Definition
LQTS is characterized by QT prolongation on the ECG, increased propensity to develop recurrent syncope, seizures and ventricular arrhythmia of torsades de pointes conferring higher risk of sudden cardiac death (SCD) in individuals with structurally normal heart. The prevalence of the disease is 1:2000 individuals. The diagnosis of LQTS relies on symptoms, QT duration on 12-lead ECG, clinical and family history and genetic testing. Currently, QTc values >470 ms in men and >480 ms in women are considered abnormal in the absence of secondary causes of QT prolongation. LQTS is an ion channel disorder 3 major ion currents have been implicated: IKR, IKS and INa.
See here the Schwartz Score to diagnose LQTS
Why to perform genetic testing in cases with LQTS?
- To confirm the diagnosis
- To select better farmacological treatment, since LQTS type 3 cases might benefit from sodium channel blockers
- To better perform risk stratification since mutation location matters
- To detect family members at risk who may need treatment with betablockers despite being asymptomatic
Our LQTS genetic test panel
LQTS Core-Panel
KCNQ1, KCNH2, SCN5A, CALM1, CALM2, CALM3.
LQTS broad Panel
CACNA1C, CAV3, CALM1, CALM2, CALM3, KCNE1, KCNE2, KCNH2, KCNJ2, KCNQ1, RYR2, SCN5A, TRDN.
Important: All our panels can be modified based on the phenotype. Please contact us if you have questions
What to expect from this test: The LQTS genetic test has a yield of 60-70%
Recommended Literature
- SCN5A mutations in 442 neonates and children: genotype-phenotype correlation and identification of higher-risk subgroups. Baruteau AE, et al. Eur Heart J. 2018 Aug 14;39(31):2879-2887. doi: 10.1093/eurheartj/ehy412.
- Interplay Between Genetic Substrate, QTc Duration, and Arrhythmia Risk in Patients With Long QT Syndrome. Mazzanti A, et al. J Am Coll Cardiol. 2018 Apr 17;71(15):1663-1671. doi: 10.1016/j.jacc.2018.01.078.
- Genetic risk stratification in cardiac arrhythmias. Napolitano C, et al. Curr Opin Cardiol. 2018 May;33(3):298-303. doi: 10.1097/HCO.0000000000000506.
- Emerging Implications of Genetic Testing in Inherited Primary Arrhythmia Syndromes. Asatryan B, Medeiros-Domingo A. Cardiol Rev. 2019 Jan/Feb;27(1):23-33. doi: 10.1097/CRD.0000000000000203.
Download here interesting open access manuscripts on genetics of LQTS