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.

AMERICAN ASSOCIATION FOR THE SURGERY OF TRAUMA, ORGAN INJURY SCALE

The American Association for the Surgery of Trauma (AAST) designates an organ injury scale for thoracic vascular injury from grade I to VI as outlined in Table 3, based on the size and severity of the injury.

Table 3 American Association for the Surgery of Trauma, Thoracic Vascular Injury Scale

a Increase one grade for multiple grade III injuries or >50% circumference involvement in grade IV injuries. Decrease one grade for grade IV injuries if <25% circumference involvement.

Modified from American Association for the Surgery of Trauma (AAST).

Grade I injuries generally involve small thoracic vessels. Grade II injuries involve named venous tributaries of the superior vena cava such as the innominate vein, internal jugular veins, subclavian veins, and azygos vein. Branched aortic vessels such as innominate artery, carotid arteries, and subclavian arteries make up grade III injuries. Grade IV injuries include large-size named extrapericardial vascular structures, whereas grade V injuries include major named intrapericardial vascular structures. Grade VI injuries are uncontained, complete transection of the thoracic aorta or pulmonary hilum.

SURGICAL MANAGEMENT

Indications for urgent surgical intervention for thoracic vascular injuries are outlined in Table 4. The choice of incisions varies depending on the location of injury (see Figure 2). For unstable patients with presumed but undiagnosed thoracic vascular injury, the most appropriate incision is a left anterolateral thoracotomy in the supine position. This incision allows excellent exposure to the heart and aorta for resuscitative efforts. Furthermore, it can easily be converted to a clamshell incision by extending transternally to the contralateral side to provide exposure to the right lung hilum, ascending aorta, and right subclavian vessels. Median sternotomy is the incision of choice for innominate, right subclavian, right carotid, and proximal left carotid arterial injuries. Oblique cervical or transverse supraclavicular extensions can be added to provide further exposure. Left posterolateral thoracotomy in the lateral decubitus position provides the best exposure for known injuries to the descending thoracic aorta and left lung hilum.

Table 4 Indications for Operative Repair of Thoracic Great Vessel Injury

Patients with ascending/transverse aortic injury rarely survive long enough to be transported to the trauma center. Most of these blunt injuries require the use of interposition grafts and cardiopulmonary bypass for repair. In selected patients with penetrating trauma small anterior or lateral lacerations of the ascending aorta can be primarily repaired without the use of cardiopulmonary bypass. Complex injuries involving posterior aspects of the ascending aorta and pulmonary artery are also repaired with cardiopulmonary bypass. Exposure of the transverse arch can be improved by extending the median sternotomy incision to the neck and dividing the innominate vein.

Innominate artery and proximal left common carotid artery injuries are best approached via median sternotomy incision with cervical extension if necessary. Division of the innominate vein provides excellent exposure to the transverse aortic arch for proximal control. In patients with small, partial tears of the distal innominate artery, primary repair with 4-0 polypropylene suture is often possible. In most cases, innominate artery injuries are best managed using the bypass exclusion technique¹⁸ (Figure 3). This approach allows management without the use of systemic heparinization, cardiopulmonary bypass, or hypothermic circulatory arrest. A 10-mm knitted tube graft is used to create a proximal ascending aorta to distal innominate artery bypass. After the bypass is completed, the injury at the origin of the aortic duct is oversewn. Injuries to the proximal left common carotid artery can also be managed in a similar fashion.

Figure 3 Bypass-exclusion technique for management of innominate artery injuries. (A) Severe intimal disruption may be associated with minimal external hematoma. (B) A site is selected for aortotomy along the ascending aorta, and a prosthetic graft is sewn end to side. A partial occluding vascular clamp is placed at the origin of the innominate artery and a vascular clamp is placed across the distal innominate artery. The artery is divided between the clamps. (C) The repair is completed by an end-to-end anastomosis of the graft to the distal innominate artery and by oversewing the native origin of the innominate artery on the aorta.

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

Known isolated injuries to the descending thoracic aorta are best approached through a left posterolateral thoracotomy incision in the fourth intercostal space. Most patients with descending thoracic aortic injuries have concomitant injuries in other body compartments. Prioritizing surgical treatment for each of these compartmental injuries can be a challenge. In general, for patients with a stable mediastinal hematoma and unstable intra-abdominal injury, exploratory laparotomy should be performed first.

