Acute dissecting aneurysm of the ascending thoracic aorta causing obstruction and thrombosis of the right pulmonary artery.

We present the case of a 69-year-old man with a history of hypertension and a recent pelvic fracture who presented with acute chest pain, shortness of breath, and severe hypotension. The history of recent pelvic fracture and the clinical manifestations, including the sudden onset of acute respiratory distress, hypotension, and hypoxemia, indicated pulmonary embolism; however, at surgery the patient was found to have an acute dissection of the ascending aorta with obstruction and thrombosis of the right pulmonary artery. This case emphasizes the need to consider such a diagnosis in patients who have unilateral absence of perfusion to the right lung.