Evaluación y validación diagnóstica de las variables iQT, razón iQTRR, razón iRTRR para el diagnóstico DEQTc prolongado / Validation of iQT, iQTRR, iRT/RR ratio for estimation of QTc

ANTECEDENTES: El intervalo QT representa la despolarización y repolarización ventricular y su prolongación está asociada a un mayor riesgo de arritmias graves y muerte súbita. Depende de la frecuencia cardíaca y su rápida valoración es difícil de obtener en la práctica clínica. Una forma que facilita este proceso es medir sólo el intervalo QT pero este no siempre se relaciona con un intervalo QTc prolongado. Debido a esto, se postula que una variable compuesta debería tener mejor rendimiento diagnóstico para este objetivo. OBJETIVO: Describir la correlación de 3 variables electrocardiográficas; intervalo QT (iQT), razón del intervalo QT intervalo RR (%iQTRR) y razón del intervalo RT intervalo RR (%iRTRR), en relación a la variable QT corregido (iQTc). Se efectuó una evaluación diagnóstica y validación de las variables mencionadas para establecer el diagnóstico de intervalo QT largo y las propiedades diagnósticas de las mismas para el diagnóstico de iQTc prolongado según la fórmula Bazett. METODOS Y RESULTADOS: Se efectuó un estudio transversal descriptivo-relacional, usando una muestra no probabilística formada por 220 electrocardiogramas registrados en la base de datos del centro cardiovascular. Las mediciones provenían de ECGs registrados en reposo con medición con cáliper de los intervalos QT y RR en derivadas D2 y/o V5, expresadas en milisegundos. Se excluyó la presencia de isquemia, preexcitación y repolarización precoz. Se obtuvo como resultado que la variable razón iQTRR tiene mejor correlación, concordancia, sensibilidad y valor predictivo negativo para el diagnóstico del iQTc prolongado, versus las variables iQT y razón iRTRR, principalmente en mujeres. CONCLUSIONES: La variable razón iQTRR tiene una mejor correlación, concordancia, sensibilidad y valor predictivo negativo (VPN) para el diagnóstico del iQTc prolongado, comparado con las variables iQT y razón iRTRR, principalmente, en mujeres. Utilizando ambas variables este efecto se potencia y permite concluir que si una mujer tiene un iQT observado <470 ms, y una razón QTRR< 47,5%, esto se corresponde con un intervalo QTc normal, con un VPN de 100% .

BACKGROUND: The QT interval (QT) includes depolarization and repolarization phases of cardiac cycle. Its prolongation is associated to an increa sed risk of serious arrhythmia and sudden death. QT depends on heart rate and it is usually corrected using the Bazett formula (QTc). Prolonged QT is not usually well related to QTc. We postulate that a composite formula muy have a greater value for predicting serious arrhythmia. AIM: To correlate the predictive value of a different approach to estimate a corrected QT interval: the ratio of RT to RR intervals (QT/RR, expressed as a percentage METHODS and RESULTS: A non probabilistic sample of 220 ECGs were obtained from our data base. ECGs were recorded at rest and measurements were performed in leads Ds and/or V5 using zetcalipers, the values being expressed in ms. The presence of ischemia, pre excitation and early repolarization were excluded. The QT/RR ratio showed better correlation, concordance, sensitivity, and negative predicted value with the usual QTc interval compared to QT alone or de RT/RR ratio, especially so in women.

Arritmias e alterações cardíacas no paciente cirrótico / Arrhythmias and cardiac alterations in the cirrhotic patient

No Brasil, a cirrose é um problema de saúde pública, que afeta aproximadamente 2 milhões de pessoas. As causas mais comuns são a doença hepática alcoólica, as hepatites virais e a doença hepática não alcoólica. A relação entre desordens cardíacas e hepatopatias é descrita na literatura, e a mais importante delas é o prolongamento do intervalo QT. A cirrose, independente de sua causa, é uma patologia frequentemente encontrada na população brasileira. Por este motivo, elucidar dados referentes às arritmias cardíacas em pacientes cirróticos é de grande importância dentro do estudo desta subpopulação. O objetivo deste artigo é fazer uma revisão de literatura com as informações referentes a epidemiologia, fisiopatologia, fatores de risco e prognóstico para as arritmias cardíacas em portadores de cirrose. (AU)

