INCIDENCE

Thoracic trauma is responsible for 50% of all trauma deaths nationally.⁵ The incidence of chest trauma is reported to be 12 per million per day in the United States by Beeson and Saegesser.⁶ In a large series of thoracic trauma patients, the aorta and great vessels were injured in 4% of cases.⁷ Furthermore, thoracic vascular injuries are often associated with other nonvascular injuries because of their anatomic location and mechanism of injury.

Vascular injuries of the chest often include named vessels such as aorta, innominate artery, and proximal common carotid and subclavian arteries. Right-sided vascular injuries such as pulmonary artery, inferior/superior vena cava, innominate vein, and azygos veins are also important to recognize and treat. The anatomic location of the ascending aorta makes it the most commonly injured large thoracic vessel from stab wounds, whereas gunshot wounds usually cause descending aortic injury. The vessels commonly injured in blunt trauma are the descending thoracic aorta and proximal aortic-arch vessels. With penetrating trauma, all thoracic vessels are potentially susceptible to injury.

MECHANISM OF INJURY

A large number of thoracic great-vessel injuries are caused by penetrating or iatrogenic trauma.⁴ The mechanism of injury for penetrating thoracic vascular trauma is usually direct laceration or penetration of blood vessels. This type of injury can often present with external or internal hemorrhage, vascular thrombosis from intimal flap, or pseudoaneurysms. Because of the various types of missiles involved in penetrating vascular trauma, all thoracic vascular structures are at risk. External bleeding from skin tracts usually occurs with injuries to vessels at the thoracic inlet, whereas internal hemorrhage commonly occurs with aortic and caval injuries. Intrathoracic great-vessel injuries can present with internal bleeding into the mediastinum, pleural space, or pericardial sac. It is important to note that the presence of a normal palpable distal pulse does not rule out a proximal vascular injury. Penetrating vascular injuries can be completely contained by perivascular adventitia with blood flow preserved distally.

The absence of a significant amount of bleeding does not rule out vascular injury from penetrating trauma. Vascular injuries from stab wounds can often cause an intimal flap or dissection which may eventually lead to partial or complete thrombosis of injured vessels. Small vascular disruptions may not present initially with bleeding, but can present with delayed formation of a pseudoaneurysm. Gunshot blast vascular injuries are often underestimated because intimal disruption sometimes extends beyond external signs of injury. For this reason, meticulous intimal inspection from inside of the blood vessel is helpful during thoracic vascular reconstruction.

Because of the large diameter of thoracic vessels, bullets can directly enter vessels and migrate distally (Figure 1). The diagnosis of bullet embolism is often delayed because the course of the bullet may not be obvious. Bullet embolism for thoracic missiles usually lodges in the iliac and femoral vessels. The site of entry should be controlled for hemorrhage first, followed with attempts at removing the bullet emboli with endovascular intervention or separate arteriotomy.

Figure 1 Bullet embolism from the left atrium to the left carotid artery.

(Courtesy Jan Redden, Baylor College of Medicine, 1980.)

The great vessel that is the most commonly injured in blunt thoracic trauma is the descending aorta. These injuries usually involve the proximal descending aorta near the isthmus. There are two proposed mechanisms for such injuries. During anteroposterior impact in the thorax, the aorta and its branched vessels may be “pinched” between the sternum and the vertebral column, resulting in vascular disruption. In rapid-deceleration thoracic injuries from either frontal or side-impact motor vehicle accidents, the point of attachment of pulmonary veins, vena cava, and the relative immobility of the descending aorta at the level of the ligamentum arteriosum and diaphragm increase their susceptibility to rupture.

DIAGNOSIS

Patients with penetrating thoracic vascular trauma often present with hemodynamic instability from uncontrolled hemorrhage into the mediastinum, pleural space, or pericardial sac, and are taken emergently to the operating room for surgical management. These injuries are typically diagnosed intraoperatively during resuscitative thoracotomy. In contrast, patients with blunt thoracic trauma are often initially hemodynamically stable with multiple other injuries that may mask a significant concomitant vascular injury.

