Long QT Syndrome

Prevalence of cLQTS: Approximately 1:5000 live births.

Incidence of cLQTS: 1 in 10,000.

60–70% of those diagnosed are females.

Males under 10 y of age have the highest mortality.

Pts usually present in childhood with a cardiac event.

Torsades de pointes

Sudden cardiac death

Sympathetic stimulation with laryngoscopy, pain, etc.

Electrolyte abnormalities: hypokalemia, hypocalcemia, and hypomagnesemia

cLQTS is diagnosed when the corrected QT interval is >500 ms in the absence of other causes

Jervell and Lange-Nielsen syndrome is cLQTS associated with deafness; Romano-Ward syndrome is cLQTS without deafness

aLTQS is most commonly drug induced or caused by an electrolyte abnormality

Pathophysiology: Arrhythmogenic prolongation of the QT interval caused by mutated genes encoding the cardiac myocyte ion channels

Most common gene mutations: LQT1, LQT2, and LQT3.

aLTQS primarily prolongs the QT interval by blockade of the rapid delayed I _Kr , encoded by HERG.

Drug-induced: succinylcholine, ketamine, atropine, quinolone and macrolide antibiotics, dexmedetomidine, and ondansetron.