CCI ECG Rhythm Interpretation 3 — Questions and Answers
Question 1: A rhythm strip shows irregularly irregular narrow QRS complexes with no discernible P waves and a wavy baseline. What is the diagnosis?
- Atrial fibrillation (Correct answer)
- Multifocal atrial tachycardia
- Atrial flutter
- Junctional tachycardia
Correct answer: Atrial fibrillation
Atrial fibrillation produces an irregularly irregular ventricular response, absent organized P waves, and a fibrillatory baseline.
Question 2: What is the normal duration of the QRS complex in adults?
- 0.06–0.10 seconds (Correct answer)
- 0.12–0.20 seconds
- 0.20–0.28 seconds
- 0.04–0.06 seconds
Correct answer: 0.06–0.10 seconds
A normal QRS complex measures 0.06–0.10 seconds (60–100 ms); a duration ≥0.12 seconds is considered abnormally wide.
Question 3: Which lead is best used to identify P wave morphology and distinguish atrial rhythms?
- Lead II (Correct answer)
- Lead aVR
- Lead V1
- Lead aVL
Correct answer: Lead II
Lead II is parallel to the normal P wave vector, making P waves most upright and prominent, ideal for rhythm analysis.
Question 4: A patient's ECG shows a rhythm at 40 bpm with wide QRS complexes and no associated P waves. What rhythm is this?
- Idioventricular rhythm (Correct answer)
- Junctional escape rhythm
- Accelerated junctional rhythm
- Third-degree AV block with junctional escape
Correct answer: Idioventricular rhythm
An idioventricular (ventricular escape) rhythm originates in the ventricles at 20–40 bpm with wide, bizarre QRS complexes and no P wave relationship.
Question 5: Torsades de pointes is most commonly associated with which ECG finding?
- Prolonged QT interval (Correct answer)
- Shortened PR interval
- Wide QRS with delta waves
- ST elevation in multiple leads
Correct answer: Prolonged QT interval
Torsades de pointes is a polymorphic ventricular tachycardia that occurs in the setting of a prolonged QT interval, which predisposes to triggered activity.
Question 6: In a patient with right bundle branch block (RBBB), which lead typically shows the classic RSR' (rabbit ears) pattern?
- V1 (Correct answer)
- V5
- Lead I
- aVF
Correct answer: V1
RBBB produces a wide QRS with a characteristic RSR' (M-shaped or 'rabbit ear') pattern in lead V1 due to delayed right ventricular activation.
Question 7: What is the maximum allowable QTc interval considered normal in women?
- ≤460 ms (Correct answer)
- ≤440 ms
- ≤500 ms
- ≤420 ms
Correct answer: ≤460 ms
A corrected QT interval (QTc) >460 ms in women is considered prolonged; women have a naturally longer QTc than men (men: >440 ms).
CCI ECG Rhythm Interpretation 3
A rhythm strip shows irregularly irregular narrow QRS complexes with no discernible P waves and a wavy baseline.
What is the diagnosis?