CRAT Bundle Branch Blocks and Fascicular Blocks

Question 1

What minimum QRS duration is required to diagnose a complete bundle branch block?

Accepted Answer

≥0.12 seconds

Answer

≥0.08 seconds

Answer

≥0.10 seconds

Answer

≥0.14 seconds

Question 2

In right bundle branch block (RBBB), which leads classically display the rSR' ('rabbit ears') pattern?

Accepted Answer

Leads V1 and V2

Answer

Leads I and aVL

Answer

Leads II and III

Answer

Leads V5 and V6

Question 3

In right bundle branch block, a wide, slurred S wave is characteristically seen in which leads?

Accepted Answer

I, aVL, V5, and V6

Answer

V1 and V2

Answer

V3 and V4

Answer

II, III, and aVF

Question 4

Which of the following correctly describes an INCOMPLETE right bundle branch block?

Accepted Answer

QRS 0.10–0.11 sec with rSR' in V1

Answer

QRS ≥0.12 sec with rSR' in V1

Answer

QRS ≥0.12 sec without rSR' pattern

Answer

QRS <0.10 sec with right axis deviation

Question 5

The secondary R wave (R') seen in lead V1 during RBBB represents delayed depolarization of which cardiac structure?

Accepted Answer

Right ventricle

Answer

Left ventricle

Answer

Interventricular septum

Answer

AV node

Question 6

Which ECG feature best helps distinguish LBBB from RBBB when the QRS complex is wide?

Accepted Answer

QRS morphology in leads V1 and V6

Answer

PR interval duration

Answer

P wave axis

Answer

QT interval duration

Question 7

Aberrant ventricular conduction most commonly produces a morphology resembling which bundle branch block?

Accepted Answer

Right bundle branch block

Answer

Left bundle branch block

Answer

Left anterior fascicular block

Answer

Bifascicular block