A 45-year-old man, who had been diagnosed with primary pulmonary hypertension (PPH) 8 years before, was referred to our hospital because of short breath and lower-limb edema. Findings of chest X-ray, electrocardiogram, and cardiac ultrasound showed right atrial and ventricular dilatation/hypertrophy that were compatible with advanced PPH. Chest enhanced computed tomography (CT), however, unexpectedly showed that contrast in the main pulmonary artery was diluted by blood flow from the descending aorta. On electrocardiography-synchronized CT, the arterial duct connecting the main pulmonary artery and descending aorta was clearly delineated. As a result, the long-standing diagnosis of PPH was corrected to secondary pulmonary arterial hypertension caused by patent ductus arteriosus, thanks to the “reverse” enhancement on CT.