Focused history and physical examination in the trauma room are helpful in arriving at a specific vascular injury diagnosis. In penetrating trauma, it can be helpful to note the type of instrument used, length of the knife, caliber of the gun, and patient’s distance from the firearm. While often unreliable, this information may help the surgeon to develop a mental picture of the trajectory of penetrating missile injury and to formulate a surgical treatment plan. In blunt thoracic trauma, the mechanism of injury is of particular importance to allow the surgeon to estimate the amount of kinetic energy transferred as it relates the geometry of the patient’s body upon impact. Emergency medical personnel can also provide information regarding amount of blood loss in the field and hemodynamic stability during transport.

Indicators of possible thoracic vascular injury are outlined in Table 1. The single most important screening tool for thoracic vascular trauma is the anteroposterior chest radiograph. There are numerous radiographic findings suggesting thoracic vascular injury as outlined in Table 2. One of the most reliable radiographic findings suggestive of blunt thoracic vascular injury is alteration of the aortic knob contour on chest radiograph.

Table 1 Indicators of Possible Thoracic Vascular Injury

Table 2 Radiological Findings Suggesting Great Vessel Injury

Arteriography remains the “gold standard” imaging study for evaluation of suspected thoracic vascular injury. It is important to note that preoperative angiography is never indicated in hemodynamically unstable patients with suspected thoracic vascular injury. In hemodynamically stable patients with suspected penetrating injury to the innominate, carotid, or subclavian arteries, preoperative arteriography is indicated to provide information on the type of incisions to make for proximal control of these branched aortic vessels (Figure 2). Furthermore, the proximity of missile trajectory to brachiocephalic vessels is an indication for arteriography in order to definitively rule out an injury. In blunt thoracic trauma, the need for arteriography is determined by mechanism of injury, physical examination, and screening chest radiograph. Fifty percent of patients with blunt thoracic vascular injury present without any external signs of injury.⁸ Seven percent of patients with blunt injury to the aorta and its branched vessels have a normal-appearing mediastinum on screening chest radiograph.⁹ Therefore, additional imaging studies are indicated in patients with either physical examination or chest radiograph suggesting thoracic vascular injury.

Figure 2 Various thoracic incisions that may be employed to manage thoracic vascular injuries. (A) Median sternotomy. (B) Combined anterolateral thoracotomy and supraclavicular incision (less commonly with sternotomy to form “trapdoor” thoracotomy). (C) Posterolateral thoracotomy. (D) Anterolateral thoracotomy (the universal incision for patients in extremis). (E) Extension of left anterolateral thoracotomy to right from clamshell incision.

(Courtesy Jan Redden, Baylor College of Medicine, 1980.)

In patients with a significant mechanism of injury, but a benign physical examination and normal admission chest radiograph, it is reasonable to repeat a delayed chest radiograph to screen for radiographic evidence of thoracic vascular injury with a follow-up arteriography for a definitive diagnosis. Contrast-enhanced spiral computed tomography (CT) of the chest is being used more frequently for evaluating thoracic trauma. The sensitivity of chest CT scan for thoracic vascular injury ranges from 54% to 80%.^10–16 The negative predictive value of a chest CT scan is close to 100% in evaluating thoracic vascular injury.^10–16 Therefore, it is also reasonable to use chest CT scan as a screening tool in stable patients with significant mechanism of injury, normal-appearing admission chest radiograph, and benign physical examination to rule out an underlying thoracic vascular injury. However, any positive findings on CT scan should be followed by the “gold standard” arteriography for definitive diagnosis of thoracic vascular injury before operative intervention.

Magnetic resonance angiography (MRA) has been used in sporadic case reports for thoracic vascular injury. Its application in acutely injured trauma patients is neither ideal nor practical because of the difficulty in monitoring and managing patients in the magnetic resonance coil suites. To date, the use of MRA in evaluating thoracic vascular trauma has not been studied.

Transesophageal echocardiography (TEE) offers several potential advantages to arteriography in evaluating thoracic vascular injury. Avoidance of intravenous contrast, the concomitant information gained on cardiac function, and its portability are potential advantages compared with arteriography. However, published literature reports sensitivity and specificity of 85.7% and 92.0% for TEE compared with 89.0% and 100% for arteriography, respectively, in diagnosing aortic injury.¹⁷ TEE is also heavily technician and operator dependent. Furthermore, the ascending aorta, proximal aortic arch, and branch aortic vessel are extremely difficult to visualize with TEE. Therefore, its use in evaluating thoracic vascular injury is not routinely recommended.