Case Presentation:

               A 24-year-old man with no past medical history was brought to the emergency department after being struck in the chest by a post while docking a water taxi. On arrival, he complained of shortness of breath and chest pain. Physical exam revealed an alert man with normal vital signs, a bleeding 2.5cm sternal laceration and left upper lobe rales.

An electrocardiogram (ECG) showed sinus rhythm with a right bundle branch block (RBBB) at 83 beats per minute (bpm) (Figure 1). Troponin I levels were elevated at 14 ng/mL. Computed tomography of the chest revealed a left upper lobe opacity consistent with pulmonary contusion. An ECG repeated several hours later showed resolution of the RBBB with residual 1-mm ST segment elevations in leads I and avL at 101 bpm (Figure 2). In fact, there were delayed leftward forces in this ECG, indicating no baseline right bundle delay. Transthoracic echocardiography showed no abnormalities.

The patient was diagnosed with cardiac and pulmonary contusions. He was admitted, had no arrhythmia on telemetry, and was discharged in stable condition. At follow-up two weeks later, he felt well and had no complaints.

Discussion:

Blunt cardiac trauma can lead to left ventricular dysfunction, valvular regurgitation, and dysrhythmias. The presence of a transient right bundle branch block in the setting of myocardial contusion is a described, but under-recognized occurrence. First demonstrated in animal experiments where a single external chest trauma caused transient intra-ventricular block, the first case of a transient RBBB in man was documented in 1952 in a 22 year-old man thrown from a motorcycle.

Due to their anterior location, the right ventricle and bundle branch are at particular risk of injury in trauma, with RBBB estimated to be present in 7-9% of cases of cardiac contusion. Conduction abnormalities manifest within 24 to 48 hours after injury, but show no correlation between arrhythmia complexity and degree of contusion. In one study however, the combination of abnormal ECG and troponin showed high sensitivity in identifying clinically significant cardiac contusion. Echocardiography can confirm these findings.

Conclusions:

Transient RBBB following blunt cardiac injury is an under-recognized manifestation of cardiac contusion. In patients presenting with abnormal ECGs and elevated troponins, it is important to consider rhythm monitoring and echocardiography, as these patients are at higher risk of complication and/or increased morbidity. However, as in our patient, full recovery without clinical sequelae is also common.