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: Unknown
What is not true of “a” wave of venous pulsations in neck? 
Select and explain. 
A. Exaggerated in tricuspid stenosis, B. Abolished in atrial fibrillation, C. Occurs just after in carotid artery, D. Exaggerated in complete heart block when P wave falls between QRS and T waves
C: Occurs just after in carotid artery
Answer: C: Occurs just after in carotid artery 
Explanation: There is no valve at junction of superior vena cava (SVC) and right atrium (RA) therefore right atrial pressure changes are transmitted to the jugular vein in the neck. “a” wave is due to atrial systole. Some blood regurgitates into the great veins when atria contracts, even though the orifices of IVC and SVC are constricted. In addition veins inflow stops, causing rise in venous pressure, contributing to the” a” wave.