A) time delay in\[A-V\]node
B) \[S-A\]nodal conduction time
C) increased ventricular contraction
D) time interval between onset of ventricular contraction.
Correct Answer: A
Solution :
: The PR interval is the time in seconds (usually 0.12 to 0.20 seconds) from the beginning of the P wave to the beginning of the QRS complex. It corresponds to the time lag from the onset of atrial depolarization to the onset of ventricular depolarization. This time lag allows atrial systole to occur, filling the ventricles before ventricular systole. Most of the delay occurs in the AV node. The PR interval is longer with high vagal tone. A prolonged PR interval corresponds to impaired AV conduction. A prolonged PR indicates a first degree heart block, while a shorting may indicate an accessory bundle, such as seen in Wolff- Parkinson-White syndrome.
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