Síndrome do QT longo congênito: o que sabemos até o momento? / Congenital long QT syndrome: what do we know so far?

Síndrome do QT longo congênito é uma síndrome arrítmica hereditária caracterizada por prolongamento do intervalo QT no eletrocardiograma de 12 derivações, torsades de pointes e maior chance de morte súbita cardíaca. A síndrome do QT longo congênito possui padrão autossômico dominante (síndrome de Romano-Ward), bem como padrão autossômico recessivo raro (síndrome de Jervell e Lange-Nielsen). Desde 1957, quando Jervell e Lange-Nielsen relataram os primeiros casos de síndrome do QT longo congênito familiarcom surdez congênita, a compreensão dos mecanismos genéticos e eletrofisiológicos dessa afecção melhorousignificativamente os métodos diagnósticos e os tratamentos. No entanto, tornou-se evidente que a síndrome do QT longo congênito nem sempre pode ser explicada pela mutação de um único gene. Esta revisão teve por objetivo resumir as características da síndrome do QT longo congênito (principalmente LQT1, LQT2 e LQT3) e descrever brevemente os mais recentes avanços no diagnóstico clínico e no tratamento da afecção...

Congenital long QT syndrome is an inherited arrhythmia syndrome characterized by a prolonged QT interval on the 12-lead electrocardiogram, torsades de pointes and a higher chance of sudden cardiac death. Congenital long QT syndrome includes an autosomal dominant pattern (Romano-Ward syndrome) as well as a rare autosomal recessive pattern (Jervell and Lange-Nielsen syndrome). Since 1957 when Jervell and Lange Nielsen reported the first familial long QT syndrome with congenital deafness, the understanding of genetic and electrophysiological mechanisms of long QT syndrome has significantly improved diagnostic methods and treatments. However, is clear that long QT syndrome cannot always be explained by a single gene mutation. This review is aimed at summarizing the characteristics of congenital long QT syndrome (mainly LQT1, LQT2 e LQT3) and briefly describe the most recent advances in long QT syndrome clinical diagnostics and treatment...

Síndrome de Andersen-Tawil / Andersen-Tawil Syndrome

A síndrome de Andersen-Tawil é uma condição rara composta por arritmias ventriculares, paralisia periódica e dimorfismo. É uma doença de canal iônico cardíaco, possui herança de forma autossômica dominante e é classificada como tipo 7 da síndrome do QT longo congênito. A síndrome de Andersen-Tawil é a única canalopatia que une a excitabilidade dos músculos cardíaco e esquelético. Os pacientes podem ser assintomáticos ou minimamente sintomáticos, apesar da elevada carga de arritmia com ectopia ventricular frequente e taquicardia ventricular bidirecional. No entanto, continuam a ser pacientes com risco de arritmias potencialmente fatais, incluindo torsades de pointes e fibrilação ventricular, embora com menor frequência que as observadas em outras síndromes de arritmia genética. Nesta revisão a doença foi abordada sob o ponto de vista dos diagnósticos clínico e molecular, com ênfase nas manifestações cardíacas...

Andersen-Tawil syndrome is a rare condition consisting of ventricular arrhythmias, periodic paralysis, and dysmorphic features. It is a cardiac ion channel disease, with autosomal dominant inheritance and is classifiedas type 7 of the congenital long QT syndromes. Andersen-Tawil syndrome is a unique channelopathy which linkscardiac and skeletal muscle excitability. Patients may be asymptomatic, or minimally symptomatic despite a higharrhythmia burden with frequent ventricular ectopy and bidirectional ventricular tachycardia. However, patients remain at risk for life-threatening arrhythmias, including torsades de pointes and ventricular fibrillation, although less frequently than observed in other genetic arrhythmia syndromes. In this review we address the disease from the point of view of clinical and molecular diagnosis with emphasis on cardiac manifestations...

