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Long QT Syndrome

8 genes / 24 genes

Long QT syndrome is a genetic disease associated with abnormal cardiac ion channel function, which manifests itself through the lengthening of the QT interval on the electrocardiogram. This abnormality predisposes to the development of ventricular arrhythmias that can lead to syncope, cardiac arrest, and sudden death; these can be the first manifestations of the disease at any age. The estimated prevalence of the disease is 1/2,000, affecting individuals of different ethnicities. The transmission pattern is generally autosomal dominant, with the recessive form of the disease being much rarer (Jervell and Lange-Nielsen syndrome, where it is associated with neurosensorial loss of hearing).

LongQTSyndrome Long QT Syndrome
Patients with diagnosed long QT syndrome (Schwartz score >3 or QTc >500 ms).Patients under clinical suspicion of long QT syndrome:

  • Asymptomatic subjects with serial ECGs showing QTc values >460 ms (prepubescent) or >480 ms (adults).
  • Subjects with a personal or family history of sudden death.
  • Subjects with a history of syncope of unknown origin.
  • Subjects with ventricular fibrillation of unknown origin.

Relatives of patients with genetic diagnosis of long QT syndrome.

  • HRS/EHRA/APHRS expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromes: document endorsed by HRS, EHRA, and APHRS in May 2013 and by ACCF, AHA, PACES, and AEPC in June 2013.
  • Priori SG et al. Heart Rhythm. 2013 Dec;10(12):1932-63.
  • HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies: this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Ackerman MJ, Priori SG, et al. Europace. 2011 Aug;13(8):1077-109.
  • Recommendations for the use of genetic testing in the clinical evaluation of inherited cardiac arrhythmias associated with sudden cardiac death: Canadian Cardiovascular Society/Canadian Heart Rhythm Society joint position paper. Gollob MH et al, Can J Cardiol. 2011 Mar-Apr;27(2):232-45.
  • Clinical utility gene card for: long-QT syndrome (types 1-13). Beckmann BM1, Wilde AA, Kääb S.et al. Eur J Hum Genet. 2013 Oct;21(10).
  • Genetic testing for long QT syndrome and the category of cardiac ion channelopathies. Modell SM, Bradley DJ, Lehmann MH. PLoS Curr. 2012 May 3.
The yield of genetic testing in correctly characterized subjects is approximately 75%-80%. The clinical specificity of the test is close to 95%. The positive clinical predictive value (possibility of carriers developing the disease throughout their life) depends on the identified variant, with an average of 60%. Around 5% of cases can be carriers of more than one variant in the same or different genes.

Long QT Syndrome Panel

8 genes

This panel includes the genes where most mutations with clinically proven association responsible for long QT syndrome are identified.

KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, KCNJ2, CACNA1C, RYR2

Long QT Syndrome Extended Panel

24 genes

This panel includes priority genes that are most frequently associated with the development of long QT syndrome. It also includes secondary genes associated with this entity, although with a lower level of evidence, as well as candidate genes of which only functional evidence of association exists.

It is indicated in those cases where an unequivocal clinical diagnosis of long QT syndrome exists and no mutations were identified by the 8-gene panel. This allows identifying variants potentially associated with the phenotype in those genes where the responsible mutations are less prevalent.

It should be considered as a first approach when an exhaustive genetic study of this pathology is intended, since this is the most complete panel on the market. The extended study can also be useful in families under suspicion of complex genotypes, with an important variability in phenotypic expression among its members.

KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, KCNJ2, CACNA1C, AKAP9, ANK2, CALM1, CALM2, CAV3, KCNJ5, RYR2, SCN4B, SNTA1, TRDN, FHL2*, HCN4*, KCNA5*, KCND3*, KCNE1L*, KCNE3*, SCN1B*

Notes on Genes

Priority Genes: These genes include >70% of the mutations that have been previously associated with the development of hypertrophic cardiomyopathy and/or their testing is recommended by the guidelines. Secondary genes: Other genes related to the disease. *Candidate genes: With no evidence, but likely to be related to the phenotype.