Open and Endovascular Approaches to Aortic Trauma

Trauma to the great vessels can occur from either blunt or penetrating mechanisms and involve either the thoracic or abdominal aorta. Injuries of the thoracic aorta can occur in the ascending aorta, the arch, or the descending aorta.

Penetrating Trauma: Open Approach

For patients who arrive alive at the hospital with penetrating aortic injuries, the diagnosis is primarily clinical. Physical examination can suggest a trajectory that traverses the midline. An emergency chest radiograph, with arrow markers indicating entry and exit wounds, can help determine trajectory. Thoracic aorta trauma can present as cardiac tamponade or massive hemothorax. Lower-energy wounds, such as stab wounds, can form a small, contained pseudoaneurysm.

Formerly, a mediastinal traverse trajectory was by itself an indication for operation. Currently, a computed tomographic scan of the chest enables the localization of trajectory, to rule out aortic injuries. Aortography for lower-energy thoracic aortic injury in the stable patient can be deceiving, because the large dye column can obscure a small pseudoaneurysm.

Penetrating thoracic aortic injury is often found during an exploratory operation in a patient who is hypotensive and in extremis. An emergency thoracotomy can be extended to a bilateral arterolateral thoracotomy for optimal exposure. In stable patients with injuries that have been localized, other incisions can be considered. A median sternotomy provides good access to the ascending aorta and arch. For known injuries of the descending thoracic aorta that are associated with no other injuries, a posterolateral thoracotomy can be used.

Adjunctive measures during these procedures include making an initial incision of a size adequate for good visualization and using fine sutures for the repair of aortic injuries in young patients, who have soft aortas. Our service also does not resuscitate the patient until the bleeding has been controlled.

Penetrating abdominal aortic injuries can be very challenging. Their management is guided by recognizing the distribution pattern of the retroperitoneal hematoma. The retroperitoneal hematoma can be divided into 3 categories: supramesocolic, inframesocolic, and pelvic.

A supramesocolic hematoma suggests a supraceliac aortic injury. Proximal control through the lesser sac is not useful because massive blood loss precludes visualization. The left medial visceral rotation (Mattox maneuver) enables visualization of the entire supraceliac aorta. Intravascular balloons can also be used for proximal aortic occlusion. Hybrid procedures that achieve intravascular control during laparotomy are increasingly being performed.

After exposure, primary repair can often be accomplished with a fine polypropylene suture. Multiple injuries can be connected and closed in linear fashion. Dacron patch aortoplasty and Dacron graft interposition can be used if needed.

For an inframesocolic hematoma, the exposure is similar to that of an infrarenal aneurysm. Proximal control of the aorta can be obtained immediately below the renal arteries or at the diaphragm, and distal control can be obtained at the common iliac arteries. The injury is repaired with standard reconstruction techniques.

For a patient with a large pelvic hematoma from a penetrating injury, vascular control outside of the hematoma can be helpful. Total pelvic isolation is gained through vascular control at the inlet and outlet of the pelvis, and then by walking the clamps in toward the injury as it is exposed. Shunts, such as chest tubes, endotracheal tubes, or carotid shunts, can be used to establish temporary control, in a damage-control fashion. New techniques involving intravascular balloon occluders and covered stents have been used in selected cases.

Blunt Trauma: Open Approach

Blunt trauma to the thoracic aorta can occur in the ascending aorta, the arch, or the descending aorta. These patients present after a significant deceleration injury and a large number die at the scene. Those who survive to reach an emergency center are most commonly those with injuries to the descending thoracic aorta, because injuries to the ascending aorta or arch are usually fatal.

The evaluation for blunt trauma is approached by looking for elements of the patient's history, physical examination, and imaging studies that suggest significant energy transfer.

The operative approach depends on the location of the injury. For ascending aorta or arch injury, repairs are accomplished via a median sternotomy, accompanied by cardiopulmonary bypass (CPB). Although primary repair is sometimes an option, frequently a Dacron tube graft is needed for the ascending aorta. For an injury that extends into the arch, circulatory arrest with profound hypothermia might be necessary. The risk of full heparinization for CPB and, therefore, an increased risk of intracranial bleeding with associated head injuries, has to be weighed against the risk of aortic rupture in the event that therapeutic delay is chosen. Many of these cases can wait for days or weeks until repairs are safe. Brachiocephalic artery injuries are actually pinch injuries, between the sternum and the spine. They are repaired via the bypass principle (Fig. 1).¹

Fig. 1 Bypass principle to repair blunt brachiocephalic artery injury.¹ A) Blunt injury at the junction of the proximal brachiocephalic artery and the aortic arch is a pinch injury involving the intima and media. B) A 10-mm Dacron tube graft is anastomosed end-to-side onto the ascending aorta. The arch is controlled with a partial occluding clamp, and the distal brachiocephalic artery is transected. C) The distal anastomosis is performed end-to-end to the brachiocephalic artery without need for shunts, heparin, or cardiopulmonary bypass. The lesion on the aortic arch is oversewn, completing the repair. (Image by Jan Redden; © 1980, Baylor College of Medicine. Used by permission.)

