Rescue of expression and function of long QT syndrome-causing mutant hERG channels by enhancing channel stability in the plasma membrane.

The human ether-g-go-go-related gene (hERG) encodes the Kv11.1 (or hERG) channel that conducts the rapidly activating delayed rectifier potassium current (IKr). Naturally occurring mutations in hERG impair the channel function and cause long QT syndrome type 2 (LQT2). Many missense hERG mutations lead to a lack of channel expression on the cell surface, representing a major mechanism for the loss-of-function of mutant channels. While it is generally thought that a trafficking defect underlies the lack of channel expression on the cell surface, in the present study, we demonstrate that the trafficking defective mutant hERG G601S can reach the plasma membrane but is unstable and quickly degrades, which is akin to Wild Type (WT) hERG channels under low K+ conditions. We previously showed that Serine (S) residue at 624 in the innermost position of the selectivity filter of hERG is involved in hERG membrane stability such that substitution of Serine 624 with Threonine (S624T) enhances hERG stability and renders hERG insensitive to low K+ culture. Here, we report that the intragenic addition of S624T substitution to trafficking defective hERG mutants G601S, N470D and P596R led to a complete rescue of the function of these otherwise loss-of-function mutant channels to a level similar to the WT channel, representing the most effective rescue means for the function of mutant hERG channels. These findings not only provide novel insights into hERG mutation-mediated channel dysfunction, but also point to the critical role of S624 in hERG stability on the plasma membrane.

Ventricular Fibrillation Arrest Triggered by Antiemetics Revealing an Underlying Long QT Syndrome in a Young Woman.

Undiagnosed phenomena such as long QT syndrome can have devastating effects on patients. Our case, involving a woman in her 30s, highlights the serious effects of undiagnosed long QT and how antiemetic medications can precipitate cardiac events that can lead to fatalities. Various medications are known to prolong QT intervals, and clinicians must be aware of the side effects of some of these commonly used medications. While survival was achieved in this case, education and reflection can act as a tool to help improve global standards of care in this subgroup of the population.

Congenital Long QT Syndrome in Children and Adolescents: A General Overview.

Congenital long QT syndrome (LQTS) represents a disorder of myocardial repolarization characterized by a prolongation of QTc interval on ECG, which can degenerate into fast polymorphic ventricular arrhythmias. The typical symptoms of LQTS are syncope and palpitations, mainly triggered by adrenergic stimuli, but it can also manifest with cardiac arrest. At least 17 genotypes have been associated with LQTS, with a specific genotype-phenotype relationship described for the three most common subtypes (LQTS1, -2, and -3). ß-Blockers are the first-line therapy for LQTS, even if the choice of the appropriate patients needing to be treated may be challenging. In specific cases, interventional measures, such as an implantable cardioverter-defibrillator (ICD) or left cardiac sympathetic denervation (LCSD), are useful. The aim of this review is to highlight the current state-of-the-art knowledge on LQTS, providing an updated picture of possible diagnostic algorithms and therapeutic management.

Fetal Arrhythmia Leading to a Diagnosis of Congenital Long QT Syndrome Type II.

We describe the case of an asymptomatic young pregnant woman with a diagnosis of congenital long QT syndrome type II in the context of in utero fetal 2:1 heart block and ventricular tachycardia. The presentation, clinical considerations, and management of the mother and baby in the antepartum and postpartum periods are discussed.

Congenital Long QT Syndrome (LQTS) in Infancy: A Challenging Case.

Long QT syndrome (LQTS), is an arrhythmia disorder, related to ventricular myocardial repolarization characterized by a prolonged QT interval on the electrocardiogram that can lead to symptomatic ventricular arrhythmias and increase the mortality rate. The prevalence of congenital LQTS is about 1 in 2000 live births. Here, we report the case of a two-month-old female, with a significant family history of early death, who was brought to our emergency with an episode of blueish discoloration. The initial workup was positive for COVID-19 in the respiratory panel, so she was admitted as a case of bronchiolitis. It was a challenge because of the overlapping presentation between a serious condition and other common pediatric illnesses. Furthermore, the paper aims to increase awareness of this condition among physicians and emphasizes the importance of obtaining a complete medical history, physical examination, and family screening in selected cases to facilitate early diagnosis and timely management.

Congenital Long QT Syndrome, Coinciding With Cavitary Mycobacterium avium Lung Infection, Led to Cardiac Arrest.