QT longo congênito em portador de marcapasso definitivo e nefropatiaespoliadora de magnésio / Congenital long QT syndrome in a pacemaker user and renal magnesium wasting syndrome

A síndrome do QT longo congênito representa importante distúrbio genético, e está associada asíncope, parada cardíaca e morte súbita. O diagnóstico é baseado principalmente na medida do intervalo QT corrigido associada a critérios clínicos e história familiar. A estratificação de risco auxilia na decisão terapêutica. Relatamos o caso de uma paciente com síndrome do QT longo congênito, portadora de marcapasso definitivo e nefropatia espoliadora de magnésio, que evoluiu com necessidade de upgrade para cardiodesfibrilador implantávelna ocasião da troca do gerador do dispositivo.

The congenital long QT syndrome represents an important genetic disorder related to syncope, cardiac arrest and sudden death. The diagnosis is mainly based on corrected QT interval measurement associated with clinical criteria and family history. The risk stratification of patients with long QT syndrome has implications in the prognosis and treatment. We report a case of a patient with congenital long QT syndrome, with cardiac pacemaker who required an upgrade to implantable cardioverter defibrillator at the time of the generator replacement.

Long QT syndrome revisited.

Congenital Long QT Syndrome (cLQTS) is an inherited disease in children and adolescents who have structurally normal hearts but present with sudden death in a high proportion of untreated patients. More than 300 mutations have been identified in 7 LQT genes. Diagnosis still depends on ECG, clinical presentations and family history. Molecular genetic testing is useful to unravel borderline family members of LQT probands, but it continues to be a research tool at present. Beta blockers remain the mainstay of treatment. ICDs are highly effective in reducing SCD for high risk patients. Gene based therapy is still preliminary. Considerable thought is needed to address and treat the asymptomatic LQT family members. The main cause of Acquired LQTS is inhibition of Ikr current, usually by drugs. Care must be taken to avoid further exposure to QT prolonging drugs or conditions. Physicians need to be aware of the pharmacodynamic and pharmacokinetic interactions of various important drugs.

El síndrome del intervalo QT prolongado desde el punto de vista de un cardiólogo / Long-QT syndrome: a cardiologist's point of view

El síndrome del QT prolongado congénito está representado por un conjunto de entidades que obedecen a mutaciones genéticas que afectan los canales de potasio o de sodio del sarcolema de los cardiomiocitos. La característica común de todas las formas es la prolongación del intervalo QT que predispone a la aparición de una taquicardia ventricular polimórfica atípica denominada torsade de pointes, la cual en ocasiones puede degenerar en fibrilación ventricular y muerte súbita. Actualmente se conocen siete variantes de la enfermedad y la terapéutica incluye medidas farmacológicas y no farmacológicas. El síndrome puede responder también a causas secundarias por uso de drogas cardiológicas y no cardiológicas y siendo esta forma de presentación es más frecuente que la de origen genético. El Primer Simposio Internacional de QT Prolongado en Internet (http://www.lqts-symposium.org) ha generado un interesante debate que hace propicia la ocasión para realizar una síntesis acerca de las características de esta entidad.

Clinical characteristics of 5 Chinese LQTS families and phenotype-genotype correlation / 华中科技大学学报（医学）（英德文版）

In order to assess the clinical manifestations and electrocardiogram (ECG) characteristics of Chinese long QT syndrome (LQTS) patients and describe the phenotype-genotype correlation, the subjects from 5 congenital LQTS families underwent clinical detailed examination including resting body surface ECG. QT interval and transmural dispersion of repolarization (TDR) were manually measured. Five families were genotyped by linkage analysis (polymerase chain reacting-short tandem repeat, PCR-STR). The phenotype-genotype correlation was analyzed. Four families were LQT2, 1 family was LQT3. Twenty-eight gene carriers were (14 males and 14 females) identified from 5 families. The mean QTc and TDRc were 0.56 +/- 0.04 s (range 0.42 to 0.63) and 0.16 +/- 0.04 s (range 0.09 to 0.24) respectively. 35.7% (10/28) had normal to borderline QTc (< or = 0.460 s). There was significant difference in QTc and TDRc between the patients with symptomatic LQTS and those with asymptomatic LQTS, and there was significant difference in TDRc between the asymptomatic patients and normal people also. A history of cardiac events was present in 50% (14/28), including 9 with syncope, 2 with sudden death (SD) and occurred in the absence of beta-blocker. Three SDs occurred prior to the diagnosis of LQTS and had no ECG record. Two out of 5 SDs (40%) occurred as the first symptom. Typical LQT2 T wave pattern were found in 40% (6/15) of all affected members. The appearing-normal T wave was found in one LQT3 family. Low penetrance of QTc and symptoms resulted in diagnostic challenge. ECG patterns and repolarization parameters may be used to predict the genotype in most families. Genetic test is very important for identification of gene carriers.

