A patient is given a drug that prolongs the P-R interval of the electrocardiogram (ECG). What is the most likely action of the drug?
A) Reduced conduction velocity of the atrial fibers
B) Delayed repolarization of the ventricular fibers
C) Reduced conduction velocity of atrioventricular (AV) nodal fibers
D) Increased conduction velocity of the atrial fibers
E) Increased force of contraction of the right ventricle

Question

Quizplus · Accepted Answer

The P-R interval on an ECG represents the time from the onset of atrial depolarization to the onset of ventricular depolarization. A drug that prolongs the P-R interval most likely slows down the conduction velocity through the atrioventricular (AV) nodal fibers, as this is where the delay occurs.

A Patient Is Given a Drug That Prolongs the P-R