Congenital long QT syndrome is a cardiac disorder leading to arrhythmias and sudden cardiac death. We present a case of a 55-year-old woman with altered mental status experiencing cardiac arrest caused by congenital long QT syndrome, coincidentally found with Mycobacterium avium complex lung infection. Genetic testing identified a pathogenic mutation in the KCNH2 gene. (Level of Difficulty: Intermediate.).

Unlocking the Potential of Left Cardiac Sympathetic Denervation: A Scoping Review of a Promising Approach for Long QT Syndrome.

Left cardiac sympathetic denervation (LCSD) has emerged as an alternative therapy for individuals diagnosed with long QT syndrome (LQTS), a genetic disorder characterized by abnormal electrical activity in the heart and sudden cardiac death (SCD). This review examines the history and rationale behind LCSD in LQTS treatment, as well as the procedure, its efficacy, and indications along with the adverse effects that may be associated with it. LQTS presents with prolonged QT intervals on an electrocardiogram and can manifest as seizures, fainting, and SCD. Beta-blockers are the primary treatment for LQTS but some patients do not respond well to these medications or experience side effects. Additionally, implantable cardioverter-defibrillators (ICDs) are not always effective in preventing arrhythmias and can lead to complications. LCSD might offer an alternative approach by disrupting sympathetic activity in the heart. In humans, LCSD reduces the release of norepinephrine, normalizes the QT interval, and decreases the likelihood of life-threatening heart rhythms. The procedure does not impair heart rate or cardiac function due to the compensatory effects of the right cardiac sympathetic nerves. The surgical procedure for LCSD involves the removal of the lower half of the stellate ganglion and thoracic ganglia. Complete denervation is essential for optimal outcomes, while incomplete procedures are considered unacceptable. Traditional and minimally invasive approaches, such as video-assisted thoracic surgery (VATS), are available, with VATS offering shorter hospital stays and fewer complications. In conclusion, LCSD provides a viable treatment option for individuals with LQTS who do not respond well to beta-blockers or require additional protection beyond medication or ICDs. Further research and clinical experience are needed to enhance its acceptance and implementation in routine practice.

Congenital Long QT Syndrome and Cardiac Arrest in a Military Tactical Athlete.

We present a case of a U.S. marine who experienced cardiac arrest during military Special Forces underwater diving exercises whose evaluation revealed congenital long QT syndrome. This case highlights the expanding role for systematic electrocardiogram screening in target athletic and military populations given their stress and tactical exposures. (Level of Difficulty: Advanced.).

Current gaps in knowledge in inherited arrhythmia syndromes.

The 3 most common inherited arrhythmia syndromes-Brugada syndrome, congenital long QT syndrome and catecholaminergic polymorphic ventricular tachycardia-were initially described in the previous century. Since then, research has evolved, which has enabled us to identify patients prior to the onset of potentially life-threatening symptoms. However, there are significant gaps in knowledge that complicate clinical management of these patients today. With this review paper, we aim to highlight the most important knowledge gaps in clinical research of these inherited arrhythmia syndromes.

A method for successfully implanting an implantable cardioverter-defibrillator wrapped with an expanded polytetrafluoroethylene sheet in a patient with metal allergy.

Contact dermatitis is a severe complication of cardiac-device implantation that may be observed in patients with metal allergies. Some studies have suggested that wrapping cardiac devices with expanded polytetrafluoroethylene (ePTFE) sheets is effective in preventing contact dermatitis. Most of these studies involved pacemakers, whereas those on implantable cardioverter-defibrillators (ICDs) are rare. Herein, we report a method for the successful implantation of an ICD wrapped with an ePTFE sheet in a patient with metal allergy. The metal part of the ICD generator was tightly wrapped with an ePTFE sheet, which was sewn with ePTFE sutures approximating the edges of the generator. After the wrapping procedure, the patient entered the operating room, and the generator and an ePTFE-coated dual-coil shock lead were implanted via a standard procedure. The shock impedance in the coil-to-can vector was high immediately after the implantation, but it reduced to less than half of its initial value over a period of two weeks post-surgery. The patient did not develop any new skin problems during the 20-month follow-up. This is a method for successfully preventing contact dermatitis; however, attention to the associated high risk of infection is required. Learning objective: Wrapping an implantable cardioverter-defibrillator with an expanded polytetrafluoroethylene sheet was effective in preventing contact dermatitis after implantation. The shock impedance in the coil-to-can vector was high immediately after implantation but reduced to approximately half of its initial value with time.

Precision medicine for long QT syndrome: patient-specific iPSCs take the lead.

