Symptomatic hiatal hernia (HH) is most often revealed by gastroesophageal reflux disease, but there are atypical presentations some of which are life-threatening. We report the case of a 57-year-old woman brought to the emergency department with isolated shortness of breath for 24 h. Initial explorations revealed unexplained hyperlactatemia (6.4 mmol/L) without clinical or biological evidence of hypovolemia, distributive, obstructive or cardiogenic shock. Two hours after admission, we observed a decreased of blood pressure and an increase of lactate level to 7.9 mmol/L. A bedside echocardiography revealed an extra-cardiac left atrial compression and thoracoabdominal computed tomography showed a large sliding HH compressing the left atrium. After an upper gastrointestinal endoscopy permitting the aspiration of gastric contents, a repair surgery was performed without complications and patient was discharge three days later. Emergency physicians should be aware that HH can be a rare cause of cardiac symptoms by heart compression and certainly use echocardiography for unexplained hemodynamic failure.