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Journal of the American Heart... Jul 2022Background Diagnosis is particularly challenging in concealed or asymptomatic long QT syndrome (LQTS). Provocative testing, unmasking the characterization of LQTS, is a... (Meta-Analysis)
Meta-Analysis Review
Background Diagnosis is particularly challenging in concealed or asymptomatic long QT syndrome (LQTS). Provocative testing, unmasking the characterization of LQTS, is a promising alternative method for the diagnosis of LQTS, but without uniform standards. Methods and Results A comprehensive search was conducted in PubMed, Embase, and the Cochrane Library through October 14, 2021. The fixed effects model was used to assess the effect of the provocative testing on QTc interval. A total of 22 studies with 1137 patients with LQTS were included. At baseline, QTc interval was 40 ms longer in patients with LQTS than in controls (mean difference [MD], 40.54 [95% CI, 37.43-43.65]; <0.001). Compared with the control group, patients with LQTS had 28 ms longer ΔQTc upon standing (MD, 28.82 [95% CI, 23.05-34.58]; <0.001), nearly 30 ms longer both at peak exercise (MD, 27.31 [95% CI, 21.51-33.11]; <0.001) and recovery 4 to 5 minutes (MD, 29.85 [95% CI, 24.36-35.35]; <0.001). With epinephrine infusion, QTc interval was prolonged both in controls and patients with QTS, most obviously in LQT1 (MD, 68.26 [95% CI, 58.91-77.60]; <0.001) and LQT2 (MD, 60.17 [95% CI, 50.18-70.16]; <0.001). Subgroup analysis showed QTc interval response to abrupt stand testing and exercise testing varied between LQT1, LQT2, and LQT3, named Type Ⅰ, Type Ⅱ, and Type Ⅲ. Conclusions QTc trend Type Ⅰ and Type Ⅲ during abrupt stand testing and exercise testing can be used to propose a prospective evaluation of LQT1 and LQT3, respectively. Type Ⅱ QTc trend combined epinephrine infusion testing could distinguish LQT2 from control. A preliminary diagnostic workflow was proposed but deserves further evaluation.
Topics: Electrocardiography; Epinephrine; Exercise Test; Genotype; Humans; Long QT Syndrome
PubMed: 35861842
DOI: 10.1161/JAHA.122.025246 -
Circulation. Arrhythmia and... May 2020Long QT syndrome (LQTS) is a leading cause of sudden cardiac death in early life and has been implicated in ≈10% of sudden infant deaths and unexplained stillbirths....
BACKGROUND
Long QT syndrome (LQTS) is a leading cause of sudden cardiac death in early life and has been implicated in ≈10% of sudden infant deaths and unexplained stillbirths. The purpose of our study was to use fetal magnetocardiography to characterize the electrophysiology and rhythm phenotypes of fetuses with de novo and inherited LQTS variants and identify risk factors for sudden death before birth.
METHODS
We reviewed the fetal magnetocardiography database from the University of Wisconsin Biomagnetism Laboratory for fetuses with confirmed LQTS. We assessed waveform intervals, heart rate, and rhythm, including the signature LQTS rhythms: functional 2° atrioventricular block, T-wave alternans, and torsade de pointes (TdP).
RESULTS
Thirty-nine fetuses had pathogenic variants in LQTS genes: 27 carried the family variant, 11 had de novo variants, and 1 was indeterminate. De novo variants, especially de novo SCN5A variants, were strongly associated with a severe rhythm phenotype and perinatal death: 9 (82%) showed signature LQTS rhythms, 6 (55%) showed TdP, 5 (45%) were stillborn, and 1 (9%) died in infancy. Those that died exhibited novel fetal rhythms, including atrioventricular block with 3:1 conduction ratio, QRS alternans in 2:1 atrioventricular block, long-cycle length TdP, and slow monomorphic ventricular tachycardia. Premature ventricular contractions were also strongly associated with TdP and perinatal death. Fetuses with familial variants showed a lower incidence of signature LQTS rhythm (6/27=22%), including TdP (3/27=11%). All were live born.
