Inherited long QT syndrome: clinical manifestation, genetic diagnostics, and therapy

Family Relationships Associated With Communication and Testing for Inherited Cardiac Conditions

The purpose of this study was to identify characteristics of family relationships associated with communication of genetic risk and testing behaviors among at-risk relatives in families with an inherited cardiac condition. Data were collected from 53 patients and parents of children with an inherited cardiac condition through interviews, pedigrees, and surveys. Associations were examined among family relationship characteristics and whether at-risk relatives were informed about their risk and tested for disease. Of 1,178 at-risk relatives, 52.5% were informed about their risk and 52.1% of those informed were tested. Emotional closeness, relationship quality, and communication frequency had significant bivariate associations with genetic risk communication. Communication frequency was associated with genetic risk communication and testing in multivariate models. This study provides new insight into the extent of genetic risk communication and testing in families with inherited cardiac conditions. Family relationships, especially communication frequency, are critical factors in family communication of genetic risk.

Change and dispersion of QT interval during treatment with quetiapine extended release versus aripiprazole in children and adolescents with first-episode psychosis: results from the TEA trial

OBJECTIVE

The aim of this study was to compare the effect of quetiapine extended release (ER) versus aripiprazole on corrected QT interval (QTc) and QT dispersion (QTd) in youths with first-episode psychosis.

METHODS

Youths 12-17 years were randomized to quetiapine ER (daily dose range = 50 to 800 mg) or aripiprazole (daily dose range = 2.5 to 30 mg) in a 12-week double-blinded trial and examined at weeks 0, 4, and 12. Primary outcome was QTc change using Hodges formula (QTcH); secondary outcomes included QTcH > 450 ms, QTcH > 500 ms, QTcH change > 60 ms, QTd, and heart rate (HR).

RESULTS

Among 113 randomized youths, follow-up ECG was available for 93 patients (82.3%) (age = 15.8 ± 1.3 years, males = 34.4%, schizophrenia = 67.7%). Quetiapine ER treatment (n = 47) was associated with a significant increase in QTcH of + 6.8 ± 20.2 ms (p = 0.025), while the change from baseline in patients receiving aripiprazole (n = 46) was non-significant (- 3.4 ± 18.9 ms, p = 0.225). One patient in the quetiapine ER group had a QTcH change of + 62.3 ms. Age, sex, smoking, body mass index, and concomitant medication were not significantly associated with QTcH change, but higher baseline potassium was correlated to higher QTcH change in the quetiapine ER group. The HR increased significantly with quetiapine ER (+ 11.0 ± 14.2 bpm, p < 0.001) but not with aripiprazole (- 0.8 ± 12.0 bpm, p = 0.643). QTd did not significantly change with quetiapine ER or aripiprazole.

CONCLUSION

QTcH and HR increased significantly with quetiapine ER, although changes were small and likely not clinically significant in otherwise healthy patients. QTcH and HR were unchanged with aripiprazole. No significant change in QTd was seen. ClinicalTrials.gov: NCT01119014, EudraCT: 2009-016715-38.

TRPM4 non-selective cation channel variants in long QT syndrome

Background

Long QT syndrome (LQTS) is an inherited arrhythmic disorder characterized by prolongation of the QT interval, a risk of syncope, and sudden death. There are already a number of causal genes in LQTS, but not all LQTS patients have an identified mutation, which suggests LQTS unknown genes.

Methods

A cohort of 178 LQTS patients, with no mutations in the 3 major LQTS genes (KCNQ1, KCNH2, and SCN5A), was screened for mutations in the transient potential melastatin 4 gene (TRPM4).

Results

Four TRPM4 variants (2.2% of the cohort) were found to change highly conserved amino-acids and were either very rare or absent from control populations. Therefore, these four TRPM4 variants were predicted to be disease causing. Furthermore, no mutations were found in the DNA of these TRPM4 variant carriers in any of the 13 major long QT syndrome genes. Two of these variants were further studied by electrophysiology (p.Val441Met and p.Arg499Pro). Both variants showed a classical TRPM4 outward rectifying current, but the current was reduced by 61 and 90% respectively, compared to wild type TRPM4 current.

