Electrical alternans on ECG indicates a large pericardial effusion with tamponade physiology. What is the most appropriate immediate clinical action?

• A. Urgent evaluation for tamponade physiology
• B. Start heparin
• C. Initiate thrombolysis
• D. Start diuretics

Answer: (A)

Electrical alternans signals a large pericardial effusion with tamponade physiology, where fluid around the heart constrains filling and drops cardiac output. The immediate priority is urgent evaluation for tamponade physiology—use rapid bedside imaging, especially focused echocardiography, to confirm tamponade signs such as diastolic collapse of the right ventricle or atrium and signs of restricted filling. This confirmation triggers urgent drainage, typically via pericardiocentesis or surgical drainage, to relieve the pressure.

Anticoagulation with heparin is inappropriate here because it increases bleeding risk without addressing the effusion. Thrombolysis likewise has no role in tamponade and can cause serious bleeding. Diuretics would reduce preload and worsen the hemodynamic instability seen with tamponade.