CONCLUSIONS
The malignancy of de novo LQTS variants was remarkably high and demonstrate that these mutations are a significant cause of stillbirth. Their ability to manifest rhythms not known to be associated with LQTS increases the difficulty of echocardiographic diagnosis and decreases the likelihood that a resultant fetal loss is attributed to LQTS. Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT03047161.
Topics: Cause of Death; Databases, Factual; Female; Fetal Heart; Genetic Predisposition to Disease; Gestational Age; Heart Rate, Fetal; Heredity; Humans; Long QT Syndrome; Magnetocardiography; Mutation; Phenotype; Predictive Value of Tests; Pregnancy; Prenatal Diagnosis; Risk Assessment; Risk Factors; Stillbirth
PubMed: 32421437
DOI: 10.1161/CIRCEP.119.008082 -
Pharmacology & Therapeutics Aug 2017Since the early 1990s, the concept of primary "inherited" arrhythmia syndromes or ion channelopathies has evolved rapidly as a result of revolutionary progresses made in... (Review)
Review
Since the early 1990s, the concept of primary "inherited" arrhythmia syndromes or ion channelopathies has evolved rapidly as a result of revolutionary progresses made in molecular genetics. Alterations in genes coding for membrane proteins such as ion channels or their associated proteins responsible for the generation of cardiac action potentials (AP) have been shown to cause specific malfunctions which eventually lead to cardiac arrhythmias. These arrhythmic disorders include congenital long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, short QT syndrome, progressive cardiac conduction disease, etc. Among these, long QT and Brugada syndromes are the most extensively studied, and drugs cause a phenocopy of these two diseases. To date, more than 10 different genes have been reported to be responsible for each syndrome. More recently, it was recognized that long QT syndrome can be latent, even in the presence of an unequivocally pathogenic mutation (silent mutation carrier). Co-existence of other pathological conditions in these silent mutation carriers may trigger a malignant form of ventricular arrhythmia, the so called torsade de pointes (TdP) that is most commonly brought about by drugs. In analogy to the drug-induced long QT syndrome, Brugada type 1 ECG can also be induced or unmasked by a wide variety of drugs and pathological conditions; so physicians may encounter patients with a latent form of Brugada syndrome. Of particular note, Brugada syndrome is frequently associated with atrial fibrillation whose therapeutic agents such as Vaughan Williams class IC drugs can unmask the dormant and asymptomatic Brugada syndrome. This review describes two types of drug-induced arrhythmias: the long QT and Brugada syndromes.
Topics: Animals; Brugada Syndrome; Death, Sudden, Cardiac; Humans; Long QT Syndrome
PubMed: 28527921
DOI: 10.1016/j.pharmthera.2017.05.001 -
CMAJ : Canadian Medical Association... Aug 2011
Topics: Adrenergic beta-Antagonists; Adult; British Columbia; Child, Preschool; Electrocardiography; Female; Humans; KCNQ1 Potassium Channel; Long QT Syndrome; Mutation; Prognosis
PubMed: 21482651
DOI: 10.1503/cmaj.100138 -
International Journal of Molecular... Mar 2019The QT interval occupies a pivotal role in drug development as a surface biomarker of ventricular repolarization. The electrophysiologic substrate for QT prolongation... (Review)
Review
The QT interval occupies a pivotal role in drug development as a surface biomarker of ventricular repolarization. The electrophysiologic substrate for QT prolongation coupled with reports of non-cardiac drugs producing lethal arrhythmias captured worldwide attention from government regulators eventuating in a series of guidance documents that require virtually all new chemical compounds to undergo rigorous preclinical and clinical testing to profile their QT liability. While prolongation or shortening of the QT interval may herald the appearance of serious cardiac arrhythmias, the positive predictive value of an abnormal QT measurement for these arrhythmias is modest, especially in the absence of confounding clinical features or a congenital predisposition that increases the risk of syncope and sudden death. Consequently, there has been a paradigm shift to assess a compound's cardiac risk of arrhythmias centered on a mechanistic approach to arrhythmogenesis rather than focusing solely on the QT interval. This entails both robust preclinical and clinical assays along with the emergence of concentration QT modeling as a primary analysis tool to determine whether delayed ventricular repolarization is present. The purpose of this review is to provide a comprehensive understanding of the QT interval and highlight its central role in early drug development.
