Superior vena cava obstruction due to markedly enlarged right pulmonary artery in Eisenmenger syndrome

A 24-year-old man, with Down syndrome, partial atrioventricular septal defect, and non-restrictive patent ductus arteriosus, had previously documented dilatation and thrombosis of his right pulmonary artery (RPA) secondary to his Eisenmenger syndrome. His clinical situation had been reasonably stable when he presented with increasing dyspnoea and cough. Chest X-ray (CXR) on admission (Panel B) showed significant increase in the size of the RPA when compared with a film obtained 5 years earlier (Panel A). CT pulmonary angiography (CTPA) was performed on a Siemens Somatom 64 scanner. This revealed massive dilatation of the RPA (Panel C) with extensive thrombus (asterisk) in the RPA. This markedly enlarged RPA impinged on the right main bronchus (Panel D) posteriorly (black arrowhead), as well as on the superior vena cava (SVC) anteriorly (white arrowhead). The SVC was severely compressed, but this compression involved only that portion of the SVC caudal to the insertion of the azygos vein (Panel E). The azygos vein was noted to be dilated, as were the intercostal veins (Panel E). We submit that, unlike previous cases of SVC obstruction by an enlarged RPA, there was no SVC syndrome in this case, because the SVC compromise occurred caudal to the insertion of the azygos vein and the expanding RPA had not yet obstructed the azygos arch. The upper body venous drainage could be accommodated, therefore, through the azygos system. Panels A and B. CXRs from 2001 and 2006, respectively. The white arrows point to a very prominent MPA segment on the left of the cardiac silhouette. The white arrowheads indicate the massively dilated RPA, which is markedly larger in 2006. Panels C and D. CTPA transaxial images obtained after injection of contrast into the right antecubital vein. Panel C was obtained at the level of the carina and demonstrates the enlarged MPA and RPA. Most of the RPA is obliterated by the thrombus (asterisk). Panel D is more caudal. It demonstrates the degree of extension of the thrombus in both anterior–posterior and right–left directions. The small black arrowhead indicates some compression of the right main bronchus and the large white arrowhead (in both panels) shows the marked flattening and lumen compromise of the SVC. The azygos vein (white arrow) is unusually well opacified. A row of small white arrowheads denotes a line of calcification within the thrombus. Panel E. Three-dimensional volume rendered image showing the SVC from a right oblique view and its entry into the right atrium. The dilated RPA and thrombus have been removed for clarity. The SVC has been markedly attenuated (white arrowhead) by the mass effect of the massively enlarged RPA. The azygos vein and its arch are very well seen decompressing the SVC. The small white arrows point to the prominent intercostal veins. Ao, aorta; DA, descending aorta; LPA, left pulmonary artery; MPA, main pulmonary artery.