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KEY FACTS

Terminology
- Traumatic injury of aorta (TAI) as result of motor vehicle collision (MVC), fall, or, less commonly, penetrating trauma
- Synonyms: Acute TAI, blunt traumatic aortic rupture, blunt aortic trauma, blunt aortic injury, aortic transection, traumatic aortic pseudoaneurysm
- Minimal aortic injury (MAI)
Imaging
- Radiography - Wide mediastinum: Hematoma, exclusion of TAI - 1st rib fracture: Severe trauma, possible TAI
- CTA: Imaging modality of choice - Aortic isthmus (90%); commonly on inferomedial aspect - Direct: Intramural hematoma; intimal flap; pseudoaneurysm - Indirect: Periaortic hematoma; irregular aortic contour; sudden aortic caliber change - Sensitivity 98%; specificity 80%
Top Differential Diagnoses
- Wide mediastinum of other etiology
- Mediastinal hematoma: Other causes
- Ductus diverticulum (type III)
- Infundibulum of bronchial-intercostal trunk
- Atherosclerotic ulceration
- Fusiform enlargement proximal descending aorta
Clinical Issues
- No specific or sensitive signs or symptoms until hemodynamic instability ensues
- Urgent diagnosis; 50% die within 24 hours if untreated
- Cause of death in 20% of high-speed MVCs
- Treatment - Surgical repair: 70-85% survival (up to 20% surgical mortality)

TERMINOLOGY

Abbreviations
- Traumatic aortic injury (TAI)
Synonyms
- Acute TAI (ATAI)
- Aortic transection
- Blunt aortic injury (BAI)
- Blunt aortic trauma (BAT)
- Blunt traumatic aortic rupture (BTAR)
- Traumatic aortic pseudoaneurysm
- Minimal aortic injury (MAI)
- Significant aortic injury (SAI)
Definitions
- Traumatic injury of aorta as result of motor vehicle collision (MVC), fall or, less commonly, penetrating trauma - Partial tear vs. complete rupture

IMAGING

General Features

Best diagnostic clue

- **Widened mediastinum** on AP chest radiography
- **Intramural hematoma (IMH), intimal flap,** **pseudoaneurysm or rupture** on CTA

Location

- **Aortic isthmus (90% of initial survivors)**; commonly along inferomedial aspect at level of left pulmonary artery
- Ascending aorta (5-14% of initial survivors)
        - Most die at scene of accident
- Diaphragmatic hiatus (1-12%)
        - May be associated with diaphragmatic injury
- Multiple sites rarely affected

Morphology
```
- SAI
```

Radiographic Findings

Radiography

- **Indirect signs** related to mediastinal hemorrhage
- Signs of TAI: Sensitive but not specific
- Most signs present in 30-70% of patients
        - **Widened superior mediastinum** (> 8 cm or > 25% of transthoracic diameter)
        - **Left apical pleural****cap**
        - Abnormal aortic arch contour
        - Obscuration of AP window
        - Right tracheal &/or endotracheal tube shift
        - Right enteric tube shift
        - Wide paravertebral stripe
        - Wide right paratracheal stripe
        - Inferior displacement of left mainstem bronchus
- 1st rib fracture indicates severe trauma and possible TAI
        - 1st rib protected by clavicle and scapula, requires considerable force to break
        - Frequency of TAI is 15-30%
- Any of aforementioned signs requires further investigation to exclude aortic transection
- Normal chest radiograph (7%)
- Chronic pseudoaneurysm (2% of survivors)
        - Peripherally calcified mass at aorticopulmonary window

