This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Electric altemans is seen in: 
Select and explain. 
A. Cardiac tamponade, B. Restrictive cardiomyopathy, C. Constructive pericarditis, D. Right Ventricular MI (RVMI)
A: Cardiac tamponade
Answer: A: Cardiac tamponade 
Explanation: Answer is A (Cardiac tamponade) Electrical alternans refers to a beat-to-beat alteration in one or more components of the ECG signal. Total electrical alternans (P-QRS-T) with sinus tachycardia is a relatively specific sign for pericardial effusion, often with cardiac tamponade. Feature Cardiac Tamponade Constrictive Pericarditis Restrictive Cardiomyopathy RVMI Electrical Alternans May be present Absent Absent Absent