Left Cardiac Sympathetic Denervation Monotherapy in Patients With Congenital Long QT Syndrome

The proarrhythmogenic role of autonomics and emerging neuromodulation approaches to prevent sudden death in cardiac ion channelopathies

Ventricular arrhythmias in cardiac channelopathies are linked to autonomic triggers, which are sub-optimally targeted in current management strategies. Improved molecular understanding of cardiac channelopathies and cellular autonomic signalling could refine autonomic therapies to target the specific signalling pathways relevant to the specific aetiologies as well as the central nervous system centres involved in the cardiac autonomic regulation. This review summarizes key anatomical and physiological aspects of the cardiac autonomic nervous system and its impact on ventricular arrhythmias in primary inherited arrhythmia syndromes. Proarrhythmogenic autonomic effects and potential therapeutic targets in defined conditions including the Brugada syndrome, early repolarization syndrome, long QT syndrome, and catecholaminergic polymorphic ventricular tachycardia will be examined. Pharmacological and interventional neuromodulation options for these cardiac channelopathies are discussed. Promising new targets for cardiac neuromodulation include inhibitory and excitatory G-protein coupled receptors, neuropeptides, chemorepellents/attractants as well as the vagal and sympathetic nuclei in the central nervous system. Novel therapeutic strategies utilizing invasive and non-invasive deep brain/brain stem stimulation as well as the rapidly growing field of chemo-, opto-, or sonogenetics allowing cell-specific targeting to reduce ventricular arrhythmias are presented.

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

Pediatric cardiomyopathies (CMs) and electrical diseases constitute a heterogeneous spectrum of disorders distinguished by structural and electrical abnormalities in the heart muscle, attributed to a genetic variant. They rank among the main causes of morbidity and mortality in the pediatric population, with an annual incidence of 1.1-1.5 per 100,000 in children under the age of 18. The most common conditions are dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Despite great enthusiasm for research in this field, studies in this population are still limited, and the management and treatment often follow adult recommendations, which have significantly more data on treatment benefits. Although adult and pediatric cardiac diseases share similar morphological and clinical manifestations, their outcomes significantly differ. This review summarizes the latest evidence on genetics, clinical characteristics, management, and updated outcomes of primary pediatric CMs and electrical diseases, including DCM, HCM, arrhythmogenic right ventricular cardiomyopathy (ARVC), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), and short QT syndrome (SQTS).

Precision therapy in congenital long QT syndrome

Long QT syndrome (LQTS) is a potentially life-threatening, but highly treatable genetic heart disease. LQTS-directed therapies often consist of beta-blockers (BBs), left cardiac sympathetic denervation (LCSD), and/or an implantable cardioverter defibrillator (ICD). However, in clinical practice, many patient-specific and genotype-directed permutations exist. Herein, we aim to review the spectrum of treatment configurations utilized at a single, tertiary center specializing in the care of patients with LQTS to demonstrate optimal LQTS-directed management is not amenable to a "one-size-fits-all" approach but instead benefits from patient- and genotype-tailored strategies.

Precision Medicine and Cardiac Channelopathies: Human iPSCs Take the Lead

Sudden cardiac death (SCD) is one of the leading causes of death worldwide, usually involving young people. SCD remains a critical public health problem accounting for 185,000-450,000 deaths annually, representing around 7%-18% of all deaths globally. As per evidence, ∼2%-54% of sudden unexpected deaths in people under the age of 35 years fail to show evidence of structural cardiac abnormalities at autopsy, making ion channelopathies the probable causes in such cases. The most generally recognized cardiac ion channelopathies with genetic testing are long QT syndrome (LQTS), Brugada syndrome (BrS), short QT syndrome (SQTS), and catecholaminergic polymorphic ventricular tachycardia (CPVT). The substantial progress in understanding the genetics of ion channelopathies in the last 2 decades has obliged the early diagnosis and prevention of SCD to a certain extent. In this review, we analyze the critical challenges and recent advancements in the identification, risk stratification, and clinical management of potentially fatal cardiac ion channel disorders. We also emphasize the application of precision medicine (PM) and artificial intelligence (AI) for comprehending the underlying genetic mechanisms, especially the role of human induced pluripotent stem cell (iPSC) based platforms to unravel the primary refractory clinical problems associated with channelopathies.

