1/47. Congenital long-QT syndrome: a case report illustrating diagnostic pitfalls.This article reviews the clinical course of a 10-year-old child with a lifelong history of seizures and congenital deafness who presented after an episode of sudden cardiac arrest secondary to long-QT syndrome-induced torsade de pointes. Jervell-Lange-Nielsen syndrome is a rare cardioauditory syndrome in which affected subjects are susceptible to recurrent syncope and sudden death from ventricular dysrhythmias, usually before the second decade of life. Careful evaluation of suspected subjects is important because of the variability of the QTc interval. Recent research has identified specific gene sequences that encode ion channels responsible for both prolonged QTc interval and deafness. Treatment of symptomatic cardiac disease with beta-blockers in combination with pacemakers and automated internal cardioverter defibrillators can markedly improve quality of life and suppress ventricular dysrhythmias even in the most severely affected subjects. The recent identification of gene sequences identifying some congenital long-QT syndromes may improve screening methods for affected patients and lead to potential therapeutic intervention.- - - - - - - - - - ranking = 1keywords = life (Clic here for more details about this article) |
2/47. haloperidol-induced torsade de pointes.OBJECTIVE: To report a case of torsade de pointes related to the administration of high-dose intravenous haloperidol for the treatment of severe agitation. CASE SUMMARY: Reports in the literature of intravenous haloperidol-induced torsade de pointes are rare. We describe the case of a 41-year-old white woman with no predisposing factors who developed torsade de pointes 55 minutes after a dose of intravenous haloperidol 80 mg (total dosage 915 mg over 7 d). The results of the electrocardiogram were consistent with torsade de pointes and showed a prolonged QTc interval of 610 milliseconds. Intravenous magnesium sulfate 2 g/100 mL NaCl 0.9% was administered, which controlled the arrhythmia. The patient received one additional 80-mg haloperidol dose six hours after the arrhythmia-triggering dose, without reoccurrence of torsade de pointes. haloperidol was then discontinued, and the patient had no further arrhythmias. CONCLUSIONS: Our case report and others from the literature suggest that intravenous haloperidol administration may prolong QT intervals in some patients, precipitating the potentially life-threatening arrhythmia torsade de pointes. Clinicians should be aware of haloperidol's potential to induce torsade de pointes, since it is used regularly for agitation and delirium in the critical care arena.- - - - - - - - - - ranking = 0.33333333333333keywords = life (Clic here for more details about this article) |
3/47. Assessment of ventricular repolarization in deaf-mute children.The long qt syndrome is a congenital disease with frequent familial transmission, characterized primarily by prolongation of the QT interval and by the occurrence of life-threatening arrhythmias. The syndrome may be familial, with or without congenital deafness, or it may be idiopathic. We attempted to assess ventricular repolarization and to identify patients with the Jervell and Lange-Nielsen syndrome among 132 deaf-mute school children. Five deaf-mute subjects had Jervell and Lange-Nielsen syndrome. The deaf-mute subjects were divided into two subgroups according to the length of their QT intervals: group 1 included 5 cases with the long QT interval (>440 msec), and group 2 included 127 subjects with the normal QT interval (< or =440 msec). Group 3 was composed of 96 control subjects. The mean QT, QTc, JT, and JTc intervals (418 /-70, 500 /-38, 302 /- 65, and 389 /-36 msec, respectively) in group 1 were significantly longer than those of group 2 (344 /-23, 408 /-22, 249 /-34, and 291 /-28 msec, respectively) and group 3 (325 /-11, 383 /-26, 228 /-36, and 269 /-46 msec, respectively). The dispersion (d) values (QT-d, QTc-d, JT-d, and JTc-d; 63 /-10, 73 /-8, 60 /-8, and 62 /-11 msec, respectively) of group 1 were significantly longer than those of group 2 (49 /-16, 43 /-11, 48 /-21, and 45 /-18 msec, respectively) and group 3 (33 /-13, 33 /-14, 28 /-16, and 27 /-14 msec, respectively) at similar mean RR intervals. Also, the mean QT, QTc, JT, and JTc intervals and the dispersion values (QT-d, QTc-d, JT-d, and JTc-d) in group 2 were significantly longer than those of group 3 at similar mean RR intervals. Consequently, in this study, we determined that the deaf-mute children who did not meet the criteria for Jervell and Lange-Nielsen syndrome still had evidence of subtle derepolarization abnormalities evidenced by intermediate prolongation of QTc, JTc, and the corresponding measures of dispersion, and we believe an electrocardiogram examination of deaf-mute subjects will reveal this potentially life-threatening syndrome.- - - - - - - - - - ranking = 0.66666666666667keywords = life (Clic here for more details about this article) |
