Tratamiento con radiofrecuencia de la tormenta eléctrica: evolución y seguimiento / Radiofrequency treatment for electrical storm: evolution and monitoring

Resumen Introducción y objetivos: La tormenta eléctrica (TE) se caracteriza por episodios repetidos de taquicardia ventricular o fibrilación ventricular relacionados con mal pronóstico a corto y largo plazos. El objetivo fue evaluar la prevalencia, resultados y supervivencia de los pacientes sometidos a tratamiento intervencionista por TE en un centro de referencia. Métodos: Estudio unicéntrico, observacional y retrospectivo. Se revisaron los procedimientos de ablación por TE y se evaluaron las características basales de los pacientes, tipo de procedimiento, mortalidad total, recurrencia de arritmia, mortalidad cardiovascular y necesidad de trasplante. Resultados: Desde enero de 2009 hasta diciembre de 2016 se realizaron 67 procedimientos (38% de complejos: 19% de ablación endoepicárdica, 7.5% de crioablación epicárdica quirúrgica, 3% de simpatectomía, 3% de inyección coronaria con alcohol; 6% de apoyo con oxigenación con membrana extracorpórea) en 41 pacientes (61% de causa isquémica) por TE. La mortalidad intraprocedimiento fue del 1.5%. La mediana de seguimiento fue de 23.5 meses (RIQ, 14.2-52.7). Tras el primer ingreso por TE (uno o varios procedimientos), la mortalidad a un año fue de 9.8%. La incidencia acumulada de trasplante cardiaco por TE fue de 2.4%. En el análisis multivariado, el riesgo de recurrencias arrítmicas o muerte por cualquier causa fue significativamente mayor en pacientes con arritmias clínicas inducibles (HR, 9.03; p = 0.017). Conclusiones: El tratamiento de pacientes con TE, instituido en un centro de referencia y con experiencia, se relacionó con una tasa baja de recurrencia y supervivencia elevada, con una tasa de trasplante cardiaco por TE muy baja. Ante una recurrencia temprana es recomendable practicar un nuevo procedimiento durante el ingreso.

Abstract Introduction and objective: Electrical storm (ES) is characterized by repeated episodes of ventricular tachycardia or ventricular fibrillation, with poor short and long term prognosis. Our objective was to evaluate the prevalence, results of interventional treatment and survival of patients undergoing interventional treatment for ES in our center. Methods: Retrospective, unicentric and observational study. ES ablation procedures were revised and data regarding baseline characteristics of the patients, type of procedure, total mortality, recurrence of arrhythmia, cardiovascular mortality and the need for transplantation were evaluated. Results: From January 2009 to December 2016, 67 procedures (38% complex procedures: 19% epicardial ablation, 7.5% surgical epicardial crioablation, 3% simpatectomy, 3% coronary alcohol injection, 6% extracorporeal membrane oxygenation support) were performed in 41 patients (61% Ischemic etiology) due to ES. Intraprocedural mortality was 1.5%. The median follow-up was 23.5 months (IQR [14.2-52.7]). After the first admission for ES (one or several procedures), 1-year mortality was 9.8%. The cumulative incidence of cardiac transplantation was 2.4%. The risk of arrhythmic recurrences or death was significantly higher in patients with inducible clinical arrhythmias after ablation (HR: 9.03, p = 0.017). Conclusions: The treatment of patients with ES, performed in a reference center, allows obtaining good rates of recurrence and survival, with very low rates of cardiac transplantation for ES. In the presence of an early recurrence, it is advisable to perform a new procedure during admission.

Early prognostic value of an Algorithm based on spectral Variables of Ventricular fibrillAtion from the EKG of patients with suddEn cardiac death: A multicentre observational study (AWAKE) / Valor pronóstico precoz de un algoritmo basado en variables espectrales de la fibrilación ventricular del ECG de pacientes con muerte súbita cardiaca: estudio observacional multicéntrico (AWAKE)

