This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
Pulsus alternans occurs in - 
Select and explain. 
A. Constrictive pericarditis, B. Viral myocarditis, C. Hypokalemia, D. Myocardial infarction
D: Myocardial infarction
Answer: D: Myocardial infarction 
Explanation: pulses alternans is seen in 3 conditons a)large pericardial effusion b)left ventricular failure c)asthma so the answer is MI where there is left ventricular failure. Ref Harrison 20th edition pg 1523