ACLS ACLS Cardiac Rhythms and ECG Interpretation 2 — Questions and Answers
Question 1: A patient has third-degree (complete) heart block. Which ECG finding is characteristic?
- P waves and QRS complexes with no relationship to each other (AV dissociation) (Correct answer)
- Progressively lengthening PR interval followed by a dropped beat
- Constant PR interval with occasional dropped QRS
- Narrow QRS at 100 bpm with normal P waves
Correct answer: P waves and QRS complexes with no relationship to each other (AV dissociation)
Complete heart block shows complete AV dissociation — P waves and QRS complexes fire independently at different rates with no consistent PR relationship.
Question 2: What ECG finding is associated with hyperkalemia that warrants immediate ACLS intervention?
- Peaked (tall, narrow, tent-shaped) T waves (Correct answer)
- Prolonged QT interval
- Delta waves
- ST depression in V1–V3
Correct answer: Peaked (tall, narrow, tent-shaped) T waves
Hyperkalemia classically produces tall, peaked, tent-shaped T waves as an early ECG sign, which can progress to wide QRS, sine wave pattern, and cardiac arrest.
Question 3: In ACLS, which ECG finding is a classic sign of right ventricular strain in massive pulmonary embolism?
- S1Q3T3 pattern (S wave in I, Q wave and T inversion in III) (Correct answer)
- ST elevation in V1–V4
- Delta waves in multiple leads
- Prolonged PR interval
Correct answer: S1Q3T3 pattern (S wave in I, Q wave and T inversion in III)
The S1Q3T3 pattern (large S in lead I, Q wave and inverted T in lead III) is a classic ECG sign of acute right heart strain seen in massive pulmonary embolism.
Question 4: Asystole on ECG appears as what pattern?
- A flat (isoelectric) line with no electrical activity (Correct answer)
- Coarse irregular baseline
- Regular slow wide QRS complexes
- P waves only with no QRS
Correct answer: A flat (isoelectric) line with no electrical activity
Asystole appears as a flat isoelectric line on ECG, confirming the absence of any organized cardiac electrical activity.
Question 5: Which ECG finding indicates Wolff-Parkinson-White (WPW) syndrome that is important in ACLS?
- Short PR interval with a delta wave (slurred QRS upstroke) (Correct answer)
- Prolonged QRS with left bundle branch morphology
- Absent P waves with irregular QRS
- Deep Q waves in inferior leads
Correct answer: Short PR interval with a delta wave (slurred QRS upstroke)
WPW is identified by a short PR interval (<0.12 s) and a delta wave (slurred initial QRS deflection) caused by ventricular pre-excitation via an accessory pathway.
Question 6: During ACLS, a monitor shows fine ventricular fibrillation (fine VF). What is the correct next step?
- Defibrillate immediately — fine VF is still a shockable rhythm (Correct answer)
- Treat as asystole with epinephrine only
- Begin synchronized cardioversion
- Confirm in two leads and observe for 2 minutes
Correct answer: Defibrillate immediately — fine VF is still a shockable rhythm
Fine VF remains a shockable rhythm; immediate defibrillation is indicated regardless of amplitude — delaying shock worsens outcomes.
ACLS ACLS Cardiac Rhythms and ECG Interpretation 2
A patient has third-degree (complete) heart block.
Which ECG finding is characteristic?