DISSECTED AORTA, SONOGR.,Aortic dissection of the ascending aorta - Cardiac ultrasound. Dissecting aneurysm of the aorta is a longitudinal tear of the aorta wall. This tear can be provoked, as here, by an hematoma (dissecting or intramural hematoma), separating tunica intima (internal layer) from the adventitia (external layer of the artery wall). This hematoma conducts to the medianecrosis, progressive destruction of the media (intermediary layer of the wall), and thus to the dissection.