Conclusions

This study supports the view that TRPM4 could account for a small percentage of LQTS patients. TRPM4 contribution to the QT interval might be multifactorial by modulating whole cell current but also, as shown in Trpm4^−/− mice, by modulating cardiomyocyte proliferation. TRPM4 enlarges the subgroup of LQT genes (KCNJ2 in Andersen syndrome and CACNA1C in Timothy syndrome) known to increase the QT interval through a more complex pleiotropic effect than merely action potential alteration.

Mutation analysis for the detection of long QT-syndrome (LQTS) associated SNPs

Congenital long QT-syndrome (LQTS) is an inherited cardiac arrhythmia, which is characterized by a prolonged QT interval which predisposes to sudden cardiac death due to ventricular arrhythmias. The altered functions are based on different mutations in LQTS-associated genes. In this study, we performed a mutation analysis for the detection of 125 LQTS-associated single nucleotide polymorphisms (SNPs) focused on the genes KCNQ1, KCNH2, and SCN5A by using the SNaPshot multiplex minisequencing technique. Furthermore, we investigated 152 autopsy-negative cases from younger adults and infants, as well as samples from patients with clinically suspicion for LQTS, in which we found two types of variations.

Improved Clinical Risk Stratification in Patients with Long QT Syndrome? Novel Insights from Multi-Channel ECGs

Background

We investigated whether multichannel ECG-recordings are useful to risk-stratify patients with congenital long-QT syndrome (LQTS) for risk of sudden cardiac death under optimized medical treatment.

Methods

In 34 LQTS-patients (11 male; age 31±13 years, QTc 478±51ms; LQT1 n = 8, LQT2 n = 15) we performed a standard 12-channel ECG and a 120-channel body surface potential mapping. The occurrence of clinical events (CE; syncope, torsade de pointes (TdP), sudden cardiac arrest (SCA)) was documented and correlated with different ECG-parameters in all lead positions.

Results

Seven patients developed TdP, four survived SCA and 12 experienced syncope. 12/34 had at least one CE. CE was associated with a longer QTc-interval (519±43ms vs. 458±42ms; p = 0.001), a lower T-wave integral (TWI) on the left upper chest (-1.2±74.4mV*ms vs. 63.0±29.7mV*ms; p = 0.001), a lower range of T-wave amplitude (TWA) in the region of chest lead V8 (0.10±0.08mV vs. 0.18±0.07mV; p = 0.008) and a longer T-peak-T-end time (TpTe) in lead V1 (98±23ms vs. 78±26ms; p = 0.04). Receiver-operating-characteristic (ROC) analyses revealed a sensitivity of 96% and a specificity of 75% (area under curve (AUC) 0.89±0.06, p = 0.001) at a cut-off value of 26.8mV*ms for prediction of CE by TWI, a sensitivity of 86% and a specificity of 83% at a cut-off value of 0.11mV (AUC 0.83±0.09, p = 0.002) for prediction of CE by TWA and a sensitivity of 83% and a specificity of 73% at a cut-off value of 87ms (AUC 0.80±0.07, p = 0.005) for prediction of CE by TpTe.

Conclusions

Occurrence of CE in LQTS-patients seems to be associated with a prolonged, low-amplitude T-wave.

Corrected QT changes during antipsychotic treatment of children and adolescents: a systematic review and meta-analysis of clinical trials

OBJECTIVE

To evaluate the effect of antipsychotics on the corrected QT (QTc) interval in youth.

METHOD

We searched PubMed (http://www.ncbi.nlm.nih.gov/pubmed) for randomized or open clinical trials of antipsychotics in youth <18 years with QTc data, meta-analyzing the results. Meta-regression analyses evaluated the effect of age, sex, dose, and study duration on QTc. Incidences of study-defined QTc prolongation (>440-470 milliseconds), QTc >500 milliseconds, and QTc change >60 milliseconds were also evaluated.

