CPEN Cardiac Emergencies 3 — Questions and Answers
Question 1: A 6-year-old presents with syncope during exercise and ECG shows a QTc of 520 ms. Which condition does this suggest?
- Hypertrophic cardiomyopathy
- Long QT syndrome (Correct answer)
- Brugada syndrome
- Complete heart block
Correct answer: Long QT syndrome
A QTc >460 ms in children (>480 ms in adults) indicates long QT syndrome, which predisposes to polymorphic VT (torsades de pointes).
Question 2: A 13-year-old athlete collapses during a game and is found to be in ventricular fibrillation. After one defibrillation attempt, CPR is resumed. What is the next pharmacologic intervention per PALS?
- Lidocaine 1 mg/kg IV
- Epinephrine 0.01 mg/kg IV (Correct answer)
- Amiodarone 5 mg/kg IV
- Magnesium sulfate 25–50 mg/kg IV
Correct answer: Epinephrine 0.01 mg/kg IV
Epinephrine is given every 3–5 minutes during pulseless arrest, starting after the first rhythm check shows persistent shockable or non-shockable rhythm.
Question 3: Torsades de pointes is best treated with:
- Synchronized cardioversion and amiodarone
- Magnesium sulfate IV (Correct answer)
- Adenosine IV push
- Verapamil IV
Correct answer: Magnesium sulfate IV
IV magnesium sulfate (25–50 mg/kg) is the treatment of choice for torsades de pointes, shortening the QT and stabilizing the membrane.
Question 4: Which electrolyte abnormality is MOST likely to precipitate ventricular arrhythmias in a pediatric patient?
- Hypernatremia
- Hypocalcemia
- Hypokalemia (Correct answer)
- Hypermagnesemia
Correct answer: Hypokalemia
Hypokalemia prolongs the QT interval and increases myocardial excitability, predisposing to ventricular arrhythmias including torsades de pointes.
Question 5: A 2-month-old infant has a resting heart rate of 58 bpm with a wide QRS and no relationship between P waves and QRS complexes. This ECG finding is consistent with:
- First-degree AV block
- Second-degree AV block Mobitz I
- Complete (third-degree) AV block (Correct answer)
- Sinus bradycardia
Correct answer: Complete (third-degree) AV block
Complete AV block shows atrioventricular dissociation: P waves and QRS complexes fire independently with no consistent relationship.
Question 6: Congenital complete heart block in a newborn is most commonly associated with maternal:
- Lupus erythematosus (anti-Ro/La antibodies) (Correct answer)
- Gestational diabetes
- Hypothyroidism
- Group B streptococcal infection
Correct answer: Lupus erythematosus (anti-Ro/La antibodies)
Maternal anti-Ro (SSA) and anti-La (SSB) antibodies cross the placenta and damage the fetal AV node, causing congenital complete heart block.
Question 7: A symptomatic child with complete heart block and a heart rate of 35 bpm should initially be treated with:
- IV atropine 0.02 mg/kg (Correct answer)
- IV adenosine 0.1 mg/kg
- Transcutaneous pacing
- IV amiodarone 5 mg/kg
Correct answer: IV atropine 0.02 mg/kg
Atropine is the first pharmacologic intervention for symptomatic bradycardia with a perfusing rhythm before pacing.
CPEN Cardiac Emergencies 3
A 6-year-old presents with syncope during exercise and ECG shows a QTc of 520 ms.
Which condition does this suggest?