Electrical Alternans in a Critically Ill Patient

CASE SUMMARY: A 39-year-old man presented with hematemesis, bloody diarrhea, and dyspnea. The electrocardiogram revealed electrical alternans, and the focused echography revealed a severe circumferential pericardial effusion. Despite this classic electrocardiogram finding, the patient remained normotensive, without the typical clinical triad of tamponade, reflecting the slow progression of tamponade physiology. Pericardiocentesis drained 1,250 mL of hemorrhagic fluid, with immediate resolution of electrical alternans. Cytology confirmed metastatic pulmonary carcinoma as the underlying etiology. TAKE-HOME MESSAGES: Electrical alternans is highly suggestive of a large pericardial effusion but does not invariably indicate tamponade. Tamponade does not invariably present with the typical clinical triad of hypotension, jugular venous distension, and muffled heart sounds, particularly in slowly progressive cases. In patients without a history of trauma, hemorrhagic pericardial effusion strongly suggests malignancy and prompts further diagnostic evaluation, irrespective of patient age.