CT Findings

NECT

- Often shows mediastinal hematoma, rarely shows site of tear

CTA

- Imaging modality of choice
        - Direct visualization of aortic tear, markedly reducing need for aortography
        - Sensitivity: 98%, specificity: 80%
- **Direct signs**
        - IMH
        - **Intimomedial flap ± thrombus**
        - **Pseudoaneurysm or contained rupture**
        - Rarely complete rupture with active extravasation
        - Aortic dissection
- Indirect signs
        - Periaortic/mediastinal hematoma
        - Irregular aortic contour
        - Sudden aortic caliber change; pseudocoarctation: Best seen on MPR
- MAI: Absent contour abnormality
        - 10% of acute TAI (ATAI)
        - Increased diagnosis due to improved spatial resolution of CT
        - Intimal flap (small < 1 cm; large > 1 cm) ± thrombus; IMH without contour abnormality
        - May remain stable or resolve
- SAI: Contour abnormality present
        - IMH + contour abnormality; pseudoaneurysm (< or > 1 cm); aortic rupture
- More severe injuries: Have both direct and indirect findings
- Pitfalls of TAI
        - Pulsation or streak artifact, especially at aortic root
                  - ECG gating required
        - Ambiguous findings
                  - Use different slice thickness, imaging plane, reconstruction kernel, or different phase of cardiac cycle
- Mimics of TAI
        - Ductus diverticulum; infundibulum; other causes of mediastinal hematoma; atherosclerotic plaque
- Chronic traumatic pseudoaneurysm
        - Develop in undiagnosed or untreated injuries
        - At isthmus; with extensive peripheral calcification; ± thrombus
        - Calcification protects against rupture

MR Findings
- MR generally has no role in evaluation of acute trauma - Limited by issues related to transportation and monitoring of critically injured patients - Used to identify IMH in stable patients and for follow-up
Echocardiographic Findings
- Transesophageal ECG - Demonstration of intimal tear, transection - Visualization of hemopericardium - May be technically difficult to perform in severely injured patients - Most commonly used intraoperatively when CT cannot be performed
Angiographic Findings
- Angiography - Previously considered gold standard for evaluating aorta and great vessels - Sensitivity: 100% - Specificity: 98% - Using chest radiography as guide, 10 negative angiograms performed for each TAI diagnosed - Small risk of rupture

Imaging Recommendations

Best imaging tool

- **CTA is imaging modality of choice**

Protocol advice

- Thin slices, MPR, and 3D volume rendering essential for treatment planning
- ECG gating required for evaluation of aortic root and ascending aorta

DIFFERENTIAL DIAGNOSIS

Widened Mediastinum on Chest Radiograph
- False-positives: Rotation, supine positioning, expiratory imaging, mediastinal fat
Mediastinal Hematoma: Other Causes
- Caused by injury to mediastinal veins, great vessels, pulmonary arteries, or vertebral body fractures
- Arterial injury not identified
- Hematoma usually away from aorta with intact fat plane
Ductus Diverticulum (Type III)
- Remnant of closed or partially closed ductus arteriosus
- Inferomedial outpouching of aortic isthmus
- Smooth, gently sloping shoulders with obtuse angle with aortic wall
- Often calcified; no intimal flap
Infundibulum of Bronchial-Intercostal Trunk
- Takeoff may show bump in aortic contour
- Cone-shaped, smooth walled, with artery at its apex
Atherosclerotic Ulceration
- More common in older patients
- Other coexisting aortic plaques
Normal-Variant Fusiform Dilation of Proximal Descending Aorta
- No intimomedial flap

PATHOLOGY

General Features

Etiology

- Theories of pathogenesis
        - Rapid deceleration injury with shearing forces greatest at levels of aortic immobility: Ligamentum arteriosum, aortic root, and diaphragmatic hiatus
                  - Lateral direction in side-impact collisions; anteroposterior direction in head-on collisions
        - Osseous pinch: Aorta compressed between anterior chest wall (manubrium, medial clavicles, 1st rib) and spine; transverse tear at aortic isthmus
        - Water hammer effect: Sudden marked increase in intravascular pressure during aortic compression; transverse tear at isthmus
        - Multivariate hypothesis likely: Shearing, torsion, stretching, hydrostatic forces

