Long QT syndrome (extended panel) [36 genes]

Long QT syndrome is a genetic disease associated with the abnormal functioning of ion channels located in the membranes of cardiac cells, which is manifested by the prolongation of the QT interval in the electrocardiogram, sometimes associated with abnormalities in the T wave. Prevalence in the general population is at least 1 / 2,500 individuals. This abnormality predisposes to the development of ventricular arrhythmias that can manifest as syncope, cardiac arrest, and sudden death, these being the first signs of the disease at any age. In many cases, the disease manifests itself during childhood and adolescence, with a high mortality among index cases (50% after 10 years without treatment). The inheritance pattern is generally autosomal dominant, with recessive forms being much rarer, some of which are associated with neurosensory deafness (Jervell and Lange-Nielsen Syndrome) or neuromuscular alterations (Triadina Knock-out syndrome).

The estimated prevalence of the disease is at least 1 / 2,500 individuals in the general population.

The result of the genetic study in long QT syndrome has diagnostic, prognostic, and therapeutic implications. Detecting a pathogenic genetic variant is a diagnostic criterion, and the test can be used with predictive value for disease. Relatives of an index case with a confirmed diagnosis may present asymptomatic, with a normal QTc interval and still be exposed to a malignant arrhythmic event in certain situations. In these cases, the genetic study allows us to detect at-risk carriers who must have an adequate clinical follow-up, lifestyle recommendations, and treatment. On the other hand, the genetic study determines the long QT subtype and this has repercussions on the prognosis and therapeutic decisions.

Performing a genetic study is indicated in patients diagnosed with long QT syndrome. The main international clinical recommendation guidelines recommend it with a level of evidence I.
The genetic study is indicated in:
– Patients with a diagnosis of long QT syndrome:
  • Patients with QTc ≥480ms or risk score >3.
  • Patients with QTc>460ms in the presence of arrhythmic syncope or cardiac arrest.
– Patients with high clinical suspicion of long QT syndrome:
  • Asymptomatic individuals with serial electrocardiograms with QTc values >460ms (prepubertal) or >480ms (adults).
  • Individuals with a personal or family history of sudden death.
  • Individuals with a previous history of syncope of undetermined origin.
  • Individuals with ventricular fibrillation of undetermined origin.
This expanded panel is indicated in cases where the clinical diagnosis of long QT syndrome is clearly established and no pathogenic variants have been identified in the basic panel. This panel allows identifying variants potentially associated with the phenotype in those genes identified with less frequency.

Genetic study performance: 75-80%.

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Long QT syndrome (extended panel)

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Techniques: Exome, NGS capture panel

Turnaround time (TAT): 25 days

Ref. S-201906403

Long QT syndrome (extended panel): View panel

This panel includes the genes in which most of the pathogenic variants responsible for long QT syndrome are identified. It also includes secondary genes that have been associated with this entity, although with less evidence, and candidate genes for which there is only functional evidence.

  • CACNA1C
  • CALM1
  • CALM2
  • CALM3
  • KCNE1
  • KCNE2
  • KCNH2
  • KCNJ2
  • KCNQ1
  • SCN5A
  • AKAP9
  • ALPK3
  • ANK2
  • CAV3
  • KCNJ5
  • NAA10
  • RYR2
  • SCN4B
  • SLC22A5
  • TECRL
  • TRDN
  • CAVIN1*
  • FHL2*
  • HCN4*
  • KCNA5*
  • KCND2*
  • KCND3*
  • KCNE3*
  • KCNE5*
  • NOS1AP*
  • RNF207*
  • SCN1B*
  • SCN3B*
  • SCN4A*
  • SNTA1*
  • TRPM4*

Priority Genes : Genes where there is sufficient evidence (clinical and functional) to consider them associated with the disease; they are included in the clinical practice guidelines.
Secondary Genes: Genes related to the disease, but with a lower level of evidence or that constitute sporadic cases.
* Candidate Genes: Not enough evidence in humans, but potentially associated with the disease.

Related panels
Arrhythmias and sudden death without structural cardiopathy general panel [100 genes]

Panel that include long QT syndrome genes

Cardiomyopathies, arrhythmias and sudden death general panel [288 genes]

Panel that include long QT syndrome genes

References

  1. Wilde AM, Semsarian C, Márquez MF, et al. European Heart Rhythm Association (EHRA)/Heart Rhythm Society (HRS)/Asia Pacific Heart Rhythm Society (APHRS)/Latin American Heart Rhythm Society (LAHRS) Expert Consensus Statement on the State of Genetic Testing for Cardiac Diseases. Heart Rhythm.2022;19(7):e1-e60. doi: 10.1016/j.hrthm.2022.03.1225. PMID: 35390533.
  2. Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2022;43(40):3997-4126. PMID: 36017572.