In Brazil, cirrhosis is a public health problem affecting approximately 2 million people. The most common causes are alcoholic liver disease, viral hepatitis, and non-alcoholic liver disease. The relationship between cardiac disorders and liver diseases is described in the literature, and the most important one is the QT interval prolongation. Cirrhosis, regardless of its causes, is a pathology that is frequently found in the Brazilian population. For this reason, elucidating data regarding cardiac arrhythmias in cirrhotic patients is of great importance within the study of this subpopulation. The aim of this article is to review the literature with information on the epidemiology, pathophysiology, risk factors, and prognosis for cardiac arrhythmias in patients with cirrhosis. (AU)

The Effects of Trimetazidine on QT-interval Prolongation and Cardiac Hypertrophy in Diabetic Rats / Os Efeitos da Trimetazidina no Prolongamento do Intervalo QT e na Hipertrofia Cardíaca em Ratos Diabéticos

Abstract Background: Trimetazidine (TMZ) is an anti-ischemic drug. In spite of its protective effects on cardiovascular system, there is no scientific study on the usefulness of TMZ treatment for prolonged QT interval and cardiac hypertrophy induced by diabetes. Objectives: To evaluate the effects of TMZ on QT interval prolongation and cardiac hypertrophy in the diabetic rats. Methods: Twenty-four male Sprague-Dawley rats (200-250 g) were randomly assigned into three groups (n = 8) by simple random sampling method. Control (C), diabetic (D), and diabetic administrated with TMZ at 10 mg/kg (T10). TMZ was administrated for 8 weeks. The echocardiogram was recorded before isolating the hearts and transfer to a Langendorff apparatus. Hemodynamic parameters, QT and corrected QT interval (QTc) intervals, heart rate and antioxidant enzymes were measured. The hypertrophy index was calculated. The results were evaluated by one-way ANOVA and paired t-test using SPSS (version 16) and p < 0.05 was regarded as significant. Results: The diabetic rats significantly indicated increased hypertrophy, QT and QTc intervals and decreased Left ventricular systolic pressure (LVSP), Left ventricular developed pressure (LVDP), rate pressure product (RPP), Max dp/dt, and min dp/dt (±dp/dt max), heart rate, superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase in the heart. Treatment with TMZ in the diabetic animals was significantly improved these parameters in comparison to the untreated diabetic group. Conclusions: TMZ improves QTc interval prolongation and cardiac hypertrophy in diabetes.

Resumo Fundamento: A trimetazidina (TMZ) é uma droga anti-isquêmica. Apesar de seus efeitos protetores sobre o sistema cardiovascular, não há estudos científicos sobre a utilidade do tratamento com TMZ para o intervalo QT prolongado e a hipertrofia cardíaca induzida pelo diabetes. Objetivo: Avaliar os efeitos da TMZ no prolongamento do intervalo QT e na hipertrofia cardíaca em ratos diabéticos. Métodos: Vinte e quatro ratos machos Sprague-Dawley (200-250 g) foram distribuídos aleatoriamente em três grupos (n = 8) pelo método de amostragem aleatória simples. Controle (C), diabético (D) e diabético administrado com TMZ a 10 mg/kg (T10). A TMZ foi administrada por 8 semanas. O ecocardiograma foi registrado antes de isolar os corações e transferir para um aparelho de Langendorff. Foram medidos os parâmetros hemodinâmicos, intervalo QT e intervalo QT corrigido (QTc), frequência cardíaca e enzimas antioxidantes. O índice de hipertrofia foi calculado. Os resultados foram avaliados pelo one-way ANOVA e pelo teste t pareado pelo SPSS (versão 16) e p < 0,05 foi considerado significativo. Resultados: Os ratos diabéticos indicaram hipertrofia aumentada, intervalos QT e QTc e diminuição da pressão sistólica no ventrículo esquerdo (PSVE), pressão desenvolvida no ventrículo esquerdo (PDVE), duplo produto (DP), Max dp/dt e min dp/dt (± dp/dt max), frequência cardíaca, superóxido dismutase (SOD), glutationa peroxidase (GPx) e catalase no coração. O tratamento com TMZ nos animais diabéticos melhorou significativamente esses parâmetros em comparação com o grupo diabético não tratado. Conclusões: A TMZ melhora o prolongamento do intervalo QTc e a hipertrofia cardíaca no diabetes.

