DC Dysrhythmia ECG Monitoring & Analysis 3 — Questions and Answers
Question 1: On a standard ECG, each small box on the horizontal axis represents how much time at standard paper speed?
- 0.04 seconds (Correct answer)
- 0.10 seconds
- 0.20 seconds
- 0.40 seconds
Correct answer: 0.04 seconds
At the standard paper speed of 25 mm/second, each small (1 mm) box on the horizontal axis equals 0.04 seconds.
Question 2: A patient's rhythm strip shows sawtooth flutter waves at 300 bpm with a ventricular rate of 75 bpm. What AV conduction ratio is present?
- 2:1
- 3:1
- 4:1 (Correct answer)
- 6:1
Correct answer: 4:1
An atrial rate of 300 bpm with a ventricular rate of 75 bpm yields a 4:1 conduction ratio (300 ÷ 75 = 4).
Question 3: Which of the following is the MOST dangerous complication associated with an uncorrected prolonged QT interval?
- Atrial fibrillation
- Torsades de pointes (Correct answer)
- Accelerated junctional rhythm
- Sinus bradycardia
Correct answer: Torsades de pointes
Torsades de pointes, a polymorphic ventricular tachycardia, is the life-threatening dysrhythmia directly associated with prolonged QT intervals.
Question 4: An ECG strip shows wide QRS complexes (0.14 sec) with a right bundle branch block pattern and no visible P waves. The rate is 42 bpm. This most likely represents:
- Idioventricular rhythm (Correct answer)
- Junctional bradycardia
- Accelerated idioventricular rhythm
- Sinus bradycardia with bundle branch block
Correct answer: Idioventricular rhythm
A ventricular escape rhythm at 20–40 bpm with wide bizarre QRS complexes and absent P waves is characteristic of idioventricular rhythm.
Question 5: When analyzing a 6-second rhythm strip, you count 9 QRS complexes. What is the approximate heart rate?
- 54 bpm
- 90 bpm (Correct answer)
- 108 bpm
- 72 bpm
Correct answer: 90 bpm
Multiplying the number of complexes in 6 seconds by 10 gives the rate: 9 × 10 = 90 bpm.
Question 6: Capture beats in a wide-complex tachycardia are significant ECG findings because they confirm:
- Ventricular origin of the tachycardia (Correct answer)
- Supraventricular origin with aberrancy
- Hyperkalemia-induced conduction change
- Pacemaker malfunction
Correct answer: Ventricular origin of the tachycardia
Capture beats are narrow QRS complexes that occur during wide-complex tachycardia when a supraventricular impulse briefly captures the ventricles, confirming AV dissociation and ventricular tachycardia.
Question 7: A monitored patient develops sudden onset of a regular narrow-complex tachycardia at 180 bpm with no visible P waves. The MOST likely diagnosis is:
- Sinus tachycardia
- Atrial flutter with 2:1 block
- AV nodal reentrant tachycardia (AVNRT) (Correct answer)
- Multifocal atrial tachycardia
Correct answer: AV nodal reentrant tachycardia (AVNRT)
Sudden-onset regular narrow-complex tachycardia at 150–250 bpm with no visible P waves is the classic presentation of AVNRT.
DC Dysrhythmia ECG Monitoring & Analysis 3
On a standard ECG, each small box on the horizontal axis represents how much time at standard paper speed?