Long QT syndrome (LQTS) is a detrimental arrhythmia syndrome mainly caused by dysregulated expression or aberrant function of ion channels. The major clinical symptoms of ventricular arrhythmia, palpitations and syncope vary among LQTS subtypes. Susceptibility to malignant arrhythmia is a result of delayed repolarisation of the cardiomyocyte action potential (AP). There are 17 distinct subtypes of LQTS linked to 15 autosomal dominant genes with monogenic mutations. However, due to the presence of modifier genes, the identical mutation may result in completely different clinical manifestations in different carriers. In this review, we describe the roles of various ion channels in orchestrating APs and discuss molecular aetiologies of various types of LQTS. We highlight the usage of patient-specific induced pluripotent stem cell (iPSC) models in characterising fundamental mechanisms associated with LQTS. To mitigate the outcomes of LQTS, treatment strategies are initially focused on small molecules targeting ion channel activities. Next-generation treatments will reap the benefits from development of LQTS patient-specific iPSC platform, which is bolstered by the state-of-the-art technologies including whole-genome sequencing, CRISPR genome editing and machine learning. Deep phenotyping and high-throughput drug testing using LQTS patient-specific cardiomyocytes herald the upcoming precision medicine in LQTS.

The diagnostic role of T wave morphology biomarkers in congenital and acquired long QT syndrome: A systematic review.

INTRODUCTION: QTc prolongation is key in diagnosing long QT syndrome (LQTS), however 25%-50% with congenital LQTS (cLQTS) demonstrate a normal resting QTc. T wave morphology (TWM) can distinguish cLQTS subtypes but its role in acquired LQTS (aLQTS) is unclear. METHODS: Electronic databases were searched using the terms "LQTS," "long QT syndrome," "QTc prolongation," "prolonged QT," and "T wave," "T wave morphology," "T wave pattern," "T wave biomarkers." Whole text articles assessing TWM, independent of QTc, were included. RESULTS: Seventeen studies met criteria. TWM measurements included T-wave amplitude, duration, magnitude, Tpeak-Tend, QTpeak, left and right slope, center of gravity (COG), sigmoidal and polynomial classifiers, repolarizing integral, morphology combination score (MCS) and principal component analysis (PCA); and vectorcardiographic biomarkers. cLQTS were distinguished from controls by sigmoidal and polynomial classifiers, MCS, QTpeak, Tpeak-Tend, left slope; and COG x axis. MCS detected aLQTS more significantly than QTc. Flatness, asymmetry and notching, J-Tpeak; and Tpeak-Tend correlated with QTc in aLQTS. Multichannel block in aLQTS was identified by early repolarization (ERD30% ) and late repolarization (LRD30% ), with ERD reflecting hERG-specific blockade. Cardiac events were predicted in cLQTS by T wave flatness, notching, and inversion in leads II and V5 , left slope in lead V6 ; and COG last 25% in lead I. T wave right slope in lead I and T-roundness achieved this in aLQTS. CONCLUSION: Numerous TWM biomarkers which supplement QTc assessment were identified. Their diagnostic capabilities include differentiation of genotypes, identification of concealed LQTS, differentiating aLQTS from cLQTS; and determining multichannel versus hERG channel blockade.

Cerebral Seizures in an Adolescent with Jervell and Lange-Nielsen Syndrome: It May Not Be Epilepsy.

A 13-year-old girl with Jervell and Lange-Nielsen syndrome associated congenital long QT syndrome (LQTS) and central deafness was admitted for generalized seizures. LQTS had been diagnosed after birth and confirmed at genetic testing. ß-blocker treatment was immediately started. Despite this, since the age of 12 months, recurrent cerebral seizures occurred leading to the diagnosis of epilepsy. Anti-convulsive therapy was initiated but without success. At the last admission, nadolol dosage seemed infratherapeutic. Considering malignant ventricular arrhythmias as the cause of seizures, the ß-blocker dosage was adjusted to weight and levels of magnesium and potassium optimized. Furthermore, the patient received an implantable Medtronic Reveal LINQ Recorder®. Since then, the adolescent has been asymptomatic with no arrhythmia documented. LQTS is due to one or more mutations of genes coding for ion channels. It may induce malignant ventricular arrhythmias and is a major cause of sudden cardiac death in children. Generalized cerebral seizures are extra-cardiac manifestations caused by decreased cerebral perfusion during ventricular arrhythmia. They are commonly misinterpreted as manifestations of epilepsy. For any patient with known or unknown LQTS who presents seizures with resistance to anti-convulsive therapy, a cardiac electrophysiological investigation should be performed promptly to ensure etiological diagnosis and optimize treatment.

Mechanical QT and JT intervals by M-mode echocardiography: An extrapolation from the concurrent electrocardiographic tracings.

