Abstract
Embryologically, conotruncal abnormalities result from abnormal development of the conotruncal septum expressing variably as double outlet right ventricle, tetralogy of Fallot, absent pulmonary valve syndrome, complete transposition, corrected transposition, and pulmonary atresia with ventricular septal defect (PA-VSD). It is not very uncommon to see a VSD with one single large artery overriding the defect, along with nonvisualization of the right ventricular outflow tract and ventricular origin of the Pulmonary artery. In situations with above findings and a near normal four chamber heart view the differential diagnosis include common arterial trunk (CAT), and pulmonary atresia with VSD and rare disorders like aortic atresia. CAT is characterized by a single great artery supplying the coronary, cranial and pulmonary circulation. Similar findings in PA-VSD may create confusion in prenatal diagnosis of these two conditions, more so in CAT type II/III. The diagnosis of CAT type I is comparatively easy as the pulmonary artery arises immediately beyond the origin of the trunk. This article discusses a case, the approach to and differential diagnosis of a single great artery overriding a VSD with a near normal four chamber view. The role of cardiac screening during the early morphology scan and the role of 4D imaging with color and power Doppler angiography are also highlighted for the correct diagnosis and description of spatial relationships of the vessels and chambers. Correct prenatal diagnosis of these conditions is important for patient counseling and prognostication.
Keywords
VSD - Override - Pulmonary atresia - Common arterial trunk - Bilateral SVC - Pulmonary atresia with VSD - MAPCA
