A 14-year-old boy collapses during exercise. His ECG shows a prolonged QTc of 520 ms with a broad-based T-wave morphology and no notching. Family history reveals paternal sudden death at age 30. Which genetic channelopathy is most likely?

• A Long QT syndrome type 2 (KCNH2 mutation)
• B Brugada syndrome
• C Long QT syndrome type 1 (KCNQ1 mutation) ✓
• D Catecholaminergic polymorphic ventricular tachycardia (CPVT)

Explanation

LQT1 (caused by loss-of-function mutations in KCNQ1 encoding the slow delayed rectifier potassium channel IKs) characteristically shows a broad-based T wave without notching. Events classically occur during exercise or swimming (adrenergic triggers). LQT2 (KCNH2) shows notched or bifid T waves and events triggered by sudden auditory stimuli. Brugada syndrome shows right bundle branch block pattern with ST elevation in V1–V3, not prolonged QT. CPVT presents with exercise-induced bidirectional or polymorphic VT with a normal resting QT.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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