ECG ECG Rhythm Interpretation 3 — Questions and Answers
Question 1: A PR interval that is consistently prolonged beyond 0.20 seconds but every P wave conducts to a QRS indicates which rhythm?
- First-degree AV block (Correct answer)
- Second-degree AV block Type I
- Third-degree AV block
- Normal sinus rhythm
Correct answer: First-degree AV block
A fixed, prolonged PR interval with every beat conducting defines first-degree AV block.
Question 2: A rhythm shows progressive PR interval lengthening until a QRS is dropped, then the cycle repeats. This describes which block?
- Second-degree AV block Type I (Wenckebach) (Correct answer)
- First-degree AV block
- Second-degree AV block Type II
- Third-degree AV block
Correct answer: Second-degree AV block Type I (Wenckebach)
Progressive PR lengthening followed by a dropped beat is the pattern of Mobitz I (Wenckebach).
Question 3: In third-degree (complete) AV block, what is the relationship between P waves and QRS complexes?
- They are completely independent of each other (Correct answer)
- Every P wave conducts to a QRS
- PR interval progressively lengthens
- P waves are absent
Correct answer: They are completely independent of each other
In complete heart block the atria and ventricles beat independently, so P waves and QRS complexes have no fixed relationship.
Question 4: A premature, wide, bizarre QRS complex that occurs earlier than expected with no preceding P wave is called what?
- Premature ventricular contraction (PVC) (Correct answer)
- Premature atrial contraction (PAC)
- Junctional escape beat
- Sinus pause
Correct answer: Premature ventricular contraction (PVC)
A wide, early QRS without a preceding P wave is a premature ventricular contraction.
Question 5: Second-degree AV block Type II (Mobitz II) is characterized by what pattern?
- Constant PR interval with intermittent dropped QRS complexes (Correct answer)
- Progressive PR lengthening then a dropped beat
- Complete AV dissociation
- Prolonged PR with all beats conducting
Correct answer: Constant PR interval with intermittent dropped QRS complexes
Mobitz II shows a fixed PR interval with sudden non-conducted P waves and dropped QRS complexes.
Question 6: A junctional rhythm arising from the AV node typically produces which finding?
- Inverted or absent P waves with a rate of 40-60 bpm (Correct answer)
- Upright P waves at 100 bpm
- Sawtooth flutter waves
- Wide QRS at 180 bpm
Correct answer: Inverted or absent P waves with a rate of 40-60 bpm
Junctional rhythms arise near the AV node, causing inverted or absent P waves at a rate of about 40-60 bpm.
Question 7: Three or more PVCs in a row at a rate over 100 bpm should be identified as what?
- Ventricular tachycardia (Correct answer)
- Atrial flutter
- Sinus tachycardia
- Bigeminy
Correct answer: Ventricular tachycardia
A run of three or more consecutive PVCs above 100 bpm meets the definition of ventricular tachycardia.
ECG ECG Rhythm Interpretation 3
A PR interval that is consistently prolonged beyond 0.20 seconds but every P wave conducts to a QRS indicates which rhythm?