Active clinical trials for "Long QT Syndrome"

To assess the effect of ERB-041 after multiple oral doses on cardiac repolarization as assessed by the QTc interval.

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.

Female sex is an independent risk factor for the potentially fatal drug-induced arrhythmia (irregular heartbeat) known as torsades de pointes (TdP), which is associated with prolongation of the corrected QT (QTc) interval on the electrocardiogram (ECG). Mechanisms for this increased risk in women are not well-understood. QTc interval duration has been shown to fluctuate throughout the phases of the menstrual cycle. Evidence indicates that the QTc interval response to drugs that may cause TdP is greater during the menses and ovulation phases of the menstrual cycle, during which serum progesterone concentrations are lowest, and lesser during the luteal phase, during which serum progesterone concentrations are highest. Additional evidence from our laboratory suggests that progesterone may be protective against TdP. Specific Aim 1: Establish the influence of oral progesterone administration as a preventive method by which to diminish the degree of drug-induced QT interval prolongation in women. Working hypothesis: Oral progesterone administration effectively attenuates enhanced drug-induced QT interval response in women. To test this hypothesis, progesterone or placebo will be administered in a crossover fashion to women during the menses phase of the menstrual cycle. QTc interval response to low-dose ibutilide, a drug known to lengthen the QT interval, will be assessed. The primary endpoint will be individually-corrected QT interval (QTcI) response to ibutilide, in the presence and absence of progesterone, which will be assessed by: 1) Effect on maximum change in QTcI, and 2) Area under the QTcI interval-time curves (AUEC). At the conclusion of this study, we will have established that oral progesterone administration is a safe and effective method of attenuating drug-induced QT interval prolongation.

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.

Torsades de pointes (TdP) is a potentially fatal ventricular arrhythmia associated with corrected QT (QTc) interval prolongation. More than 50 commonly used drugs available on the US market may cause QTc interval prolongation and TdP. While TdP occurs more commonly in women, 33-45% of all cases of TdP have occurred in men. Older age is a risk factor for drug-induced TdP in men, possibly due to declining serum testosterone concentrations. Available evidence shows an inverse relationship between QTc intervals and serum testosterone concentrations. In addition, experimental data, including those from the investigators' laboratory, suggest that both exogenous testosterone or progesterone administration may be protective against prolongation of ventricular repolarization and TdP. Specific Aim: Establish the influence of transdermal testosterone administration and oral progesterone administration as preventive methods by which to diminish the degree of drug-induced QT interval prolongation in men 65 years of age or older. Hypothesis: Transdermal testosterone administration and oral progesterone administration both effectively attenuate drug-induced QT interval response in older men. To test this hypothesis, transdermal testosterone, oral progesterone or placebo will be administered in a 3-way crossover study to men 65 years of age or older. QTc interval response to low-dose ibutilide will be assessed. The primary endpoints will be Fridericia-corrected QT interval (QTF) response to ibutilide, in the presence and absence of testosterone, and in the presence or absence of progesterone: 1) Effect on pre-ibutilide QTF, 2) Effect on maximum post-ibutilide QTF, 3) Effect on % change in post-ibutilide QTF, and 2) Area under the QTF interval-time curves.

The purpose of this study is to further develop and evaluate a diagnostic procedure suitable for use in an inexpensive diagnostic instrument suitable for screening for Long QT Syndrome (LQTS) in the primary care environment.

The objectives of the protocol are to: (1) evaluate the uptake of cascade screening and preventative therapies after the implementation of a simplified screening process and (2) assess proband and family member perspectives about the return of research results and cascade screening for the KCNQ1 Thr224Met variant. The investigators will conduct a mixed methods study in the Old Order Amish community where the KCNQ1 variant is enriched over 100,000-fold compared to other populations. The intervention will offer free, mail-in, saliva-based genetic testing for family members of probands. The rate of uptake of testing and preventative therapy after the intervention is implemented (i.e. when 'simplified' free, mail-in, saliva-based testing was available) will be compared to data from before the intervention (i.e. when 'traditional' $50 blood-based testing was available to family members) when uptake was essentially zero. The primary outcome is the rate of uptake of cascade screening with the intervention ('simplified'). The secondary outcomes include: extent of disclosure of genotype results before and after the intervention, proportion of informed relatives who get screened before and after the intervention, and the uptake of appropriate preventative care (e.g. seeing a cardiologist and/or taking beta-blocker). The tertiary outcomes are demographic characteristics associated with uptake of cascade screening or uptake of preventative therapy. The investigators will also assess qualitative themes surrounding the return of results process and cascade screening using interviews.

This is a single-center, randomized, double-blind, placebo-controlled study to be conducted in 2 parts: single ascending dose (SAD) incorporating a food effect arm and multiple ascending dose (MAD). Potential participants for each part will undergo screening procedures within 28 days of enrollment.

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 primary objective of this research study is to test the hypothesis that late sodium current blocking drugs (mexiletine or lidocaine) can attenuate the effect of hERG potassium channel blocking drugs (dofetilide) on ventricular repolarization (QTc) by shortening early repolarization (J-Tpeakc). The secondary object is to assess the ability of calcium channel block (diltiazem) to reduce the QTc prolongation associated with hERG block (moxifloxacin).