Implante coclear en paciente con síndrome de Q-T prolongado / Cochlear implantation in a patient with elongated Q-T syndrome / Implante coclear em paciente com síndrome de Q-T alongado

El síndrome de Q-T prolongado es una afección que se caracteriza por interrupción del ritmo cardíaco normal. Esta enfermedad es causada por mutación en genes que codifican los canales de voltaje de potasio o sodio, interrumpiendo de esta forma el flujo de dichos iones en el músculo cardíaco. En algunos casos este flujo iónico también se encuentra alterado a nivel del oído interno, por lo cual puede encontrarse asociado a hipoacusia neurosensorial profunda. El diagnóstico se basa en la electrocardiografía y el cuadro clínico, caracterizado por ataques sincopales recurrentes, crisis convulsivas o muerte súbita como primera manifestación. En los casos asociados a hipoacusia neurosensorial profunda, el implante coclear como tratamiento de la sordera presenta riesgos adicionales debido a la posibilidad de arritmias cardíacas y muerte súbita; por lo cual existen consideraciones perioperatorias especiales.

Prolonged Q-T syndrome is a condition characterized by disruption of normal heart rhythm, presented as a prolonged QT interval. This disease is caused by mutation in genes encoding the potassium or sodium voltage channels, thus disrupting the flow of such ions into the cardiac muscle. In some cases this inonic flow is also altered at the level of the inner ear, which may be associated with deep neurosensorial hearing loss. The diagnosis is based on electrocardiography and the clinical picture, characterized by recurrent syncopal attacks, seizures or sudden death as the first manifestation. In cases associated with deep neurosensory hearing loss, the cochlear implant as a treatment for deafness presents additional risks due to the possibility of cardiac arrhythmias and sudden death; for which there are special peri-operative considerations.

Síndrome Q-T prolongada é uma condição caracterizada por uma ruptura do ritmo cardíaco normal, apresentado como um intervalo prolongado de QT. Esta doença é causada por mutação em genes que codificam os canais de tensão de potássio ou de sódio, interrompendo assim o fluxo de tais íons para o músculo cardíaco. Em alguns casos, este fluxo inônico também é alterado no nível da orelha interna, o que pode estar associado à perda auditiva neurosensorial profunda. O diagnóstico é baseado em eletrocardiografia e no quadro clínico, caracterizado por ataques de síncopes recorrentes, convulsões ou morte súbita como a primeira manifestação. Nos casos associados à perda auditiva neurosensorial profunda, o implante coclear como tratamento para surdez apresenta riscos adicionais devido à possibilidade de arritmias cardíacas e morte súbita; para o qual há considerações perioperatórias especiais

Alteraciones electrocardiográficas en anorexia nervosa: revisión crítica de la literatura / Electrocardiographic abnormalities in anorexia nervosa: a critical review of the literature

