Tag Archives: thoracic aorta

Mechanisms for Blunt Aortic Injury

What kinds of mechanisms can actually cause a thoracic aortic injury? Most physicians are aware that it involves sudden deceleration. This includes falls from a height and head-on car crashes. However, other mechanisms are associated with this injury as well.

Sudden acceleration can also tear the aorta. This can occur from a rear-end type car crash where one car is stopped and the other is traveling at a high rate of speed. It can also occur when pedestrians are struck by a car.

T-bone crashes also have a significant association with aortic injury. Twenty years ago, this was not really recognized, but now we know better.

One very interesting mechanism that I’ve seen about 5 times is the torso crush. This can occur when heavy objects tip over onto someone’s chest. I’ve seen this injury when multiple sheets of plywood have fallen on someone, and when a ditch caved in and the patient was crushed by dirt.

So when should you be concerned about the aorta enough to image it? In all cases, there must be a significant mechanism (see above). Falling over or being bumped at low speed just can’t do it. It’s also very rare in children under 10. I use the following guidelines:

  • Significant mechanism plus any one chest x-ray finding (see last 2 days of discussion)
  • Extreme mechanism alone. I define this as a closing velocity > 60mph, although you probably won’t know exactly how fast they were really going. You’ll need to estimate based on the usual speed on that particular road in the case of a car crash. Err on the side of predicting a higher speed. Extreme mechanism also includes pedestrian struck at moderate speed or better and torso crush.
  • Physical signs or symptoms consistent with aortic injury. These include tearing chest pain, especially between the shoulder blades, and pulse discrepancy (right radial pressure higher than left radial)

The gold standard screening test is now the helical chest CT. If the results are indeterminate, then a good old-fashioned aortogram may be needed.

Thoracic Aortic Injury in Very Young Children

Trauma professionals routinely worry about the thoracic aorta when evaluating adults after major blunt trauma. The question is, how much do we have to worry about blunt thoracic aortic injury in children?

Younger children are more elastic, and their organs tend to withstand more punishment than adults. After reviewing the literature, I’ve come to the conclusion that this injury is very rare in children in the single digit age range. It’s difficult to find a good paper that addresses this question. The majority include kids up to age 16 or 18, which really skews the results. These patients are most commonly involved in motor vehicle crashes, although a significant number are also pedestrians struck by cars. 

The National Trauma Data Bank (NTDB) was queried for all children <18 years old sustaining blunt injury with at least 1 diagnosis code. There were nearly 27,000 records matching these criteria. Of these, only 34 had an injury to the thoracic aorta. And in the age range under 10, there were only 2! Both of these children were in very high energy car crashes.

The bottom line: Injury to the thoracic aorta practically never happens in children in the single digit age range. As they get closer to adolescence, they behave more like adults and become more susceptible. The diagnosis should be only be entertained in small children who are involved in very high-energy car crashes. Falls from the usual heights (2-3 stories) are probably not significant enough to cause it. A chest xray may show a full mediastinum, but this will most likely be due to a normal thymus. If investigation is warranted, the standard is to obtain a helical CT of the chest. This study would most likely be obtained anyway to evaluate the torso in a high-energy mechanism. Aortorgraphy is no longer used.

Reference: Trooskin, et al. Risk factors for blunt thoracic injury in children. J Pediatric Surg 40(1):98, 2005.