DC Dysrhythmia Cardiac Rhythm Interpretation 2 — Questions and Answers
Question 1: A patient's ECG shows a regular rhythm with a rate of 150 bpm, narrow QRS complexes, and no visible P waves before each QRS. What is the most likely dysrhythmia?
- Atrial flutter with 2:1 block (Correct answer)
- Junctional tachycardia
- Ventricular tachycardia
- Second-degree AV block Type II
Correct answer: Atrial flutter with 2:1 block
Atrial flutter with 2:1 block classically presents at 150 bpm with flutter waves that may be buried in the QRS, producing apparent absence of discrete P waves.
Question 2: On a rhythm strip, the PR interval measures 0.28 seconds and is constant, with every P wave followed by a QRS complex. Which conduction abnormality is present?
- Second-degree AV block Mobitz I
- Second-degree AV block Mobitz II
- First-degree AV block (Correct answer)
- Third-degree AV block
Correct answer: First-degree AV block
First-degree AV block is characterized by a PR interval greater than 0.20 seconds that is constant, with every P wave conducting to a QRS.
Question 3: A rhythm strip shows grouped beating with progressive lengthening of the PR interval until a P wave fails to conduct, then the cycle repeats. This pattern describes which block?
- Third-degree AV block
- Second-degree AV block Mobitz II
- Second-degree AV block Mobitz I (Wenckebach) (Correct answer)
- Junctional escape rhythm
Correct answer: Second-degree AV block Mobitz I (Wenckebach)
Mobitz I (Wenckebach) is defined by progressive PR prolongation until a QRS is dropped, creating grouped beating.
Question 4: Which ECG finding most strongly distinguishes ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy?
- Heart rate above 150 bpm
- QRS duration greater than 0.14 seconds with AV dissociation (Correct answer)
- Absence of P waves
- Irregular RR intervals
Correct answer: QRS duration greater than 0.14 seconds with AV dissociation
AV dissociation combined with a QRS wider than 0.14 seconds is the most reliable criterion for diagnosing VT over SVT with aberrancy.
Question 5: A patient's ECG shows a delta wave, short PR interval, and wide QRS. Which syndrome is associated with this pattern?
- Brugada syndrome
- Long QT syndrome
- Wolff-Parkinson-White (WPW) syndrome (Correct answer)
- Lown-Ganong-Levine syndrome
Correct answer: Wolff-Parkinson-White (WPW) syndrome
WPW syndrome is characterized by a delta wave (slurred QRS upstroke), shortened PR interval, and widened QRS due to ventricular pre-excitation via an accessory pathway.
Question 6: On a rhythm strip you identify P waves occurring at a rate of 70 bpm and QRS complexes occurring independently at 35 bpm with no consistent relationship between them. What rhythm is this?
- Second-degree AV block Mobitz II
- Accelerated junctional rhythm
- Complete (third-degree) AV block (Correct answer)
- Sinus bradycardia with PVCs
Correct answer: Complete (third-degree) AV block
Complete (third-degree) AV block shows total AV dissociation where P waves and QRS complexes march out independently at different rates.
Question 7: A rhythm shows regularly occurring narrow QRS complexes at 45 bpm with no preceding P waves. What is the most likely escape rhythm?
- Junctional escape rhythm (Correct answer)
- Idioventricular escape rhythm
- Accelerated idioventricular rhythm
- Sinus bradycardia
Correct answer: Junctional escape rhythm
Junctional escape rhythms originate in the AV node or bundle of His, produce narrow QRS complexes, and typically fire at 40–60 bpm when higher pacemakers fail.
DC Dysrhythmia Cardiac Rhythm Interpretation 2
A patient's ECG shows a regular rhythm with a rate of 150 bpm, narrow QRS complexes, and no visible P waves before each QRS.
What is the most likely dysrhythmia?