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
A wave in JVP is absent in: 
Select and explain. 
A. Atrial fibrillation, B. Heart block, C. Tricuspid regurgitation, D. Complete heart block
A: Atrial fibrillation
Answer: A: Atrial fibrillation 
Explanation: Ans. (a) Atrial fibrillationRef: Harrison 19th ed. /1443-1444* A wave in JVP is due to atrial contraction. In atrial fibrillation, since the atria are twitching, the power of atria is reduced to a level that a wave would be absent.* Heart block will have large a waves.* Tricuspid Regurgitation has absent x and large v waves.* Constrictive Pericarditis has a large y descent.