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
WPW syndrome is caused by: 
Select and explain. 
A. Bundle Branch Block, B. Right sided accessory pathway, C. Ectopic pacemaker in atrium, D. Left bundle Branch block
B: Right sided accessory pathway
Answer: B: Right sided accessory pathway 
Explanation: Answer is B (Right sided accessory pathway) Wolf Parkinson White syndrome is caused by the presence of on additional / accessory pathway (connection) between the atria and ventricle. The acessary pathway (called bundle of Kent) may be present as a connection between the left atrium and left ventricle (Left sided) or as a connection between the right atrium and right ventricle (Right sided). Pre excitation resulting from left sided accessory pathways is called Type A Pre-excitation Pre excitation resulting from right sided accessory pathway is called Type B Pre-excitation The most common accessary pathways leading to pre-excitation syndromes (WPW) are left sided (connecting left atrium to left ventricle).