CRAT - Certified Rhythm Analysis Technician Atrioventricular (AV) Blocks Questions and Answers

Question 1

A rhythm analysis technician observes an ECG strip where the PR interval is consistently 0.26 seconds for every beat. The rhythm is regular, with an atrial and ventricular rate of 68 bpm. Each P wave is followed by a QRS complex. What is the correct interpretation?

Accepted Answer

First-Degree AV Block

Answer

First-Degree AV Block is characterized by a prolonged but constant PR interval greater than 0.20 seconds. [9, 11] In this rhythm, every P wave is conducted to the ventricles, resulting in a 1:1 relationship between P waves and QRS complexes. [1] The rate is within the normal sinus range, and the PR interval of 0.26 seconds is the key diagnostic feature.

Question 2

Which of the following ECG findings is the defining characteristic of Second-Degree AV Block, Mobitz I (Wenckebach)?

Accepted Answer

Progressive lengthening of the PR interval until a QRS complex is dropped.

Answer

The hallmark of Second-Degree AV Block, Mobitz I (Wenckebach) is the progressive prolongation of the PR interval over several beats, culminating in a P wave that is not followed by a QRS complex (a dropped beat). [2, 6, 18] After the dropped beat, the cycle typically repeats.

Question 3

A patient's ECG shows a regular atrial rate of 80 bpm and an irregular ventricular rate of approximately 40 bpm. The PR interval for all conducted beats is constant at 0.22 seconds. There are P waves that are not followed by a QRS complex. This pattern is most consistent with which arrhythmia?

Accepted Answer

Second-Degree AV Block, Mobitz II

Answer

Second-Degree AV Block, Mobitz II is characterized by intermittently non-conducted P waves without progressive PR interval prolongation. The PR interval of the conducted beats remains constant. [14, 20] This type of block is more serious than Mobitz I because it often occurs below the AV node and can progress to complete heart block. [3, 17]

Question 4

A CRAT is analyzing a rhythm strip and observes complete AV dissociation. The atrial rate (P-P interval) is regular at 100 bpm, and the ventricular rate (R-R interval) is regular at 42 bpm. There is no consistent relationship between the P waves and the QRS complexes. What is this rhythm?

Accepted Answer

Third-Degree AV Block

Answer

Third-Degree (Complete) AV Block is defined by the complete absence of conduction between the atria and ventricles. [4, 13] This results in AV dissociation, where the atria and ventricles beat independently of each other, each controlled by its own pacemaker. [15, 16] The ECG shows regular P-P intervals and regular R-R intervals, but the two are not related.

Question 5

Which of the following atrioventricular blocks is considered more clinically significant and has a higher risk of progressing to a complete heart block, often requiring pacemaker implantation?

Accepted Answer

Second-Degree AV Block, Mobitz II

Answer

Second-Degree AV Block, Mobitz II is considered more dangerous than Mobitz I because the block is typically located in the His-Purkinje system, which is less stable. [14, 20] This rhythm has a significant risk of progressing suddenly to Third-Degree (Complete) AV Block and causing severe bradycardia or asystole, which is why a permanent pacemaker is often indicated. [3, 27]

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Atrioventricular (AV) Blocks Questions and Answers