There are several open approaches to the repair of descending thoracic aortic injuries, including clamp repair, atrial–femoral bypass, and full CPB. All of the techniques put the spinal cord at risk because they require isolation of a segment of the aorta between vascular clamps. Atrial–femoral bypass can be performed with centrifugal pumps, without heparin. This method has the potential advantage of increasing distal aortic perfusion; but, most significantly, it unloads the left ventricle during aortic clamping. This can be a significant advantage in treating the older patient who has heart disease. Currently, atrial–femoral bypass is probably the most commonly used approach; however, it is important that each provider use the technique that yields the best available results.

Despite all efforts, paraplegia rates in the 20% range have been reported, together with mortality rates in the 20% to 30% range. These complications are inherent in patients with multisystem injuries. The complications of such injuries can incur substantial medicolegal risk. It is important to understand that, despite best efforts and best care, intraoperative complications, adverse sequelae such as paraplegia, and deaths still occur.

Blunt Trauma: Endovascular Approach

Mattox and Wall² have proposed a classification of blunt thoracic aortic injuries into 3 groups, on the basis of presentation. Group 1 patients are unstable or die at the scene. Group 2 patients are unstable during transport and have a high mortality rate. Group 3 patients present at the hospital in stable condition and are evaluated. It has been observed that many patients who were initially thought not to have aortic injury were found several hours later, during evaluation, to have such injury. These patients were hemodynamically stable. In addition, many patients with blunt aortic injuries could not undergo acute repair, usually due to cerebrovascular injuries. With the aid of anti-impulse therapy, clinicians have often been able to temporize these injuries for days, weeks, or months.

Recently, many centers have begun treating blunt aortic injuries with endovascular techniques. As always, the key to success for endovascular repair is planning. A proximal and distal seal zone of 1 to 2 cm in length is needed. Whether to cover the subclavian artery and whether to perform a carotid–subclavian bypass are matters of controversy. Our service often finds it necessary to cover the left subclavian artery and therefore to evaluate the cerebral circulation. A carotid–subclavian bypass may be indicated for patients with a dominant left vertebral artery, a blind posterior inferior cerebellar artery, or a left internal mammary artery–left anterior descending coronary artery bypass.

Imaging adjuncts, such as multiplanar formatting of the chest computed-tomographic scan (in order to align the slices with the aorta), can assist in measurements. For difficult cases, a center-line-of-flow analysis can be used to determine precisely the seal zones, diameters, and lengths. Key measurements include the diameters of the proximal and distal seal areas and the length of coverage by the graft. These dimensions determine whether an appropriate graft configuration can be achieved with commercially available devices.

Access can present tremendous challenges. Young trauma patients often have small access vessels. Most morbidity and death in cases involving endovascular repair is associated with iliac injuries during access. Patients with small access vessels can be managed with retroperitoneal exposure of the abdominal aorta or common iliac artery, either of which can be directly cannulated or otherwise reached via a short Dacron tube graft. In the operating room, a confirmatory arteriogram is obtained before graft deployment, to verify the nature and extent of the injury.

Several reports from an American Association for the Surgery of Trauma (AAST) multicenter study have been presented by Demetriades and colleagues,^3-5 noting a change in the approach to the management of blunt aortic injuries. In the Journal of Trauma in March 2008,³ these authors noted that endografts were used in the repair of 65% of these injuries, most often in patients with an associated severe injury or of advanced age. Endografts were associated with low mortality rates and decreased transfusion requirements, but there was considerable risk of device-related sequelae. Further noted was an urgent need for improvement of the endovascular devices available for trauma. In a follow-up report,⁴ Demetriades and associates compared 2 multicenter aortic-injury studies for the AAST, from different time periods. They noted that, over time, there had been increases in delayed repair and local complications, together with decreases in open repair, mortality rates, and paraplegia. In a final report,⁵ Demetriades and colleagues stratified repairs as early (≤24 hr) or delayed (>24 hr). They observed that 39% of the repairs were delayed.

Endovascular repair of these injuries continues to be a challenge. The treatments and the devices are evolving. In the short term, for multi-injury patients with complications, there appear to be advantages to endovascular repair, as described by the AAST multicenter study. However, the long-term results of endograft repairs are not known.