FCPS TOACS · Long QT Syndrome Mock Test

❓ Q1. Describe the ECG findings.

✅ Model Answer:
• ECG: prolonged QT interval, QTc >0.46 sec (520 ms in this case). Broad-based, notched T waves (LQT2 pattern).
• QTc = QT / √(RR interval) [Bazett formula].
• Normal QTc: <0.44 sec (440 ms) in children, <0.45 sec in adolescents.

❓ Q2. What are the three most common genetic types of LQTS? What are their respective gene mutations and clinical triggers?

✅ Model Answer:
• LQT1 (KCNQ1): Exercise/swimming trigger, broad T waves.
• LQT2 (KCNH2): Auditory/emotion trigger, notched T waves.
• LQT3 (SCN5A): Sleep/rest trigger, long ST segment.
• Jervell and Lange-Nielsen: LQT + deafness (autosomal recessive, KCNQ1/KCNE1).

❓ Q3. What is the Schwartz score? How is it used in the diagnosis of LQTS?

✅ Model Answer:
• Clinical diagnostic tool: points for ECG (QTc >480 ms = 3 pts), syncope (stress = 2 pts), TdP (2 pts), family history of LQTS/SCD (1 pt each).
• ≥4 points: high probability (diagnosis). 3 points: intermediate (consider genetic testing). ≤2 points: low probability.

❓ Q4. This child had syncope. If she developed Torsades de Pointes (TdP) in the ED, what is the acute management?

✅ Model Answer:
• TdP with pulse: IV magnesium 25-50 mg/kg, correct K+ >4.5, stop QT-prolonging drugs, overdrive pacing if bradycardic.
• Pulseless TdP: Defibrillation (2 J/kg → 4 J/kg), CPR, epinephrine, magnesium. Avoid amiodarone (may prolong QT).

❓ Q5. What is the first-line pharmacologic treatment for LQTS? Which beta-blocker is preferred and why?

✅ Model Answer:
• Beta-blockers – reduce sympathetic tone, prevent arrhythmias.
• Preferred: Propranolol (non-selective, good CNS penetration) – especially for LQT1 and LQT2. Nadolol (long-acting) is also effective.
• Dose: Propranolol 1-3 mg/kg/day TID. Nadolol 1-2 mg/kg/day once daily.

❓ Q6. When is an ICD (implantable cardioverter-defibrillator) indicated in a child with LQTS?

✅ Model Answer:
• Cardiac arrest survivors (aborted SCD).
• Recurrent syncope despite optimal beta-blocker therapy.
• High-risk genotypes: LQT3, Jervell and Lange-Nielsen.
• QTc >550 ms (especially in LQT1/LQT2).
• Family history of SCD despite beta-blockers.

❓ Q7. What lifestyle modifications are recommended for a child with LQTS? What activities should be avoided?

✅ Model Answer:
• Avoid: QT-prolonging drugs, competitive swimming (LQT1), loud noises (LQT2), dehydration, electrolyte disturbances.
• Treat fever promptly. Inform school/coaches. Family should learn CPR.

❓ Q8. List common drugs that prolong the QT interval and should be avoided in LQTS patients.

✅ Model Answer:
• Macrolides (erythromycin, clarithromycin), fluoroquinolones (ciprofloxacin), antipsychotics (haloperidol, risperidone), antiarrhythmics (sotalol, quinidine), antidepressants (tricyclics), ondansetron, methadone.
• Use CredibleMeds.org for comprehensive list.

❓ Q9. This child has a maternal grandmother who died suddenly. How would you screen the family for LQTS? What is the role of genetic testing?

✅ Model Answer:
• First-degree relatives: ECG, exercise stress test, Holter, genetic testing (if proband has pathogenic variant).
• Genetic testing: identifies mutation, enables cascade screening. 50% risk for each child (autosomal dominant).

❓ Q10. How do you differentiate cardiac syncope from a seizure in this child?

✅ Model Answer:
• Cardiac syncope: Trigger (exercise/emotion), rapid recovery, no post-ictal confusion. ECG shows prolonged QT.
• Seizure: Tonic-clonic movements, cyanosis, tongue biting, post-ictal confusion. ECG normal.

❓ Q11. How do electrolyte abnormalities affect the QT interval? What is the ECG finding in hypokalemia and hypocalcemia?

✅ Model Answer:
• Hypokalemia: Prolongs QT, prominent U waves, increases TdP risk. Target K+ >4.5.
• Hypocalcemia: Prolongs ST segment (QT prolongation).
• Hyperkalemia: peaked T waves, wide QRS. Hypercalcemia: shortens QT.

❓ Q12. What is Jervell and Lange-Nielsen syndrome? How does it differ from Romano-Ward syndrome?

✅ Model Answer:
• Jervell and Lange-Nielsen (JLN): Autosomal recessive, LQTS + sensorineural deafness (KCNQ1/KCNE1). High risk of SCD – ICD often indicated.
• Romano-Ward: Autosomal dominant, no deafness, less severe.

❓ Q13. What is the long-term prognosis for a child with congenital LQTS?

✅ Model Answer:
• With beta-blockers: risk of SCD reduced from ~50% to <5%.
• Prognosis depends on genotype, QTc length, age at presentation.
• Lifelong follow-up: annual ECG, Holter, exercise test. Psychosocial support important.

⚕️ FCPS MCPS IMM MD Paediatrics TOACS · Mock Test