Long QT Syndrome

Key points

• Inherited delayed ventricular repolarisation → VT/collapse/sudden death; LQT1 & LQT2 = alpha subunit of slow delayed rectifier potassium channel.
• Normal QTc < 430 ms (males), < 450 ms (females).
• Congenital: Jervell-Lange-Nielsen (with deafness) · Romano-Ward (no deafness).
• Drug causes: amiodarone, sotalol, class 1a · TCAs, SSRIs (esp. citalopram) · methadone · chloroquine · terfenadine · erythromycin · haloperidol.
• Other causes: hypocalcaemia, hypokalaemia, hypomagnesaemia · acute MI · myocarditis · hypothermia · subarachnoid haemorrhage.
• LQT1: exertional syncope, often swimming. LQT2: syncope after emotional stress/auditory stimuli.

Decision points in this pathway

• Congenital or acquired?

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