Polypharmacy, Gender Disparities, and Ethnic and Racial Predispositions in Long QT Syndrome: An In-Depth Review

Long QT syndrome (LQTS) is a complex disorder of cardiac electrophysiology. It is characterized by delayed myocardial polarization leading to QT prolongation and alterations on the ST segment and T wave visible on electrocardiogram (ECG). Syncope is a common manifestation, and torsade de pointes (TdP) can lead to sudden cardiac death. Three major LQTS genes (KCI31, KCNH2, and SCN5) lead to most of the cases of LQTS. Lifestyle modifications, beta blockers, and implantable cardioverter defibrillator (ICD) placement are the main treatments for LQTS. Polypharmacy, including QT-prolonging drugs, has been shown to worsen LQTS. The impact on potassium channels and the human ether-a-go-go-related gene (hERG) is the mechanism behind the QT interval prolongation caused by these medications. There is an increased incidence of LQTS among African-American men and women as compared to Caucasians. Women with LQTS tend to have a higher mortality rate from the condition, especially during menstruation and shortly after giving birth. Genetic testing is reserved to those patientswho exhibit either a strong clinical index of suspicion or experience persistent QT prolongation despite their lack of symptoms. Knowing the genetics, racial, and gender discrepancies can help improve patient management and a better comprehension on each case. Proper understanding of how ion channels function and their interaction with medications will lead to a better comprehension and to develop effective forms to treat those patients.

Anesthetic management for inhibiting sympathetic activation in an adolescent patient diagnosed with catecholaminergic polymorphic ventricular tachycardia and undergoing left cardiac sympathetic denervation: A case report

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic disorder in which catecholamine release during exercise or emotional stress cause fatal tachyarrhythmias. In this paper, we discuss methods to minimize the sympathetic stimulation that can occur during the perioperative period in patients undergoing left cardiac sympathetic denervation to surgically treat CPVT.

Quelling the Storm: A Review of the Management of Electrical Storm

Heightened sympathetic input to the myocardium potentiates cardiac electrical instability and may herald an electrical storm. An electrical storm is characterized by 3 or more episodes of ventricular tachycardia, ventricular fibrillation, or appropriate internal cardiac defibrillator shocks within 24 hours. Management of electrical storms is resource-intensive and inevitably requires careful coordination between multiple subspecialties. Anesthesiologists have an important role in acute, subacute, and long-term management. Identifying the phase of an electrical storm and understanding the characteristics of each morphology may help the anesthesiologist anticipate the management approach. In the acute phase, management of an electrical storm is aimed at providing advanced cardiac life support and identifying reversible causes. After initial stabilization, subacute management focuses on dampening the sympathetic surge with sedation, thoracic epidural, or stellate ganglion blockade. Definitive long-term management with surgical sympathectomy or catheter ablation also may be warranted. Our objective is to provide an overview of electrical storms and the anesthesiologist's role in management.

Bilateral Cardiac Sympathetic Denervation in Patients with Congenital Long QT Syndrome

BACKGROUND

Long QT syndrome (LQTS) is a potentially lethal, yet treatable genetic heart disease for which left cardiac sympathetic denervation (LCSD) is a class I recommendation. Recent reports have suggested bilateral CSD (BiCSD) as the initial surgical denervation therapy in LQTS.

OBJECTIVE

To determine the frequency and settings in which BiCSD was used in a tertiary referral center with expertise in LCSD.

METHODS

We performed retrospective review of 234 LCSD patients/1,638 (14%) LQTS patients who underwent sympathetic denervation at our institution to identify the subset with BiCSD. Cardiac events (CEs) before LCSD, after LCSD, and after completion of BiCSD were recorded and defined as being an appropriate ICD shock, arrhythmic syncope or sudden cardiac arrest.

RESULTS

Only 11 patients (4.7%, 6[55%] females) had BiCSD at our institution. Patients who received BiCSD trended towards being younger at diagnosis (6±15 vs. 14±13 years, p=0.06) and being more likely to be symptomatic (73% vs. 53%, p=0.07) than the larger LCSD-only cohort. Continued CEs post-LCSD (3.8 CEs per patient on average) was the predominant determinant to return for BiCSD. Over 60 combined years of follow-up, 4 patients have not had a post-BiCSD CE, while the other 7 patients average 3.6 non-lethal CEs.

CONCLUSIONS

Less than 5% of all patients receiving denervation therapy underwent BiCSD. When BiCSD was chosen, it was almost always done in a staged sequential manner starting with LCSD first and when driven by the arrhythmogenicity of the LQTS substrate, despite otherwise optimized guideline-directed therapies.

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.

Implantable defibrillators in primary prevention of genetic arrhythmias. A shocking choice?

