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
All of the following are features of Mobiz type I block except- 
Select and explain. 
A. Constant PR interval, B. Normal QRS morphology, C. Regular atrial rhythm, D. Atrial rate more than ventricular rate
A: Constant PR interval
Answer: A: Constant PR interval 
Explanation: Type 1 Second-degree AV block, also known as Mobitz I or Wenckebach periodicity, is almost always a disease of the AV node. ... Today, Mobitz I hea block is characterized by progressive prolongation of the PR interval on consecutive beats followed by a blocked P wave (i.e., a dropped QRS complex Ref Harrison 20th edition pg 1443