PR Intervals Review

1. The PR interval is the distance from the beginning of the ________ to the beginning of the__________.

• P wave, Q wave

• P wave, S wave

• R wave, T wave.

• PR segment, Q wave.

The PR interval denotes depolarization of the heart from the

• Bundle of His through the ventricles

• SA node through the atria, AV node, and His-Purkinje system

• AV node through the bundle of His

• SA node through the atria and AV node

A normal PR interval

• is usually present with all sinus and junctional dysrhythmias.

• indicates the impulse originated from the AV junction (or close to it) and traveled through the atria and AV node in a regular and unobstructed course.

• consists of the P wave and a flat line.

• is seen with wandering atrial pacemaker and multifocal atrial tachycardia.

The PR interval is normally ____ to ____ seconds in duration.

• 0.06, 0.12

• 0.10, 0.12

• 0.12, 0.16

• 0.12, 0.20

A PR interval of less than 0.12 seconds indicates:

• an intermittent blocking of the impulse as it passes through the AV node.

• an increased rate of impulse discharge from the SA node.

• a pacemaker site which is either in or close to the AV junction.

• a delay in conduction of the impulse between the SA node and the ventricles.

A PR interval of greater than 0.20 seconds indicates:

• an intermittent blocking of the impulse as it passes through the AV node.

• an increased rate of impulse discharge from the AV junction.

• a pacemaker site which is either in or close to the AV junction.

• a delay in conduction of the impulse between the SA node and the ventricles.

PR intervals are considered normal if they are:

• shorter than 0.12 seconds.

• consistently the same duration.

• vary in duration.

• longer than 0.20 seconds.

The P'R intervals may vary from beat to beat in:

• sinus dysrhythmia.

• junctional escape.

• wandering atrial pacemaker.

• 3rd – degree AV block.

The PR intervals are not measurable in:

• wandering atrial pacemaker.

• atrial flutter

• 2nd - degree AV heart block, Type I.

• premature atrial complexes.