CET Arrhythmia Recognition & Classification 2 — Questions and Answers
Question 1: A patient's ECG shows a regular rhythm at 150 bpm with narrow QRS complexes and no visible P waves. Which arrhythmia is most likely?
- Atrial flutter with 2:1 block (Correct answer)
- Ventricular tachycardia
- Sinus tachycardia
- Junctional tachycardia
Correct answer: Atrial flutter with 2:1 block
Atrial flutter with 2:1 block typically presents at ~150 bpm with flutter waves that may be hidden within QRS or T waves, producing a regular narrow-complex tachycardia.
Question 2: Which feature on an ECG best distinguishes Wolff-Parkinson-White (WPW) syndrome from a bundle branch block?
- Delta wave at the onset of the QRS (Correct answer)
- Prolonged PR interval
- Wide QRS complex
- Inverted P waves
Correct answer: Delta wave at the onset of the QRS
The delta wave — a slurred upstroke at the beginning of the QRS — is the hallmark of WPW caused by ventricular pre-excitation via an accessory pathway.
Question 3: A rhythm strip shows P waves with at least three distinct morphologies and an irregular rate between 100–150 bpm. This is consistent with:
- Multifocal atrial tachycardia (MAT) (Correct answer)
- Atrial fibrillation
- Wandering atrial pacemaker
- Sinus arrhythmia
Correct answer: Multifocal atrial tachycardia (MAT)
MAT is defined by three or more distinct P-wave morphologies with a ventricular rate above 100 bpm, most commonly seen in patients with severe COPD.
Question 4: On an ECG, second-degree AV block Type II (Mobitz II) is characterized by:
- Constant PR interval with sudden non-conducted P waves (Correct answer)
- Progressive PR lengthening before a dropped beat
- Varying PR intervals with no pattern
- Complete dissociation of P waves and QRS complexes
Correct answer: Constant PR interval with sudden non-conducted P waves
Mobitz II features a fixed PR interval followed by an unexpected dropped QRS, indicating infranodal conduction failure and a higher risk of complete heart block.
Question 5: Which of the following arrhythmias is characterized by 'sawtooth' flutter waves at approximately 300 bpm on the ECG?
- Atrial flutter (Correct answer)
- Atrial fibrillation
- Ventricular flutter
- Supraventricular tachycardia
Correct answer: Atrial flutter
Atrial flutter produces characteristic sawtooth flutter waves (F waves) at ~300 bpm, best seen in leads II, III, aVF, and V1.
Question 6: A patient has an ECG showing a regular wide-complex tachycardia at 180 bpm. The QRS morphology is identical to their baseline ECG showing LBBB. This most likely represents:
- SVT with aberrant conduction (Correct answer)
- Ventricular tachycardia
- Accelerated idioventricular rhythm
- Torsades de pointes
Correct answer: SVT with aberrant conduction
When wide-complex tachycardia has the same morphology as a pre-existing bundle branch block, SVT with aberrancy is favored over ventricular tachycardia.
Question 7: An ECG shows regularly spaced P waves that never conduct to the ventricles, with an independent ventricular rate of 38 bpm. This describes:
- Third-degree (complete) AV block (Correct answer)
- Second-degree AV block Mobitz I
- Second-degree AV block Mobitz II
- High-degree AV block
Correct answer: Third-degree (complete) AV block
Complete (third-degree) AV block features complete dissociation between atrial and ventricular activity, with an escape rhythm maintaining ventricular function.
CET Arrhythmia Recognition & Classification 2
A patient's ECG shows a regular rhythm at 150 bpm with narrow QRS complexes and no visible P waves.
Which arrhythmia is most likely?