Background: Congenital long QT syndrome (CLQTS) is a life-threatening ion channelopathy leading to syncope and sudden death. Early diagnosis during the prenatal period and timely intervention can prevent sudden cardiac death and catastrophic consequences of this genetic ion channelopathy. Fetal magnetocardiography and fetal electrocardiography (ECG) enable the measurement of fetal QT and JT intervals, but their inherently technically challenging and/or resource-intensiveness nature preclude their routine clinical application. On the other hand, the high-temporal resolution of M-mode echocardiography makes it a well-suited and widely available modality for the measurement of cardiac events. Aims and Objectives: We aimed to investigate the mechanical counterparts of the electrical QT and JT intervals on M-mode echocardiographic images of the tricuspid, mitral and aortic valves, and aortic wall. Methods: We performed a prospective study on consecutive children referred to the outpatient pediatric cardiology clinic at a tertiary children's hospital. We defined M-mode echocardiographic landmark points on tracings of tricuspid annular planar systolic excursion, mitral and aortic valves, and aortic wall with simultaneous electrocardiographic recording. We measured the mean±SD of the absolute time difference and RR-adjusted time difference in cases with non-coincident ECG events and echocardiographic landmarks. Results: Fifty healthy children were enrolled in the study. In 47 (94%) out of the 50 children, Q was coincident with the starting point of the tricuspid annular plane systolic excursion. In all children, the Q was coincident with the mid-point of the A-C line of the mitral valve. In 38 (76%) cases, there was a bump on the anterior wall of the aortic root immediately before the change in the slope of the aortic wall. This was coincident with the Q wave in 100% of cases. In all cases, the J point coincided with the point of acceleration of velocity on TAPSE. In all children, the J point coincided with the initial maximal opening of the aortic cusps. The end of the T wave occurred coincident with the peak of the tricuspid annular planar systolic excursion in 47 children (94%). In 48 children (96%), the end of the T wave coincided with the aortic cusps' closure point. Conclusions: Based on our findings, we propose to measure the averaged mechanical QT and JT intervals by using an angled M-mode tracing of the aortic and mitral valve in five consecutive beats in the parasternal long-axis view. This is the first study on mechanical QT and JT intervals in healthy children. The study opens the horizons into the in-utero diagnosis of congenital long QT syndrome by measuring fetal QT and JT intervals using the widely available M-mode echocardiography.

Severity of congenital long QT syndrome disease manifestation and risk of depression, anxiety, and mortality: a nationwide study.

AIMS: We examined if a congenital long QT syndrome (cLQTS) diagnosis and severity of cLQTS disease manifestation was associated with increased risk of depression, anxiety, and all-cause mortality. METHODS AND RESULTS: All patients with known cLQTS in Denmark were identified using nationwide registries and specialized inherited cardiac disease clinics (1994-2016) and followed for up to 3 years after their cLQTS diagnosis. Risk factors for depression, anxiety, and all-cause mortality were determined using multivariable Cox proportional-hazards regression. An age- and sex-matched control population was identified (matching 1:4). Overall, 589 patients with cLQTS were identified of which 119/589 (20.2%) developed depression or anxiety during follow-up compared with 302/2356 (12.8%) from the control population (P < 0.001). Severity of cLQTS disease manifestation was identified for 324/589 (55%) of patients with cLQTS; 162 were asymptomatic, 119 had ventricular tachycardia (VT)/syncope, and 43 had aborted sudden cardiac death (aSCD). In multivariable models, patients with aSCD, VT/syncope, or unspecified cLQTS disease manifestation had a higher risk of developing depression or anxiety compared with the control population (hazard ratio [HR]=2.4, 95% confidence interval [CI]: 1.1-5.1; HR = 1.9, 95% CI: 1.2-3.0; HR = 1.6, 95% CI: 1.1-2.3, respectively). Asymptomatic patients had similar risk of developing depression or anxiety as the control population (HR = 1.2, 95% CI: 0.8-1.9). During follow-up, 10/589 (1.7%) patients with cLQTS died compared with 27/2356 (1.1%) from the control population (P = 0.5). Furthermore, 4/10 who died had developed depression or anxiety. CONCLUSION: A severe cLQTS disease manifestation was associated with a greater risk of depression or anxiety. All-cause mortality for patients with cLQTS was low.

