PALS Tachycardia 2 — Questions and Answers
Question 1: A 4-year-old presents with a heart rate of 200 bpm, narrow QRS complexes, and no P waves visible. The child is alert and playing. What is the most likely rhythm?
- Sinus tachycardia
- Supraventricular tachycardia (SVT) (Correct answer)
- Ventricular tachycardia
- Atrial flutter
Correct answer: Supraventricular tachycardia (SVT)
SVT typically presents with abrupt-onset rates >180-220 bpm, narrow QRS, absent or retrograde P waves, and the child may still be alert if compensated.
Question 2: Which vagal maneuver is most appropriate as a first-line intervention for a stable child with SVT?
- Carotid sinus massage
- Ice water facial immersion
- Valsalva maneuver (Correct answer)
- Ocular pressure
Correct answer: Valsalva maneuver
The Valsalva maneuver (bearing down or blowing through an occluded straw) is safe and commonly used in older children with stable SVT.
Question 3: A 7-year-old with SVT fails two doses of adenosine. The child remains stable with a HR of 220 bpm. What is the next recommended intervention?
- Immediate defibrillation
- Synchronized cardioversion at 0.5-1 J/kg
- Amiodarone 5 mg/kg IV (Correct answer)
- Procainamide infusion
Correct answer: Amiodarone 5 mg/kg IV
After adenosine failure in stable SVT, amiodarone 5 mg/kg IV over 20-60 minutes is a recommended second-line agent in PALS.
Question 4: What is the key ECG feature that distinguishes sinus tachycardia from SVT in an infant?
- QRS duration >0.12 seconds
- Presence of upright P waves before each QRS in leads I and aVF (Correct answer)
- Heart rate exceeding 200 bpm
- ST segment depression
Correct answer: Presence of upright P waves before each QRS in leads I and aVF
In sinus tachycardia, normal upright P waves precede each QRS in leads I and aVF, whereas SVT typically lacks visible or has abnormal P waves.
Question 5: A 2-year-old is brought in with a heart rate of 280 bpm, poor perfusion, and altered mental status. What is the immediate treatment?
- Adenosine 0.1 mg/kg IV push
- Synchronized cardioversion starting at 0.5-1 J/kg (Correct answer)
- Amiodarone 5 mg/kg IV over 20 min
- Vagal maneuvers
Correct answer: Synchronized cardioversion starting at 0.5-1 J/kg
Unstable SVT with hemodynamic compromise requires immediate synchronized cardioversion at 0.5-1 J/kg, escalating to 2 J/kg if needed.
Question 6: Which of the following findings would most strongly suggest that an infant's tachycardia is sinus tachycardia rather than SVT?
- Heart rate of 220 bpm
- Rate variability with activity and crying (Correct answer)
- Absent P waves on ECG
- Abrupt onset reported by caregiver
Correct answer: Rate variability with activity and crying
Sinus tachycardia varies with physiological stressors such as crying, fever, or agitation, while SVT tends to have a fixed, non-varying rate.
Question 7: When using synchronized cardioversion for pediatric SVT, what is the recommended initial energy dose?
- 0.5-1 J/kg (Correct answer)
- 2-4 J/kg
- 5 J/kg
- 10 J/kg
Correct answer: 0.5-1 J/kg
PALS guidelines recommend starting synchronized cardioversion for SVT at 0.5-1 J/kg and increasing to 2 J/kg if the initial dose is ineffective.
PALS Tachycardia 2
A 4-year-old presents with a heart rate of 200 bpm, narrow QRS complexes, and no P waves visible.
The child is alert and playing.
What is the most likely rhythm?