BACKGROUND
A 30-year-old man is brought to the emergency department by ambulance after a high-velocity motor vehicle accident. The patient was the restrained driver when his car skidded out of control on an icy road and hit a tree head-on at approximately 60 mph. Emergency personnel report that the patient was conscious at the scene but unable to get out of his car because the steering column had collapsed, pinning him into his seat. He required extrication from his vehicle.
In the ambulance and on arrival to the emergency department, the patient's only complaint is severe chest pain that radiates to his back. He has also progressively developed shortness of breath.
On physical examination, the patient is conscious and in moderate distress secondary to the pain in his chest. His heart rate is 84 beats per minute, and his initial blood pressure is 124/67 mm Hg. His respiratory rate is 16 breaths per minute, and his temperature is [snip].7°F. He has superficial abrasions on his face and scalp, with intact dentition. His pupils are both 4 mm and reactive. He can move his eyes in all directions on command. Abrasions and bruising are observed over the sternum, which is tender to palpation. The patient's lungs are clear, with equal breath sounds on both sides. Palpation reveals no tenderness over the ribs or abdomen. He has no evidence of extremity injury and can move his arms and legs without difficulty.
An anteroposterior (AP) chest radiograph was obtained in the trauma room (see Image 1). Following this, a CT of the chest and an arteriogram were obtained (see Images 2-3).
What is the diagnosis?
Hint
Look at the proximal descending aorta on the arteriogram and CT scan.
Answer
Acute traumatic aortic injury (ATAI): The portable chest radiograph demonstrates a widened mediastinum with an irregular aortic contour (see Image 1), which suggest ATAI. A follow-up contrast-enhanced CT scan of the chest was obtained (see Image 2). Because of the CT findings, an aortogram was obtained (see Image 3). The chest CT and arteriographic results established the diagnosis of ATAI with pseudoaneurysm formation.
ATAI most commonly results from a clinically significant deceleration injury, such as a fall from extreme height or high-speed motor vehicle collision. The mechanism of injury involves a combination of shearing and torsional forces, which occur where the course of the aorta is fixed. The most common site of injury (85%) is the aortic isthmus, where the ligamentum arteriosum (remnant of the fetal ductus arteriosus) attaches the left pulmonary artery to the inferior surface of the aortic arch. Other sites of injury include the ascending aorta and aortic root (where it is fixed at the valve plane) and at the diaphragmatic hiatus.
By some estimates, as many as 15% of deaths from motor vehicle accidents are due to injury to the thoracic aorta, and only 10-20% of patients with ATAI survive the initial trauma because of a high rate of exsanguination due to hemodynamically unstable injuries and aortic transection. Among survivors, the untreated mortality rate is high: approximately 80% in 1 hour, 85% in 24 hours, and [snip]% within 3 months. In addition, patients with untreated ATAI who survive may develop chronic pseudoaneurysm.
Initial evaluation is AP chest radiography performed in the trauma bay. Chest radiographic findings suggestive of an ATAI may include mediastinal widening, an indistinct aortic knob or abnormal aortic contour, rightward displacement of the trachea or nasogastric tube, inferior displacement of the left mainstem bronchus, a left apical pleural cap, fractures of the first or second rib, pneumothorax, and pulmonary contusion (see Image 1). Of note, many of the chest radiographic findings result from associated mediastinal hemorrhage and hematoma formation and are not from the aortic injury itself.
If the patient's presentation and/or chest radiographic results suggest aortic injury, contrast-enhanced chest CT should be performed. The scans may show not only associated mediastinal hemorrhage or hematoma surrounding or adjacent to the aorta but also direct evidence of ATAI. Finding may include abrupt changes in the contour of the aorta or branch vessels, an intimal flap or pseudocoarctation, or an aortic pseudoaneurysm (see Image 2). Frank extravasation of contrast material is an indication for aggressive management.
Aortography can be useful when the chest CT results are nondiagnostic though the index of suspicion is high or when the CT scans fail to completely demonstrate or help in characterizing the injury. However, with new-generation multidetector-row helical CT scanners, aortography is performed less frequently now than in the past. The aortic angiogram may show subtle intimal tears, complete transection, traumatic aneurysms, dissection, and coarctation. As many as 20% of patients have multiple injuries, and the arch vessels should be evaluated carefully because they are commonly injured. A ductus diverticulum, likely the remnant of the ductus arteriosum, is found in approximately 10% of the population and is characterized as a smooth anteromedial bulge at the aortic isthmus that lacks intimal irregularity and that has a normal washout of contrast material. This normal anatomic variant should not be confused with an aortic injury.
Treatment for ATAI depends on severity of injury and the stability of the patient's condition. Most contained injuries can be managed on a semielective basis. Other life-threatening injuries (eg, severe head injury, hemorrhage from other organs [eg, liver spleen], extensive burns, coagulopathy, acidosis, hypothermia) should be treated as a priority. The aim of ATAI management in patients with these conditions is to reduce the risk of rupture by aggressively controlling their systolic blood pressure to <120 mm Hg.
Surgical repair is indicated when patients are hemodynamically unstable, when they have evidence of penetrating aortic injury, or when images show extravasation of contrast material or a rapidly expanding hematoma. Endovascular repair with stent placement may be used in patients who are hemodynamically stable, in those with other comorbidities that exclude them as candidates for operative repair, or in those with multiple injuries. The patient in this case successfully underwent endovascular stent placement and had a favorable outcome.
ATAI most commonly results from a clinically significant deceleration injury, such as a fall from extreme height or high-speed motor vehicle collision. The mechanism of injury involves a combination of shearing and torsional forces, which occur where the course of the aorta is fixed. The most common site of injury (85%) is the aortic isthmus, where the ligamentum arteriosum (remnant of the fetal ductus arteriosus) attaches the left pulmonary artery to the inferior surface of the aortic arch. gd q.n
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