CRAT Bundle Branch Blocks and Fascicular Blocks 3

Question 1

The left bundle branch divides into how many main fascicles?

Accepted Answer

Two

Answer

One

Answer

Three

Answer

Four

Question 2

Left anterior fascicular block (LAFB) is characterized by which QRS axis on a 12-lead ECG?

Accepted Answer

Left axis deviation (−45° to −90°)

Answer

Normal axis (0° to +90°)

Answer

Right axis deviation (+90° to +180°)

Answer

Extreme right axis deviation (+180° to −90°)

Question 3

Which set of criteria correctly describes left anterior fascicular block (LAFB)?

Accepted Answer

Left axis deviation, small Q in I and aVL, small R in II/III/aVF, QRS <0.12 sec

Answer

Right axis deviation, small Q in II and III, QRS ≥0.12 sec

Answer

Left axis deviation, rSR' in V1, QRS ≥0.12 sec

Answer

Right axis deviation, broad S in I and V6, QRS ≥0.12 sec

Question 4

The combination of right bundle branch block (RBBB) and left anterior fascicular block (LAFB) is called:

Accepted Answer

Bifascicular block

Answer

Trifascicular block

Answer

Complete heart block

Answer

Hemiblock

Question 5

A patient with bifascicular block (RBBB + LAFB) also has a prolonged PR interval. This pattern is clinically significant because it suggests:

Accepted Answer

Disease in all three fascicles with risk of progressing to complete AV block

Answer

Increased vagal tone causing benign bradycardia

Answer

Accelerated AV nodal conduction

Answer

An accessory pathway as in WPW syndrome

Question 6

Left posterior fascicular block (LPFB) produces which axis deviation, and in which leads are small Q waves characteristically seen?

Accepted Answer

Right axis deviation; Q waves in II, III, and aVF

Answer

Left axis deviation; Q waves in I and aVL

Answer

Right axis deviation; Q waves in V1 and V2

Answer

Left axis deviation; Q waves in V5 and V6

Question 7

Which condition must be excluded BEFORE diagnosing left posterior fascicular block (LPFB)?

Accepted Answer

Right ventricular hypertrophy and lateral wall MI must be ruled out

Answer

QRS duration must exceed 0.12 seconds

Answer

ST elevation must be present in inferior leads

Answer

The patient must have a documented history of hypertension