Abstract Objective: Ventricular fibrillation (VF)-related sudden cardiac death (SCD) is a leading cause of mortality and morbidity. Current biological and imaging parameters show significant limitations on predicting cerebral performance at hospital admission. The AWAKE study (NCT03248557) is a multicentre observational study to validate a model based on spectral ECG analysis to early predict cerebral performance and survival in resuscitated comatose survivors. Methods: Data from VF ECG tracings of patients resuscitated from SCD will be collected using an electronic Case Report Form. Patients can be either comatose (Glasgow Coma Scale GCS --- ≤8) survivors undergoing temperature control after return of spontaneous circulation (RoSC), or those who regain consciousness (GCS = 15) after RoSC; all admitted to Intensive Cardiac Care Units in 4 major university hospitals. VF tracings prior to the first direct current shock will be digitized and analyzed to derive spectral data and feed a predictive model to estimate favorable neurological performance (FNP). The results of the model will be compared to the actual prognosis. Results: The primary clinical outcome is FNP during hospitalization. Patients will be categorized into 4 subsets of neurological prognosis according to the risk score obtained from the predictive model. The secondary clinical outcomes are survival to hospital discharge, and FNP and survival after 6 months of follow-up. The model-derived categorisation will be also compared with clinical variables to assess model sensitivity, specificity, and accuracy. Conclusions: A model based on spectral analysis of VF tracings is a promising tool to obtain early prognostic data after SCD.

Resumen Objetivo: La muerte súbita (MS) por fibrilación ventricular (FV) es una importante causa de morbilidad y mortalidad. Los métodos biológicos y de imagen actuales muestran limitaciones para predecir el pronóstico cerebral al ingreso hospitalario. AWAKE es un estudio observacional, multicéntrico, con el objetivo de validar un modelo basado en el análisis espectral del elec- trocardiograma (ECG), que predice precozmente el pronóstico cerebral y la supervivencia en pacientes resucitados y en estado de coma. Métodos: Se recogerán datos de los ECG con FV de pacientes reanimados de MS. Los pacientes pueden ser tanto supervivientes en estado de coma (Glasgow Coma Scale GCS ≤ 8) sometidos a control de temperatura tras la recuperación de circulación espontánea (RCE), como aquellos que recuperan la consciencia (GCS = 15) tras RCE; todos ellos ingresados en unidades de terapia intensiva cardiológica de 4 hospitales de referencia. Los registros de FV previos al primer choque se digitalizarán y analizarán para obtener datos espectrales que se incluirán en un modelo predictivo que estime el pronóstico neurológico favorable (PNF). El resultado del modelo se comparará con el pronóstico real. Resultados: El objetivo principal es el PNF durante la hospitalización. Los pacientes se categorizarán en 4 subgrupos de pronóstico neurológico según la estimación de riesgo obtenida en el modelo predictivo. Los objetivos secundarios son supervivencia al alta hospitalaria, y PNF y supervivencia a los 6 meses. El resultado de este modelo también se comparará con el pronóstico según variables clínicas. Conclusiones: Un modelo basado en el análisis espectral de registros de FV es una herramienta prometedora para obtener datos pronósticos precoces tras MS por FV.

Value of the Qrs-T Angle in Predicting the Induction of Ventricular Tachyarrhythmias in Patients with Chagas Disease / Valor do Ângulo Qrs-T na Predição de Indução de Taquiarritmias Ventriculares em Pacientes Chagásicos

Background: The QRS-T angle correlates with prognosis in patients with heart failure and coronary artery disease, reflected by an increase in mortality proportional to an increase in the difference between the axes of the QRS complex and T wave in the frontal plane. The value of this correlation in patients with Chagas heart disease is currently unknown. Objective: Determine the correlation of the QRS-T angle and the risk of induction of ventricular tachycardia / ventricular fibrillation (VT / VF) during electrophysiological study (EPS) in patients with Chagas disease. Methods: Case-control study at a tertiary center. Patients without induction of VT / VF on EPS were used as controls. The QRS-T angle was categorized as normal (0-105º), borderline (105-135º) or abnormal (135-180º). Differences between groups for continuous variables were analyzed with the t test or Mann-Whitney test, and for categorical variables with Fisher's exact test. P values < 0.05 were considered significant. Results: Of 116 patients undergoing EPS, 37.9% were excluded due to incomplete information / inactive records or due to the impossibility to correctly calculate the QRS-T angle (presence of left bundle branch block and atrial fibrillation). Of 72 patients included in the study, 31 induced VT / VF on EPS. Of these, the QRS-T angle was normal in 41.9%, borderline in 12.9% and abnormal in 45.2%. Among patients without induction of VT / VF on EPS, the QRS-T angle was normal in 63.4%, borderline in 14.6% and abnormal in 17.1% (p = 0.04). When compared with patients with normal QRS-T angle, those with abnormal angle had a fourfold higher risk of inducing ventricular tachycardia / ventricular fibrillation on EPS [odds ratio (OR) 4; confidence interval (CI) 1.298-12.325; p = 0.028]. After adjustment for other variables such as age, ejection fraction (EF) and QRS size, there was a trend for the abnormal QRS-T angle to identify patients with ...

