Follow-up of 316 molecularly defined pediatric long-QT syndrome patients: clinical course, treatments, and side effects

Genetic Diagnostics Contribute to the Risk Stratification for Major Arrhythmic Events in Pediatric Patients with Long QT Syndrome Type 1–3

Long QT syndrome (LQTS) is an inherited arrhythmic disorder associated with sudden cardiac death (SCD). This study aimed to identify the clinical and molecular genetic risk factors that contribute to major arrhythmic events (MAEs) in patients with genetically confirmed childhood onset LQTS 1–3. This study was a retrospective double-center study. An MAE was defined as the occurrence of SCD, aborted SCD, appropriate implantable cardioverter defibrillator discharge, or sustained ventricular tachycardia. During a median follow-up of 4.6 years (range 0.1–24.3 years), MAEs occurred in 18 (17.8%) of 101 patients diagnosed with LQTS at a median of 7.7 years (range 0.0–18.0 years) despite the use of beta-blockers in 91.6% of patients at the last follow-up. A multivariate analysis identified a genetic diagnosis of LQTS2 and LQTS3 and variants within the KCNH2 S5-loop-S6 pore region as independent risk factors for MAEs, independent of the QTc value or a history of syncope detected from a univariate analysis. MAEs occur frequently in childhood onset LQTS despite beta-blocker treatment. A detailed molecular genetic diagnosis can contribute to the arrhythmia risk stratification and optimize the use of preventive measures in this vulnerable patient population.

The Outcome of Long QT Syndrome, a Korean Single Center Study

Congenital long QT syndrome is an inherited cardiac channelopathy, causing fatal arrhythmia. In this study, we conducted a retrospective cohort study on 105 congenital LQTS patients and its outcome in a tertiary center. The 10-year event free survival rate was 73.2%, and the outcome was different according to the genotypes. With treatment, all survived except one. The genetic analysis and risk stratification may be essential for better outcome and further nationwide and large scaled studies are required.

Background and Objectives

Although long QT syndrome (LQTS) is a potentially life-threatening inherited cardiac channelopathy, studies documenting the long-term clinical data of Korean patients with LQTS are scarce.

Methods

This retrospective cohort study included 105 patients with LQTS (48 women; 45.7%) from a single tertiary center. The clinical outcomes were analyzed for the rate of freedom from breakthrough cardiac events (BCEs), additional treatment needed, and death.

Results

LQTS was diagnosed at a median age of 11 (range, 0.003–80) years. Genetic testing was performed on 90 patients (yield, 71.1%). The proportions of genetically confirmed patients with LQTS types 1, 2, 3, and others were 34.4%, 12.2%, 12.2%, and 12.2%, respectively. In the symptomatic group (n=70), aborted cardiac arrest was observed in 30% of the patients. Treatments included medications in 60 patients (85.7%), implantable cardioverter-defibrillators in 27 (38.6%; median age, 17 years; range, 2–79 years), and left cardiac sympathetic denervation surgery in 7 (10%; median age, 13 years; range, 2–34). The 10-year BCE-free survival rate was 73.2%. By genotype, significant differences were observed in BCEs despite medication (p<0.001). The 10-year BCE-free survival rate was the highest in patients with LQTS type 1 (81.8%) and the lowest in those with multiple LQTS-associated mutations (LQTM). All patients with LQTS survived, except for one patient who had LQTM.

Conclusions

Good long-term outcomes can be achieved by using recently developed genetically tailored management strategies for patients with LQTS.

Long QT syndrome with potassium voltage-gated channel subfamily H member 2 gene mutation mimicking refractory epilepsy: case report

BACKGROUND

Epileptic seizures can be difficult to distinguish from other etiologies that cause cerebral hypoxia, especially cardiac diseases. Long QT syndrome (LQTS), especially LQTS type 2 (LQT2), frequently masquerades as seizures because of the transient cerebral hypoxia caused by ventricular arrhythmia. The high rate of sudden death in LQTS highlights the importance of accurate and early diagnosis; correct diagnosis of LQTS also prevents inappropriate treatment with anti-epileptic drugs (AEDs).

CASE PRESENTATION

We report a case of congenital LQT2 with potassium voltage-gated channel subfamily H member 2 gene (KCNH2) mutation misdiagnosed as refractory epilepsy and treated with various AEDs for 22 years. The possibility of cardiac arrhythmia was suspected after the patient presented to the emergency room and the electrocardiograph (ECG) monitor showed paroxysmal ventricular tachycardia during attacks. Atypical seizure like attacks with prodromal uncomfortable chest sensation and palpitation, triggered by auditory stimulation, and typical ventricular tachycardia monitored by ECG raised suspicion for LQT2, which was confirmed by exome sequencing and epileptic seizure was ruled out by 24-h EEG monitoring. Although the patient rejected implantation of an implantable cardioverter defibrillator, β blocker was given and the syncope only attacked 1-2 per year when there was an incentive during the 5 years follow up.

