A 62 years old man with carcinoma of lung presented to emergency depament with respiratory distress. His ECG showed electrical alternans. The most likely diagnosis is: (A) Pneumothorax, (B) Pleural effusion, (C) Cardiac tamponade, (D) Constrictive pericarditis
Answer is C. Ref Harrison 19 th ed pg 1759-60 Electrical alternans refers to beat-to-beat alteration in one or more components of the ECG signal. Total electrical alternans with sinus tachycardia is a relatively specific sign for pericardial effusion, often with cardiac tamponade.