Tension pneumomediastinum: earth-heart sign

Presentation

Immunosuppressed patient that two months before hospital admission started to feel malaise, shortness of breath, cough and diarrhea. His respiratory status worsened in the last 48 hours. In the ambulance, the patient was hypotensive, tachycardic and with low blood oxygen saturation levels. His body temperature was 41ºC. Upon arrival at hospital, the patient was stabilized and carried directly to critical care unit. A diagnosis of Pneumocystis pneumonia was established. Trimethoprim/sulfamethoxazole was used with concomitant methylprednisolone as treatment. On the third day of hospitalization, the patient suffered an acute respiratory deterioration and hemodynamic instability that required mechanical ventilation.

Patient Data

Age: 35 years
Gender: Male

Chest X-ray annotated image

X-ray

Posteroanterior chest x-ray: A1) Radiological findings of pneumomediastinum such as gas around ascending aorta (arrows), gas in neck tissues and subcutaneous emphysema (arrowhead) and Naclerio V sign. A2) Normal chest radiograph on twelfth postoperative day. B1) Earth-heart Sign: The cardiac silhouette appears to be flattened. This sign reflects cardiac compression caused by tension pneumomediastinum. B2) Normal cardiac silhouette on twelfth postoperative day after gas drainage.

Case Discussion

Chest radiography showed bilateral reticular interstitial opacification and new onset of pneumomediastinum and subcutaneous emphysema. CT scan revealed how pneumomediastinum caused a posterior displacement of the heart, which compressed the right heart chambers. The patient underwent a 4 cm transverse cervicotomy and a Penrose drain was placed in the anterior mediastinum. Postoperative course was favorable and the patient was discharged on the 28th day.

Tension pneumomediastinum is an exceptional and potentially lethal condition. It causes an increase in intramediastinal pressure that leads to collapse of the cardiac chambers, restriction of cardiac filling, and reduction of stroke volume and cardiac output.

The Earth-heart Sign reflects cardiac compression caused by tension pneumomediastinum. The cardiac silhouette appears to be flattened. It was called Earth-Heart sign because the cardiac silhouette resembles the shape of an oblate sphere like planet Earth. If we compare with a previous normal chest x-ray, we can observe an increased transverse cardiac diameter (TCD) and a decreased vertical cardiac diameter (VCD). Moreover, the difference between TCD and VCD (TCD/VCD) is greater than on a normal chest x-ray 1.

In an appropriate clinical setting, the presence of Earth-Heart sign, together with classic radiological features of pneumomediastinum, on a chest x-ray, are highly suggestive of tension pneumomediastinum. 

License: This radiological sign was published in Lancet in February 2014 1. The author has the copyright license to reproduce part of his publication on this case discussion at Radiopaedia. 

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