CMC Cardiac Arrhythmia Management 1 — Questions and Answers
Question 1: A patient presents with a narrow-complex tachycardia at 160 bpm with regular rhythm and retrograde P waves. Which arrhythmia is most likely?
- Atrial fibrillation
- Atrioventricular nodal reentrant tachycardia (AVNRT) (Correct answer)
- Ventricular tachycardia
- Atrial flutter with 2:1 block
Correct answer: Atrioventricular nodal reentrant tachycardia (AVNRT)
AVNRT characteristically produces a narrow-complex regular tachycardia with retrograde P waves buried in or just after the QRS complex due to simultaneous atrial and ventricular activation.
Question 2: Which finding on a 12-lead ECG is most characteristic of Wolff-Parkinson-White (WPW) syndrome during sinus rhythm?
- Prolonged PR interval greater than 200 ms
- Short PR interval with a delta wave (Correct answer)
- Widened QRS with left bundle branch block morphology
- ST-segment elevation in leads V1-V4
Correct answer: Short PR interval with a delta wave
WPW syndrome is characterized by a short PR interval (<120 ms) and a slurred upstroke of the QRS called a delta wave, caused by ventricular pre-excitation via the accessory pathway.
Question 3: A patient with symptomatic bradycardia due to complete heart block is hemodynamically unstable. What is the immediate treatment of choice?
- Oral metoprolol 25 mg
- Transcutaneous pacing (Correct answer)
- IV adenosine 6 mg bolus
- Synchronized cardioversion
Correct answer: Transcutaneous pacing
Transcutaneous pacing is the immediate stabilizing therapy for hemodynamically unstable complete heart block while preparing for transvenous pacing or definitive permanent pacemaker placement.
Question 4: On telemetry, you observe a regular rhythm at 75 bpm with no visible P waves and narrow QRS complexes. Which rhythm is most consistent with this pattern?
- Accelerated junctional rhythm (Correct answer)
- Atrial fibrillation
- Sinus arrest with junctional escape
- First-degree AV block
Correct answer: Accelerated junctional rhythm
Accelerated junctional rhythm originates in the AV junction and presents as a regular narrow-complex rhythm at 60-100 bpm with absent, retrograde, or buried P waves.
Question 5: Which medication is the first-line pharmacologic treatment for stable monomorphic ventricular tachycardia in a patient with preserved ejection fraction?
- Adenosine IV
- Amiodarone IV (Correct answer)
- Digoxin IV
- Diltiazem IV
Correct answer: Amiodarone IV
IV amiodarone is the preferred antiarrhythmic for stable monomorphic ventricular tachycardia because it effectively terminates VT and is safe across a broad range of cardiac function.
Question 6: A patient develops torsades de pointes during ECG monitoring. Which electrolyte abnormality is most commonly associated with this arrhythmia?
- Hypernatremia
- Hyperkalemia
- Hypomagnesemia (Correct answer)
- Hypercalcemia
Correct answer: Hypomagnesemia
Hypomagnesemia prolongs the QT interval and lowers the threshold for torsades de pointes; IV magnesium sulfate is both the diagnostic and therapeutic intervention of choice.
Question 7: Which feature best distinguishes atrial flutter from atrial fibrillation on an ECG?
- Irregular ventricular response in atrial flutter
- Sawtooth flutter waves at ~300 bpm in atrial flutter (Correct answer)
- Narrow QRS complexes in atrial fibrillation only
- Absence of P waves in atrial flutter
Correct answer: Sawtooth flutter waves at ~300 bpm in atrial flutter
Atrial flutter is characterized by regular sawtooth-pattern flutter waves occurring at approximately 250-350 bpm (typically ~300 bpm), best seen in the inferior leads, distinguishing it from the irregularly irregular fibrillatory baseline of atrial fibrillation.
CMC Cardiac Arrhythmia Management 1
A patient presents with a narrow-complex tachycardia at 160 bpm with regular rhythm and retrograde P waves.
Which arrhythmia is most likely?