calculated to characterize diastolic pulmonary flow. Group 1 patients all had a large ventricular septal defect, normal biventricular size and function, and dilated main and branch pulmonary arteries. Group 2 patients had dilated main but smaller branch pulmonary arteries, moderate right ventricular dilation with severe dysfunction, and limited or absent tricuspid inflow. Group 1 demonstrated shorter acceleration time and earlier peak velocity, resulting in a smaller DAT/RT ratio. We speculate that free communication between the fetal aorta and the ventricles may limit atrial inflow and elevate diastolic pressure, affecting cardiac output, ventricular function, and atrioventricular valve development. With an intact ventricular septum, these physiologic and anatomic repercussions are limited to the right ventricle, but with a ventricular septal defect, both ventricles would experience similar consequences and cardiac performance could be critically impaired.