Blunt cardiac injury

Blunt cardiac injury (BCI) is most commonly the result of sudden deceleration or direct precordial impact and encompasses a spectrum of structural and functional cardiac derangements that may occur after trauma to the heart ⁷.

Terminology

While sometimes referred to with general terms such as cardiac contusion, blunt cardiac injury represents a spectrum of injuries that may be stratified according to injury severity (the AAST injury scoring scale is sometimes used) or anatomical structure affected. 

Epidemiology

Blunt cardiac injury may account for an estimated 20% of fatalities occurring as a result of a motor vehicle collision ³.

Injury occurs from several mechanisms ^11-12:

• direct precordial blunt trauma

• cardiac compression between the sternum, ribs and thoracic spine

• laceration from displaced sternal and rib fractures

• indirect forces transmitted from below the diaphragm

Clinical presentation

Presenting symptoms may be non-specific, vary greatly, and appear attributable to coexisting injuries and/or pre-existing medical conditions including:

• chest pain

• dyspnea

• palpitations

• presyncope

ECG

Features on the electrocardiogram include ⁷:

• sinus tachycardia

• pathologic Q wave formation

• elevation of the ST segment

• new bundle branch blocks and/or atrioventricular (AV) nodal blocks

• ventricular fibrillation

  • in the context of an injury not producing structural damage referred to as commotio cordis

• premature ventricular contractions ⁸

Radiographic features

Plain radiograph

A chest radiograph may demonstrate cardiac signs or associated traumatic features, including:

• mediastinal widening

• cardiomegaly due to pericardial effusion

• pneumopericardium

• sternal fracture

• rib fractures

Ultrasound

Sonographic features of blunt cardiac injury are highly variable. Manifestations detectable by transthoracic echocardiography may appear as follows, based on the structure injured ⁴:

• ventricular septal rupture

  • new ventricular septal defect

• cardiac rupture

  • most commonly of the left ventricle

  • in surviving patients, right atrial injury is more common, which may result in:

    • pericardial effusion

    • cardiac tamponade

• coronary arterial injury

• valvular injury

  • may include disruption of the subvalvular apparatus

    • chordae tendinae rupture

    • papillary muscle rupture

  • aortic valve the most commonly involved

    • aortic regurgitation

  • tricuspid valve also commonly affected

    • tricuspid regurgitation

  • mitral annular disruption also reported, with mitral regurgitation

• contractile dysfunction

  • most commonly of the left ventricle

    • regional wall motion abnormalities

    • global depression of systolic function

• pericardial laceration

  • appearance of the air gap sign ²

Transesophageal echocardiography (TOE) is considered a superior modality, also highly sensitive for associated great vessel injuries, including ³:

• thoracic aortic rupture

  • vast majority occur at the isthmus

    • pseudocoarctation pattern is characteristic, with a spectral Doppler derived pressure gradient across the isthmus exceeding 20 mmHg

  • periaortic hematoma

  • hemopericardium

  • hemothorax

CT

CT imaging features of blunt cardiac injury are can be divided into direct and indirect signs ^8-12:

• direct

  • focal or diffuse myocardial hypoenhancement

    • right ventricular contusion is more common due to the anterior position of the ventricle but less commonly visible on CT due to the thick wall thickness

    • has a sharp border with normal myocardial (c.f. myocardial infarction)

  • focal or diffuse myocardial thickening and edema

  • myocardial rupture

    • very rare as almost always fatal

    • most commonly affects the right ventricle (due to anterior position and thinner wall)

  • ventricular septal rupture which can be immediate or up to 48 hours delayed

  • abnormal ventricular wall motion

    • on ECG-gated functional cardiac CT which is not perfromed in the usual trauma CT protocol

  • focal coronary artery dissection, thrombosis or occlusion

    • on ECG-gated CTCA which is not perfromed in the usual trauma CT protocol

    • LAD is the most commonly affected vessel

  • valve disruption

    • mitral and aortic valve injuries are most common

    • papillary muscle rupture

  • pericardial laceration with or without cardiac herniation

• indirect

  • hemopericardium

  • pneumopericardium

  • mediastinal fat stranding or haemomediastinum

  • pulmonary contusions or lacerations

  • hemothorax

  • anterior rib fractures

  • costal cartilage fracture

  • sternal fractures

  • traumatic aortic injuries

Iatrogenic injuries may also be seen such as a malpositioned intercostal catheter in the pericardial space or a cardiac chamber.

Differential diagnosis

• myocardial infarction causes focal ventricular myoardial hypoenhancement

  • infarct usually has a indistint border and is confined to an arterial terrritory ¹¹