Electrophysiology Questions - Set 1¶
Question 1¶
A 2-month-old with SVT is found to have WPW on baseline ECG. Which medication is CONTRAINDICATED for chronic prophylaxis?
A) Propranolol B) Flecainide C) Digoxin D) Amiodarone E) Sotalol
Answer
**Correct Answer: C** **Digoxin is contraindicated in WPW** because: - Slows AV node conduction - May accelerate accessory pathway conduction - In atrial fibrillation: can cause VF - Risk of rapid conduction down bypass tract **Board Pearl:** WPW + Digoxin = contraindicated (accelerates pathway conduction)Question 2¶
What is the first-line medication for CPVT prophylaxis?
A) Mexiletine B) Flecainide C) Nadolol D) Verapamil E) Amiodarone
Answer
**Correct Answer: C** **Non-selective beta-blockers** (nadolol) are first-line for CPVT: - Block catecholamine-triggered arrhythmias - Nadolol preferred (long-acting, once daily) - Add flecainide if breakthrough events - Exercise restriction regardless **Board Pearl:** CPVT = nadolol first-line; add flecainide if neededQuestion 3¶
Which Long QT syndrome genotype responds best to beta-blocker therapy?
A) LQT1 B) LQT2 C) LQT3 D) LQT7 E) LQT8
Answer
**Correct Answer: A** **LQT1** (KCNQ1 potassium channel): - Events triggered by adrenergic surge - Beta-blockers most effective (reduce events by 90%+) - Swimming particularly dangerous - Avoid sympathetic triggers **Board Pearl:** LQT1 = best response to beta-blockers; swimming is high-risk triggerQuestion 4¶
A newborn has complete heart block with ventricular rate of 45 bpm and wide QRS escape. Echocardiogram is normal. Mother has positive anti-Ro antibodies. What is the next step?
A) Observation with close monitoring B) Isoproterenol drip C) Temporary pacing and plan for permanent pacemaker D) IVIG administration E) Atropine bolus
Answer
**Correct Answer: C** Pacemaker indications in congenital CHB: - Rate <55 bpm (or <70 with CHD) - Wide QRS escape rhythm - Ventricular dysfunction - Symptoms This baby has rate 45 AND wide QRS = **pacemaker indicated** **Board Pearl:** CCHB + rate <55 or wide QRS = pacemaker indicatedQuestion 5¶
What is the typical ventricular rate during SVT in a neonate?
A) 150-180 bpm B) 180-220 bpm C) 220-280 bpm D) 280-320 bpm E) Variable, depending on pathway
Answer
**Correct Answer: C** Neonatal SVT typically has rates of **220-280 bpm** (some up to 300): - Higher than older children/adults - Short refractory periods in infants - Rate >220 helps distinguish from sinus tachycardia **Board Pearl:** Neonatal SVT rate = 220-280 bpm typicallyQuestion 6¶
A 15-year-old collapses during basketball. Rhythm strip shows polymorphic VT. ECG after resuscitation shows normal QTc and no structural heart disease on echo. What diagnosis should be suspected?
A) Long QT syndrome B) Brugada syndrome C) CPVT D) Hypertrophic cardiomyopathy E) Commotio cordis
Answer
**Correct Answer: C** **CPVT**: - Exercise-induced polymorphic VT - **Normal resting ECG and echo** - Diagnose with exercise stress test - RyR2 or CASQ2 mutations Normal QTc rules out LQTS; no structural disease rules out HCM. **Board Pearl:** Normal resting ECG + exercise-induced polymorphic VT = CPVTQuestion 7¶
What is the mechanism of adenosine in terminating SVT?
A) Blocks accessory pathway conduction B) Blocks AV nodal conduction C) Slows sinus node automaticity D) Increases vagal tone E) Blocks atrial conduction
Answer
**Correct Answer: B** Adenosine causes **transient AV nodal block**: - Breaks reentrant circuit involving AV node - Does NOT block accessory pathways directly - Very short half-life (~10 seconds) - May unmask WPW pattern after conversion **Board Pearl:** Adenosine = AV nodal block; doesn't affect accessory pathwaysQuestion 8¶
A child has frequent PACs with some blocked (non-conducted). Parents are concerned. What is the appropriate management?
A) Electrophysiology study B) Start propranolol C) Holter monitor for quantification D) Reassurance - benign finding E) Echocardiogram to rule out structural disease
Answer
**Correct Answer: D** Frequent PACs in children are **benign**: - Very common, especially in neonates - Usually resolve spontaneously - No treatment needed - Echo only if structural disease suspected for other reasons **Board Pearl:** PACs in children = benign; reassurance is appropriateQuestion 9¶
Which ECG finding is most specific for Brugada syndrome?
A) Type 1 coved ST elevation in V1-V2 B) Type 2 saddleback ST elevation in V1-V2 C) Epsilon waves in V1-V3 D) Early repolarization in inferior leads E) T-wave alternans
Answer
**Correct Answer: A** **Type 1 coved pattern** is the ONLY diagnostic pattern: - ≥2mm coved ST elevation in V1-V2 - Followed by T-wave inversion - Can be spontaneous or drug-induced - Type 2 (saddleback) requires provocation to confirm **Board Pearl:** Brugada = Type 1 coved ST only is diagnostic; Type 2 needs provocationQuestion 10¶
What is the appropriate ICD programming strategy in a child to minimize inappropriate shocks?
A) Low detection rate, short detection time B) High detection rate, long detection time C) Only VF zone, no VT zone D) ATP disabled, shocks only E) Maximum output for all therapies