Gross Pathologic & Surgical Features
- 90% at aortic isthmus - From origin of left subclavian artery to ligamentum arteriosum, often anteromedially
- 7-8% involve aortic root; 2% involve descending aorta at diaphragmatic hiatus
- Ascending aortic tear: 20% of coroner cases; rarely survive long enough to reach hospital - In autopsy series, only 45-58% involve isthmus compared to 95% in surgical series
- In abdominal aorta: Infrarenal segment is commonly affected - Lap belt compression - Associations: Lumbar spine fracture, pelvic fracture, injury to bowel, solid organs, spleen
- Range: Intimal hemorrhage to complete transection
- Transverse tears: Segmental (55%) or circumferential (45%); partial (65%) or transmural (35%)
- Noncircumferential tears more common posteriorly
- May involve aortic layers to varying degrees - Survivors: Pseudoaneurysm usually contained by adventitia, or, occasionally, mediastinal structures - Adventitial injuries occur in 40% of cases and are almost always fatal due to rapid exsanguination

CLINICAL ISSUES

Presentation
- Most common signs/symptoms
```
- No specific or sensitive signs or symptoms until hemodynamic instability ensues
- May have chest pain or dyspnea
```
- Other signs/symptoms
```
- Acute coarctation syndrome rare
        - Upper extremity hypertension
        - Decreased femoral pulses
```
- Urgent diagnosis needed, as 50% expire within 24 hours if untreated
- Multiple associated injuries: Diaphragm rupture, lung contusion, rib fracture (1st rib), sternal fracture head injury, injury to heart, spleen, and liver

Demographics

Epidemiology

- Cause of death in 20% of high-speed MVCs

Natural History & Prognosis
- 80-90% mortality
- 85% die at site of trauma, most often from MVC
- Survival depends on time from injury to intervention
- 2% long-term survival
Treatment
- Surgical repair - For aortic root, ascending aorta, and arch - Delayed repair may be acceptable in many cases - Other injuries increase mortality of immediate repair - 70-85% surgical survival quoted (up to 20% surgical mortality) - Paraplegia in 10%; directly related to cross-clamp time - Lower rates of paraplegia with techniques that integrate perfusion distal to clamped aorta
- β-adrenergic blocking agents decrease wall stress
- Endovascular stent graft repair - Typically for isthmus, descending thoracic aorta, or abdominal aorta - Less invasive than surgical repair - Feasible in patients with multiple comorbid injuries - Complete pseudoaneurysm resolution reported at 3 months - Technical success in excluding tear approaches 100% - Lower operative times, blood loss, paraplegia, and mortality compared with open surgical repair - Require regular imaging follow-up for evaluation of complications
- Isolated injuries to intima (10%) may require no treatment and have been shown to resolve - Limited data on optimal management

DIAGNOSTIC CHECKLIST

Consider
- Careful evaluation of chest radiograph in trauma for indirect signs of aortic transection
Image Interpretation Pearls
- Consider chronic pseudoaneurysm in any patient with vascular calcification at aorticopulmonary window

