Cases reported "Long QT Syndrome"

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1/85. ventricular fibrillation related to reversal of the neuromuscular blockade in a patient with long qt syndrome.

    The long qt syndrome (LQTS) is associated with syncopal attacks or even sudden death at a young age due to ventricular fibrillation. We report a patient with an undiagnosed LQTS who had an episode of cardiac arrest during the final part of general anesthesia, immediately after the drugs for reversal of the neuromuscular blockade were given. We suggest that the administration of glycopyrronium might have been the provoking factor in this patient.
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2/85. Preoperative hypoglycaemia, propranolol and the Jervell and Lange-Nielsen syndrome.

    The Jervell and Lange-Nielsen syndrome is an autosomal recessive trait characterized by deafness and electrocardiographic changes. These changes include prolongation of the QT interval and T-wave inversion. Treatment may include the use of beta-blockers to prevent the development of malignant ventricular arrhythmias and sudden death. We report a patient with this syndrome, who was receiving propranolol orally and who became hypoglycaemic during the preoperative fasting period prior to cochlear implantation.
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3/85. A variant of long qt syndrome manifested as fetal tachycardia and associated with ventricular septal defect.

    Two patients with a novel variant of long qt syndrome are described. The clinical course was characterised by an in utero onset of ventricular tachycardia and atrioventricular block (at 26 and 30 weeks' gestational age, respectively), and an association with a ventricular septal defect. Studies of both patients' families identified relatives with prolonged QT interval, syncope, or sudden death. One patient died of intractable ventricular tachycardia at 4 days old. The other received beta blocker treatment and a pacemaker. She died suddenly at the age of 10 months. The unique association with ventricular septal defect and the malignant clinical course warrants further molecular diagnosis of this novel variant of long qt syndrome.
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4/85. Splicing mutations in KCNQ1: a mutation hot spot at codon 344 that produces in frame transcripts.

    BACKGROUND: Long-QT syndrome is a monogenic disorder that produces cardiac arrhythmias and can lead to sudden death. At least 5 loci and 4 known genes exist in which mutations have been shown to be responsible for the disease. The potassium channel gene KCNQ1, previously named KVLQT1, on chromosome 11p15.5 is one of these. methods AND RESULTS: We initially analyzed one family using microsatellite markers and found linkage to KCNQ1. mutation detection showed a G to C change in the last base of exon 6 (1032 G-->C) that does not alter the coded alanine. Restriction digest analysis in the family showed that only affected individuals carried the mutation. A previous report suggested that a G to A substitution at the same position may act as a splice mutation in KCNQ1, but no data was given to support this hypothesis nor was the transcription product identified. We have shown by reverse-transcription polymerase chain reaction that 2 smaller bands were produced for the KCNQ1 gene transcripts in addition to the normal-sized transcripts when lymphocytes of affected individuals were analyzed. Sequencing these transcripts showed a loss of exon 7 in one and exons 6 and 7 in the other, but an in-frame transcript was left in each instance. We examined other families in whom long-QT syndrome was diagnosed and found another unreported splice-site mutation, 922-1 G-->C, in the acceptor site of intron 5, and 2 of the previously reported 1032 G-->A mutations. All these showed a loss of exons 6 and 7 in the mutant transcripts, validating the proposal that a consensus sequence is affected in the exonic mutations and that the integrity of the base at position 1032 is essential for correct processing of the transcript. CONCLUSIONS: The 6 cases already reported in the literature with the 1032 G-->A transition, the novel 1032 G-->C transversion, and a recent G-->T transversion at the same base show that codon 344 is the second most frequently mutated after codon 341, suggesting at least two hotspots for mutations in KCNQ1.
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5/85. 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.
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6/85. Romano-Ward long qt syndrome: identification of a HERG mutation in a Taiwanese kindred.

    romano-ward syndrome is an autosomal dominant long-QT syndrome (LQTS) that predisposes affected individuals to sudden death from tachyarrhythmias. We investigated the molecular basis of LQTS in a Taiwanese kindred. Clinical and genetic analyses revealed that a mutation was linked to the human ether-a-go-go-related gene (HERG). The coding sequences and exon-intron borders of HERG were amplified by means of polymerase chain reaction and subjected to single-strand conformation polymorphism (SSCP) analysis. An exon with an aberrant SSCP pattern was cloned and sequenced to study the molecular lesion. A C-->T transition in codon 614, leading to substitution of a valine for an alanine residue in the pore region of the HERG protein, was identified. Analysis with Bsp12861 endonuclease digestion showed the mutation to be present in all affected family members. Given that an unaffected paternal uncle had inherited the same allele from the grandfather as the proband's father, a de novo mutation had apparently occurred in the father and was transmitted to his offspring. In addition to offering presymptomatic genetic diagnosis, identification of the disease-causing mutation may suggest new therapeutic approaches for treatment and prevention of this cardiovascular disease.
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7/85. Homozygosity for a HERG potassium channel mutation causes a severe form of long qt syndrome: identification of an apparent founder mutation in the Finns.