Introducción: La anorexia nervosa (AN) es un trastorno de la conducta alimentaria y, entre sus causas de mortalidad, las arritmias cardiacas y la muerte súbita son frecuentes, por lo que es indispensable la monitorización electrocardiográfica. Se han descrito muchos hallazgos con resultados contradictorios, por lo que es necesaria una revisión crítica de la literatura científica. Metodología: Revisión de los estudios relevantes sobre cambios electrocardiográficos en AN, consultados en PubMed desde 1974 hasta febrero de 2014, utilizando los términos MeSH: Eating disorders, nervosa anorexia, sinusal bradycardia, QT prolongation, QT dispersion, electrocardiography, EKG, electrocardiogram. Resultados y discusión: Las dos alteraciones más comunes reportadas incluyen la bradicardia sinusal y los cambios en la repolarización evidenciados en prolongación del QT e incremento de su dispersión. Los trastornos electrolíticos parecen ser la causa de estas alteraciones en algunos pacientes, pero otras razones se discuten en detalle, como la desviación del eje del QRS a la derecha, la alteración en variabilidad de la frecuencia cardiaca, R en derivación V6 de bajo voltaje, disminución de la amplitud del QRS y onda T y alargamiento del QRS. La mayoría de los autores hablan de reversibilidad de los cambios después del tratamiento. Conclusiones: Estos resultados siguen apoyando la necesidad de valorar a los pacientes con AN con electrocardiogramas inicial y de seguimiento, para el diagnóstico temprano y tratamiento de alteraciones cardiovasculares relacionadas con alta morbimortalidad. También apoyan la necesidad del uso racional de psicofármacos para no aumentar el riesgo de arritmias cardiacas y muerte súbita.

Background: Anorexia nervosa is an eating disorder in which cardiac arrhythmias and sudden death are frequent causes of mortality, which makes electrocardiographic monitoring indispensable in these patients. There are many suggestive findings but results are contradictory, making a critical review of the scientific literature is necessary. Methods: The most relevant studies on electrocardiographic (EKG) changes in patients with AN, found in PubMed from 1974 to February 2014, were reviewed using the MeSH terms: eating disorders, nervosa anorexia, sinus bradycardia, QT prolongation, QT dispersion, electrocardio graphy, EKG, and electrocardiogram. Findings and discussion: The two most common EKG findings reported in the literature are sinus bradycardia and changes in depolarization, as shown by prolongation and increased dispersion of the QT interval. Electrolyte disturbances seem to be the cause of these disturbances in some patients, but other reasons are also discussed in detail, such as QRS right axis deviation, disturbances of heart rate variability, low R wave voltage in V6, amplitude decrease of the QRS and T wave, and QRS prolongation. The majority of authors report that these changes are reversible after treatment of AN. Conclusions: These findings support the need for initial and follow-up EKGs in patients with AN and for early diagnosis and treatment of cardiovascular disturbances that are associated with morbidity and mortality. They also support the need for the rational use of psychop harmacology, and that does not increase the risk of arrhythmias and sudden death in these patients.

Síndrome de Jervell y Lange-Nielsen / Jervell and Lange-Nielsen Syndrome

El síndrome de Jervell y Lange-Nielsen es una forma poco frecuente de síndrome de QT largo. Su herencia es autosómica recesiva y se manifiesta con sordera neurosensorial. Revisamos el caso de una niña de 7 años implantada coclear bilateral. Tras un episodio sincopal se realiza el diagnóstico de síndrome de QT largo, el estudio genético confirma el diagnóstico. Recomendamos realizar electrocardiograma a todos los niños con hipoacusia severa con el objeto de descartar este síndrome.

The Jervell and Lange-Nielsen (JLNS) is an uncommon form of long QT syndrome. His inheritance is autosomal recessive and manifests as a sensorineural deafness. We review the case of a 7 year old girl bilateral cochlear implanted. After a syncope episode, a long QT syndrome was confirmed by genetic study. We recommend electrocardiogram (ECG) to all children with severe hearing loss in order to rule out this syndrome.

Placement of an implantable cardioverter-defibrillator in an infant with congenital long QT syndrome: Anesthetic considerations.

Sudden cardiac arrest (SCA) in children is a rare, but catastrophic event. Children with cardiac pathology at particular risk include those with congenital long QT syndrome (CLQTS) and hypertrophic cardiomyopathy. CLQTS is a genetic disorder of the cardiac ion channels and is associated with significant risk of malignant ventricular arrhythmias and SCA. For symptomatic, untreated patients, the mortality rate is approximately 20% for the first year and 50% at ten years. Use of an implantable cardioverter-defibrillator (ICD) is recommended for the prevention of SCA in this patient population. We report a case of CLQTS, who after successful resuscitation from SCA, underwent ICD placement at our center.

