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
A -wave in JVP indicates: 
Select and explain. 
A. Atrial relaxation, B. Atrial contraction, C. Bulging of tricuspid valve into right atrium, D. Ventricular contraction
B: Atrial contraction
Answer: B: Atrial contraction 
Explanation: Ans. B: Atrial contraction Waves - a - presystolic; produced by right atrial contraction - c - bulging of tricuspid valve into the right atrium during ventricular systole (isovolumic phase) - v - occurs in late ventricular systole; increased blood in right atrium from venous return Descents - x - combination of atrial relaxation, downward movement of the tricuspid valve and ventricular systole - y - tricuspid valve opens and blood flows in to the right ventricle Abnormal waveform causes Dominant a wave - Pulmonary stenosis - Pulmonary hypeension - Tricuspid stenosis Cannon a wave - Complete hea block - Paroxysmal nodal tachycardia Ventricular tachycardia Dominant v wave - Tricuspid regurgitation Absent x descent - Atrial fibrillation Exaggerated x descent - Cardiac tamponade - Constrictive pericarditis Sharp y descent - Constrictive pericarditis - Tricuspid regurgitation Slow y descent - Right atrial myxoma