Original Article
Guidelines for the Diagnosis and Management of Familial Long QT Syndrome

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Definition and Prevalence

Long QT syndrome (LQTS) is a familial condition causing syncope and sudden death through rapid ventricular tachycardia (torsade de pointes), which can deteriorate to ventricular fibrillation, in otherwise fit and healthy young people. Prevalence is at least 1 in 5000 and may be up to 1 in 1000. Clinical diagnosis is made from a combination of suspicious history, family history and the 12 lead ECG, which typically reveals a heart-rate corrected QT interval (QT//R–R interval = QTc) of greater than

Familial LQTS Disease Genes

LQTS is most commonly inherited in an autosomal dominant manner. Thus, each child of an affected parent has a 50% chance of inheriting a disease-causing gene mutation. Eight genetic forms of LQTS are known where in most a dysfunctional cardiac cell channel results in prolongation of the cardiac action potential, and thus the QT interval (Table 1). About one third of families with LQTS do not yet have a recognised genetic locus. The commonest genotypes are types 1 and 2; about 8% are type 3.

Genetic Screening

The

REMOVAL OF TRIGGERS

All gene carriers must avoid medications which prolong the QT interval, can cause torsade de pointes or lower serum potassium levels. A constantly updated list is available at www.qtdrugs.org (list 3).

With all forms of LQTS some degree of limitation in sporting activity is required. The limitation needs to be more severe with LQT1, or those who have already experienced events during exercise, than LQT2 and 3. They should not become professional athletes and all highly competitive sports are to

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Cited by (19)

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    Citation Excerpt :

    LQTS is characterized by prolonged ventricular repolarization and susceptibility to syncope and SCD through VT (TdP), which can deteriorate into VF [25]. A clinical diagnosis is made from a combination of clinical history, family history, and 12-lead ECG, which typically reveals a heart rate-corrected QT interval (QT interval divided by the square root of the RR interval in seconds=QTc) of greater than 0.46 s in women and 0.45 s in men [25]. LQTS is most commonly inherited in an autosomal dominant fashion and has been associated with mutations in 15 genes.

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