4/47. Evidence for a cardiac ion channel mutation underlying drug-induced QT prolongation and life-threatening arrhythmias.The aim of this study was to test the hypothesis that some cases of drug-induced arrhythmias depend on genetic predisposition. Excessive prolongation of the QT interval and life-threatening arrhythmias (torsades de pointes or ventricular fibrillation) may occur in response to a variety of cardiac and noncardiac drugs, with detrimental effects on patient safety and the investments made by the pharmaceutical industry. Moss and Schwartz hypothesized that some drug-induced arrhythmias might represent cases of "forme fruste" of the congenital long qt syndrome (LQTS). The availability of molecular screening techniques for LQTS genes allowed us to test this hypothesis. An elderly female patient with documented cardiac arrest related to cisapride, a prokynetic drug that blocks I(Kr), and transiently prolonged QT interval underwent mutational analysis of the known LQTS-related genes performed by single-strand conformational polymorphism and dna sequencing. Double-electrode voltage clamp in xenopus oocytes as the expression system was used to study the in vitro cellular phenotype caused by the genetic defect in coexpression with the wild-type (WT) gene. Molecular analysis revealed a heterozygous mutation leading to substitution of a highly conserved amino acid in the pore region of KvLQT1. This mutation was present not only in the patient with ventricular fibrillation but also in her two adult asymptomatic sons who have a normal QT interval. in vitro expression of the mutated KvLQT1 protein showed a severe loss of current with a dominant negative effect on the WT-KvLQT1 channel. Our findings demonstrate that some cases of drug-induced QT prolongation may depend on a genetic substrate. Molecular screening may allow identification among family members of gene carriers potentially at risk if treated with I(Kr) blockers. Evolving technology may lead to rapid screening for mutations of candidate genes that cause drug-induced life-threatening arrhythmias and allow early identification of individuals at risk.- - - - - - - - - - ranking = 2keywords = life (Clic here for more details about this article) |
5/47. Report of a life-threatening arrhythmia after hospital discharge in a liver transplant recipient with previously unknown congenital long qt syndrome.The long qt syndrome affects heart rhythm by prolonging ventricular repolarisation; it is potentially life-threatening since it can evolve into torsades de pointes (a polymorphic ventricular tachycardia) and/or ventricular fibrillation. The case is presented of a 55-year-old liver transplant recipient with a genetically determined long qt syndrome not detected by the standard preoperative cardiological evaluation. It was mild in the immediate post-operative period but developed into torsades de pointes after discharge, probably as a result of therapy. This case was particularly challenging because the first arrhythmic episodes were short and electocardiographically silent, and thus the related faints were thought to have a neurological basis. When the true cause emerged during a monitored episode of torsades de pointes, electric defibrillation was used to restore sinus rhythm and isoproterenol administered to increase heart rate and thus shorten the prolonged QT interval Long-term control was obtained by means of an implantable intracardiac defibrillator. In orthotopic liver transplant recipients with long qt syndrome, particular attention should be given to post-operative therapy as some routinely used drugs can trigger life-threatening ventricular arrhythmias.- - - - - - - - - - ranking = 2keywords = life (Clic here for more details about this article) |
6/47. torsades de pointes caused by mibefradil.We report a case of symptomatic torsades de pointes due to QTc prolongation by mibefradil, which potentially explains unexpected deaths related to this drug. Multiple episodes of torsades de pointes were documented in a 76-year-old woman with significant QTc prolongation of 0.53 s. After discontinuation of mibefradil QTc intervals normalized and no further ventricular tachyarrythmias were observed. We conclude that mibefradil can cause QTc prolongation and life threatening ventricular dysrhythmias.- - - - - - - - - - ranking = 0.33333333333333keywords = life (Clic here for more details about this article) |
7/47. Compound cardiac toxicity of oral erythromycin and verapamil.OBJECTIVE: To report a case of complete atrioventricular (AV) block and QTc prolongation following coadministration of high-dose verapamil and erythromycin. CASE SUMMARY: A 79-year-old white woman was admitted to the hospital due to extreme fatigue and dizziness. On admission, heart rate was 40 beats/min and blood pressure was 80/40 mm Hg. An electrocardiogram showed complete atrioventricular (AV) block, escape rhythm of 50 beats/min, and QTc prolongation 583 msec. This event was attributed to concomitant treatment with verapamil 480 mg/d and erythromycin 2,000 mg/d, which was prescribed one week before admission. DISCUSSiON: This is the first case published describing complete AV block and prolongation of QTc following coadministration of erythromycin and verapamil. CYP3A4 is the main isoenzyme responsible for metabolism of erythromycin and verapamil. Both drugs are potent inhibitors of CYP3A4 and of p-glycoprotein; this may be the basis for the pharmacokinetic interaction between erythromycin and verapamil. In addition to being a woman, our patient had other risk factors for QT prolongation: slow baseline heart rate (probably induced by verapamil), left-ventricular hypertrophy, and possibly ischemic heart disease. CONCLUSIONS: This life-threatening arrhythmia was probably the result of a pharmacokinetic and/or pharmacodynamic interaction of high-dose verapamil and erythromycin.- - - - - - - - - - ranking = 0.33333333333333keywords = life (Clic here for more details about this article) |