    OBJECTIVES: We studied the clinical characteristics and molecular background underlying a severe phenotype of long qt syndrome (LQTS). BACKGROUND: Mutations of cardiac ion channel genes cause LQTS, manifesting as increased risk of ventricular tachycardia and sudden death. methods: We studied two siblings showing prolonged QT intervals corrected for heart rate (QTc), their asymptomatic parents with only marginally prolonged QTc intervals and their family members. The potassium channel gene HERG was screened for mutations by deoxyribonucleic acid sequencing, and the electrophysiologic consequences of the mutation were studied in vitro using the whole-cell patch-clamp technique. RESULTS: A novel missense mutation (L552S) in the HERG channel, present in the homozygous state in the affected siblings and in the heterozygous state in their parents, as well as in 38 additional subjects from six LQTS families, was identified. One of the homozygous siblings had 2:1 atrioventricular block immediately after birth, and died at the age of four years after experiencing unexplained hypoglycemia. The other sibling had an episode of torsade de pointes at the age of two years. The mean QTc interval differed significantly (p < 0.001) between heterozygous symptomatic mutation carriers (500 /- 59 ms), asymptomatic mutation carriers (452 /- 34 ms) and noncarriers (412 /- 23 ms). When expressed in vitro, the HERG-L552S formed functional channels with increased activation and deactivation rates. CONCLUSIONS: Our data demonstrate that homozygosity for a HERG mutation can cause a severe cardiac repolarization disorder without other phenotypic abnormalities. Absence of functional HERG channels appears to be one cause for intrauterine and neonatal bradycardia and 2:1 atrioventricular block.
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8/85. Control of idiopathic ventricular fibrillation by implantable cardioverter-defibrillator in a child who survived sudden death.

    Idiopathic ventricular fibrillation (VF) is extremely rare in children who have not previously undergone cardiac surgery. patients resuscitated from idiopathic VF remain at risk for recurrence. The use of an implantable cardioverter-defibrillator (ICD) effectively prevents such recurrences. We report the case of a 12-year-old girl who had a history of recurrent syncope and had survived an episode of VF. Serial studies after prolonged but successful resuscitation, including echocardiography, an electrocardiogram (ECG), and coronary angiography failed to reveal abnormal cardiac structures responsible for VF. No abnormal conduction pathways or abnormal early or late after depolarization were found on electrophysiologic study. The ST segments of the 12-lead ECG remained normal after procainamide challenge. The patient underwent ICD implantation 2 weeks after admission and syncope did not recur during a follow-up of 14 months. This report emphasizes that idiopathic VF may be responsible for syncope in children. ICD therapy prevents the recurrence of idiopathic VF and the associated risk of sudden death.
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9/85. Prolonged QT interval and sudden infant death--report of two cases.

    In the two cases where infants died suddenly and unexpectedly the electrocardiogram (ECG) of a younger sibling (case 1) and of a living twin (case 2) led to the suspicion that the two infants could have died from long qt syndrome (LQTS). In case 1, a His bundle (HB) dispersion and a pronounced hypoplasia of the right external nucleus arcuatus were detected. In case 2, a severe interstitial pneumonia and an accompanying mild myocarditis were found by histology. Molecular genetic investigations of the coding regions of the genes, HERG, KVLQT1 and SCN5A gave no indication for the mutations, thus, affecting related myocardial ion channels as possible sources of inhomogeneity of repolarisation.Since a molecular genetic deviation could not yet be elaborated the possible role of related disturbance remains unknown.
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10/85. cochlear implantation in Jervell and Lange-Nielsen syndrome.

    Jervell and Lange-Nielsen syndrome represents a rare, autosomal recessive cause of congenital deafness. Affected patients have a characteristic prolongation of the QT interval on electrocardiogram, along with cardiac arrhythmias, recurrent syncopal episodes, and a predisposition to sudden death. We present the first reported case of cochlear implantation in a child with Jervell and Lange-Nielsen syndrome. Special perioperative precautions were required, including cardiac monitoring for 48 hours, perioperative beta blockade, and special anesthetic considerations. Because sudden patient death has been associated with exposures to loud sounds in patients with prolonged QT syndrome without hearing loss (Ward-Romano syndrome), initial cochlear implant stimulation was performed with cardiac monitoring. This patient has responded well to cochlear implantation with 11 months of implant use. The patient has achieved limited open-set word comprehension and significantly improved speech, as is expected for her age. Although the patient had no problems with cardiac arrhythmias at surgery, she has since experienced a syncopal episode requiring placement of an automatic pacemaker and defibrillator. The implant has continued to work well despite the pacemaker and defibrillator. cochlear implantation can be relatively safely performed in patients with Jervell and Lange-Nielsen syndrome, provided proper precautions are followed.
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