Congenital Long QT Syndrome presenting as epilepsy.

Epilepsy can sometimes be mimicked in children by other organic conditions. We present a 11 year old boy with the congenital long QT syndrome who had recurrent "seizures" for five years which had been treated as epilepsy.

Role of left cardiac sympathetic denervation in the management of congenital long QT syndrome.

Congenital long QT syndrome (LQTS) is a rare but life-threatening disorder affecting cardiac electrophysiology. It occurs due to mutation in genes encoding for the ion channels in ventricular cell membrane. Syncopal attacks and cardiac arrest are the main symptoms of the disease. Anti-adrenergic therapy with oral beta-blockers has been the mainstay of treatment for LQTS. However, up to 30% of patients fail to respond to medical therapy and remain symptomatic. An alarming 10% of patients still experience cardiac arrest or sudden cardiac death during the course of therapy. Left cardiac sympathetic denervation (LCSD) has been used as an alternative therapy in patients who are resistant to beta-blockers. Although LCSD appears effective in reducing the frequency of syncopal attacks and improving the survival rate in both the short and long-term, its use has not gained popularity. The recent advent of minimally invasive thoracoscopic sympathectomy may improve the acceptance of LCSD by physicians and patients in the future. The primary objective of this article was to review the current evidence of the clinical efficacy and safety of LCSD in the management of LQTS. The review was based on Medline search of articles published between 1966 and 2002.

Implante pediátrico de cardioversor-desfibrilador pela via transtorácica transatrial / Pediatric cardioverter-defibrillator

Os autores relatam o caso de uma criança de 23 meses de idade, portadora de síndrome do QT longo congênito,submetida a implante de cardioversor-desfibrilador atrioventricular. A criança apresentou três episódios de fibrilação ventricular revertida após manobras convencionais de ressuscitação cardiopulmonar e desfibrilação transtorácica externa, previamente ao implante. Devido a descontinuidade da fabricação de placas epimiocárdicas, foi utilizado a via transtorácica para o implante dos cabos-eletrodos, com abordagem epimiocárdica para o eletrodo atrial e endocárdica transatrial para o implante do eletrodo ventricular convencional

The congenital long QT syndrome.

OBJECTIVE: The long QT syndrome (LQTS) is a disorder of the electrical system of the heart, due to dysfunction of the ion channels and involving the repolarisation process. The inherited form occurs when there is a mutation in one of the genes which encode the making of a channel. Prolongation of the QT interval renders the patient vulnerable to an arrythmia called torsade de pointes, resulting in syncope and sudden death. METHODS: Three children with the congenital long QT syndrome presented to the pediatric department, one of them also having a 2:1 atrio-ventricular block. The parents and siblings of these children were screened for the long QT syndrome with an electrocardiogram. 2D echocardiography was done to rule out structural abnormalities and audiometry for deafness. RESULTS: Four family members were identified on screening to have LQTS. Propranolol was started on all children with LQTS. The child with heart block also received a pacemaker. LQTS must be considered in all patients presenting with syncope especially if associated with deafness and/or a family history of sudden deaths in infancy or childhood. CONCLUSION: The corrected QT interval must be determined in all children with heart block since the two conditions are often associated.

Síndrome de QT largo congénito y su manejo con marcapaso permanente / Congenital long QT syndrome and its management with permanent pacemaker

Dos pacientes con síndrome de QT largo congénito y taquicardias ventriculares polimorfas recurrentes rebeldes a bloqueadores beta adrenérgicos, fueron tratados adecuadamente con terapia eléctrica con marcapaso permanente. Se discute el papel de la estimulación cardiaca con marcapaso, en el contexto de otras modalidades terapéuticas, a la luz de los recientes conocimientos de las alteraciones cromosómicas y de los canales iónicos