The principles of managing descending thoracic aortic injuries are proximal/distal control, addressing the injured segment, and reestablishing continuity of blood flow. Most blunt traumatic injuries in the descending thoracic aorta originate medially at the level of the ligamentum arteriosum. The most expeditious way of obtaining proximal control is to follow the left subclavian artery proximally to the aortic arch and place an umbilical tape around the aortic arch between the takeoff of the left common carotid artery and the left subclavian artery. An umbilical tape is also passed around the left subclavian artery. Care should be taken to try to avoid injury to the left recurrent laryngeal nerve as it courses posteriorly around the aortic arch near the ligamentum arteriosum. The next maneuver is to achieve vascular control distal to the anticipated injury. It is important to examine the entire length of the descending thoracic aorta in order to identify any additional tears, especially at the level of the diaphragm. There are several approaches to the basic vascular repair of the descending thoracic aorta. First is the simple clamp-and-sew technique without the use of shunts or left heart bypass. Second is the use of a passive shunt, which is less commonly used. Some surgeons advocate the use of active partial left heart bypass for repairing descending thoracic aortic injuries (Figure 4). All of these adjunct techniques should be familiar to surgeons managing this type of injury. The hematoma is entered after proximal and distal control is established. Intercostal vessels are not routinely oversewn. The extent of the injury is inspected from both external and internal aspects of the aorta. Simple partial lacerations of the aorta can be primarily closed with running sutures using 4-0 polypropylene. Complex injuries often require an interposition graft.

Figure 4 Adjuncts in the management of descending thoracic aortic injuries. (A) Simple clamp and sew technique with proximal and distal control using vascular clamps. (B) Active left atriofemoral bypass with partial left-heart bypass. (C) Passive ascending to descending thoracic aorta with shunt.

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

Heated debate continues in the literature on whether active distal perfusion decreases the dreaded morbidity of paraplegia in the management of descending thoracic aortic injuries. There are reports supporting both sides of the argument. The length of aortic cross clamp time has been argued as an independent factor contributing to increased incidence of postoperative paraplegia. Numerous studies, however, have shown that the incidence of postoperative paraplegia is multifactorial and cannot be attributed to any single cause.^19–26 All distal perfusion techniques have potential complications including those from cannulation sites or from systemic heparinization. Regardless of the technique used, the overall incidence of postoperative paraplegia averages 8% according to various studies.^23,27–30 To date, no prospective randomized trial has documented the superiority of any single technique.

Median sternotomy with right-sided cervical extension is the incision of choice for right subclavian artery injury. Proximal left subclavian artery injury is best repaired through a left posterolateral thoracotomy in the fourth intercostal space. Exposure of the distal left subclavian artery can be obtained through a left supraclavicular incision with proximal control via a third interspace anterolateral incision. While seldom needed, injury to multiple segments of the left subclavian artery can be managed by combining the two incisions to create a “trapdoor” incision. Injury to the phrenic nerve, lying anterior to the scalenus anticus muscle, should be avoided during exposure of the subclavian artery. The left clavicle can be divided or resected to provide better exposure if necessary. After obtaining proximal and distal control, either primary repair or interposition knitted or polytetrafluoroethylene grafts may be used depending on the extent of injury. Because of the soft nature of the subclavian artery, mobilization for end-to-end anastomosis is generally difficult. Subclavian artery injuries are often associated with concomitant brachial plexus injuries; therefore, it is helpful to note the preoperative neurological examination. Subclavian venous injuries are exposed similarly as subclavian artery injuries. Venous injuries are repaired by either primary venorrhaphy or ligation.

Intrapericardial pulmonary artery injuries are best approached with a median sternotomy incision. Main pulmonary artery and proximal right pulmonary artery are readily accessible upon opening the pericardium. The proximal left pulmonary artery is exposed by dissecting between the superior vena cava and the ascending aorta. Small anterior injuries are primarily repaired with running 4-0 polypropylene sutures with the use of a partial occluding vascular clamp. More complex and posterior injuries may require the use of cardiopulmonary bypass. Distal extrapericardial pulmonary artery injuries are approached with thoracotomy incisions. In selected patients, pneumonectomy may be the life-saving procedure of choice for major hilar injuries.

Injuries to the thoracic vena cava are extremely difficult to manage surgically because of its anatomic location. A median sternotomy incision provides optimal exposure. Simple anterior lacerations can be primarily repaired with a partial occluding vascular clamp. Posterior injuries may require the use of total cardiopulmonary bypass. Subsequent repair is accomplished from inside the right atrium. Occasionally, an intracaval shunt may be a useful adjunct.

Intrapericardial pulmonary venous injuries are rare and diagnosed intraoperatively during an empiric emergent thoracotomy. The optimal incision is a left anterolateral thoracotomy that allows access to the posterior aspect of the heart. Extrapericardial pulmonary venous injuries in stable patients are approached from posterolateral thoracotomy incisions. Simple lacerations can be closed primarily. Massive hemorrhage can be controlled with temporary hilar occlusion. If a pulmonary vein must be ligated for life-saving measures, appropriate pulmonary lobectomy should follow.

