Case report

A 26-year-old female presented to the emergency department (ED) after a high-speed motorbike crash. Her vital signs were stable, and she had a left anterior chest wall bruise and an abrasion over her left abdomen. Chest X-ray did not show haemopneumothorax or wide mediastinum. Extended focussed assessment with sonography in trauma (eFAST) that was done by the ED specialist was negative. The patient’s electrocardiogram (ECG) showed normal sinus rhythm and troponin was normal. A computed tomography (CT) scan was done, and the image is shown in Figure 1. What is the diagnosis?

Answer: A 10mm displaced mid-sternal fracture associated with a large retrosternal haematoma causing mass effect on the heart with compression in the antero-posterior plane.

View Figure 1–2.

Discussion

A retrosternal haematoma is defined as a haematoma deep to the sternum without a fat plane between the haematoma and the sternum. It is seen in about 70% of patients with sternal fracture, and especially in those with a displaced, mid-body sternal fracture. In patients with blunt chest trauma, it develops secondary to bleeding from the sternal fracture, soft tissue contusion or injury to surrounding vascular structures.[[1]] It may enlarge in size, secondary to associated active bleeding from damage to an internal thoracic artery, intercostal artery or a mediastinal vessel.[[2,3]] Considering the thickness of the adjacent sternum, retrosternal haematomas can be classified as Grade 1 (retrosternal haematoma less than half the thickness of the sternum), Grade 2 (retrosternal haematoma more than half the thickness of the sternum), and Grade 3 (retrosternal haematoma measuring the full thickness of the sternum).

Although rarely reported, it can compress the chambers of the heart, leading to extra-pericardial tamponade and haemodynamic compromise. The onset of cardiac tamponade from extra-pericardial retrosternal haematoma is usually more insidious compared to pericardial tamponade secondary to cardiac rupture. The patient remained haemodynamically stable in the intensive care unit (ICU), and transthoracic echocardiography did not show signs of cardiac tamponade or any regional wall motion abnormality from a potential associated cardiac contusion. After a few days, a repeat CT revealed spontaneous reduction in the size of retrosternal haematoma with no mass effect (see Figure 2).

As sternal fractures are associated with some degree of retrosternal haematoma, repeat imaging is not indicated in all patients to assess for haematoma resolution or fracture union. Repeat imaging with transthoracic echocardiography or CT scan is only indicated if there is deterioration of the patient’s condition, and the expanding retrosternal haematoma leads to physiological signs of cardiac tamponade (tachycardia, narrow pulse pressure, hypotension, pulsus paradoxus, jugular venous distention, muffled heart sounds). Prompt surgical management with sternotomy for haematoma evacuation and/or ligation or angio-embolisation of the bleeding vessel is required. As seen in our patient with retrosternal haematoma pressing on the cardiac chambers during radiological evaluation, a high level of clinical suspicion and close haemodynamic monitoring is required for early identification of physiological signs of impending cardiac tamponade.