Fundamento: O ângulo QRS-T mostra correlação com prognóstico em pacientes com insuficiência cardíaca e doença coronariana, traduzido por um aumento na mortalidade proporcional ao aumento na diferença entre os eixos do complexo QRS e da onda T no plano frontal. Até hoje, nenhuma informação a este respeito foi obtida em pacientes com cardiopatia chagásica. Objetivo: Correlacionar o ângulo QRS-T com a indução de taquicardia ventricular / fibrilação ventricular (TV / FV) em chagásicos durante estudo eletrofisiológico (EEF). Métodos: Estudo caso-controle em centro terciário. Pacientes sem indução de TV / FV ao EEF foram utilizados como controles. O ângulo QRS-T foi categorizado como normal (0-105º), limítrofe (105-135º) e anormal (135-180º). As diferenças entre os grupos foram analisadas pelo teste t ou teste de Mann-Whitney para variáveis contínuas, e teste exato de Fisher ou qui-quadrado para variáveis categóricas. Valores de p < 0,05 foram considerados significativos. Resultados: De 116 pacientes submetidos ao EEF, 37,9% foram excluídos por estarem com dados incompletos / prontuários inativos ou pela impossibilidade de se calcular corretamente o ângulo QRS-T (presença de bloqueio de ramo esquerdo e fibrilação atrial). De 72 pacientes incluídos, 31 induziram TV / FV ao EEF. Destes, o ângulo QRS-T se encontrava normal em 41,9%, limítrofe em 12,9% e anormal em 45,2%. No grupo de pacientes sem indução de TV / FV, o ângulo QRS-T se encontrava normal em 63,4%, limítrofe em 14,6% e anormal em 17,1% (p = 0,04). Quando comparados aos pacientes com ângulo QRS-T normal, o risco de indução de TV / FV nos pacientes com ângulo anormal foi quatro vezes maior [odds ratio (OR) 4; intervalo de confiança ...

Differences of ventricular late potential between acute STEMI and NSTEMI patients / Diferencias del potencial tardío ventricular entre pacientes con infartos agudos STEMI y NSTEMI

OBJECTIVE: To discuss the positive rate of ventricular late potential (VLP) between patients with acute ST-segment elevation myocardial infarction (STEMI) and patients with acute non NSTEMI. METHODS: One hundred and sixty-three cases of acute myocardial infarction (90 patients with STEMI and 73 with NSTEMI), admitted to the first hospital of China Medical University between June 2011 and August 2011, underwent VLP examination. RESULTS: The VLP positive rate of the STEMI group was 54.4%, while that of the NSTEMI group was 38.4%, and the differences have statistical meaning (χ2 = 4.186, p < 0.05). The occurrence rate of ventricular arrhythmia in VLP positive patients was 11.7%, while in VLP negative patients it was 3.5% (χ2 = 4.005, p < 0.05). CONCLUSION: The VLP positive rate of the STEMI group is higher than that of the NSTEMI group.

OBJETIVO: Analizar la tasa positiva del potencial tardío ventricular (PTV) entre pacientes con infarto agudo del miocardio sin elevación del segmento ST (NSTEMI por sus siglas en inglés) y el infarto agudo del miocardio con elevación del segmento ST (STEMI por sus siglas en inglés). MÉTODOS: Ciento sesenta y tres casos de infarto agudo de miocardio (90pacientes con STEMI) y 73 con NSTEMI, ingresados en la Universidad primer hospital de Medicina China entre junio y agosto de 2011, fueron sometidos a examen de PTV. RESULTADOS: La tasa positiva PVT del grupo STEMI fue 54.4%, mientras que la del grupo NSTEMI fue 38.4%, y las diferencias tienen significado estadístico (χ² = 4.186, p < 0.05). La tasa de ocurrencia de arritmia ventricular en pacientes PVTpositivos fue 11.7%, mientras que en los pacientes PVT negativos fue 3.5% (χ² = 4.005, p < 0.05). CONCLUSIÓN: La tasa PTV positiva del grupo STEMI es mayor que la del grupo NSTEMI.

