AKT · Cardiovascular/Arrhythmias & conductionlow yield

Long QT syndrome & channelopathies

Inherited ion-channel dysfunction → abnormal repolarisation (long/short QT, Brugada, CPVT)

Overview

Inherited (or acquired) cardiac ion-channel disorders that predispose to malignant ventricular arrhythmias and sudden cardiac death in structurally normal hearts. Long QT syndrome prolongs repolarisation → torsades; Brugada syndrome shows coved ST elevation in V1–V2 → VF; CPVT causes exercise-induced polymorphic VT. Family history of sudden death is the key clue.

Recognise

Syncope or cardiac arrest, often on exertion, emotion or with arrhythmogenic drugs; family history of young sudden death
Long QT: QTc >450 ms (men)/>470 ms (women); risk of torsades. Acquired causes: drugs (macrolides, antipsychotics, antiarrhythmics), hypokalaemia, hypomagnesaemia
Brugada: coved (type 1) ST elevation in V1–V2; CPVT: bidirectional/polymorphic VT on exercise

Red flags

Documented torsades/VF or aborted sudden death → ICD
QT-prolonging drugs + electrolyte disturbance can precipitate torsades — review the drug chart

Differentials & how to tell them apart

Vasovagal syncopeclear trigger/prodrome, normal QTc, no family history of sudden death

Epilepsypost-ictal phase, tongue-biting — but cardiac syncope can mimic seizures

Structural heart disease (HCM, ARVC)abnormal echo/cardiac MRI — channelopathy hearts are structurally normal

Torsades de pointes — polymorphic VT with a twisting axis (rhythm strip)
CardioNetworks ECGpedia / CC BY-SA 3.0 — Wikimedia Commons

Investigations

12-lead ECG with QTc measurement; provocation/genetic testing; electrolytes (K, Mg, Ca); ajmaline/flecainide challenge for Brugada; exercise testing for CPVT; family screening and cascade genetic testing.

Management

Beta-blocker + avoid QT-prolonging drugs/triggers; ICD for high risk

1Confirm with ECG (QTc, Brugada pattern) ± provocation/genetic testing; correct electrolytes and stop QT-prolonging drugs (acquired long QT).Gate: Aborted sudden death or documented sustained ventricular arrhythmia → ICD, not drugs alone.
2Beta-blocker for long QT/CPVT; genotype-specific trigger avoidance; family (cascade) screening of first-degree relatives.

Beta-blocker (long QT, CPVT) — first-line; reduces arrhythmic events

Avoid QT-prolonging drugs; correct K/Mg — give patients a list of drugs to avoid; treat acquired long QT by removing the cause

ICD — for survivors of cardiac arrest or high-risk patients

Avoid triggers (exercise/swimming in LQT1, fever/Na-channel-blockers in Brugada) — lifestyle and trigger avoidance is genotype-specific

Key points

Exertional/emotional syncope or young sudden death in the family with a structurally normal heart = channelopathy. Long QT → torsades (beta-blocker, avoid QT drugs); Brugada → coved ST in V1–V2 (avoid fever/Na-channel blockers). High risk → ICD.

Monitor & prognosis

Serial QTc, device checks, family screening; drug-avoidance counselling.

Good with beta-blockade/ICD and trigger avoidance; untreated carries sudden-death risk.

Source: ESC/NICE; cardiac genetics services