ACLS ACLS Cardiac Rhythms & ECG Interpretation 1 — Questions and Answers
Question 1: On an ECG, what characteristic finding confirms ventricular fibrillation (VF)?
- Regular wide QRS complexes at >150 bpm
- Chaotic, disorganized electrical activity with no identifiable QRS complexes (Correct answer)
- Regular narrow QRS complexes at 300 bpm
- P waves with prolonged PR interval
Correct answer: Chaotic, disorganized electrical activity with no identifiable QRS complexes
VF appears as chaotic, irregular waveforms with no identifiable P waves, QRS complexes, or T waves.
Question 2: Which ECG rhythm is characterized by a regularly irregular pattern with no P waves and a sawtooth baseline at ~300 bpm?
- Atrial fibrillation
- Atrial flutter (Correct answer)
- Multifocal atrial tachycardia
- AV nodal reentrant tachycardia
Correct answer: Atrial flutter
Atrial flutter produces characteristic sawtooth flutter waves at ~300 bpm, most visible in leads II, III, aVF, and V1.
Question 3: In ACLS, pulseless electrical activity (PEA) is best described as:
- VF with a detectable pulse
- An organized ECG rhythm without a palpable pulse (Correct answer)
- Asystole with occasional P waves
- Rapid wide-complex tachycardia
Correct answer: An organized ECG rhythm without a palpable pulse
PEA is defined as organized electrical activity on the monitor with absent pulse, requiring CPR and investigation of reversible causes.
Question 4: What is the hallmark ECG finding of first-degree AV block?
- Dropped QRS complexes
- PR interval > 200 ms with every P wave followed by a QRS (Correct answer)
- Progressive PR lengthening
- Complete dissociation of P and QRS
Correct answer: PR interval > 200 ms with every P wave followed by a QRS
First-degree AV block shows a consistently prolonged PR interval (>200 ms) with every P wave followed by a QRS complex.
Question 5: Which type of second-degree AV block is considered more dangerous and often requires pacing?
- Mobitz Type I (Wenckebach)
- Mobitz Type II (Correct answer)
- First-degree AV block
- Accelerated junctional rhythm
Correct answer: Mobitz Type II
Mobitz Type II block features a fixed PR interval with sudden dropped beats and can progress to complete heart block without warning.
Question 6: What ECG finding is the hallmark of Wolff-Parkinson-White (WPW) syndrome?
- Prolonged QT interval
- Delta wave with short PR interval (Correct answer)
- Tall peaked T waves
- Prominent U waves
Correct answer: Delta wave with short PR interval
WPW is identified by a delta wave (slurred QRS upstroke), short PR interval (<120 ms), and widened QRS due to pre-excitation.
ACLS ACLS Cardiac Rhythms & ECG Interpretation 1
On an ECG, what characteristic finding confirms ventricular fibrillation (VF)?