CONCLUSIONS

Our case illustrates how long LQTS can masquerade convincingly as epilepsy and can be treated wrongly with AEDs, putting the patient at high risk of sudden cardiac death. Careful ECG evaluation is recommend for both patients with first seizure and those with refractory epilepsy.

Comparative Characteristics of Beta-Blockers in Patients with Congenital Long QT Syndrome

Congenital long QT syndrome is a pathology that requires special attention and knowledge about the safety and effectiveness of various medications. Prolongation of the QT interval due to congenital or acquired causes is an important factor in the development of an unfavorable life forecast with the formation of an elongated QT syndrome. With an unfavorable course, patients suffer from loss of consciousness, episodes of tachycardia. Often, stable polymorphic ventricular tachycardia develops. The risk of sudden cardiac death in this pathology can vary from 0.33% to 5%. In people who have suffered an episode of cardiac arrest, and do not have a permanent prescribed antiarrhythmic therapy, the mortality rate reaches 50% within 15 years. Preventive administration of antiarrhythmic drugs is not always effective. A positive result of treatment depends on the severity of long QT syndrome and its genotype. Beta-blockers are often prescribed to patients of different ages with various cardiac pathologies, including for the prevention of arrhythmia in long QT syndrome. Beta-blockers differ in various pharmacokinetic and pharmacodynamic parameters (lipophilicity/hydrophilicity, selectivity, presence/absence of internal sympathomimetic activity), which, along with the variant of the disease genotype, can affect their effectiveness and safety in the considered pathology. This review article presents the results of major studies on the safety and effectiveness of different groups of beta blockers in various variants of long QT syndrome. The preferred beta-blockers for various genotypes of the syndrome were determined, and a comparative characteristic of beta-blockers for their safety and preventive effectiveness was given.

The Efficacy of Beta-Blockers in Patients With Long QT Syndrome 1-3 According to Individuals' Gender, Age, and QTc Intervals: A Network Meta-analysis

Long QT syndrome (LQTS) is an arrhythmic heart disease caused by congenital genetic mutations, and results in increased occurrence rates of polymorphic ventricular tachyarrhythmias and sudden cardiac death (SCD). Clinical evidence from numerous previous studies suggested that beta blockers (BBs), including atenolol, propranolol, metoprolol, and nadolol, exhibit different efficacies for reducing the risk of cardiac events (CEs), such as syncope, arrest cardiac arrest (ACA), and SCD, in patients with LQTS. In this study, we identified relevant studies in MEDLINE, PubMed, embase, and Cochrane databases and performed a meta-analysis to assess the relationship between the rate of CEs and LQTS individuals with confounding variables, including different gender, age, and QTc intervals. Moreover, a network meta-analysis was not only established to evaluate the effectiveness of different BBs, but also to provide the ranked efficacies of BBs treatment for preventing the recurrence of CEs in LQT1 and LQT2 patients. In conclusion, nadolol was recommended as a relatively effective strategy for LQT2 in order to improve the prognosis of patients during a long follow-up period.

Overt long QT syndrome in children presenting with seizure disorders in Pakistan

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Materials and Methods:

Results:

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Targeting the β-adrenergic receptor in the clinical management of congenital long QT syndrome

The long QT syndrome (LQTS) is largely treated pharmacologically with β-blockers, despite the role of sympathetic activity in LQTS being poorly understood. Using the trigger-substrate model of cardiac arrhythmias in this review, we amalgamate current experimental and clinical data from both animal and human studies to explain the mechanism of adrenergic stimulation and blockade on LQT arrhythmic risk and hence assess the efficacy of β-adrenoceptor blockade in the management of LQTS. In LQTS1 and LQTS2, sympathetic stimulation increases arrhythmic risk by enhancing early afterdepolarizations and transmural dispersion of repolarization. β-Blockers successfully reduce cardiac events by reducing these triggers and substrates; however, these effects are less marked in LQTS2 compared with LQTS1. In LQTS3, clinical and experimental investigations of the effects of sympathetic stimulation and β-blocker use have produced contradictory findings, resulting in significant clinical uncertainty. We offer explanations for these contradicting results relating to study sample size, the dose of the β-blocker administered associated with its off-target Na⁺ channel effects, as well as the type of β-blocker used. We conclude that the antiarrhythmic efficacy of β-blockers is a genotype-specific phenomenon, and hence the use of β-blockers in clinical practice should be genotype dependent.

