This is a genotype with recommended actions if clinically confirmed. In brief:
- Arrhythmias may be triggered by certain factors depending on which of the 3 genes carry a mutation; physical or emotional stress for KCNQ1 gene mutations (the LQT1 condition), at rest, during emotional stress or with sudden noises for KCNH2 mutations (LQT2), and at rest or during sleep for SCN5A mutations (LQT3).
- LQT3 patients have the highest risk for cardiac events, compared to LQT1 and LQT2. A normal QT interval provides a good prognosis, while a QT interval exceeding 500ms provides the highest risk of symptoms. Risk of sudden cardiac death (SCD) is also increased during the immediate post-partum period, particularly in women with LQT2.
- Beta blockade should be initiated in those who have had symptoms, those with a definite long QT interval, and in those with a positive genetic diagnosis but a normal QT interval.
- Implantation with a cardioverter defibrillator (ICD) along with continued use of beta blockers can be effective in reducing SCD in LQTS patients. Family members who have not been excluded for LQTS should avoid medications contra-indicated in LQTS, beta blockers should be proposed, and sensible limitations should be placed on sporting activities.
- Among at least 5 categories of "circumstances to avoid" are competitive sports activities and drugs known to prolong the QT interval or deplete potassium and magnesium; see the full report (URL below) for other activities that are not recommended.
- First degree relatives of patients with LQTS should undergo an ECG to determine QT interval and genetic testing.
The full ClinGen Actionability report about the three forms of Romano-Ward Long QT Syndrome (LQTS) can be found here.
Genetic counseling may be available to you through your health-care network. In the US, genetic counselors may be found via this webpage of the National Society of Genetic Counselors.