Many previously unexplained life-threatening ventricular arrhythmias and sudden cardiac deaths (SCDs) in young individuals are now recognized to be genetic in nature and are ascribed to a growing number of distinct inherited arrhythmogenic diseases. These include hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (VT), and short QT syndrome. Because of their lower frequency compared to coronary disease, risk factors for SCD are not very precise in patients with inherited arrhythmogenic diseases. As randomized studies are generally non-feasible and may even be ethically unjustifiable, especially in the presence of effective therapies, the risk assessment of malignant arrhythmic events such as SCD, cardiac arrest due to ventricular fibrillation (VF), appropriate implantable cardioverter defibrillator (ICD) interventions, or ICD therapy on fast VT/VF to guide ICD implantation is based on observational data and expert consensus. In this document, we review risk factors for SCD and indications for ICD implantation and additional therapies. What emerges is that, allowing for some important differences between cardiomyopathies and channelopathies, there is a growing and disquieting trend to create, and then use, semi-automated systems (risk scores, risk calculators, and, to some extent, even guidelines) which then dictate therapeutic choices. Their common denominator is a tendency to favour ICD implantation, sometime with reason, sometime without it. This contrasts with the time-honoured approach of selecting, among the available therapies, the best option (ICDs included) based on the clinical judgement for the specific patient and after having assessed the protection provided by optimal medical treatment.

Spectrum and Prevalence of Side Effects and Complications with Guideline Directed Therapies for Congenital Long QT Syndrome

BACKGROUND

Beta blockers (BBs), sodium channel blockers (SCBs), left cardiac sympathetic denervation (LCSD), and implantable cardioverter defibrillators (ICDs) are used to prevent or counter long QT syndrome (LQTS)-triggered syncope, seizures, and sudden cardiac death (SCD). The spectrum and extent of side effects/complications associated with these guideline-directed therapies (GDTs) remain unknown.

OBJECTIVE

Identify the types/prevalence of treatment-associated side effects/complications for patients with the most common LQTS subtypes following GDT.

METHODS

Retrospective analysis was performed on 1310 patients with type 1, 2 or 3 LQTS (LQT1-LQT3) evaluated in Mayo Clinic's Windland Smith Rice Genetic Heart Rhythm Clinic (average age at diagnosis 22±18 years; average treated follow-up 5±5 years) and treated with ≥1 of the common GDTs for LQTS.

RESULTS

BBs were used in 1102 (84%), SCBs in 104 (8%), LCSD in 197 (15%), and an ICD in 251 (19%) patients. Overall, 54% of patients reported at least one treatment-associated side effect/complication. 490/1102 (44%) patients treated with BBs reported side effects with fatigue (381; 35%) being most common. 28/104 (27%) SCB-treated patients reported side effects, most common being GI distress/vomiting (18, 17%). 80/197 (41%) patients reported side effects after LCSD, most reporting neuropathic pain (57; 29%). 129/251 (51%) patients experienced ≥1 complication after ICD implantation, including inappropriate shocks (46, 18%).

CONCLUSION

Although LQTS-triggered SCD is uncommon in the properly treated patient, this study demonstrates that contemporary GDTs for LQTS are not innocuous. Their treatment-related side effects are not trivial and should compel an ongoing quest for new LQTS therapies.

Congenital Long QT Syndrome

Congenital long QT syndrome (LQTS) encompasses a group of heritable conditions that are associated with cardiac repolarization dysfunction. Since its initial description in 1957, our understanding of LQTS has increased dramatically. The prevalence of LQTS is estimated to be ∼1:2,000, with a slight female predominance. The diagnosis of LQTS is based on clinical, electrocardiogram, and genetic factors. Risk stratification of patients with LQTS aims to identify those who are at increased risk of cardiac arrest or sudden cardiac death. Factors including age, sex, QTc interval, and genetic background all contribute to current risk stratification paradigms. The management of LQTS involves conservative measures such as the avoidance of QT-prolonging drugs, pharmacologic measures with nonselective β-blockers, and interventional approaches such as device therapy or left cardiac sympathetic denervation. In general, most forms of exercise are considered safe in adequately treated patients, and implantable cardioverter-defibrillator therapy is reserved for those at the highest risk. This review summarizes our current understanding of LQTS and provides clinicians with a practical approach to diagnosis and management.

Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome characterised by adenergically mediated bidirectional and/or polymorphic ventricular tachycardia. CPVT is a significant cause of autopsy-negative sudden death in children and adolescents, although it can also affect adults. It is often caused by pathogenic variants in the cardiac ryanodine receptor gene as well as other rarer genes. Early identification and risk stratification is of major importance. β-blockers are the cornerstone of therapy. Sodium channel blockers, specifically flecainide, have an additive role. Left cardiac sympathetic denervation is playing an increasing role in suppression of arrhythmia and symptoms. Concerns have been raised, however, about the efficacy of implantable cardioverter defibrillator therapy and the risk of catecholamine driven proarrhythmic storms. In this review, we summarise the clinical characteristics, genetics, and diagnostic and therapeutic strategies for CPVT and describe recent advances and challenges.

Clinical Genetics of Inherited Arrhythmogenic Disease in the Pediatric Population

Sudden death is a rare event in the pediatric population but with a social shock due to its presentation as the first symptom in previously healthy children. Comprehensive autopsy in pediatric cases identify an inconclusive cause in 40-50% of cases. In such cases, a diagnosis of sudden arrhythmic death syndrome is suggested as the main potential cause of death. Molecular autopsy identifies nearly 30% of cases under 16 years of age carrying a pathogenic/potentially pathogenic alteration in genes associated with any inherited arrhythmogenic disease. In the last few years, despite the increasing rate of post-mortem genetic diagnosis, many families still remain without a conclusive genetic cause of the unexpected death. Current challenges in genetic diagnosis are the establishment of a correct genotype-phenotype association between genes and inherited arrhythmogenic disease, as well as the classification of variants of uncertain significance. In this review, we provide an update on the state of the art in the genetic diagnosis of inherited arrhythmogenic disease in the pediatric population. We focus on emerging publications on gene curation for genotype-phenotype associations, cases of genetic overlap and advances in the classification of variants of uncertain significance. Our goal is to facilitate the translation of genetic diagnosis to the clinical area, helping risk stratification, treatment and the genetic counselling of families.

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.

OUP accepted manuscript

Proper management of patients affected by genetic disorders causing life-threatening arrhythmias is important for several reasons, including even societal ones, given the predominantly young age of those affected. Incorrect management often has dire consequences, ranging from unnecessary psychologic damage for the patients whose life becomes too limited by the fear of sudden death to equally avoidable tragedies when the entire armamentarium of effective therapies is not fully utilized. In this review, we focus primarily on long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) and deal specifically with the clinical impact of the most commonly used cardiac sympathetic denervation (CSD), namely left cardiac sympathetic denervation (LCSD). The two of us have used LCSD in the management of our patients with either LQTS or CPVT for a very long time and have been involved in ∼500 such interventions. It is on the basis of this personal and direct experience that we wish to share our views with clinical cardiologists and electrophysiologists, adult and paediatric, and with genetic cardiologists. We will begin by reviewing the history and rationale underlying sympathetic denervation therapy and will continue with a disease-specific intensification of therapy, and then with a discussion on how the impressive efficacy of LCSD should translate into guideline-directed therapy in both current and future guidelines, in order to upgrade the quality of care in the era of precision medicine.

ICD shocks and complications in patients with inherited arrhythmia syndromes

Background

There is limited information on the long-term outcomes of ICDs in patients with inherited arrhythmia syndromes.

Methods

Prospective registry study of inherited arrhythmia patients with an ICD. Incidence of therapies and complications were measured as 5-year cumulative incidence proportions and analyzed with the Kaplan-Meier method. Incidence was compared by device indication, diagnosis type and device type. Cox-regression analysis was used to identify predictors of appropriate shock and device complication.

Results

123 patients with a mean follow up of 6.4 ± 4.8 years were included. The incidence of first appropriate shock was 56.52% vs 24.44%, p < 0.05 for cardiomyopathy and channelopathy patients, despite similar ejection fraction (61% vs 60%, p = 0.6). The incidence of first inappropriate shock was 13.46% vs 56.25%, p < 0.01 for single vs. multi-lead devices. The incidence of first lead complication was higher for multi-lead vs. single lead devices, 43.75% vs. 17.31%, p = 0.04. Patients with an ICD for secondary prevention were more likely to receive an appropriate shock than those with primary prevention indication (HR 2.21, CI 1.07-4.56, p = 0.03). Multi-lead devices were associated with higher risk of inappropriate shock (HR 3.99, CI 1.27-12.52, p = 0.02), with similar appropriate shock risk compared to single lead devices. In 26.5% of patients with dual chamber devices, atrial sensing or pacing was not utilized.

Conclusion

The rate of appropriate therapies and ICD complications in patients with inherited arrhythmia is high, particularly in cardiomyopathies with multi-lead devices. Risk-benefit ratio should be carefully considered when assessing the indication and type of device in this population.

