In a lateral impact crash, what mechanism can cause an aortic tear?

• A. Shear forces tearing the intima
• B. Direct rupture of the adventitia
• C. Dissection of the media
• D. External compression of the aorta

Answer: (A)

In a high-energy lateral crash, rapid deceleration creates shear forces across the aortic wall, especially where the aorta is relatively fixed, such as near the ligamentum arteriosum. Those shear forces tend to tear the inner lining first—the intima. An intimal tear lets blood enter and dissect through the media, which can then lead to a dissection or even rupture, but the initiating injury from this scenario is the intimal tear caused by shear stress. Other options describe later consequences or less typical mechanisms in blunt trauma: direct rupture of the outer layer is not the usual initiating event, medial dissection generally follows an intimal breach, and external compression doesn’t explain an initial aortic tear in a lateral impact.