Unexpected traumatic rupture of left atrium mimicking aortic rupture.

Left atrial (LA) rupture is rare following blunt chest injury. We describe a case of blunt LA rupture that was treated surgically. This report is intended to alert practitioners for a need of a close multiple disciplinary collaborations among them for optimal management of patients with this type of trauma; because other non-cardiac injuries involving the head, abdomen, or extremities are considered covariates for in-hospital mortality. As in the present case, the patient eventually died from associated extrathoracic injuries. The diagnosis of LA rupture is by exclusion. However, the initial radiological reading may be misinterpreted, because this injury can easily be mistaking for an aortic rupture. The final reappraisal of the chest imaging studies should be interpreted by a skilled radiologist to avoid misdiagnosis. Subtle radiological features can help distinguish aortic thoracic injury as illustrated in this patient. These factors may be useful to the practicing surgeon in deciding surgical approach.

INTRODUCTION

Thoracic aortic disruption most often results from a high-speed motor vehicle collision. A finding of left atrial dome disruption as the cause of cardiovascular collapse following blunt trauma is unusual. Its diagnosis is difficult, and if left untreated the mortality is high.

CASE REPORT

A 32-year-old man sustained multiple injuries following a high-speed dirt bike collision at 70 mph. On initial resuscitation in the emergency department (ED) his systolic blood pressure was < 50 mmHg. The extended Focused Assessment with Sonography for Trauma examination (eFAST) revealed pericardial effusion. A chest radiograph showed a widened superior mediastinum and left pneumothorax. His other injuries included bilateral lung contusions, mid sternal transverse fracture, open fractures of left radius/ulna and left tibial/fibular shafts, and multiple cerebral contusions. The patient responded to intravenous fluids administration and stabilized by the trauma team (blood pressure 110/60 mmHg, pulse 95 beats per minute with normal respirations). He was sent to the radiography suite after a left thoracostomy tube was inserted. The initial interpretation of the chest computed tomographic (CT) angiography could not rule out an aortic injury.[see Figure 1a-c] However, the re-evaluation of the CT by the radiologist revealed significant mediastinal hematoma but with an intact thoracic aorta. Because the patient became suddenly hemodynamically unstable and the eFAST was positive, he was taken to the operating room for emergent median sternotomy to determine the source of mediastinal hemorrhage. The time between the ED arrival to the sternotomy incision was approximatly 2 hours. Exploration revealed a large amount of blood in the pericardial cavity which seemed to be coming posterior to the aortic root. Conclusive evaluation of this area was possible onlsy when cardiopulmonary bypass (CBP) was established. A transverse tear of 2.5 cm in length was identified in the roof of the left atrium (LA) [Figure 2]. The tear was closed with simple suture technique using pledgetted 4-0 Prolene. The CPB time was 45 minutes. His hospital course was complicated by refractory multiorgan failure which led to his death 17 days after the accident. A chest CT scan obtained 1 day before patient expired showed an unchanged curvilinear area of enhancement adjacent to the left bronchus [Figure 3].

Figure 1

(a) Initial AP portable chest radiograph shows widening of the superior mediastinum (wide right paratracheal stripe, loss of aortic knob contour in a young patient) and extension of blood into the left apical extrapleural space (arrows), all consistent with a mediastinal hematoma (b) Axial enhanced CT images on day of injury through the aortic isthmus show a curvilinear area of enhancement (arrows) extending from the isthmus, consistent with a bronchial or intercostal artery. Appearance unlikely to represent aortic pseudoaneurysm (c) Coronal and sagittal reconstructions confirm curvilinear/tubular areas of enhancement in the vicinity of the aortic isthmus

Figure 2

Interoperative photograph showing the left atrial dome rupture

Figure 3

Unchanged curvilinear areas of enhancement (arrows) 16 days after injury, 1 day before patient expired

COMMENT

This case illustrates several facts associated with LA rupture that are useful for practicing surgeons and ED team. Cardiac rupture is rare following blunt chest trauma (1/2400).[1] One postulated mechanism of injury leading to atrial rupture is a sudden impact on the heart by the sternum during late systole following high-speed motor vehicle crashes. Unlike in the more common ventricular rupture, immediate death is delayed in atrial rupture because of the low pressure chamber that may allow the patient to survive transport to the hospital.[2] The possibility of survival therefore implies that a prompt resuscitation and rapid management should be undertaken.

LA rupture is distinctly uncommon. It is not usually considered in the differential diagnosis following blunt chest trauma associated with mediastinal hemorrhage. Given the fact that aortic transection is a more frequent injury in this type of trauma, it remains the most likely diagnosis. The diagnosis of LA rupture is by exclusion that can easily be mistaken by the care team.[34]

Based on our practice, evaluation of traumatic mediastinal hemorrhage is tailored to patient's condition. For unstable state, a rapid transesophageal echocardiography and a chest radiograph can be done while resuscitation is continuing. Whereas, if the patient has hemodynamically improved, even for a short period of time as in this patient, then an initial evaluation of the screening CT angiogram should be obtained ruling out aortic injury. However, the detailed concluding interpretation should be appraised by a radiologist. Our tertiary trauma center has a radiologist who is available for consultation 24 hours a day and is actually present in the ED. In this case, the final reviews of the CT angiogram argued for a more elusive process as the origin for the mediastinal hematoma ruling out aortic rupture.

This patient's clinical presentation underscores the risk of managing a sinister LA rupture. Operative planning for an aortic rupture includes a left thoracotomy. In our patient, this surgical approach would not have been the optimal one, because an LA rupture should be appropriately managed via a mid-sternotomy with excellent exposure of the heart and mediastinum instead of a left thoracotomy. Notwithstanding, a left thoracotomy incision can be extended laterally to the right through a clamshell approach and the sternum is divided transversely, this technique comes with its own disadvantages that have to be weighed against benefits. Its known disadvantages include bilateral ligation of the internal thoracic artery is necessary, the possibility of a flail chest exists with important repercussions in the patient's respiratory functions, and the added operative time and potential for more bleeding are not minimal.

CONCLUSIONS

Whereas LA rupture is uncommon and is the less expected cause of a wide mediastinum following blunt chest trauma, it can easily be confused with thoracic aortic injury. In all similar cases radiology consultation should be obtained to guide further management before carrying out cardiac operation. The outcome depends on associated multisystem injuries that require a coordinated execution of care by multi-disciplinary teams. The associated non-cardiac injuries probably contributed to our patient's demise.