A 47-year-old, previously healthy man is transported to the emergency department after he was involved in a high-speed, head-on motor vehicle collision. The patient was wearing a seat belt; he did not hit his head or lose consciousness. However, he has had chest pain and shortness of breath since the incident. On arrival, blood pressure is 160/90 mm Hg and pulse is 115/min. Bruising and tenderness are noted over the anterior chest wall. Neck veins are flat, and the trachea is central. Breath sounds are symmetric, and heart sounds are normal. The abdomen is soft and nontender. There are no significant extremity injuries, but bilateral femoral pulses are weak compared to the radial pulses. Chest x-ray reveals a widened mediastinum. While being prepared for surgery, the patient becomes unresponsive. The pulse is no longer detectable, and the cardiac monitor demonstrates sinus tachycardia. Despite aggressive resuscitation efforts, the patient dies. Autopsy examination is most likely to reveal an injury involving which of the following areas of the thoracic aorta?
Show Explanatory Sources
Show Explanatory Sources
Rapid deceleration during a high-speed motor vehicle collision can lead to blunt aortic injury (BAI) due to a combination of forces (eg, shearing) on the aorta. These forces can affect some or all of the layers (ie, intima, media, adventitia). Most patients exsanguinate rapidly (due to full-thickness injury that ruptures the adventitia); however, in a minority of cases (~20%), delayed rupture can allow survival until surgical treatment. A high index of suspicion is crucial because symptoms may be nonspecific (eg, chest pain, shortness of breath).
Depending on the extent and location of vessel injury, some findings suggestive of BAI include:
BAI occurs most often at transition zones between mobile and fixed portions of the aorta. The most common site of injury is the aortic isthmus (C), which is tethered by the ligamentum arteriosum and is relatively immobile compared to the adjacent descending aorta; the isthmus is particularly susceptible to BAI due to intrinsic weakness of the aortic wall in this area.
(Choices A and B) The aortic root (A) and the ascending aorta near the arch (B) are both transition zones and can be damaged by high-speed traumatic injury. However, these areas are affected less often than the aortic isthmus. In addition, this patient's circulation is preserved in the upper extremities compared to the lower extremities, which is more characteristic of an injury distal to the brachiocephalic and left subclavian arteries. Injury to the proximal aorta is classically associated with complications such as hemopericardium (eg, jugular vein distension), coronary artery dissection (eg, ST-segment elevation), and aortic valve disruption (eg, diastolic regurgitation murmur).
(Choices D and E) The distal thoracic aorta is also susceptible to injury just proximal to the diaphragm due to tethering at the diaphragmatic hiatus. However, this is a less common site for traumatic rupture than the more proximal portions of the aorta.
Educational objective:
Impacts causing the thorax to rapidly decelerate (eg, high-speed motor vehicle collisions) can result in blunt aortic injury, especially at transitions between relatively mobile and fixed zones. The most common site of injury is the aortic isthmus, just distal to the attachment of the ligamentum arteriosum.