ACLS ACLS Cardiac Rhythms & ECG Interpretation 2 — Questions and Answers
Question 1: On a monitor strip, you see regular, wide QRS complexes at 180 bpm with no discernible P waves and the patient has a pulse. What is the most likely rhythm?
- Ventricular fibrillation
- Supraventricular tachycardia with aberrancy
- Ventricular tachycardia (VT) with pulse (Correct answer)
- Accelerated idioventricular rhythm
Correct answer: Ventricular tachycardia (VT) with pulse
Regular wide-complex tachycardia at 180 bpm with a pulse is treated as ventricular tachycardia until proven otherwise.
Question 2: Which ECG feature best differentiates a junctional rhythm from a sinus rhythm?
- QRS duration greater than 120 ms
- Absent, inverted, or retrograde P waves (Correct answer)
- PR interval greater than 200 ms
- Right bundle branch block pattern
Correct answer: Absent, inverted, or retrograde P waves
Junctional rhythms originate in the AV node and produce absent, inverted, or retrograde P waves because atrial activation is not antegrade.
Question 3: A patient in cardiac arrest has no rhythm visible on the monitor (flat line). After confirming lead connections and gain, what is the appropriate ACLS action?
- Immediately defibrillate
- Continue high-quality CPR and administer epinephrine (Correct answer)
- Administer amiodarone 300 mg
- Check for carotid pulse and stop CPR
Correct answer: Continue high-quality CPR and administer epinephrine
Asystole is a non-shockable rhythm; management is high-quality CPR, epinephrine every 3–5 minutes, and investigation of reversible causes.
Question 4: Which ECG pattern is associated with hyperkalemia and should prompt immediate intervention?
- Prolonged QT with U waves
- Peaked (tall, narrow) T waves, widened QRS, flattened P waves (Correct answer)
- Short PR interval with delta wave
- ST depression in lateral leads
Correct answer: Peaked (tall, narrow) T waves, widened QRS, flattened P waves
Hyperkalemia produces peaked T waves early, then PR prolongation, P wave flattening, wide QRS, and ultimately a sine-wave pattern that can degenerate into VF.
Question 5: A narrow-complex tachycardia at 160 bpm begins and terminates abruptly. Which rhythm does this pattern best describe?
- Sinus tachycardia
- Atrial fibrillation
- Paroxysmal supraventricular tachycardia (PSVT) (Correct answer)
- Multifocal atrial tachycardia
Correct answer: Paroxysmal supraventricular tachycardia (PSVT)
PSVT (most commonly AVNRT) characteristically starts and stops abruptly, producing a regular narrow-complex tachycardia.
Question 6: In third-degree (complete) AV block, what is the relationship between P waves and QRS complexes?
- Fixed PR interval with all P waves conducted
- Progressive PR lengthening until a beat is dropped
- Complete dissociation — P waves and QRS complexes are independent (Correct answer)
- P waves occur after every other QRS
Correct answer: Complete dissociation — P waves and QRS complexes are independent
In complete heart block, the atria and ventricles are paced by independent pacemakers with no relationship between P waves and QRS complexes.
ACLS ACLS Cardiac Rhythms & ECG Interpretation 2
On a monitor strip, you see regular, wide QRS complexes at 180 bpm with no discernible P waves and the patient has a pulse.
What is the most likely rhythm?