The Multifaced Perspectives of Genetic Testing in Pediatric Cardiomyopathies and Channelopathies

Pediatric inherited cardiomyopathies (CMPs) and channelopathies (CNPs) remain important causes of death in this population, therefore, there is a need for prompt diagnosis and tailored treatment. Conventional evaluation fails to establish the diagnosis of pediatric CMPs and CNPs in a significant proportion, prompting further, more complex testing to make a diagnosis that could influence the implementation of lifesaving strategies. Genetic testing in CMPs and CNPs may help unveil the underlying cause, but needs to be carried out with caution given the lack of uniform recommendations in guidelines about the precise time to start the genetic evaluation or the type of targeted testing or whole-genome sequencing. A very diverse etiology and the scarce number of randomized studies of pediatric CMPs and CNPs make genetic testing of these maladies far more particular than their adult counterpart. The genetic diagnosis is even more puzzling if the psychological impact point of view is taken into account. This review aims to put together different perspectives, state-of-the art recommendations-synthetizing the major indications from European and American guidelines-and psychosocial outlooks to construct a comprehensive genetic assessment of pediatric CMPs and CNPs.

Practice Variation among an International Group of Genetic Counselors on when to Offer Predictive Genetic Testing to Children at Risk of an Inherited Arrhythmia or Cardiomyopathy

Cascade predictive genetic testing is available for many families as a means to identify individuals at risk of long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy (HCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC). The general issue of offering predictive genetic testing to minors has been an area of ethical debate among genetic counselors and other healthcare professionals for many years. An online questionnaire was circulated to four international genetic counseling associations to assess the views of cardiac genetic counselors regarding when to offer predictive genetic testing to children at risk of LQTS, CPVT, HCM, and ARVC. Analysis was both quantitative and qualitative. The study sample comprised 98 respondents. The majority reported that they offer predictive genetic testing before 5 years of age to children at risk of LQTS (83%) and CVPT (75%) and before 10 years of age to children at risk of HCM (66%) or ARVC (70%). Influencing factors included country of practice, clinical setting, and years of experience. The rationale provided for when to offer predictive genetic testing is encompassed by the ethical principles of beneficence, non-maleficence, autonomy, and informed consent. In conclusion, significant practice variation exists among cardiac genetic counselors regarding predictive genetic testing for children at risk of an inherited cardiomyopathy. These variations call for more research in the area to assist with the development of evidence-based guidelines.

Clinical and molecular genetic risk determinants in adult long QT syndrome type 1 and 2 patients : Koponen et al. Follow-up of adult LQTS patients

Background

Long QT syndrome (LQTS) is an inherited cardiac disorder predisposing to sudden cardiac death (SCD). We studied factors affecting the clinical course of genetically confirmed patients, in particular those not receiving β-blocker treatment. In addition, an attempt was made to associate risk of events to specific types of KCNQ1 and KCNH2 mutations.

Methods

A follow-up study covering a mean of 18.6 ± 6.1 years was conducted in 867 genetically confirmed LQT1 and LQT2 patients and 654 non-carrier relatives aged 18–40 years. Cox regression models were used to evaluate the contribution of clinical and genetic risk factors to cardiac events.

Results

In mutation carriers, risk factors for cardiac events before initiation of β-blocker included LQT2 genotype (hazard ratio [HR] = 2.1, p = 0.002), female gender (HR = 3.2, p < 0.001), a cardiac event before the age of 18 years (HR = 5.9, p < 0.001), and QTc ≥500 ms (vs < 470 ms, HR = 2.7, p = 0.001). LQT1 patients carrying the KCNQ1 D317N mutation were at higher risk (HR = 3.0–3.9, p < 0.001–0.03) compared to G589D, c.1129-2A > G and other KCNQ1 mutation carriers after adjusting for gender, QTc duration, and cardiac events before age 18. KCNH2 c.453delC, L552S and R176W mutations associated with lower risk (HR = 0.11–0.23, p < 0.001) than other KCNH2 mutations.

Conclusions

LQT2 (compared to LQT1), female gender, a cardiac event before age 18, and long QT interval increased the risk of cardiac events in LQTS patients aged 18 to 40 years. The nature of the underlying mutation may be associated with risk variation in both LQT1 and LQT2. The identification of high-risk and low-risk mutations may enhance risk stratification.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0574-0) contains supplementary material, which is available to authorized users.

The Role of KCNQ1 Mutations and Maternal Beta Blocker Use During Pregnancy in the Growth of Children With Long QT Syndrome

OBJECTIVE

Two missense mutations in KCNQ1, an imprinted gene that encodes the alpha subunit of the voltage-gated potassium channel Kv7.1, cause autosomal dominant growth hormone deficiency and maternally inherited gingival fibromatosis. We evaluated endocrine features, birth size, and subsequent somatic growth of patients with long QT syndrome 1 (LQT1) due to loss-of-function mutations in KCNQ1.