Topics: Animals; Arrhythmias, Cardiac; Drug Development; Electrocardiography; Heart; Heart Ventricles; Humans; Long QT Syndrome
PubMed: 30884748
DOI: 10.3390/ijms20061324 -
Swiss Medical Weekly 2013The long QT syndrome (LQTS) is a leading cause of sudden death in the young. It is not as rare as previously assumed, given its established prevalence of 1:2,000 live... (Review)
Review
The long QT syndrome (LQTS) is a leading cause of sudden death in the young. It is not as rare as previously assumed, given its established prevalence of 1:2,000 live births. It is characterised by prolongation of the QT interval and by the occurrence of syncope, due to torsades-des-pointes ventricular tachycardia, cardiac arrest and sudden death; these life-threatening cardiac events are usually, but not always, associated with physical or emotional stress. It is a genetic disorder, and knowledge of the genotype impacts significantly on management. Extremely effective therapies are available, which makes the existence of undiagnosed affected and symptomatic patients inexcusable. Indeed, mortality for properly treated patients has now declined to around 1% over a 10-year period. This review, aimed at the clinical cardiologist, discusses briefly the essential genetic information and focuses primarily on the main issues of diagnosis and therapy. One special point of interest is in the impact of genetics on clinical management and the potential medicolegal consequences of not pursuing genetic screening in the proband and hence in the family members.
Topics: Adrenergic beta-Antagonists; Death, Sudden, Cardiac; Defibrillators, Implantable; Electrocardiography; Ganglionectomy; Genotype; Humans; Long QT Syndrome; Mutation; Sympathectomy
PubMed: 24089242
DOI: 10.4414/smw.2013.13843 -
Value in Health : the Journal of the... Jul 2015Recent improvements in the identification of the genetic basis of long QT syndrome (LQTS) have led to significant changes in the diagnosis and management of this... (Review)
Review
BACKGROUND
Recent improvements in the identification of the genetic basis of long QT syndrome (LQTS) have led to significant changes in the diagnosis and management of this life-threatening condition. Genetic and electrocardiogram (ECG) tests are the most relevant examples among testing strategies for LQTS, yet their cost-effectiveness remains controversial.
OBJECTIVE
The aim of this work was to review the available evidence on the cost-effectiveness of genetic and ECG testing strategies for the diagnosis of LQTS.
METHODS
We performed a systematic review of the literature on the cost-effectiveness of genetic and ECG screening strategies for the early detection of LQTS using MEDLINE, EMBASE, and CRD databases between 2000 and 2013. A weighted version of Drummond checklist was instrumental in further assessing the quality of the included studies.
RESULTS
We identified four eligible articles. Among them, genetic testing in the early detection of LQTS was cost-effective compared with no testing in symptomatic cases and not cost-effective when compared with watchful waiting in asymptomatic first-degree relatives of patients with established LQTS although it reached cost-effectiveness in higher risk subgroups, whereas ECG testing in neonates was highly cost-effective when compared with any screening strategy.
CONCLUSIONS
LQTS profiling and patients' stratification have the potential to improve the disease management. Because of the limited current knowledge in this field, the present review recommends to perform further cost-effectiveness evaluations of the genetic and ECG screening alternatives, especially within European health care systems, which are still not available in the literature on genetic testing.