8/47. Evidence for a single nucleotide polymorphism in the kcnq1 potassium channel that underlies susceptibility to life-threatening arrhythmias.INTRODUCTION: Congenital long qt syndrome (LQTS) is a genetically heterogeneous arrhythmogenic disorder caused by mutations in at least five different genes encoding cardiac ion channels. It was suggested recently that common polymorphisms of LQTS-associated genes might modify arrhythmia susceptibility in potential gene carriers. methods AND RESULTS: We examined the known LQTS genes in 95 patients with definitive or suspected LQTS. Exon-specific polymerase chain reaction single-strand conformation polymorphism and direct sequence analyses identified six patients who carried only a single nucleotide polymorphism in KCNQ1 that is found in approximately 11% of the Japanese population. This 1727G>A substitution that changes the sense of its coding sequence from glycine to serine at position 643 (G643S) was mostly associated with a milder phenotype, often precipitated by hypokalemia and bradyarrhythmias. When heterologously examined by voltage-clamp experiments, the in vitro cellular phenotype caused by the single nucleotide polymorphism revealed that G643S-KCNQ1 forms functional homomultimeric channels, producing a significantly smaller current than that of the wild-type (WT) channels. Coexpression of WT-KCNQ1 and G643S-KCNQ1 with KCNE1 resulted in approximately 30% reduction in the slow delayed rectifier K current I(Ks) without much alteration in the kinetic properties except its deactivation process, suggesting that the G643S substitution had a weaker dominant-negative effect on the heteromultimeric channel complexes. CONCLUSION: We demonstrate that a common polymorphism in the kcnq1 potassium channel could be a molecular basis for mild I(Ks) dysfunction that, in the presence of appropriate precipitating factors, might predispose potential gene carriers to life-threatening arrhythmias in a specific population.- - - - - - - - - - ranking = 1.6666666666667keywords = life (Clic here for more details about this article) |
9/47. Spontaneous onset of torsade de pointes in long-QT syndrome and the role of sympathovagal imbalance.The net effects of sympathetic and vagal activity on the QT interval and the mode of spontaneous onset of torsade de pointes (TdP) are still unclear in long-QT syndrome. Two patients with long-QT syndrome had syncope while undergoing Holter ECG investigation. The spontaneous onset of TdP in these patients was analyzed with respect to the relation between the RR and QT intervals. Both patients were high-school students (16- and 17-year-old boys) who had been diagnosed as long-QT syndrome and followed up without medical treatment because they had had neither a history of syncope nor arrhythmia induction by treadmill exercise tests. The first episode of syncope in both patients occurred during ordinary daily life and was not related to exercise or psychological stress. The dynamic changes between the RR and QT intervals associated with the spontaneous onset of TdP were analyzed by Holter ECG. Both patients showed sinus tachycardia followed by abrupt sinus bradycardia immediately before the onset of TdP. The enhanced rate of the adaptive response of the QT interval that occurred during the deceleration of the heart rate preceded the onset of TdP. These observations suggest that the complex situation that follows sympathovagal imbalance may have an important role in the dynamic change in the QT interval and initiation of TdP in patients with long-QT syndrome.- - - - - - - - - - ranking = 0.33333333333333keywords = life (Clic here for more details about this article) |
10/47. Perioperative management of long qt syndrome in a child with congenital heart disease.During cardiac catheterization, a 2(1/2)-year-old boy developed sudden cardiac arrest. The presence of a long QT interval in the electrocardiogram (ECG) along with ventricular arrhythmia and syncope at that moment enabled us to diagnose long qt syndrome (LQTS). Immediate defibrillation and beta-blocker (metoprolol) therapy saved the life of the child. cardiac catheterization was completed and the child was planned for Fontan operation. Beta-blocker coverage, prevention of sympathetic stimulation and avoidance of agents which prolong the QT interval made anesthesia uneventful. There were episodes of ventricular fibrillation (VF) in the postoperative period. The child was managed with electrical defibrillation, metoprolol and magnesium.- - - - - - - - - - ranking = 0.33333333333333keywords = life (Clic here for more details about this article) |
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