Because the azygous vein drains directly into the superior vena cava, injuries to the azygous veins can be potentially fatal. This type of injury is rarely diagnosed or suspected preoperatively. When seen in the operating room, azygous venous injuries are best managed by primary repair or division and suture ligation of both ends. Similarly, internal mammary arterial and venous injuries can cause massive hemorrhage and are often diagnosed intraoperatively. The best treatment option is simple ligation and proper documentation in the operative notes in order to eliminate the possibility of using internal mammary arteries as conduits for potential future coronary artery bypass operations.

In a dying patient with thoracic vascular injury, damage control thoracotomy is a treatment option. A left anterolateral thoracotomy incision provides the best initial exposure. The principle of damage control thoracotomy consists of the use of simpler techniques to achieve expeditious control of hemorrhage in a single setting, or temporary measures for hemorrhage control with planned second operation for definitive repair as the patient’s physiologic status is restored to a more survivable level.³¹ Hilar vascular injuries can be controlled quickly by performing pneumonectomy or lobectomy with a stapling device. For vessels greater than 5 mm, synthetic grafts may be used to avoid delays in harvesting vein grafts. Temporary ligation and placement of intravascular shunts can control hemorrhage until the patient’s physiologic status is restored to a more appropriate level for definitive repair. Ligation of the subclavian artery is often well tolerated and can be used in a damage control setting. Thoracotomy incisions can be closed quickly with towel clips; however, en-mass closure using large needles encompassing all muscle layers are more hemostatic. A “Bogotá bag” or patch closure can also be used as temporary closures in patients with cardiac dysfunction in order to prevent compression of the heart.

Young patients usually have very soft medium and large size named arteries in the chest without atherosclerotic disease. During surgical repair of thoracic vessels, any slight lateral deviation from the natural curve of the suture needle translates to increasing hemorrhage from needle holes, which on some occasions may lead to further tears in the artery and result in a fatal outcome. Gentle, precise technique provides the best repairs.

MORBIDITY AND MANAGEMENT COMPLICATIONS

Neurologic deficits often accompany injuries to thoracic vascular structures either as additional associated injuries or as postoperative morbidities. Therefore, proper preoperative documentation of the patient’s neurologic status is important. As mentioned previously, the overall average incidence of postoperative paraplegia is 8% for descending thoracic aortic repair. The anatomic proximity of the brachial plexus to the subclavian vessels is the reason for the high incidence of brachial plexopathy associated with subclavian vessel injuries. Detailed discussion with the patient and family members of these associated neurologic morbidities is warranted. Some patients experience persistent post-thoracotomy pain, which can be socially and emotionally devastating. Thus, early mobility and rehabilitation are important adjuncts to the care of these patients. In selected patients, intercostal nerve blocks may be beneficial.

A majority of patients with thoracic vascular trauma have associated multiorgan injury. As a result, a significant portion of these patients remain critically ill in the intensive care unit setting. Various pulmonary complications such as atelectasis, pneumonia, and acute respiratory distress syndrome are becoming some of the most common complications in the early postoperative period. Patients with concomitant pulmonary contusions are at an increased risk of developing acute respiratory distress syndrome. Aggressive pulmonary toilet, adequate pain control, and detailed critical care are all essential elements in preventing these complications.

MORTALITY

Thoracic vascular injuries have one of the highest mortality rates of any organ system because of the high incidence of other concomitant injuries in other body compartments. Patients with ascending aortic injuries rarely reach the hospital alive. The mortality rate remains as high as 50% for patients with ascending aortic injuries with stable vital signs on arrival to trauma centers.⁸ Injuries to the central pulmonary artery and vein are highly lethal with mortality rates in excess of 70%.⁸ Similarly, thoracic vena cava injuries are infrequent but extremely difficult to control and carries a mortality rate greater than 60%.⁸ Regardless of the surgical technique used, the mortality rate of descending thoracic aortic injuries ranges from 5% to 25%.³⁰ The overall mortality for innominate artery injuries is reported to be 25% from 1960 to 1992.¹⁸ Subclavian artery injuries have the best prognosis with an overall mortality rate of less than 5% as reported by Graham et al.³²

CONCLUSIONS

Managing patients with thoracic vascular injuries requires technical expertise and excellent surgical judgment. For this reason, taking care of patients with this type of injury can be both extremely challenging and rewarding.

Unlike abdominal injuries where midline vertical incision is the standard exploratory incision, patients with stable thoracic vascular injuries require careful preoperative planning. Because of the rigid chest wall, ill-placed incisions and incorrect intercostal space entry significantly compromise exposure for proximal/distal control of hemorrhage from thoracic vascular injuries. Although thoracic vascular injuries have one of the highest mortality rates of any trauma, superb surgical judgment along with operative precision will translate to improved patient care and outcome.