RESULTS

A total of 55 studies were meta-analyzed, evaluating 108 treatment arms covering 9 antipsychotics and including 5,423 patients with QTc data (mean age = 12.8 ± 3.6 years, female = 32.1%). Treatments included aripiprazole: studies = 14; n = 814; haloperidol: studies = 1; n = 15; molindone: studies = 3; n = 125; olanzapine: studies = 5; n = 212; paliperidone: studies = 3; n = 177; pimozide: studies = 1; n = 25; quetiapine: studies = 5; n = 336; risperidone: studies = 23; n = 2,234; ziprasidone: studies = 10, n = 523; and placebo: studies = 19, n = 962. Within group, from baseline to endpoint, aripiprazole significantly decreased the QTc interval (-1.44 milliseconds, CI = -2.63 to -0.26, p = .017), whereas risperidone (+1.68, CI = +0.67 to +2.70, p = .001) and especially ziprasidone (+8.74, CI = +5.19 to +12.30, p < .001) significantly increased QTc. Compared to pooled placebo arms, aripiprazole decreased QTc (p = .007), whereas ziprasidone increased QTc (p < .001). Compared to placebo, none of the investigated antipsychotics caused a significant increase in the incidence of the 3 studied QTc prolongation measures, but there was significant reporting bias.

CONCLUSION

Based on these data, the risk of pathological QTc prolongation seems low during treatment with the 9 studied antipsychotics in otherwise healthy youth. Nevertheless, because individual risk factors interact with medication-related QTc effects, both medication and patient factors need to be considered when choosing antipsychotic treatment.

The human ether-a-go-go-related gene activator NS1643 enhances epilepsy-associated KCNQ channels

Human ether-a-go-go-related gene (hERG) and KCNQ channels are two classes of voltage-gated potassium channels. Specific mutations have been identified that are causal for type II long QT (LQT2) syndrome, neonatal epilepsy, and benign familial neonatal convulsions. Increasing evidence from clinical studies suggests that LQT2 and epilepsy coexist in some patients. Therefore, an integral approach to investigating and treating the two diseases is likely more effective. In the current study, we found that NS1643 [1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea], a previously reported hERG activator, is also an activator of KCNQ channels. It potentiates the neuronal KCNQ2, KCNQ4, and KCNQ2/Q3 channels, but not the cardiac KCNQ1. The effects of NS1643 on the KCNQ2 channel include left shifting of voltage for reaching 50% of the maximum conductance and slowing of deactivation. Analysis of the dose-response curve of NS1643 revealed an EC50 value of 2.44 ± 0.25 μM. A hydrophobic phenylalanine (F137) located at the middle region of the voltage-sensing domain was identified as critical for NS1643 activity on KCNQ2. When testing NS1643 effects in rescuing LQT2 hERG mutants and the KCNQ2 BFNC mutants, we found it is particularly efficacious in some cases. Considering the substantial relationship between LQT2 and epilepsy, these findings reveal that NS1643 is a useful compound to elucidate the causal connection of LQT2 and epilepsy. More generally, this may provide a strategy in the development of therapeutics for LQT2 and epilepsy.

Monogene kardiale Ionenkanalerkrankungen

Genetisch bedingte (monogene) Herzerkrankungen bedürfen einer sorgsamen klinischen, genetischen und familiären Diagnostik, da die Erkrankungen mit einem hohen kardiovaskulären Risiko in jungen Jahren assoziiert sein können.

Es handelt sich zumeist um Erkrankungen durch Ionenkanalgenmutationen, die genetisch heterogen und von einer unterschiedlichen Sensitivität in der Mutationsdetektion (pro Erkrankung oder Ionenkanalgen) gekennzeichnet sind. In Analogie zu anderen Ionenkanalerkrankungen besteht oft ein episodisches Auftreten von Symptomen, das durch Trigger (meist erhöhte Herzfrequenz bei körperlicher und/oder physischer Belastung) gefördert werden kann.

Bei diesen relativ seltenen Erkrankungen ist eine frühzeitige Diagnostik und interdisziplinäre Betreuung durch Kardiologen, Kinderkardiologen und Humangenetikern (und ggf. Psychologen) sinnvoll. Mittlerweile existieren erste internationale Empfehlungen, wann eine Genotypisierung aus diagnostischer, therapeutischer oder prognostischer Sicht durchzuführen ist.

[Genetics of sudden unexplained death]

Sudden unexplained death is defined by death without a conclusive diagnosis after autopsy and it is responsible for a large percentage of sudden deaths. The progressive interaction between genetics and forensics in post-mortem studies has identified inheritable alterations responsible for pathologies associated with arrhythmic sudden death. The genetic diagnosis of the deceased enables the undertaking of preventive measures in family members, many of them asymptomatic but at risk. The implications of this multidisciplinary translational medical approach are complex, requiring the dedication of a specialized team.