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References

Selected References

Anatomy

Aortic Arch and Great Vessels

Brain/ANATOMY:a7a252f0-2ac6-402a-8c87-cfce8adc799b

Cases

{'cases': [{'authors': [{'key': '2cd036e9-d3d3-4b44-93f1-c0f8bf83ac5e', 'value': None}, {'key': 'd69a0534-8989-4b83-b19d-c3b640f22e53', 'value': 'Megan R. Saettele, MD'}, {'key': '2e78a4ff-418e-46f9-93e4-c6d95d960e35', 'value': 'Brandt C. Wible, MD'}], 'caseVersionId': '81c9c9a6-7b8a-498f-9b52-ae8887874927', 'description': 'Post-contrast CT images (#1-2) demonstrate a contour abnormality involving the proximal descending aorta with extravasation of contrast (arrows) and heterogeneous mediastinal soft tissue density consistent with blood products (open arrow). The patient was taken to the angiography suite for further evaluation. A 45-degree LAO projection aortogram with a pigtail catheter within the ascending aorta (#3) demonstrates focal irregularity involving the isthmus segment of the aorta as well as focal contrast extravasation (arrow), which both correlate with the site of suspected abnormality on CT scan. An additional aortographic image (#4) further confirms contrast extravasation (arrow). This lesion was not felt to be amenable to repair in the angiography suite, as the patient had other injuries requiring surgical evaluation. Aortic stent-graft placement was performed by vascular surgery in the operating room.\n\nComment: The vast majority of aortic injuries (~90%) involve the isthmus followed by the arch at the brachiocephalic trunk, often with avulsion of the latter. These injuries classically present as mediastinal widening on chest X-rays. Contrast-enhanced CT with thin sections allowing multiplanar reformatting is the test of choice for excluding aortic injury. Findings confirming aortic trauma include pseudoaneurysms, intramural hematoma, intraluminal filling defects, and active contrast extravasation. Angiography has been largely replaced by CT in the evaluation of aortic trauma, unless endovascular intervention is planned.', 'history': 'Patient presented to the emergency room status post high-speed automobile accident.', 'imagePoolId': '8b308ca9-b576-4f9e-9fac-ca5578c2e6ef', 'name': 'Traumatic injury to descending aorta', 'teachingPoint': None, 'demographics': '25 Years old male'}], 'caseType': 'typical', 'name': 'TYPICAL'}
{'cases': [{'authors': [{'key': 'e987d3d3-1206-48d6-824b-3347c2968855', 'value': 'Michael P. Federle, MD, FACR'}, {'key': '3d84d682-9451-4b02-99b2-e34970a5b440', 'value': 'Michael P. Federle, MD, FACR'}], 'caseVersionId': 'd8eb5368-9cf3-43d5-92a4-aab723c89f36', 'description': 'A series of axial (#1-8), coronal (#9-12), sagittal (#13-14), and curved planar (#15-16) reformations of a CECT study show multiple traumatic injuries, including a traumatic laceration of the aorta, with a mucosal flap (curved arrows, #1-2, 10-11, 15-16) and adjacent mediastinal hematoma, bilateral chest tubes in the pleural space (open arrow, #1-3), subcutaneous air in the left chest wall, extensive consolidation of the right lower lobe (black arrow, #1, 3, 12-13), and extensive rib fractures, some with displacement (curved black arrows, #5-6). The liver seems to be displaced into the right hemithorax and contains several irregular, linear and rounded foci of lower attenuation (black arrow, #7-8) indicative of hepatic laceration. The liver lies in a dependent position within the right hemithorax, almost "touching" the posterior ribs and spine.\n\nCoronal and sagittal reformations confirm the displacement of the right lobe of the liver into the right hemithorax. There is a subtle acute angulation or indentation of the surface of the liver (white arrow, #11, 13-14) at the point where the liver bulges upward into the thorax.\n\nComment: As with most cases of traumatic rupture of the diaphragm, there are numerous other injuries present in this case, which may distract or impede the radiologist from accurate diagnosis. Right-sided ruptures of the diaphragm are less common, at least clinically, than those on the left, presumably because of the protective effect of the liver. This patient had immediate aortic stent repair of the aortic laceration and subsequent repair of the right diaphragmatic laceration.', 'history': 'Seat-belted victim of high-speed motor vehicle crash.', 'imagePoolId': '1ea41479-e718-45f6-98f3-93494d6c4df2', 'name': 'Right side, on multiplanar CT', 'teachingPoint': None, 'demographics': '42 Years old male'}], 'caseType': 'variant', 'name': 'VARIANT'}

Images

Selected Images

AP chest radiograph in a young man struck by a car shows widening of the superior mediastinum , a left apical cap , a right tracheal/endotracheal and enteric tube deviation , thick paratracheal stripes, and loss of the aortic arch and the AP window .

Axial CTA in the same patient shows active contrast extravasation from the ruptured descending aorta and a large mediastinal hematoma that produces mass effect on the esophagus, airways, and pulmonary arteries.

Axial CTA in a 23-year-old man with a stab wound to the anterior chest shows mediastinal hemorrhage and laceration of the anteromedial ascending aorta with adjacent intramural hematoma .