Prevalencia del intervalo QT prolongado en diferentes patrones electrocardiográficos: estudio por teleelectrocardiografía / Increased Q-T interval in different electrocardiographic patterns: a remote recording electrocardiographic study

Introducción: El intervalo QT prolongado ha sido identificado como factor de riesgo de arritmias ventriculares incluso en personas aparentemente sanas. El objetivo de este estudio fue establecer la prevalencia de QTc prolongado en electrocardiogramas normales, con bloqueo completo de rama (BCR) y con crecimiento de ventrículo izquierdo (HVI). Métodos y Resultados: Se consideró como prolongado un valor > 440 mseg, en cada una de 4 derivaciones: D1, aVL, V5 y V6, consensuado por dos observadores. El grupo 1 estuvo formado por 8.459 trazados normales: de ellos un 84 por ciento tenían un QTc normal y un 16 por ciento tenían un QTc prolongado. El grupo 2 consistió en 2.647 trazados con bloqueo completo de rama, 532 trazados con bloqueo completo de rama izquierda (BCRI) y 2.115 con bloqueo completo de rama derecha (BCRD). De los BCRI un 51,5 por ciento de los trazados tenían QTc prolongado, lo cual observamos sólo en un 25 por ciento de los trazados con BCRD. El grupo 3 estuvo conformado por 2.503 trazados con HVI, 377 por criterio de voltaje (grupo 3a), 1.083 por criterio de voltaje y alteración de repolarización (grupo 3b) y 1.043 HVI sólo por criterio de alteración de repolarización (grupo 3c). Un 28 por ciento de las HVI por criterio de voltaje (grupo 3a) y un 29 por ciento de HVI por alteración de repolarización (grupo 3c) tenían un QTc prolongado. De las HVI por voltaje y alteración de repolarización (grupo 3b) un 42 por ciento tenían QTc prolongado. De las HVI con QTc largo, un 7.6 por ciento tenían QTc > 500 mseg. Al desglosar las HVI por grupos el grupo 3a tenía 4,7 por ciento de los trazados con QTc largo > 500 mseg, el grupo 3b un 7,9 por ciento y el grupo 3c, un 8.3 por ciento. Conclusiones: Se concluye la alta prevalencia de QTc prolongado incluso en ECG con morfología normal, pero especialmente en BCRI y en HVI por voltaje más alteraciones de repolarización. La prolongación de QTc en BCR no mostró correlación con la ...

Background. Increased Q-T interval has been identified as a risk factor for ventricular arrhythmia including normal subjects. Aim. To establish the prevalence of an increased QTc in normal electrocardiograms (N) an in those with complete bundle branch block (RBBB or LBBB) or left ventricular hypertrophy (L VH). Method. D1, aVL, V5 and V6 leads were analyzed; a > 440ms QTC agreed upon by 2 observers was considered prolonged. Results: an increased QTc was observed in 16 percent> of 8459 N subjects, 51.5 percent> of subjects with LBBB and 25 percent of those with RBBB. Among subjects with LVH, 28 percent of those with voltage only criteria for LVH and 29 percent of those with ST-T changes but no voltage criteria had increased QTc. In contrast, 42 percent> of patients with LVH exhibiting both diagnostic criteria had increased QTc. In 7.6 percent> of LVH subjects with increased QTc, this interval was >500ms, which broke down as follows: LVH by voltage criteria alone 4.7 percent>, ST-T changes alone 7.9 percent > and LVH with both voltage and ST-T criteria 8.3 percent>. In patients with complete bundle branch block, the duration of the QRS interval was not related to QTc. Conclusion. A prolonged QTc is a frequent finding in normal ECGs, much more so in subjects with LVH associated to voltage and ST-T criteria. The prognostic impact of a prolonged QTc in patients with complete bundle branch block deserves further study.

