View clinical trials related to Long QT Syndrome.
Filter by:The human ether-a-go-go-related gene HERG (encoding Kv11.1 potassium channels) is expressed in different parts of the body including the heart, pancreas and intestines. In the heart, Kv11.1 channels play a role in ending depolarization by causing repolarization. Loss-of-function mutations of HERG cause long QT syndrome, a condition of elongated QT interval that can lead to ventricular tachycardia, syncope and sudden death. Kv11.1 channels are also found in pancreatic α- and β-cells and intestinal L-cells, where they seem to play a role in the secretion of insulin, glucagon and Glucagon-Like Peptide-1 (GLP-1). Carriers of loss-of-function mutations in the HERG gene have showed increased insulin and incretin responses after glucose ingestion and decreased fasting levels of glucagon compared to matched control persons. Blockade of Kv11.1 has shown to augment glucose dependent insulin secretion and decrease low-glucose stimulated glucagon secretion in isolated α- and β- cells. The investigators of this study hypothesize that a blockade of Kv11.1 channels will increase incretin and β cell function and decrease α cell function and thus lead to lower glucose levels in humans after glucose intake. To investigate this, The investigators of this study will perform a randomized, cross sectional study of up to 40 healthy study participants who will serve as their own controls. The study participants will undergo two 6-hours oral glucose tolerance tests, one after intake of a known Kv11.1 blocker (moxifloxacin) and one control oral glucose tolerance test after intake of placebo. Prior to both tests the study participants will wear a continuous glucose monitor and on the day of the tests they will fill out a glucose questionnaire. Investigation of the physiological role of HERG in metabolism may provide a better insight on metabolic regulation.
Obstructive sleep apnea (OSA) has been associated with cardiac repolarization abnormalities and implicated in sudden cardiac death. A biologically plausible mechanism by which OSA exerts this lethality is by QT interval prolongation, a known marker of ventricular tachyarrhythmias (VTA) leading to cardiac death. Congenital long QT syndrome (LQTS) is a familial arrhythmogenic disorder characterized by prolonged QT interval on the electrocardiogram and increased propensity for VTA. Preliminary data identify an association of the extent of severity of OSA and progressive prolongation of the corrected QT interval in LQTS.
The Long QT syndrome is associated with potentially life-threatening cardiac arrhythmias as ventricular tachycardia (Torsade de pointes) as well as ventricular fibrillation, and might lead to syncope as well as sudden cardiac death (1). Good results have been achieved by treating patient at risk with beta blockers and implantable cardiac defibrillator (ICD). It is therefore important to diagnose the condition as early as possible as the disease is treatable (2). Prolonged QT duration might also be induced by the intake of numerous pharmaceutical substances, as well as with electrolyte disturbances, which also increases the risk of life-threatening cardiac arrhythmias. Furthermore, congenital LQTS can arise from mutations in one of at least 13 different genes. Many of these genes encode proteins which are constituents of ion channels. The genetically defined long QT syndrome has autosomal dominant (Romano Ward Syndrome) or autosomal recessive (Jervell and Lange-Nielsen Syndrome) inheritance. In this study we are using the hospital ECG database obtained with the GE Marquette 12SL ECG Analysis Program® at Telemark Hospital Skien recorded between March 2004 and April 2014. This database stores approximately 200 000 ECG recordings from 60 000 unique patients. By using the search algorithm in the MUSE ECG database, 2398 recordings have been be identified from 1603 patients where the corrected QT time is longer than 500 ms, and QRS is less than 120 ms. ECG recordings with QT intervals longer than 500 ms represents less than 1% of the population (5). Individuals having these recordings are selected for extensive clinical follow up. The patients will be offered the opportunity to have genetic analysis performed in order to distinguish between inherited or acquired long QT syndrome. The appropriate treatment will be initiated according to guidelines for patients with inherited QT syndrome. For patients with aquired long QT syndrome substitution of unfavourable pharmacotherapy or correction of electrolytes shall be performed in order to reduce their risk of cardiac arrhythmias. A T wave morphology score gives independent prognostic information useful for risk stratification. The purpose of this substudy is to examine if the T wave morphology score applied on the 1531 patients ECGs with QTc >500 ms, has independent prognostic value in this cohort.
The projects will try and optimise the risk stratification for patients with Long QT syndrome by investigating how the exposure of physical and acoustic stress will affect the QT-dynamics and if beta blockers protect against arrhythmias by suppressing this dynamic QT-prolongation. Furthermore, the project will investigate the effects of Spironolactone on the QT-dynamics tested by "Brisk Standing". First, patients are tested with known arrhythmic triggers and they are then administered thier normal dose of beta blockers. Hereafter, "Brisk Standing" test is performed and the patients are on Spironolactone for seven days. After seven days treatment the "Brisk Standing" is repeated.
Patients with cardiac channelopathies needing restorative dental treatment will be included in two sessions of the study, using local dental anesthetic: lidocaine 2% with epinephrine and lidocaine 2% without vasoconstrictor. The safety of the use of two cartridges (3.6 mL) will be evaluated. The patients will be their own control and will be assessed by Holter monitoring for 28 hours, blood pressure measurement and anxiety measuring.
This study will assess whether exposure response analysis of the electrocardiographic QTc and J-Tpeakc intervals in Phase 1 clinical pharmacology studies can be used to confirm that drugs that predominantly block the potassium channel encoded by the human ether-à-go-go-related gene (hERG) with approximately equipotent late sodium and/or calcium block ("balanced ion channel" drugs) do not cause J-Tpeakc prolongation and that drugs that predominantly block hERG without late sodium or L-type calcium current block ("predominant hERG" drugs) cause QTc prolongation.
