Residency · Residency · Cardiothoracic Surgery
Blunt Thoracic Aortic Injury
Introduction
Blunt thoracic aortic injury (BTAI) is the second leading cause of death in blunt trauma after traumatic brain injury. Approximately 80-85% of patients with aortic rupture die at the scene before reaching the hospital. For those who survive to hospital presentation, prompt diagnosis and management are critical, as untreated BTAI carries a mortality rate of 1% per hour in the first 48 hours. The paradigm has shifted dramatically toward thoracic endovascular aortic repair (TEVAR), which has become the standard of care.
Mechanism and Pathophysiology
BTAI results from high-energy deceleration injury, most commonly motor vehicle collisions (70-80%), falls from height, motorcycle crashes, and auto-pedestrian accidents. The aorta is tethered at the ligamentum arteriosum (aortic isthmus), just distal to the left subclavian artery, which is the most common site of injury in approximately 90% of cases. Shear forces develop between the relatively mobile aortic arch and the fixed descending aorta during rapid deceleration. Other injury sites include the ascending aorta (rare and usually immediately fatal), aortic root, and diaphragmatic hiatus. The spectrum of injury ranges from intimal tear to medial hematoma, pseudoaneurysm contained by the adventitia, and free rupture, which is usually fatal.
Classification (SVS/AAST Grading)
| Grade | Pathology | CTA Findings | Management |
|---|---|---|---|
| I | Intimal tear | No external contour abnormality | Anti-impulse therapy + serial imaging; >50% heal conservatively |
| II | Intramural hematoma / intimal flap | Small contour abnormality (<50% circumference) | Anti-impulse therapy; TEVAR if progression |
| III | Pseudoaneurysm (contained rupture) | Saccular outpouching with contained contrast | Urgent TEVAR within 24 hours |
| IV | Free rupture | Active extravasation | Emergent TEVAR or open repair |
Grade I injury involves an intimal tear without external contour abnormality. Grade II presents as intramural hematoma or intimal flap with a small external contour abnormality involving less than 50% of the circumference. Grade III is a pseudoaneurysm representing contained rupture. Grade IV is free rupture with active extravasation.
Diagnosis
Clinical Suspicion
BTAI should be suspected in any high-energy mechanism with significant deceleration forces. Associated injuries include rib fractures, sternal fracture, scapular fracture, pulmonary contusion, and hemothorax. External signs such as a steering wheel imprint or seatbelt sign across the chest raise suspicion. Hemodynamic instability or unexplained left hemothorax should prompt investigation.
Imaging
CT angiography (CTA) is the gold standard for diagnosis, with sensitivity and specificity approaching 100%, and it identifies the injury location, grade, and associated pathology. Chest radiograph findings are suggestive but not diagnostic and include widened mediastinum exceeding 8 cm, obscured aortic knob, deviation of the nasogastric tube or trachea to the right, left apical cap, depression of the left main bronchus, and first and second rib fractures. Transesophageal echocardiography (TEE) is useful intraoperatively or when CTA is not feasible but is limited by operator dependence. Aortography was the historical gold standard but is now rarely used given CTA availability.
Screening Protocol
CTA of the chest should be obtained in all blunt trauma patients with a high-energy mechanism and any suggestive chest radiograph findings. Many trauma centers have adopted a low threshold for CTA in significant blunt trauma regardless of chest radiograph findings.
Management
Initial Stabilization
Anti-impulse therapy with immediate blood pressure and heart rate control is essential to reduce aortic wall stress. Targets are systolic BP of 100-120 mmHg and heart rate below 80 bpm. Esmolol or labetalol intravenously are first-line agents, with nicardipine as an alternative. Excessive fluid resuscitation that may elevate blood pressure should be avoided. Treatment of immediately life-threatening injuries including hemorrhage, airway compromise, and traumatic brain injury takes priority over aortic repair.
Thoracic Endovascular Aortic Repair (TEVAR)
TEVAR is the standard of care for grade II-IV injuries at the aortic isthmus and is superior to open repair with lower mortality, paraplegia, and renal failure rates. The procedure involves femoral artery access (percutaneous or open cutdown), passage of a guidewire and catheter across the injury, and deployment of a covered stent graft to exclude the injury. Left subclavian artery coverage is often necessary for an adequate proximal landing zone, and revascularization with carotid-subclavian bypass may be required, especially in patients with a dominant left vertebral artery, left internal mammary artery coronary graft, or functioning left arm arteriovenous fistula. Device selection uses thoracic aortic stent grafts that are conformable and tapered, with oversizing of 10-20% relative to the native aorta. Timing favors urgent repair within 24 hours for grade III-IV injuries, while delayed repair may be considered for grade I-II injuries with intact containment and hemodynamic stability.