Análise da dispersão do intervalo QT em pacientes com infarto agudo do miocárdio: efeito da reperfusão coronariana / QT interval dispersion analysis in acute myocardial infarction patients: coronary reperfusion effect

OBJETIVO: Estudar o efeito da reperfusão precoce da artéria relacionada ao infarto sobre a dispersão do intervalo QT(deltaQT), e seu valor como marcador de reperfusão coronária e de arritmias ventriculares. MÉTODOS: Foram avaliados 106 pacientes com reperfusão (CR) e 48 pacientes sem reperfusão (SR) que receberam terapia trombolítica na fase aguda do infarto. Foram analisados os eletrocardiogramas realizados na admissão e no 4° dia de evolução. A deltaQT, definido como a diferença entre o maior e o menor intervalo QT, foram medidos no ECG de 12 derivações. RESULTADOS: Na evolução do grupo com reperfusão, houve redução significativa da deltaQT de 89,66±20,47ms para 70,95±21,65ms (p<0,001). Por outro lado, no grupo sem reperfusão, houve aumento significativo da deltaQT de 81,27±20,52ms para 91,85±24,66ms (p<0,001). Análise de regressão logística demonstrou que a magnitude de redução entre a deltaQT pré e pós-trombólise foi o fator independente que identificou mais efetivamente a reperfusão coronária (OR 1,045, p<0,0001; IC 95 por cento). Não houve diferença significativa das medidas de dispersão quando comparados os pacientes que apresentaram arritmias ventriculares nas primeiras 48 h com aqueles sem arritmias. CONCLUSÃO: Esse estudo mostra que a deltaQT reduz significativamente em pacientes com infarto agudo do miocárdio submetidos à trombólise com sucesso, aumentando nos pacientes que evoluem com a artéria fechada. A redução deltaQT entre a situação pré e pós-trombólise foi fator preditor de reperfusão coronária nesses pacientes, não apresentando correlação com arritmias ventriculares.

Increased beat-to-beat QT variability in patients with congestive cardiac failure.

BACKGROUND: QT interval on the surface electrocardiogram reflects the time for repolarization of myocardium. Prolongation of rate-corrected QT interval, QTc is strongly associated with sudden cardiac death. Recent studies using novel techniques on beat-to-beat QT interval variability have shown that an increase in QT interval variability is associated with increased sympathetic activity and is a predictor of sudden cardiac death. We studied QT variability in patients with congestive cardiac failure, as it is associated with an increase in cardiac sympathetic activity and also sudden death. METHODS AND RESULTS: We compared beat-to-beat heart rate and QT interval data in 2 3 patients with congestive cardiac failure and 19 age-matched normal controls. The electrocardiographic data were acquired in lead II configuration at a sampling rate of 1000 Hz. Heart rate variability was found to be significantly lower while QT variability measures were significantly higher in patients compared to controls. QTvi (a common log ratio of QT variability normalized for mean QT interval squared divided by heart rate variability normalized for mean heart rate squared) was also significantly higher in patients compared to controls. Clinical improvement in some of these patients is associated with a decrease in QTvi, due mainly to an increase in cardiac vagal function. CONCLUSIONS: Our results suggest a decrease in cardiac vagal and an increase in cardiac sympathetic functions in patients with congestive cardiac failure. QTvi may prove to be a useful surrogate end point to evaluate treatment effect in these patients.

Dynamics of QT dispersion in acute myocardial infarction.

