Images in cardiovascular medicine. Anterior origin of the main pulmonary artery from the arterial valvar sinus: unusual truncus arteriosus.

We describe the case of a newborn with 22q11 deletion and an unusual form of common arterial trunk with the main pulmonary artery arising anteriorly at the level of the common arterial valve sinus. Case reports: We report the case of a term newborn male who presented to our institution with a prenatal diagnosis of congenital heart disease. His mother was a 29-year-old woman with 22q11 deletion who was evaluated in the high-risk perinatal clinic after an abnormal fetal ultrasound. The initial fetal echocardiogram performed at 26 weeks of gestation showed a common arterial valve overriding a large subarterial ventricular septal defect, with no significant stenosis or regurgitation of this valve. The pulmonary arteries were not clearly identified. Subsequent fetal evaluation showed what appeared to be a main pulmonary artery arising anteriorly to the ascending aorta, very proximal to the common arterial valve, at the level of the arterial valvar sinus (Figure 1; Movie I). No infundibulum or separate right ventricular outflow tract or second semilunar valve could be visualized. Prenatal counseling was given toward the likely diagnosis of a truncus arteriosus. After an uneventful term delivery with an Apgar score of 8/8, the patient was empirically started on prostaglandin infusion until a truncus arteriosus with interrupted aortic arch could be ruled out. A chest radiograph demonstrated mild cardiomegaly with increased pulmonary blood flow consistent with left-to-right shunt (Figure 2). An echocardiogram within the first few hours of life demonstrated a single outflow tract with a trileaflet semilunar valve overriding the crest of the ventricular septum and a large subarterial ventricular septal defect. It was confirmed that the main pulmonary artery arose anterior to the aorta at the level of the arterial valvar sinus (Figure 3A through 3D; Movies IIA through IID), coursed anteriorly to the ascending aorta, and arched up above the transverse aorta before branching into confluent, good-sized leftand right-branch pulmonary arteries. The single semilunar valve was competent, with neither regurgitation nor stenosis. The aortic arch was rightward and intact. At this time, this lesion was not considered ductal dependent, and the prostaglandin infusion was discontinued. Even though the initial oxygen saturation was 85%, the patient developed unexplained desaturation by day of life 2, which motivated empirical resumption of the prostaglandin infusion. Because of the unusual echocardiographic findings, the possibility of additional sources of pulmonary blood flow, and the continued question as to whether this cardiac defect should be called truncus arteriosus type I or pulmonary atresia with ventricular septal defect and aortopulmonary window, the patient underwent a cardiac catheterization. Hemodynamic assessment revealed the right ventricular pressure and the main pulmonary arterial pressures to be isosystemic. There was no hemodynamic evidence of semilunar valve stenosis. The distal main and branch pulmonary arterial pressures were approximately half systemic, consistent with distal main pulmonary artery stenosis. Angiography revealed a main pulmonary artery arising anteriorly at the level of the sinuses of the single semilunar valve, coursing anterior to the ascending aorta (Figure 4; Movie III), arching up above the aortic arch before diving posteriorly and branching into left and right pulmonary arteries. Crisscrossing of the pulmonary arteries was noted (Figure 5; Movie IV). The aortic arch was rightward and intact, with an aberrant left subclavian artery. There was no ductus arteriosus, which made the diagnosis of truncus arteriosus likely. Chromosome analysis revealed the patient to have 22q11 deletion. On day of life 7, the patient underwent complete surgical repair (Figure 6). The main pulmonary artery was transected from the ascending aorta, and the aortopulmonary communication was closed with a bovine pericardial patch. A 12-mm Contegra graft (Medtronic, Minneapolis, Minn) was then anastomosed between the right ventricle and the transected main pulmonary artery, just proximal to its bifurcation. A secundum atrial septal defect was partly closed with a running Prolene suture (Ethicon, Inc, Somerville, NJ), leaving a 3-mm