Challenging indication of cardioverter defibrillator implantation after sudden cardiac arrest in the very young: a case series of catecholaminergic polymorphic ventricular tachycardia secondary to de novo calmodulin p.Asn98Ser

Background

Calmodulinopathy is an emerging group of primary electrical disease with various, severe, and early onset phenotype. Sudden cardiac arrest (SCA)/death can be the first symptom and current medical management seems insufficient to prevent recurrences. Implantable cardioverter-defibrillator (ICD) in the young is challenging and can be harmful.

Case summary

We report the management of two very young boys (aged 3.5 and 5.5 years old) who survived an SCA due to calmodulin mutation responsible of a catecholaminergic polymorphic ventricular tachycardia phenotype. In both case, SCA had an adrenergic trigger. Despite SCA, ICD implantation was denied by the parents. After thorough discussion with the family, the patients were managed with solely betablocker treatment and loop recorder implantation. At last follow-up of 30 and 23 months, respectively, there were no recurrence of any cardiac event.

Discussion

The benefits of ICD implantation at a very young age must be weighed against the risk complication. In the youngest, whom recreative activities are under constant supervision, the decision, jointly made with the parents, could be to postpone ICD.

Sympatho-adrenergic mechanisms in heart failure: new insights into pathophysiology

The sympathetic nervous system is activated in the setting of heart failure (HF) to compensate for hemodynamic instability. However, acute sympathetic surge or sustained high neuronal firing rates activates β-adrenergic receptor (βAR) signaling contributing to myocardial remodeling, dysfunction and electrical instability. Thus, sympatho-βAR activation is regarded as a hallmark of HF and forms pathophysiological basis for β-blocking therapy. Building upon earlier research findings, studies conducted in the recent decades have significantly advanced our understanding on the sympatho-adrenergic mechanism in HF, which forms the focus of this article. This review notes recent research progress regarding the roles of cardiac β2AR or α1AR in the failing heart, significance of β1AR-autoantibodies, and βAR signaling through G-protein independent signaling pathways. Sympatho-βAR regulation of immune cells or fibroblasts is specifically discussed. On the neuronal aspects, knowledge is assembled on the remodeling of sympathetic nerves of the failing heart, regulation by presynaptic α2AR of NE release, and findings on device-based neuromodulation of the sympathetic nervous system. The review ends with highlighting areas where significant knowledge gaps exist but hold promise for new breakthroughs.

Autonomic cardiac innervation: impact on the evolution of arrhythmias in inherited cardiac arrhythmia syndromes

The autonomic nervous system (ANS) is an essential component of arrhythmogenicity, especially in the absence of structural heart disease and channelopathy. In this article, the authors review the role and characteristics of ANS in various channelopathies. Some of these, such as most long QT syndromes and catecholaminergic polymorphic ventricular tachycardia, are highly dependent on sympathetic activation, while parasympathetic tone is an important factor for arrhythmias in other channelopathies such as Brugada syndrome or early repolarisation syndrome. Recent advances highlighting the subtle role of ANS in channelopathies are presented here, demonstrating that all is far from being so simple and straightforward and revealing some paradoxical behaviours of channelopathies in relation to discrete ANS imbalance.

Diagnosis, management and therapeutic strategies for congenital long QT syndrome

Congenital long QT syndrome (LQTS) is characterised by heart rate corrected QT interval prolongation and life-threatening arrhythmias, leading to syncope and sudden death. Variations in genes encoding for cardiac ion channels, accessory ion channel subunits or proteins modulating the function of the ion channel have been identified as disease-causing mutations in up to 75% of all LQTS cases. Based on the underlying genetic defect, LQTS has been subdivided into different subtypes. Growing insights into the genetic background and pathophysiology of LQTS has led to the identification of genotype–phenotype relationships for the most common genetic subtypes, the recognition of genetic and non-genetic modifiers of phenotype, optimisation of risk stratification algorithms and the discovery of gene-specific therapies in LQTS. Nevertheless, despite these great advancements in the LQTS field, large gaps in knowledge still exist. For example, up to 25% of LQTS cases still remain genotype elusive, which hampers proper identification of family members at risk, and it is still largely unknown what determines the large variability in disease severity, where even within one family an identical mutation causes malignant arrhythmias in some carriers, while in other carriers, the disease is clinically silent. In this review, we summarise the current evidence available on the diagnosis, clinical management and therapeutic strategies in LQTS. We also discuss new scientific developments and areas of research, which are expected to increase our understanding of the complex genetic architecture in genotype-negative patients, lead to improved risk stratification in asymptomatic mutation carriers and more targeted (gene-specific and even mutation-specific) therapies.