RIGHT PULMONARY-ARTERY OCCLUSION SECONDARY TO A DISSECTING AORTIC-ANEURYSM

This report describes a case of right pulmonary artery obstruction cau sed by a dissecting aneurysm of the thoracic aorta. Initial ventilatio n-perfusion (V/Q) scan revealed no perfusion to the right lung. Lack o f right lung perfusion plus other clinical abnormalities led to an ini tial diagnosis of massive embolism in the right lung. Bilateral pulmon ary arteriography of the thoracic and abdominal aorta revealed extrins ic compression of the right pulmonary artery near its origin and the s uggestion of an ascending aortic dissection. Subsequent ascending aort ography and computed tomography (CT) confirmed a dissection of the asc ending aorta. Aortography in the true lumen of the aorta revealed triv ial aortic insufficiency. These diagnostic procedures cofirmed the pre sence of an acute dissecting aneurysm of the ascending aorta that caus ed compression of the right pulmonary artery. The finding of a massive unilateral segmental defect with normal ventilation upon lung scannin g does not always ensure a diagnosis of acute pulmonary embolus. Patie nt presentation with massive unilateral perfusion defect merits furthe r evaluation with pulmonary arteriography.