Mutation spectrum and clinical features of congenital long QT syndrome in 20 children: a single center study / 中华实用儿科临床杂志

Objective:To explore the pathogenic genes, clinical characteristics and treatment follow-up of children with congenital long QT syndrome (LQTS).Methods:Clinical data of 20 cases diagnosed with congenital LQTS and underwent gene testing from April 15, 2011 to April 15, 2021 in Department of Pediatric Cardiology, Shandong Provincial Hospital Affiliated to Shandong University were retrospectively collected and analyzed using independent sample t-test and Fisher′ s exact probability method. Results:LQTS-related gene mutations were detected in all the 20 cases, and pathogenic or suspected pathogenic mutations were identified in 18 cases (90.0%). Five LQTS mutation genes were discovered, including KCNQ1, KCNH2, SCN5A, CACNA1C and AKAP9.Eighteen cases (90.0%) had positive symptoms, and 13 cases (65.0%) had definite inducements.The inducement of symptoms in children with LQTS type 1(LQT1) was related to exercise, the causes of syncope in LQT1 and Jervell-Lange-Nielsen syndrome type 1 (JLNS1) with complex heterozygous mutations were exercise or emotional agitation; the causes of syncope in LQTS type 2 (LQT2) were unrelated to exercise; severe exercise in LQTS type 3 (LQT3) resulted in symptoms; and seizure in LQTS type 8 (LQT8) was non-induced.The corrected QT(QTc) interval of 20 cases was (553.1±66.6) ms, with a range of 460-707 ms, among which 17 cases showed QTc≥480 ms.The electrocardiogram(ECG) manifestations of children with various types of LQTS were different.There was no significant difference in QTc between different genders, or between children with syncope and those without syncope (all P>0.05). The follow-up time was (3.4±2.3) years, ranging from 0 to 8.3 years.Seventeen children received treatment[beta blockers and implantable cardiovertor-defibrillator(ICD)] and 3 cases did not.By the end of the follow-up, 1 child died, 19 cases survived, and 2 cases of the surviving children lost consciousness. Conclusions:There is a high consistency between genetic diagnosis and clinical diagnosis of congenital LQTS.The positive rate of gene detection is 90.0%.The clinical manifestations and ECG characteristics vary with genotypes.Beta blockers are protective.ICD therapy can prevent sudden cardiac death when oral medication does not respond.

Torsades de pointes in the PACU after outpatient endoscopy: a case report.

BACKGROUND: This case demonstrates the severe electrolyte derangements that may present after a common therapy such as a bowel preparation for an outpatient procedure and the rare yet potential detrimental outcomes of those abnormalities. It also highlights the implications of long QT syndrome regarding pharmacology and treatment. CASE PRESENTATION: We present a case of 48 year-old female with severe electrolyte derangements and long QT syndrome (LQTS) leading to Torsades de Pointes (TdP), pulseless ventricular fibrillation, and unsynchronized defibrillation in the post anesthesia care unit (PACU) after uneventful upper and lower endoscopy. This led to an unanticipated intensive care unit admission for aggressive electrolyte repletion, cardiology consultation, and implantable cardioverter defibrillator (ICD) placement. CONCLUSIONS: This is a rare presentation after an outpatient procedure that would have had a detrimental outcome if not promptly diagnosed and treated appropriately. Therefore, we aim to provide further insight into the diagnosis and treatment of severe hypokalemia and long QT syndrome resulting in Torsades de Pointes and ventricular fibrillation.

Anesthesia for a Child with Congenital Long QT Syndrome, a Case Report and Literature Review.

Long QT syndrome is an inherited disorder of the heart's electrical activity that may also be associated with malignant arrhythmia and cause sudden death. In addition to this inherited condition, several commonly used anesthetic drugs can prolong the QT interval. We present here a 17-month-old male patient who underwent general anesthesia for a cochlear implant. No cardiac arrhythmia was observed in the patient, whose muscle relaxant effect was reversed using sugammadex. The application of intravenous anesthetics was preferred to maintain anesthesia for this patient and was safely applied.

Long QT-Syndrome With Torsades de Pointes Managed Considering Financial Constraints Faced by the Patient.

Long QT syndrome (LQTS) is a rare arrhythmogenic condition characterized by abnormally long QT intervals on an electrocardiogram. The prevalence varies between 1 in 3000 and 1 in 10,000 but often remains undiagnosed. It is responsible for 3000 to 4000 sudden deaths among children and adults in the United States alone. LQTS can lead to torsades de pointes which is seen as twisting of QRS complex on electrocardiogram. We report a case of a 35-year-old patient with LQTS who presented with syncope and was found to have torsades de pointes. After acute management the patient was advised for automatic implantable cardioverter defibrillator (AICD) but because of financial constraints, she was placed on beta-blockers and permanent pacemaker.