Innominate artery transection in the setting of a bovine arch

Clinical summary 

A 46-year-old woman was brought to our trauma bay intubated and with stable hemodynamics after a head-on motor vehicle collision. A chest x-ray film showed a widened mediastinum. A subsequent computed tomographic scan of the chest and aortogram revealed a contained traumatic pseudoaneurysm of the innominate artery in the setting of the bovine arch anatomy (Figure 1). The patient also had a grade III liver laceration, bilateral rib fractures leading to bilateral pneumothoraces, and multiple lower extremity orthopedic injuries. She was taken on an emergency basis to the operating room. An external fixation device was placed to stabilize the right femur and to prevent further blood loss in that compartment. A baseline abdominal flow-assisted short-term ultrasound examination was then performed and repeated every 30 minutes to exclude the presence of intraperitoneal hemorrhage from the liver laceration in the setting of heparinization for cardiopulmonary bypass. A median sternotomy was performed, and cardiopulmonary bypass was initiated via ascending aortic and right atrial cannulation. Circulatory arrest with retrograde cerebral perfusion at a flow rate of 250 to 350 mL/min and a central venous pressure of 21 to 23 mm Hg was initiated at a core bladder temperature of 15°C (Figure 2, A). One gram of methylprednisolone sodium succinate (Solu-Medrol) was given before the initiation of circulatory arrest. A complete 360° circumferential intimal transection of the innominate artery at the takeoff of the left common carotid artery was found; it was held together by only a thin region of adventitia. After the innominate artery was excised back to healthy tissue, a Hemashield interposition graft (Meadox Medicals, Inc, Oakland, NJ) was then proximally anastomosed to the aortic arch and beveled to incorporate the ostium of the left common carotid artery. The graft was then anastomosed to the distal innominate artery at the bifurcation of the right subclavian and right common carotid arteries (Figure 2, B). On completion of the repair, the vascular system was extensively deaired, and antegrade perfusion was slowly reinitiated. The total hypothermic circulatory arrest and retrograde cerebral perfusion time was 50 minutes. Total cardiopulmonary bypass time was 204 minutes. The patient was taken to the intensive care unit, where she awoke neurologically intact several hours later. During her hospitalization, she underwent numerous orthopedic operations for her various injuries but was eventually discharged to an acute rehabilitation facility. At 6 months, the patient was at home doing well without evidence of any neurologic dysfunction.

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Figure 1. A, Computed tomographic scan image demonstrating a mediastinal hematoma and 2 trunks arising from the aortic arch, thus confirming bovine anatomy. B, Arch aortogram demonstrating injury at the takeoff of the left common carotid artery from the innominate artery.

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Figure 2. A, Vascular injury and the bypass circuit, which includes a superior vena cava cannula and arteriovenous bridge. B, Completed interposition graft.

Discussion 

The innominate artery is the second most common site of blunt injury to the aortic vessels, and blunt trauma is responsible for 35% of innominate artery injuries.1 Still, fewer than 100 cases of innominate artery injury caused by blunt trauma have been documented. An interesting association has been reported between this type of injury and bovine arch anatomy, in which the left common carotid originates from the innominate artery. Although there is only an 11% normal incidence of bovine arch anatomy, 29% of patients who have innominate artery disruption exhibit this anomaly, suggesting a predisposition to sustaining blunt injury at the innominate artery.1, 2

One study3 recommended bypass of the injured segments of the arch before exploring the hematoma. This patient was placed on cardiopulmonary bypass before dissection of the hematoma. Cardiopulmonary bypass allows for greater visualization of the arch by decompressing the heart and provides more hemodynamic control. The risk of systemic anticoagulation in the setting of a grade III liver laceration and femur fracture did not escape us, and measures were taken to reduce the patient's risk by placement of an external fixator on the femur and by aggressive surveillance to detect early intraperitoneal bleeding.4

Because repair of this injury would likely disrupt most of the cerebral blood flow, the issue of cerebral perfusion had to be addressed.5 In this particular patient, retrograde cerebral perfusion was used in conjunction with deep hypothermia and circulatory arrest. Our center has had extensive experience with this technique in repair of complex arch reconstructions and acute type A dissections. Despite recent reports suggesting that retrograde cerebral perfusion may be linked to postoperative neurologic dysfunction, our experience is that the incidence of perioperative stroke is reduced. In addition, retrograde cerebral perfusion also extends greater latitude in operating time and cools the brain down roughly an additional 10°C. Finally, it provides a deairing capacity by continually bathing the cerebral vascular system in blood.5