CCT Rhythm Analysis: Ventricular/Blocks 2

Question 1

What are the ECG criteria for left bundle branch block (LBBB)?

Accepted Answer

QRS ≥ 0.12 seconds; broad monophasic R in lateral leads (I, aVL, V5-V6); rS or QS pattern in right precordial leads (V1-V2); absence of septal Q waves in lateral leads

Answer

QRS ≥ 0.12 seconds; RSR' (rabbit ears) pattern in V1; wide S waves in lateral leads

Answer

QRS < 0.12 seconds; tall R waves in V1 and V2

Answer

QRS ≥ 0.12 seconds; delta wave; short PR interval

Question 2

What ECG features differentiate right bundle branch block (RBBB) from left bundle branch block (LBBB)?

Accepted Answer

RBBB: RSR' (rabbit ears) in V1 with wide S in lateral leads; LBBB: broad monophasic R in lateral leads with QS/rS in V1

Answer

RBBB: broad R in lateral leads; LBBB: RSR' in V1

Answer

Both: identical QRS morphology, distinguished only by axis

Answer

RBBB: QRS < 0.10 s; LBBB: QRS > 0.14 s

Question 3

In third-degree (complete) AV block, what is the key ECG finding that distinguishes it from other forms of AV block?

Accepted Answer

Complete AV dissociation: P waves and QRS complexes are completely independent with no relationship between them; both have their own regular, independent rates

Answer

PR intervals are progressively lengthening with dropped beats

Answer

Non-conducted P waves occur after every 2 conducted P waves (3:2 block)

Answer

P waves occur at the same rate as QRS complexes but with very long fixed PR intervals

Question 4

What ECG characteristics define monomorphic ventricular tachycardia (VT)?

Accepted Answer

Three or more consecutive QRS complexes originating in the ventricles at a rate ≥ 100 bpm with identical QRS morphology from beat to beat

Answer

Three PVCs with different QRS morphologies occurring consecutively

Answer

P waves at 300 bpm with regular QRS complexes at 150 bpm

Answer

Wide QRS complexes at 40-60 bpm with AV dissociation

Question 5

Left anterior fascicular block (LAFB) produces which characteristic ECG finding?

Accepted Answer

Left axis deviation (axis between -30 and -90 degrees) with small R in inferior leads, deep S in lateral leads, and normal QRS duration

Answer

Right axis deviation with RBBB morphology

Answer

Wide QRS with left bundle branch block pattern

Answer

Left axis deviation with Q waves in inferior leads and prolonged QRS

Question 6

Torsades de Pointes (TdP) is a specific form of polymorphic VT associated with which underlying ECG abnormality?

Accepted Answer

Prolonged QT interval (congenital or acquired)

Answer

Short QT interval

Answer

Right bundle branch block

Answer

Pre-excitation (WPW pattern)