What is a mediastinal hematoma?

What is a Mediastinal Hematoma?

A mediastinal hematoma is a collection of blood within the mediastinal space—the central compartment of the chest cavity between the lungs—that most commonly results from traumatic aortic injury, blunt chest trauma, or iatrogenic vascular injury, though spontaneous cases can occur in anticoagulated patients. 1

Etiology and Clinical Context

Mediastinal hematomas arise from several distinct mechanisms:

• Traumatic causes are most common, with approximately 20% of motor vehicle accident fatalities demonstrating aortic rupture at autopsy, making traumatic rupture of the aorta (TRA) a leading cause 1
• Blunt chest trauma can cause mediastinal hematoma through aortic injury (45% occur at the aortic isthmus, 23% in the ascending aorta), mediastinal vascular injury, or fractures of the sternum and vertebral column 1, 2
• Iatrogenic injury during central venous catheter insertion, particularly subclavian vein cannulation, represents a recognized complication 3
• Spontaneous non-traumatic hematomas are rare but potentially life-threatening in patients on anticoagulants (warfarin, direct oral anticoagulants), occurring even at therapeutic anticoagulation levels 4
• Post-surgical bleeding following open heart surgery or other thoracic procedures 5

Anatomic Distribution and Imaging Characteristics

The location of mediastinal hematoma provides diagnostic clues:

• Posterior mediastinal hematomas suggest aortic injury at the isthmus or descending aorta, or may result from vertebral fractures 1, 4
• Anterior mediastinal hematomas can cause extrapericardial cardiac tamponade by compressing adjacent cardiac structures 2
• Hemomediastinum signs on chest radiography include widened mediastinum, abnormal aortic contour, left apical cap, loss of the aortic knob, depression of the left main bronchus, and deviation of an esophageal tube—though these findings are more often false positive than true positive for aortic injury 1

Diagnostic Approach

Contrast-enhanced CT is the imaging modality of choice because of its accessibility, noninvasiveness, rapid acquisition, and ability to evaluate the entire thorax simultaneously 5:

• CT sensitivity and specificity for aortic dissection and traumatic injury reach up to 100% and 98-99% respectively with newer-generation multidetector scanners 1
• Chest radiography alone is inadequate, with only 64% sensitivity for widened mediastinum and 71% for abnormal aortic contour, though a completely normal chest x-ray in very low-risk patients may lower the likelihood of significant pathology 1
• Transesophageal echocardiography (TEE) demonstrates 100% sensitivity and 75% specificity for mediastinal hematoma in trauma patients, with the distance between the esophageal probe and aortic wall being the most accurate sign (threshold value >3 mm) 6

Critical Imaging Pitfall

Standard FAST (Focused Assessment with Sonography for Trauma) examination can miss mediastinal hematomas because the subxiphoid view does not adequately visualize the mediastinum 2:

• For trauma patients with probable mediastinal injuries, perform an extended FAST with parasternal long-axis view 2
• Alternatively, maintain a low threshold for thoracic CT in patients with persistent symptoms, as missed mediastinal hematoma can be fatal 2

Clinical Presentation and Complications

Patients may present with:

• Acute chest discomfort or pain as the primary symptom 4
• Signs mimicking aortic coarctation: arm blood pressure higher than leg blood pressure, delayed radial versus femoral artery pulsation, harsh interscapular murmur 1
• Compressive symptoms: respiratory distress, hemodynamic instability, or cardiac tamponade when large hematomas compress the left atrium or other cardiac structures 4, 2
• Evidence of polytrauma in traumatic cases 1

Management Principles

Conservative management is commonly effective for asymptomatic or stable patients, with complete resolution possible even for large hematomas over 4 weeks 3:

• Reversal of anticoagulation in spontaneous cases associated with warfarin or other anticoagulants 4
• Serial imaging to monitor hematoma size and ensure resolution 3

Active surgical intervention should be considered when 4:

• The hematoma is symptomatic with respiratory or hemodynamic compromise
• Conservative therapy proves ineffective
• Compression of vital structures (left atrium, airways) causes clinical deterioration

Key Clinical Caveat

Clinicians must maintain awareness of spontaneous mediastinal hematoma as a potential complication of anticoagulant therapy, even at therapeutic anticoagulation levels, to facilitate prompt and proper management 4. The condition can present insidiously with non-specific symptoms like chest discomfort, potentially leading to initial misdiagnosis as gastrointestinal bleeding or other conditions 4.