CCS Cardiac Rhythm Interpretation & ECG Analysis 2

Question 1

Which ECG finding is most characteristic of a left bundle branch block (LBBB)?

Accepted Answer

QRS >0.12 s with broad monophasic R wave in V5–V6

Answer

LBBB shows a broad, slurred, or notched monophasic R wave in lateral leads (I, aVL, V5–V6) with QRS duration >0.12 seconds and absence of septal Q waves.

Question 2

What ECG triad is associated with Wolff-Parkinson-White (WPW) syndrome?

Accepted Answer

Short PR interval, delta wave, and wide QRS complex

Answer

WPW is characterized by a short PR interval (<0.12 s), a delta wave (slurred initial QRS upstroke), and wide QRS due to ventricular pre-excitation via an accessory pathway.

Question 3

Atrial flutter typically presents with what atrial rate?

Accepted Answer

250–350 bpm

Answer

Atrial flutter has a characteristic atrial rate of 250–350 bpm, producing sawtooth-pattern flutter waves most visible in inferior leads (II, III, aVF).

Question 4

Which ECG change is classically seen early in hyperkalemia?

Accepted Answer

Peaked narrow symmetrical T waves and QRS widening

Answer

Early hyperkalemia produces tall, narrow, peaked (tented) T waves; as potassium rises further, PR prolongation, QRS widening, and eventually a sine wave pattern emerge.

Question 5

Which ECG finding most strongly supports ventricular tachycardia (VT) over SVT with aberrancy?

Accepted Answer

Wide complex tachycardia with AV dissociation and QRS >0.14 seconds

Answer

AV dissociation (independent P waves and QRS complexes), along with QRS width >0.14 seconds, fusion beats, and capture beats, are hallmark features of ventricular tachycardia.

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CCS Cardiac Rhythm Interpretation & ECG Analysis 2