Topics: Age Factors; Comparative Effectiveness Research; Cost-Benefit Analysis; Electrocardiography; Genetic Predisposition to Disease; Genetic Testing; Health Care Costs; Heart Rate; Humans; Infant, Newborn; Long QT Syndrome; Models, Economic; Phenotype; Predictive Value of Tests; Young Adult
PubMed: 26297099
DOI: 10.1016/j.jval.2015.03.1788 -
Progress in Biophysics and Molecular... Jan 2016Release of Ca(2+) ions from sarcoplasmic reticulum (SR) into myocyte cytoplasm and their binding to troponin C is the final signal form myocardial contraction.... (Review)
Review
Release of Ca(2+) ions from sarcoplasmic reticulum (SR) into myocyte cytoplasm and their binding to troponin C is the final signal form myocardial contraction. Synchronous contraction of ventricular myocytes is necessary for efficient cardiac pumping function. This requires both shuttling of Ca(2+) between SR and cytoplasm in individual myocytes, and organ-level synchronization of this process by means of electrical coupling among ventricular myocytes. Abnormal Ca(2+) release from SR causes arrhythmias in the setting of CPVT (catecholaminergic polymorphic ventricular tachycardia) and digoxin toxicity. Recent optical mapping data indicate that abnormal Ca(2+) handling causes arrhythmias in models of both repolarization impairment and profound bradycardia. The mechanisms involve dynamic spatial heterogeneity of myocardial Ca(2+) handling preceding arrhythmia onset, cell-synchronous systolic secondary Ca(2+) elevation (SSCE), as well as more complex abnormalities of intracellular Ca(2+) handling detected by subcellular optical mapping in Langendorff-perfused hearts. The regional heterogeneities in Ca(2+) handling cause action potential (AP) heterogeneities through sodium-calcium exchange (NCX) activation and eventually overwhelm electrical coupling of the tissue. Divergent Ca(2+) dynamics among different myocardial regions leads to temporal instability of AP duration and - on the patient level - in T wave lability. Although T-wave alternans has been linked to cardiac arrhythmias, non-alternans lability is observed in pre-clinical models of the long QT syndrome (LQTS) and CPVT, and in LQTS patients. Analysis of T wave lability may provide a real-time window on the abnormal Ca(2+) dynamics causing specific arrhythmias such as Torsade de Pointes (TdP).
Topics: Animals; Calcium; Electrophysiological Phenomena; Humans; Intracellular Space; Long QT Syndrome; Sex Characteristics
PubMed: 26631594
DOI: 10.1016/j.pbiomolbio.2015.11.003 -
Italian Heart Journal. Supplement :... Mar 2001In clinical cardiology, resort has recently been made to molecular genetics in order to explain some mechanisms that underlie sudden cardiac death in young people with... (Review)
Review
In clinical cardiology, resort has recently been made to molecular genetics in order to explain some mechanisms that underlie sudden cardiac death in young people with structurally normal hearts. It has become evident that genetic mutations regarding cardiac ion channels may disrupt the delicate balance of currents in the action potential, thus inducing malignant ventricular tachyarrhythmias. The cardiac sodium channel gene, SCN5A, is involved in two of such arrhythmogenic diseases, the Brugada syndrome and one form of the long QT syndrome (LQT3). It is believed that these syndromes result from opposite molecular effects: Brugada syndrome mutations cause a reduced sodium current, while LQT3 mutations are associated with a gain of function. The effects of class I antiarrhythmic drugs have been used to differentiate these diseases. Intravenous flecainide is used as a highly specific test to unmask the electrocardiographic phenotype of the Brugada syndrome. On the other hand, on the basis of experimental and clinical studies, the possibility that the same drugs act as a gene-specific therapy in this disorder by contrasting the effect of mutations in LQT3 has been explored. Recent evidence shows that phenotypic overlap may exist between the Brugada syndrome and LQT3. One large family with a SCN5A mutation and a "mixed" electrocardiographic pattern (prolonged QT interval and ST-segment elevation) has been reported. Moreover, our recent data showed that flecainide challenge may elicit ST-segment elevation in some LQT3 patients. The presence of "intermediate" phenotypes highlights a remarkable heterogeneity suggesting that clinical features may depend upon the single mutation. Only deepened understanding of the genotype-phenotype correlation will allow the definition of the individual patient's risk and the development of guidelines for clinical management.
Topics: Anti-Arrhythmia Agents; Death, Sudden, Cardiac; Diagnosis, Differential; Humans; Long QT Syndrome; Syncope; Syndrome
PubMed: 11307783
DOI: No ID Found -
Anesthesiology Sep 2017
Topics: Child, Preschool; Electrocardiography; Humans; Long QT Syndrome; Male
PubMed: 28346324
DOI: 10.1097/ALN.0000000000001618