The postnatal diagnosis of Long QT Syndrome (LQTS) is suggested by a prolonged QT interval on 12 lead electrocardiogram (ECG), strengthened by a positive family history and/or characteristic arrhythmias and confirmed by genetic testing. However, for several reasons such LQTS testing cannot be performed successfully before birth. First, fetal ECG is not possible and direct measure of the fetal QT interval by magnetocardiography is limited to fewer than 10 sites world-wide. Second, while genetic testing can be performed in utero, there is risk to the pregnancy and the fetus. Third, although some fetuses present with arrhythmias easily recognized as LQTS (torsade des pointes (TdP) and/or 2° atrioventricular (AV) block, this is uncommon, occurring in <25% of fetal LQTS cases. Rather, the most common presentation of fetal LQTS is sinus bradycardia, a subtle rhythm disturbance that often is unappreciated to be abnormal. Consequently, the majority of LQTS cases are unsuspected and undiagnosed during fetal life, with dire consequences. For example, maternal medications commonly used during pregnancy can prolong the fetal QT interval and may provoke lethal fetal ventricular arrhythmias. But the most significant consequence is the missed opportunity for primary prevention of life threatening ventricular arrhythmias after birth because the infant is not suspected to have LQTS before birth. The over-arching goal of the study is to overcome the barriers to prenatal detection of LQTS. The investigators plan to do so by developing an algorithm using fetal heart rate (FHR) which will discriminate fetuses with or without LQTS. Immediate Goal: The investigators propose a multicenter pre-birth observational cohort study to develop a Fetal Heart Rate (FHR)/Gestational Age (GA) algorithm from a cohort of fetuses recruited from 13 national and international centers where one parent is known by prior genetic testing to have a mutation in one of the common LQTS genes: potassium voltage-gated channel subfamily Q member 1 (KCNQ1), potassium voltage-gated channel subfamily H member 2 (KCNH2), or sodium voltage-gated channel alpha subunit 5 (SCN5A). The investigators have chosen this population because 1) These mutations are the most common genetic causes of LQTS, and 2) Offspring will have high risk of LQTS as inheritance of these LQTS gene mutations is autosomal dominant. Thus, progeny of parents with a known mutation are at high (50%) risk of having the same parental LQTS mutation. The algorithm will be developed using FHR measured serially throughout pregnancy. All offspring will undergo postnatal genetic testing for the parental mutation as the gold standard for diagnosing the presence or absence of LQTS.
The list of medications that prolong the QT interval and can provoke torsade de pointes keeps expanding. This list includes not only antiarrhythmic drugs, but also medications with no cardiac indications. All these medications prolong the QT interval because they block a specific potassium channel on the myocardial cell membrane: the channel for the rapid component of the delayed rectifier potassium current or "IKr". The risk for developing torsade de pointes for patients taking any of the medications with IKr blockade capabilities varies from >4% for antiarrhythmic drugs to <0.01% for non-cardiac medications. The risk depends on the strength of IKr blockade, but also on specific patient characteristics. The majority of patients who develop torsade de pointes from non-cardiac medications have identifiable risk factors. In this regard, patients with a congenital long QT syndrome are prone to develop torsade de pointes when treated with QT-prolonging medications. This is because, due to their genetically defective ion channels, patients with Long QT Syndrome (LQTS) have impaired ventricular repolarization and reduced "repolarization reserve." Therefore, it is common medical practice to strongly advise patients with congenital LQTS to avoid all medications that have IKr channel blocker capabilities. it was reported that some flavonoids contained in pink-grapefruit juice block the IKr channel. These investigators also reported that drinking 1 liter of pink-grapefruit juice causes QT prolongation in healthy volunteers. The magnitude of the QT prolongation provoked by grapefruit juice was small However, drugs causing minor QT prolongation in healthy volunteers may provoke major QT prolongation in rare or sick individuals who are then at risk for developing torsade de pointes. Consequently, one could argue that, until proven otherwise, pink-grapefruit should be added to the list of "drugs" that are forbidden for patients with LQTS
The drug-induced long QT syndrome (diLQTS) describes a clinical entity in which administration of a drug produces marked prolongation of the QT interval of the electrocardiogram, associated with the development of a polymorphic ventricular tachycardia, termed torsades de pointes (TdP). The heart rate is an important variable affecting the QT interval. The QT interval normally shortens as the heart rate accelerates; however, the adaptation of the QT interval to sudden heart rate acceleration is not instantaneous. Interestingly, Holter studies show that the speed of response of the QT interval to sudden changes in heart rate (that is, the time it takes the QT interval of a given person to reach a new steady-state QT/RR relation) in healthy persons is highly individual and independent of the basic QTc. The investigators and others recently proposed the "quick standing" test as a simple bedside test that facilitates the diagnosis of congenital LQTS. The test takes advantage of the fact that as one stands up, the heart rate acceleration is abrupt while the associated QT-interval shortening is gradual. As the R-R interval shortens faster than the QT interval, the QT appears to "stretch" toward the next P wave and the corrected QT interval (QTc) for heart rate actually increases momentarily. The phenomenon of "QT stretching" is universal but is exaggerated in patients with LQTS, allowing for a simple but accurate diagnostic test. There is no data on the effects of quick standing on drug-associated form of the long QT syndrome. The investigators therefore propose the present study to better understand who these patients with drug-associated form of the long QT syndrome are and what the significance of their abnormal QT-response is.
The goal is to determine how lifestyle and exercise impact the well-being of individuals with hypertrophic cardiomyopathy (HCM) and long QT syndrome (LQTS). Ancillary study Aim: To understand how the coronavirus epidemic is impacting psychological health and quality of life in the LIVE population