Reoperação da valva mitral minimamente invasiva sem pinçamento da aorta / Minimally invasive redo mitral valve surgery without aortic crossclamp

INTRODUÇÃO: Reoperações da valva mitral apresentam maior índice de complicações quando comparadas com a primeira cirurgia. Com o domínio das técnicas videoassistidas para as primeiras cirurgias da valva mitral, os casos de reoperações passaram a despertar interesse para esses procedimentos menos invasivos. OBJETIVO: Analisar os resultados e as dificuldades técnicas da retroca valvar mitral minimamente invasiva em 10 pacientes. MÉTODO: A circulação extracorpórea foi instalada por meio de colocação de cânulas femorais e cânula na veia jugular interna direita, conduzida em 28 graus de temperatura em fibrilação ventricular. Realizada toracotomia lateral direita com 5 a 6 cm no terceiro ou quarto espaço intercostal. Pericárdio foi descolado apenas na região do átrio esquerdo no ponto da atriotomia. A aorta não foi pinçada. RESULTADOS: Foram avaliados 10 pacientes com idade média de 56,9±10,5 anos. Quatro encontravam-se em ritmo de fibrilação atrial e 6 em ritmo sinusal. O tempo médio entre a primeira operação e a reoperações foi de 11 ± 3,43 anos. O EuroSCORE médio do grupo foi de 8,3 ± 1,82. O tempo médio de fibrilação ventricular e de circulação extracorpórea foi respectivamente 70,9 ± 17,66 min e 109,4 ± 25,37 min. O tempo médio de internamento foi de 7,6 ± 1,5 dias. Não houve óbitos nessa série. CONCLUSÃO: A reoperação da valva mitral pode ser feita por meio de técnicas menos invasivas com bons resultados imediatos e baixa morbimortalidade. Entretanto, esse tipo de cirurgia requer maior tempo de circulação extracorpórea, especialmente nos casos em que o paciente já tenha uma prótese. A presença de uma mínima insuficiência aórtica também torna esse procedimento tecnicamente mais desafiador.

INTRODUCTION: Reoperations of the mitral valve have a higher rate of complications when compared with the first surgery. With the field of video-assisted techniques for the first surgery of mitral valve became routine, reoperation cases began to arouse interest for this less invasive procedures. OBJECTIVE: To assess the results and the technical difficulties in 10 patients undergoing minimally invasive redo mitral valve surgery. METHOD: Cardiopulmonary bypass was installed through a cannula placed in the femoral vessels and right internal jugular vein, conducted in 28 degrees of temperature in ventricular fibrillation. A right lateral thoracotomy with 5 to 6 cm in the third or fourth intercostal space was done, pericardium was displaced only at the point of atriotomy. The aorta was not clamped. RESULTS: Ten patients with mean age of 56.9 ± 10.5 years, four were in atrial fibrilation rhythm and six in sinusal. Average time between first operation and reoperations was 11 ± 3.43 years. The mean EuroSCORE group was 8.3 ± 1.82. The mean ventricular fibrillation and cardiopulmonary bypass was respectively 70.9 ± 17.66 min and 109.4 ± 25.37 min. The average length of stay was 7.6 ± 1.5 days. There were no deaths in this series. CONCLUSION: Mitral valve reoperation can be performed through less invasive techniques with good immediate results, low morbidity and mortality. However, this type of surgery requires a longer duration of cardiopulmonary bypass, especially in cases where the patient already has prosthesis. The presence of a minimal aortic insufficiency also makes this procedure technically more challenging.

Associação entre dissinergia miocárdica e arritmia ventricular na forma indeterminada da doença de Chagas / Association between left ventricular wall motion abnormalities and ventricular arrhythmia in the indeterminate form of Chagas disease

INTRODUÇÃO: Pacientes na forma indeterminada da doença de Chagas (FIDC) podem apresentar anormalidades contráteis segmentares, com evidências de pior prognóstico comparativamente a pacientes com estudo ecocardiográfico normal. O objetivo deste estudo foi de avaliar a associação entre a presença de anormalidade contrátil segmentar e a presença de distúrbios do ritmo cardíaco na FIDC. MÉTODOS: Foram estudados 38 pacientes na FIDC, sendo 26 pacientes sem anormalidade contrátil e 12 com presença de distúrbio contrátil ao estudo ecocardiográfico. Todos os pacientes foram submetidos a um estudo ecocardiográfico completo, incluindo o Doppler tecidual, bem como à monitorização eletrocardiográfica de 24h (Holter). RESULTADOS: Entre as diversas variáveis estudadas, foram encontradas diferenças significativas entre os dois grupos em relação à fração de ejeção (p < 0,001), dimensão sistólica do ventrículo esquerdo (p = 0,029) e tempo de contração isovolumétrica (p < 0,05) medidos pela ecocardiografia e Doppler tecidual, bem como extrassistolia ventricular isolada (p = 0,016) e em pares (p = 0,003) pela avaliação pelo Holter. CONCLUSÕES: Pacientes na FIDC que apresentam anormalidades contráteis quando avaliados pela ecocardiografia apresentam episódios mais frequentes de extrassistolia ventricular, traduzindo um maior dano morfofuncional e elétrico do coração, quando comparados a pacientes que apresentem estudo ecocardiográfico normal.