Open Surgical Repair
| Outcome | TEVAR | Open Surgical Repair |
|---|---|---|
| Mortality | 3-8% | 10-20% |
| Paraplegia | <3% | 5-15% |
| Renal failure | Lower | Higher |
| Approach | Femoral artery (percutaneous/cutdown) | Left posterolateral thoracotomy (4th ICS) |
| Bypass required | None | Partial left heart or full CPB |
| Long-term durability | Uncertain (endoleak 5-10%; reintervention 5-15% at 10 yrs) | Excellent |
| Best candidates | Most patients; isthmus injuries | Ascending aorta; young patients; TEVAR-unfavorable anatomy |
Open repair is reserved for patients unsuitable for TEVAR, including those with ascending aortic injury, inadequate anatomy for an endovascular approach, or young patients with concerns about long-term device durability. The approach is a left posterolateral thoracotomy through the 4th intercostal space. Repair uses an interposition Dacron graft with partial left heart bypass (left atrial to femoral artery) or full cardiopulmonary bypass. The clamp-and-sew technique is simpler but carries higher risk of spinal cord ischemia and renal injury. Operative mortality is 10-20% compared to less than 5% for TEVAR, and paraplegia risk is 5-15% with open repair versus less than 3% with TEVAR.
Grade I Injuries
Grade I injuries are managed with anti-impulse therapy and serial imaging, including CTA at 24-72 hours and then at 1, 3, and 6 months. More than 50% of grade I injuries heal with conservative management. Progression to a higher-grade injury or pseudoaneurysm warrants intervention.
Special Considerations
Polytrauma Patients
BTAI repair must be prioritized relative to other injuries, with hemorrhage control taking precedence. Anti-impulse therapy bridges the time to definitive repair. TEVAR can be performed rapidly and is better tolerated in polytrauma patients than open repair. Coordination with trauma surgery, neurosurgery, and orthopedic surgery enables staged injury management.
Young Patients
Long-term durability of TEVAR devices remains uncertain in patients with decades of expected survival. Potential complications include endoleak, device migration, and the need for reintervention. Lifelong surveillance imaging is required. Some centers advocate open repair for young, stable patients with favorable anatomy.
Spinal Cord Protection
Paraplegia is a devastating complication, and the risk is lower with TEVAR than with open repair. Maintaining spinal cord perfusion requires avoiding hypotension and using cerebrospinal fluid drainage for open repair. Subclavian artery coverage may increase paraplegia risk by reducing collateral spinal cord blood supply. Staged procedures and permissive hypertension post-repair may further reduce risk.
Outcomes
TEVAR mortality is 3-8% compared to 15-20% for open repair. The paraplegia rate with TEVAR is less than 3%. Long-term TEVAR results show endoleak rates of 5-10% and reintervention rates of 5-15% over 10 years. Overall survival for patients reaching the hospital alive has improved dramatically in the endovascular era.
Key Clinical Pearls
BTAI should be suspected in any high-energy deceleration mechanism, and CTA is the definitive diagnostic study that should be obtained liberally. Anti-impulse therapy targeting systolic BP below 120 mmHg and heart rate below 80 bpm should be initiated immediately upon suspicion and maintained until definitive repair. TEVAR has become the standard of care and has dramatically reduced mortality and paraplegia rates compared to open repair. Grade I injuries (intimal tears) may be managed conservatively with serial imaging, as more than 50% resolve without intervention. Left subclavian artery coverage during TEVAR requires careful evaluation of the vertebral and upper extremity circulation, with selective revascularization performed based on individual anatomy.
References
- Lee WA, Matsumura JS, Mitchell RS, et al. Endovascular repair of traumatic thoracic aortic injury: clinical practice guidelines of the Society for Vascular Surgery. Journal of Vascular Surgery. 2011;53(1):187-192.
- Fox N, Schwartz D, Salazar JH, et al. Evaluation and management of blunt traumatic aortic injury: a practice management guideline from the EAST. Journal of Trauma and Acute Care Surgery. 2015;78(1):136-146.
- Demetriades D, Velmahos GC, Scalea TM, et al. Operative repair or endovascular stent graft in blunt traumatic thoracic aortic injuries: results of the AAST multicenter study. Journal of Trauma. 2008;64(3):561-571.
- Defined Grading Scale: Azizzadeh A, Keyhani K, Miller CC III, et al. Blunt traumatic aortic injury: initial experience with endovascular repair. Journal of Vascular Surgery. 2009;49(6):1403-1408.