CRAT Atrioventricular (AV) Blocks 3

Question 1

On the ECG, which measurement defines a normal PR interval?

Accepted Answer

120-200 ms

Answer

The normal PR interval ranges from 120 to 200 ms (3 to 5 small boxes on standard ECG paper), representing atrial depolarization and AV nodal conduction time.

Question 2

In high-degree AV block with a 4:1 conduction ratio, what is the ventricular rate if the atrial rate is 80 bpm?

Accepted Answer

20 bpm

Answer

With a 4:1 AV conduction ratio and an atrial rate of 80 bpm, only 1 in 4 P waves conducts, giving a ventricular rate of 80 divided by 4 = 20 bpm.

Question 3

Which characteristic of the QRS complex in complete heart block provides a clue about the location of the escape pacemaker?

Accepted Answer

Narrow QRS suggests a junctional escape; wide QRS suggests a ventricular escape

Answer

Junctional escape pacemakers activate the ventricles via the normal His-Purkinje system, producing narrow QRS complexes, while ventricular escape foci cause wide, aberrant QRS complexes.

Question 4

Which medication is a common pharmacological cause of AV block?

Accepted Answer

Digoxin

Answer

Digoxin enhances vagal tone and slows AV nodal conduction, and toxicity can cause all degrees of AV block including complete heart block.

Question 5

AV dissociation that is NOT due to complete heart block can occur in which situation?

Accepted Answer

Accelerated junctional rhythm that exceeds the sinus rate

Answer

AV dissociation without complete block occurs when a lower pacemaker (junctional or ventricular) accelerates to exceed the sinus rate, causing the two chambers to beat independently without true block.

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT Atrioventricular (AV) Blocks 3