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
Pulsus alternans is: 
Select and explain. 
A. An innocuous feature, B. Denotes severe cardiac decompensation, C. Sign of Digoxin toxicity, D. Sign of mitral incompetence
B: Denotes severe cardiac decompensation
Answer: B: Denotes severe cardiac decompensation 
Explanation: None