CRAT Atrioventricular (AV) Blocks 2

Question 1

In first-degree AV block, which ECG finding is diagnostic?

Accepted Answer

PR interval greater than 200 ms with every P wave conducted

Answer

First-degree AV block is defined by a PR interval exceeding 200 ms (one large box) with every P wave successfully conducting to the ventricles.

Question 2

Mobitz type I (Wenckebach) second-degree AV block is best described by which pattern?

Accepted Answer

Progressive PR lengthening until a QRS is dropped, then the cycle resets

Answer

Wenckebach is characterized by progressive PR interval lengthening with each beat until one P wave is not conducted (dropped QRS), after which the cycle resets.

Question 3

Mobitz type II second-degree AV block differs from Mobitz type I primarily because it has which characteristic?

Accepted Answer

Constant PR interval with sudden unexpected dropped beats

Answer

In Mobitz type II, the PR interval remains constant and QRS complexes are dropped suddenly without warning, indicating infranodal disease and higher risk of complete heart block.

Question 4

In third-degree (complete) heart block, how do atria and ventricles relate to each other?

Accepted Answer

They beat completely independently at their own intrinsic rates

Answer

In complete heart block, no atrial impulses are conducted to the ventricles, so each chamber maintains its own independent pacemaker and rate.

Question 5

A patient has second-degree AV block with a 3:2 conduction ratio in Wenckebach pattern. How many P waves appear for every 2 QRS complexes?

Accepted Answer

3 P waves

Answer

A 3:2 conduction ratio means 3 P waves for every 2 conducted QRS complexes — one P wave in each cycle is blocked.

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT Atrioventricular (AV) Blocks 2