A young man driving at high speed collides head-on into a truck and dies before reaching hospital. Autopsy shows haemomediastinum and a complete transverse tear of the thoracic aorta. The most likely site of the tear is:

• A At the level of the diaphragmatic hiatus
• B At the root of the aorta above the aortic valve
• C Just distal to the origin of the left subclavian artery ✓
• D At the origin of the brachiocephalic trunk

Explanation

In rapid deceleration, the relatively mobile arch continues forward while the descending aorta fixed to the spinal column stops abruptly, producing maximal shear at the aortic isthmus, just distal to the origin of the left subclavian artery. This accounts for the vast majority of traumatic aortic tears. Tears at the aortic root occur but are far less typical of deceleration trauma, making option B the distractor to eliminate.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.