The Earth-Heart sign: a new diagnostic finding in a patient with tension pneumomediastinum

In July, 2013, a 33-year-old immunosuppressed man was referred to our hospital. HIV infection was diagnosed in 2008 and he left follow-up 2 years later. He was not taking antiretroviral drugs. 2 months before hospital admission, the patient started to have malaise, shortness of breath, cough, and diarrhoea. His respiratory status worsened in the 48 h before admission. In the ambulance, the patient was hypotensive and tachycardic, and had low blood oxygen saturation. His body temperature was 41°C. On physical examination, the patient was tachypnoeic and sweaty. On arrival at hospital, the patient was stabilised and carried directly to the critical care unit. Standard laboratory studies showed lymphopaenia (lymphocyte count 0·95 × 109/L) and mild neutrophilia (neutrophils 79·8%). Serum bio chemistry test results were normal. Blood gas values on room air were pH 7·52, pO2 63·9 mm Hg, pCO2 30·9 mm Hg, and HCO3 24·8 mmol/L. A thoracic CT scan showed diff use, bilateral, and symmetric ground-glass attenuation. Pneumocystis jirovecii antigen was detected in sputum analysis. Trimethoprim and sulfamethoxazole IV were used with concomitant IV methylprednisolone as treatment. On the third day of hospitalisation, the patient had acute respiratory deterioration and haemodynamic instability, and needed mechanical ventilation. Chest radiography showed bilateral reticular interstitial opacifi cation and new onset of pneumomediastinum and subcutaneous emphysema (fi gure). CT scan showed a posterior displacement of the heart caused by pneumomediastinum. This displacement compressed the right heart chambers (appendix). The patient had a 4 cm transverse cervicotomy. We placed a Penrose drain in the anterior mediastinum and evacuated the pneumomediastinum. Postoperative course was favourable and the patient was discharged on the 28th day. Tension pneumomediastinum is an exceptional and potentially lethal condition. Increased intramediastinal pressure leads to impaired central venous return through the cavae system, restricted right heart diastolic fi lling, and collapse of the cardiac chambers, resulting in reduced stroke volume and cardiac output. Early detection is essential for prompt treatment and to improve the prognosis. Posteroanterior chest radiography should be the fi rst radiological investigation. The classic radiological features of pneumomediastinum are streaky radiolucencies in the mediastinum, ring-around-artery sign, continuous diaphragm sign, or Naclerio’s V sign. In this patient, the cardiac silhouette appears fl attened, indicating cardiac compression caused by tension pneumomediastinum. We decided to call this sign the Earth-Heart sign because the cardiac silhouette resembles the shape of an oblate sphere such as the Earth. If we make a comparison with a previous normal chest radiograph, we can observe an increased transverse cardiac diameter (TCD) and a decreased vertical cardiac diameter (VCD). Moreover, the diff erence between TCD and VCD (TCD/ VCD) is greater than in a normal chest radiograph (appendix). Other radiological fi ndings include air in neck tissues, and subcutaneous emphysema. CT scan is the imaging modality of choice for patients with high suspicion of tension pneumomediastinum. CT fi ndings reveal massive accumulation of air in the mediastinum, fl attening of the anterior cardiac contour, and posterior displacement of the heart. Sometimes, pneumomediastinum can also compress the aorta, supraaortic vessels, vena cava, or tracheobronchial tree. Echocardiography can also be useful in the diagnostic process. It helps to elucidate the physiopathology and rule out alternative diagnoses. In an appropriate clinical setting, the presence of EarthHeart sign, together with the classic radiological features of pneumomediastinum in a chest radiograph, is highly suggestive of tension pneumomediastinum. The main diff erential diagnosis includes cardiac tamponade caused by pericardial eff usion. We believe that knowledge of this new radiological sign will help physicians to obtain an early diagnosis and start prompt treatment.