Fatal aortic rupture from nonpenetrating chest trauma.
Subject: Aorta, Thoracic (Injuries)
Chest (Injuries)
Traffic accidents
Blunt trauma
Authors: Benjamin, Mina Mecheal
Roberts, William Clifford
Pub Date: 04/01/2012
Publication: Name: Baylor University Medical Center Proceedings Publisher: The Baylor University Medical Center Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2012 The Baylor University Medical Center ISSN: 0899-8280
Issue: Date: April, 2012 Source Volume: 25 Source Issue: 2
Accession Number: 306359151
Full Text: A 22-year-old man died following a side impact blow in an automobile accident. Necropsy showed a large tear in the posterior wall of the aorta approximately 12 mm distal to the insertion of ligamentum arteriosum (Figures 1 and 2). Subadventitial hemorrhage was prominent in the descending thoracic aorta. The left pleural space contained large quantities of blood.


Traumatic aortic rupture is the second most common cause of death in victims of blunt chest trauma from motor vehicle accidents (1-3). Death usually (85%) occurs at the crash scene (2-4). Aortic rupture was responsible for about 15% of the deaths due to automobile accidents until seat belts and air bags were introduced. Seat belts seem to be more effective than air bags in reducing traumatic aortic injury (TAI) after blunt frontal motor vehicle crashes (5). Data from the National Automotive Sampling System Crashworthiness Data System between 1993 and 1998 indicated that seat belts reduced the incidence of TAI from 2.66% to 0.49% in crashes where an airbag did not deploy. Airbags alone do not significantly reduce TAI in survivors of frontal motor vehicle crashes. Airbags are more effective in those using seat belts, together reducing the incidence from 0.49% to 0.29% (5).

According to Christopher and colleagues (6), among patients with TAI, 71% were drivers, 23% were front-seat passengers, and 6% were back-seat passengers (6). Although most reports focused on frontal impact crashes, side impact accidents also are a major cause of TAI, especially after the introduction of seat belts (7, 8). The direction of the crash impact was known in 672 patients from the National Automotive Sampling System registry between 1998 and 2002; among those, 57% were frontal, 18% were at the driver's side, 16% at the passenger's side, 2% in the rear, and 6% in a nonhorizontal direction (6).

Although motor vehicle accidents are responsible for about 80% of the cases of TAI (9), other causes include, though much less frequently, falls from heights and crushes, penetrating (gunshot/stab) wounds, and iatrogenic causes (during interventional catheterization). If the rupture is not transmural, a partial tear may lead to an aneurysm (Figure 3).



In about 80% of reported cases of TAI, the site of the aortic tear is at the aortic isthmus between the ostium of the left subclavian artery and the ostium of the third pair of intercostal arteries (10-15). The isthmus segment of the proximal descending aorta is the least mobile portion of the thoracic aorta, being "held down" by its attachment to the pulmonary trunk via the ligamentum arteriosum. A much less common site of rupture is the ascending aorta (12).

Several mechanisms have been postulated as to why the isthmus portion is the most common site of aortic rupture. The most widely accepted theory suggests that in nonpenetrating chest traumas, sudden high-velocity deceleration is accompanied by hyperflexion of the spine leading to sudden chest compression and traction on the aortic isthmus, the point at which the mobile aortic arch meets the fixed proximal descending thoracic aorta (16-22). Another theory suggests a "shoveling effect," as a lower thoracic impact results in cranial displacement of the mediastinum and torsion of the isthmus (22). The "osseous pinch" theory suggests that the proximal descending aorta is pinched between the sternum, upper ribs, and clavicles anteriorly and the vertebral column posteriorly (23). A less favorable theory suggests a "water-hammer" effect, where an acute rise in aortic pressure exerts maximum stress on the aortic isthmus (20).

Rupture of the aorta is of course not the only type of cardiovascular injury from blunt chest trauma: rupture of the right or left ventricular free wall or ventricular septum (24), left ventricular aneurysm (25), and cardiac valve regurgitation (26) are some other cardiac consequences of blunt chest trauma.

Fatal cardiac arrest has been reported in a number of drivers of motorized vehicles. Usually, the driver becomes aware of the cardiac arrhythmia, pulls to the side of the road, and is then found pulseless slumped over the steering wheel without a crash into another vehicle or into a stationary structure on the side of the road (27).

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Mina Mecheal Benjamin, MD, and William Clifford Roberts, MD

From the Department of Internal Medicine (Benjamin) and the Baylor Heart and Vascular Institute (Roberts), Baylor University Medical Center at Dallas.

Corresponding author: William Clifford Roberts, MD, Baylor Heart and Vascular Institute, 3500 Gaston Avenue, Suite H-030, Dallas, Texas 75226 (e-mail: wc.roberts@baylorhealth.edu).
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