BACKGROUND: We studied the dynamics of QT dispersion in patients with acute myocardial infarction, and compared them with those in controls. METHODS AND RESULTS: Serial electrocardiograms of patients admitted to our institute with acute myocardial infarction were analyzed for QT dispersion, and compared with those of healthy age- and sex-matched controls. QT dispersion from 12 leads was measured as maximum QT minus minimum QT interval in ms. The mean QT dispersion of 114 +/- 29.6 ms was significantly higher in patients with acute myocardial infarction on admission as compared to 51.45 +/- 5.56 ms in controls (p < 0.001). QT dispersion showed a dynamic change in patients with acute myocardial infarction who were thrombolyzed, being 109.11 +/- 5.77 ms, 87.59 +/- 5.88 ms, 75.89 +/- 18.33 ms, and 68.20 +/- 12.66 ms on admission, post-thrombolysis, and on days 3 and 7, respectively. During a similar time period, nonthrombolyzed patients showed a QT dispersion of 132.38 +/- 36.04 ms, 130.47 +/- 34.42 ms, 111.11 +/- 24.94 ms, and 106.25 +/- 27.64 ms, respectively: the difference between the 2 groups at all periods was significant (p < 0.01). Mean QT dispersion values in patients who developed ventricular tachycardia or ventricular fibrillation were significantly higher than in patients who did not develop ventricular tachycardia or ventricular fibrillation (p < 0.01). CONCLUSIONS: Mean QT dispersion is significantly increased after acute myocardial infarction, and shows a dynamic decrease with time, the difference being more marked in thrombolyzed patients. Mean QT dispersion levels are higher in patients with ventricular tachycardia and ventricular fibrillation compared to patients with acute myocardial infarction without these arrhythmias. The changes in QT dispersion are dynamic, and it may serve as a non-invasive marker of susceptibility to malignant ventricular arrhythmias.

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

El sindrome de QT prolongado explicado a partir de las alteraciones del potencial de accion por canalopatias / Long QT syndrome and action potential for channelopathy

Las arritmias cardiacas constituyen un problema de alto impacto en cuanto a la morbimortalidad en la población general y la economía de los sistemas de salud a nivel mundial. Éstas se pueden explicar en parte por la disfunción molecular de los canales de transporte iónicos que se expresan en las membranas de las células cardiacas, cuya integridad depende no sólo del substrato genético del cual se derivan, sino también de factores postraduccionales celulares y de factores externos. Los defectos en los canales iónicos del cardiomiocito (heredados o adquiridos) que produzcan corrientes sostenidas despolarizantes o que reduzcan las corrientes repolarizantes y, por tanto, que prolonguen la duración del potencial de acción, se manifiestan en el trazado electrocardiográfico como una prolongación del intervalo QT y constituyen un substrato arritmogénico. A partir de estos conceptos han surgido nuevas teorías para explicar, desde el punto de vista molecular, eventos como la muerte súbita en adultos y en lactantes, la fibrilación ventricular idiopática y la arritmia de tipo Torsades de Pointes. La investigación de (as canalopatías permitirá abordar el problema de una manera más racional

Electrocardiographic changes following exercise in the congenitally deaf school children: relationship with Jervell Lange Neilsen syndrome (the Long QT syndrome).

The present study was conducted to test the effects of exercise stress on the ECG of the congenitally deaf children from school for deaf, in view of the occurrence of the Jervell-Lange Neilsen (Surdo Cardiac) variant of the Long QT Syndrome (LQTS) in them. An ECG Lead II was recorded at rest and after two minutes of static jogging. For comparison, the same protocol was repeated in normal healthy children from another school. ECG were analysed for the calculation of corrected QT interval (QTc) by Bazett's equation QTc = QT/square root of R-R and also for the evidence for other abnormalities. Both in the normal and deaf children, exercise did not produce significant (P > 0.05) change in QTc from their resting values. However, when pre and post exercise QTc values of deaf children were compared with normal children, the female deaf had significantly longer QTc (P < 0.01) both at rest and after exercise than normal female children. Normal children did not show significant ECG abnormality either at rest or on exercise. On the contrary many of their counter part (deaf) exhibited occasional ECG abnormality at rest but plethora of abnormalities after exercise viz., sinus arrhythmias, sinus pauses, ST depression, T-inversion, biphasic-T, notched-T, T-alternans, nodal ectopics and junctional rhythm. These results lend credence to the hypothesis of sympathetic imbalance and repolarisation defects in deaf children's heart, which in more severe form could pass into frank Jervell-Lange Neilsen variant of the Long: QT Syndrome.