DESIGN

Medical records of 104 patients with LQT1 in a single tertiary care center between 1995 and 2015 were retrospectively reviewed.

METHODS

Clinical and endocrine data of the LQT1 patients were included in the analyses.

RESULTS

At birth, patients with a maternally inherited mutation (n = 52) were shorter than those with paternal inheritance of the mutation (n = 29) (birth length, -0.70 ± 1.1 SDS vs. -0.2 ± 1.0 SDS, P < 0.05). Further analyses showed, however, that only newborns (n = 19) of mothers who had received beta blockers during pregnancy were shorter and lighter at birth than those with paternal inheritance of the mutation (n = 29) (-0.89 ± 1.0 SDS vs. -0.20 ± 1.0 SDS, P < 0.05; and 3,173 ± 469 vs. 3,515 ± 466 g, P < 0.05). Maternal beta blocker treatment during the pregnancy was also associated with lower cord blood TSH levels (P = 0.011) and significant catch-up growth during the first year of life (Δ0.08 SDS/month, P = 0.004). Later, childhood growth of the patients was unremarkable.

CONCLUSION

Loss-of-function mutations in KCNQ1 are not associated with abnormalities in growth, whereas maternal beta blocker use during pregnancy seems to modify prenatal growth of LQT1 patients-a phenomenon followed by catch-up growth after birth.

Effectiveness of beta-blockers depending on the genotype of congenital long-QT syndrome: A meta-analysis

BACKGROUND

Beta-blockers are first-line therapy in patients with congenital long-QT syndrome (LQTS).

OBJECTIVE

This study sought to determine the differences in effectiveness of beta-blockers on risk reduction according to LQTS genotype.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL databases to investigate the use of beta-blockers (atenolol, nadolol, propranolol, and metoprolol) in patients with LQTS. Hazard ratio (HR) and relative risk (RR) were extracted or calculated from studies reporting cardiac events (syncope, aborted cardiac arrest (ACA), or sudden cardiac death (SCD)).

RESULTS

Among 2,113 articles searched, 10 studies (7 registry-based cohort studies (Cohort) and 3 interrupted time series studies (ITS)) involving 9,727 patients were included. In a meta-analysis using a random-effect model, the use of beta-blocker was associated with significant risk reduction of all cardiac events (HR 0.49, p<0.001 in Cohort; RR 0.39, p<0.001 in ITS) and serious cardiac events (ACA or SCD) (HR 0.47, p<0.001 in Cohort). In both LQT1 and LQT2, the risk was reduced with beta-blocker therapy in Cohort (HR 0.59 in LQT1; HR 0.39 in LQT2) as well as ITS (RR 0.29 in LQT1; RR 0.48 in LQT2). Among the beta-blockers, nadolol showed a significant risk reduction in both LQT1 and LQT2 (HR 0.47 and 0.27, respectively), whereas atenolol and propranolol decreased the risk only in LQT1 (HR 0.36 and 0.46, respectively). Metoprolol showed no significant reduction in either genotype. In LQT3, beta-blocker therapy was not as effective as LQT1 or LQT2; however, it was inconclusive due to data insufficiency.

CONCLUSION

This meta-analysis showed that beta-blockers were effective in reducing risk of cardiac events in patients with LQTS. Among them, nadolol was effective in LQT1 and LQT2, whereas other drugs showed different effectiveness depending on LQT genotype.

Management of Patients with Long QT Syndrome

Long QT syndrome (LQTS) is a rare cardiac channelopathy associated with syncope and sudden death due to torsades de pointes and ventricular fibrillation. Syncope and sudden death are frequently associated with physical and emotional stress. Management of patients with LQTS consists of life-style modification, β-blockers, left cardiac sympathetic denervation (LCSD), and implantable cardioverter-defibrillator (ICD) implantation. Prohibition of competitive exercise and avoidance of QT-prolonging drugs are important issues in life-style modification. Although β-blockers are the primary treatment modality for patients with LQTS, these drugs are not completely effective in some patients. Lifelong ICD implantation in young and active patients is associated with significant complications. LCSD is a relatively simple and highly effective surgical procedure. However, LCSD is rarely used.

Arrhythmias and Cardiac Bedside Monitoring in the Neonatal Intensive Care Unit

Cardiac physiology is unique in neonates and infants; there are several physiologic changes that occur in the first weeks of life. Important changes can be captured on the bedside monitor and provide vital data in a noninvasive way to providers. The importance of diligent observation cannot be overstated. Bedside monitoring has improved in the last decade, which has enhanced the ability to detect changes in heart rates and rhythms. The purpose here is to review cardiac physiology, describe those arrhythmias able to be observed on bedside monitors, and highlight heart rate changes that can be early signs of sepsis.