Electrophysiology Questions - Set 2¶
Question 1¶
An infant with SVT is refractory to adenosine and cardioversion. What medication should be considered next?
A) Verapamil IV B) Digoxin IV loading C) Amiodarone IV D) Lidocaine IV E) Magnesium sulfate
Answer
**Correct Answer: C** **IV Amiodarone** for refractory SVT: - 5 mg/kg IV loading dose - Effective for most SVT mechanisms - Caution: hypotension, bradycardia - Avoid IV verapamil in infants (cardiovascular collapse) **Board Pearl:** Refractory SVT in infant = IV amiodarone; AVOID IV verapamil (dangerous)Question 2¶
A patient with Timothy syndrome (LQT8) would be expected to have which associated finding?
A) Deafness B) Syndactyly C) Marfanoid habitus D) Facial dysmorphism of Noonan syndrome E) Hyperkalemia
Answer
**Correct Answer: B** **Timothy syndrome (LQT8)**: - CACNA1C calcium channel mutation - **Syndactyly** (webbed fingers) - Autism spectrum features - Hypoglycemia - Immune dysfunction - Very high SCD risk **Board Pearl:** LQT8/Timothy syndrome = syndactyly + autism + LQTSQuestion 3¶
What is the most common mechanism of SVT in infants?
A) Atrial flutter B) AV nodal reentrant tachycardia (AVNRT) C) Accessory pathway-mediated reentry (AVRT) D) Automatic atrial tachycardia E) Junctional ectopic tachycardia
Answer
**Correct Answer: C** **AVRT** (accessory pathway) is most common in infants: - ~90% of infant SVT - Often WPW pattern on ECG - AVNRT becomes more common in older children/adolescents **Board Pearl:** Infant SVT = AVRT usually; AVNRT more common in teensQuestion 4¶
Which arrhythmia is most concerning for hemodynamic instability in a post-operative Fontan patient?
A) Sinus bradycardia B) Premature ventricular contractions C) Atrial flutter with 2:1 conduction D) First-degree AV block E) Junctional rhythm
Answer
**Correct Answer: C** **Atrial flutter in Fontan**: - Loss of AV synchrony devastating in preload-dependent circulation - Rapid ventricular response poorly tolerated - May cause acute hemodynamic collapse - Requires urgent cardioversion **Board Pearl:** Fontan + atrial flutter = hemodynamic emergencyQuestion 5¶
What is the characteristic arrhythmia trigger in LQT2?
A) Swimming B) Exercise C) Auditory stimuli (alarm clock, phone) D) Sleep E) Fever
Answer
**Correct Answer: C** **LQT2 triggers = auditory/emotional**: - Alarm clocks, phone ringing, sudden noises - Emotional stress - Postpartum period - Female sex is higher risk Avoid alarm clocks, use gentle wake-up methods. **Board Pearl:** LQT2 = auditory triggers; avoid alarm clocksQuestion 6¶
A newborn with hydrops fetalis is found to have SVT at rate 280 bpm. Atrial rate and ventricular rate are 1:1. What is the most likely mechanism?
A) Atrial flutter with variable block B) Accessory pathway-mediated tachycardia C) Sinus tachycardia with sepsis D) Chaotic atrial tachycardia E) AVNRT
Answer
**Correct Answer: B** **Fetal/neonatal SVT causing hydrops** is typically AVRT: - 1:1 AV relationship - Sustained rapid rate causes heart failure - Accessory pathway most common mechanism in this age - Treatment urgency high **Board Pearl:** Fetal hydrops + SVT = usually accessory pathway (AVRT)Question 7¶
What is the maximum dose of adenosine for SVT termination?
A) 0.1 mg/kg B) 0.2 mg/kg C) 0.3 mg/kg or 12 mg (whichever is less) D) 0.5 mg/kg E) No maximum in refractory cases
Answer
**Correct Answer: C** Adenosine dosing: - First: 0.1 mg/kg - Second: 0.2 mg/kg - Third: **0.3 mg/kg (max 12 mg)** Given rapid IV push with flush. **Board Pearl:** Adenosine max = 0.3 mg/kg or 12 mgQuestion 8¶
A 16-year-old with palpitations has a delta wave on ECG. EP study shows anterograde ERP of the pathway is 250 ms. What does this suggest?
A) Low risk - observation appropriate B) High risk - ablation recommended C) Need for pharmacological testing D) ICD indicated E) Incomplete evaluation
Answer
**Correct Answer: B** ERP ≤250 ms = **higher risk accessory pathway**: - Short refractory period = fast conduction - If AF develops, could have rapid ventricular response - Ablation recommended for pathways with ERP ≤250 ms **Board Pearl:** WPW pathway ERP ≤250 ms = higher risk, ablation recommendedQuestion 9¶
Post-operative junctional ectopic tachycardia (JET) is most commonly seen after repair of which lesion?
A) VSD B) TOF C) d-TGA (arterial switch) D) AVSD E) Coarctation
Answer
**Correct Answer: B** **JET most common after TOF and AVSD repair**: - Surgery near AV node/His bundle - Usually transient (48-72 hours) - Treat by cooling, minimizing inotropes, amiodarone if needed **Board Pearl:** Post-op JET = common after TOF/AVSD repair; near AV node surgeryQuestion 10¶
What is the appropriate rate cutoff for considering ICD therapy in congenital complete heart block?
A) <40 bpm B) <55 bpm C) <70 bpm D) <80 bpm E) Any rate with symptoms