thorakale Aortenverletzungen

Thoracic aortic injury is the most common type of traumatic aortic injury and is a critical life-threatening, and often life-ending event.

Clinical presentation

Approximately 80% of patients with thoracic aortic injury die at the scene of the trauma. In those who make it to hospital, clinical diagnosis is difficult. The signs and symptoms are non-specific and distracting injuries are often present. Clinical presentation may include chest or mid-scapular back pain, signs of external chest trauma or hemodynamic instability. Clinical suspicion is usually based on mechanism and severity of the injury, the hemodynamic status of the patient and/or the presence of related injuries. The diagnosis ultimately relies on appropriate imaging.

Pathology

Trauma to the aorta may result in:

• minimal aortic injury
• aortic laceration: a tear in the intima which may extend through the vessel wall; the tear is typically transverse
• aortic transection: laceration of all three layers of the vessel wall, also known as traumatic aortic rupture
• aortic pseudoaneurysm: aortic rupture contained by adventitia or periaortic tissue
• aortic intramural hematoma: hematoma within the wall of the aorta

An aortic dissection is a longitudinal tear in the aortic wall and is rarely a sequela of trauma.

Blunt thoracic aortic injury is uncommonly an isolated injury. A large autopsy study found that 97% of victims of aortic injury had other traumatic injuries outside the chest .

Etiology

Thoracic aortic injury can result from either blunt or penetrating trauma:

Location

• aortic isthmus: 90%
• ascending aorta: 5%
• diaphragmatic hiatus: 5%

The isthmus is the portion of the proximal descending thoracic aorta between the left subclavian artery origin and the ligamentum arteriosum. Tethering of the aorta by the ligamentum arteriosum is believed to account for the high frequency of aortic injury in this region.

The above figures represent the site of injury in those patients who present to hospital. The ascending aorta is injured in 20 -25% of cases at autopsy but most of these patients die at the scene from serious complications such as a ruptured aortic valve, coronary artery laceration or hemopericardium with pericardial tamponade.

Radiographic features

Plain radiograph

A supine chest radiograph is the initial screening investigation in the trauma patient. The mediastinum on a portable supine film can be difficult to assess, especially if taken in expiration or if the patient is rotated. Direct signs of aortic injury are not visible on chest radiographs but indirect signs may be detected: either a mediastinal hematoma or signs of concomitant chest injuries.

Signs of mediastinal hematoma:

• widened mediastinum (more than 8 cm when supine, or more than 6 cm when upright)
• indistinct or abnormal aortic contour
• deviation of trachea or NGT to the right
• depression of left main bronchus
• loss of the aortopulmonary window
• widened paraspinal stripe
• widened paratracheal stripe
• left apical pleural cap
• large left hemothorax

The detection of mediastinal hematoma on a chest radiograph has a high sensitivity for aortic injury but a low specificity because most mediastinal hematoma is due to other causes such as tearing of mediastinal vessels, sternal injury or thoracic spine injury. Only 12.5% of mediastinal hematoma is due to aortic injury. However, the negative predictive value of a normal chest radiograph of good quality is ~97% but this likely reflects the low incidence of blunt thoracic aortic injury.

CT

Non-contrast CT chest

May show indirect signs of aortic injury:

• mediastinal hematoma
• periaortic fat stranding
• other chest injuries

CTA chest

The investigation of choice. Excellent at showing direct signs of aortic injury as well as indirect signs - sensitivity 100%; specificity 100%.

Signs of mediastinal hematoma:

• abnormal soft tissue density around the mediastinal structures
• location is important – periaortic hematoma much more suggestive of aortic injury than isolated mediastinal hematoma remote from the aorta.

Signs of aortic injury:

• intraluminal filling defect (intimal flap or clot)
• abnormal aortic contour (mural hematoma)
  • sudden change in and/or decreased diameter
• pseudoaneurysm
• extravasation of contrast

Angiography (DSA)

Rarely performed due to the advent of high-quality CTA.

Signs of aortic injury:

• resistance in advancing a guidewire
• intraluminal filling defect (intimal flap or clot)
• abnormal aortic contour (mural hematoma)
• pseudoaneurysm
• extravasation of contrast

Complications:

• general risks of angiography
• dissection or rupture due to guidewire or catheter

Other imaging modalities

Generally not used in the acute setting but can include:

• MRI
• transesophageal echocardiography
• intravascular ultrasound

Treatment and prognosis

Aortic injury is a surgical emergency. Treatment is with an aortic stent graft or open repair. Mortality is very high :

• >95% if untreated
• ~80% die immediately
• >30% if in hospital and treated

Complications

• death from aortic rupture and hemorrhage
• chronic traumatic pseudoaneurysm
• embolization from pseudoaneurysm

Differential diagnosis

Other causes of widened mediastinum on a chest radiograph:

• technical factors (supine vs erect)
• vascular ectasia
• mediastinal lipomatosis
• mediastinal masses

Mimics of a mediastinal hematoma on CT include:

• artifact
• thymic tissue
• unopacified vessels
• pericardial recesses
• paramediastinal lung atelectasis

Mimics of aortic injury on CTA or conventional angiography:

• aortic pulsation motion artifact (typically left anterior and right posterior aspects of the ascending aorta)
• streaming of contrast
• aortic atheroma
• ductus diverticulum
• infundibulum of branch vessel

Siehe auch:

• Aorta
• Aorta ascendens
• apikale Pleurakappe
• thorakale Aortendissektion
• Ductus diverticulum
• Herzbeuteltamponade
• Aortentrauma
• thoracic aortic

und weiter:

• Pleurakuppenschwielen
• penetrierendes Aortenulkus (PAU)
• Aortenruptur
• vascular trauma
• Aortenisthmus
• blunt traumatic aortic injury in a traumatized child
• acquired aortic conditions
• blunt traumatic intramural aortic hematoma
• Mediastinalverbreiterung
• Verletzungen der Aorta abdominalis
• intramurales Hämatom der Aorta