Sagittal oblique aortogram following blunt chest trauma shows a large pseudoaneurysm at the aortic isthmus. CTA has largely replaced conventional angiography for the diagnosis of traumatic aortic injury (TAI) but still plays an important role in TAI treatment with endovascular stent graft placement.

Sagittal CECT in a patient involved in a motor vehicle collision shows a transverse segmental tear at the aortic isthmus without a surrounding mediastinal hematoma, consistent with MAI. The patient had no additional chest injuries, was treated conservatively, and was followed annually with CT.

Axial CTA in the same patient 5 years following trauma shows calcification and thrombus within a chronic posttraumatic aortic pseudoaneurysm.

Axial (left) and sagittal (right) CTA in a patient with blunt chest trauma show a minimal aortic injury manifesting with a focal intimal flap in the descending aorta without mediastinal hemorrhage.

Axial (left) and sagittal (right) CECT in the same patient 9 days later show resolution of the aortic abnormalities. Although minimal aortic injuries are often observed and usually resolve, there is limited data on their optimal management.

Axial CTA of the chest in a 60-year-old unrestrained man following a high-speed motor vehicle collision shows a linear tear from the anterior aspect of the descending aorta at the level of the diaphragm . The patient was hemodynamically unstable and was brought to the operating room.

AP DSA performed intraoperatively (left) in the same patient shows the aortic injury , which was successfully treated with an endovascular stent graft (right).

Additional Images

AP radiograph (left) shows abnormal soft tissue in the superior mediastinum that obscures the normal aortic contour and displaces the trachea to the right. Additionally, there is widening of the paravertebral stripe . Coronal CT shows a traumatic aortic pseudoaneurysm at the aortic isthmus with surrounding mediastinal and periaortic hematoma.

Coronal CECT shows the aortic pseudoaneurysm with surrounding mediastinal hematoma that prevents the aortic arch from being visualized on radiograph.

Coronal MIP shows the paraaortic hematoma extending along the entire course of the thoracic aorta.

AP chest radiograph shows a widened mediastinum, enlargement of the aortic arch , and tracheal deviation to the right secondary to traumatic aortic transection.

Axial CECT in the same patient shows a pseudoaneurysm at the site of aortic injury in the proximal descending aorta with surrounding mediastinal hemorrhage .

Sagittal CTA in the same patient shows the aortic tear contained by a pseudoaneurysm. Note the proximity of this injury to the ligamentum arteriosum .

Coronal CECT in a patient with TAI (not shown) shows the ligamentum arteriosum and mediastinal hemorrhage .

Coronal CECT at a more posterior level demonstrates the aortic tear .

Sagittal oblique DSA shows a contained transection of the descending aorta . An injury of this degree of severity is at a very high risk for imminent rupture. (Courtesy J. Caridi, MD.)

Axial CTA shows an aortic pseudoaneurysm resulting from a concentric aortic tear with a large surrounding mediastinal hematoma . The CTA findings are diagnostic, and there is no need for DSA.

Sagittal oblique DSA shows a tear of both the ascending aorta , near the left main coronary artery origin, and the proximal descending aorta . (Courtesy J. Caridi, MD.)

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KEY FACTS

Terminology

Imaging

Top Differential Diagnoses

Clinical Issues

TERMINOLOGY

Abbreviations

Synonyms

Definitions

IMAGING

General Features

Best diagnostic clue

Location

Morphology

Radiographic Findings

Radiography

CT Findings

NECT

CTA

MR Findings

Echocardiographic Findings

Angiographic Findings

Imaging Recommendations

Best imaging tool

Protocol advice

DIFFERENTIAL DIAGNOSIS

Widened Mediastinum on Chest Radiograph

Mediastinal Hematoma: Other Causes

Infundibulum of Bronchial-Intercostal Trunk

Atherosclerotic Ulceration

Normal-Variant Fusiform Dilation of Proximal Descending Aorta

PATHOLOGY

General Features

Etiology

Gross Pathologic & Surgical Features

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Other signs/symptoms

Demographics

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

Image Interpretation Pearls

References

Selected References

Anatomy

Aortic Arch and Great Vessels

Cases

Images

Selected Images

Additional Images

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