INTRODUCTION: Chagas' disease can lead to severe and potentially lethal damage of cardiac function. Thus, the identification of cardiac abnormalities in patients presenting the indeterminate form (IF) can be important for risk stratification. This paper aimed to demonstrate whether IF chagasic patients who presented wall motion abnormalities showed functional and electric disturbances compared to patients with normal echocardiogram and Doppler studies. METHODS: Thirty eight patients with the IF were studied, including 26 chagasic patients with normal electrocardiographic, radiological and echocardiographic exams and 12 chagasic patients showing segmental wall motion abnormalities in the echocardiographic exam. All the patients were submitted to complete echocardiogram and Doppler study, including tissue Doppler imaging (TDI) and Holter 24h monitoring. RESULTS: Among the variables evaluated, significant differences among the two groups were verified in relation to: the ejection fraction (p < 0.001); left ventricular systolic dimension (p = 0.029); isovolumic contraction time, measured by TDI in the basal segments of the left ventricle (p < 0.05); and the presence of isolated (p = 0.0005) and paired ventricular extrasystoles (p = 0.003), in the Holter monitoring. CONCLUSIONS: The indeterminate form of Chagas' disease can present cardiac wall motion abnormality, demonstrating functional and electric damage compared to chagasic patients with normal echocardiogram.

Role of the Alternans of Action Potential Duration and Aconitine-Induced Arrhythmias in Isolated Rabbit Hearts

Under conditions of Na+ channel hyperactivation with aconitine, the changes in action potential duration (APD) and the restitution characteristics have not been well defined in the context of aconitine-induced arrhythmogenesis. Optical mapping of voltage using RH237 was performed with eight extracted rabbit hearts that were perfused using the Langendorff system. The characteristics of APD restitution were assessed using the steady-state pacing protocol at baseline and 0.1 microM aconitine concentration. In addition, pseudo-ECG was analyzed at baseline, and with 0.1 and 1.0 microM of aconitine infusion respectively. Triggered activity was not shown in dose of 0.1 microM aconitine but overtly presented in 1.0 microM of aconitine. The slopes of the dynamic APD restitution curves were significantly steeper with 0.1 microM of aconitine than at baseline. With aconitine administration, the cycle length of initiation of APD alternans was significantly longer than at baseline (287.5 +/- 9.6 vs 247.5 +/- 15.0 msec, P = 0.016). The functional reentry following regional conduction block appears with the progression of APD alternans. Ventricular fibrillation is induced reproducibly at pacing cycle length showing a 2:1 conduction block. Low-dose aconitine produces arrhythmogenesis at an increasing restitution slope with APD alternans as well as regional conduction block that proceeds to functional reentry.

Cardiac herniation following completion pneumonectomy for bronchiectasis.

Sporadic reports on cardiac herniation are available in the literature; most of them had followed intrapericardial pneumonectomies for malignant pulmonary tumors. We present an uncommon event of heart herniation after a completion pneumonectomy indicated for chronic bronchiectasis. A 35-year-old male patient was operated for left completion pneumonectomy. A 6 cm Χ 4 cm area of adherent pericardium near the obtuse margin of heart was removed during surgery. During head-end elevation of the bed in postoperative intensive care unit, patient got accidentally tilted to the left side, which resulted in ventricular fibrillation. Chest cavity was re-opened for cardiopulmonary resuscitation. Left ventricle was found herniating through the pericardial deficiency into the left-thoracic cavity with the cardiac apex touching chest wall. During surgical re-exploration, the pericardial deficiency was closed with a synthetic Dacron patch. Hemodynamic condition remained stable in the immediate postoperative period. Patients had infection of the left thoracic cavity after 5 weeks, for which he was subjected to thoracoplasty and omentopexy. Prompt recognition with timely intervention is life saving from cardiac herniation. Strategy of closing the pericardial defect after pneumonectomy should be followed routinely, irrespective of the indication for pneumonectomy.

Curso de Atualização em Cardiologia: aula 8: Arritmias para conduta clínica / Course Updating in Cardiologyclass 8: Arrhythmias for clinical conduct

As arritmias cardíacas apresentam grande prevalência na prática clínica diária e, desta forma, o diagnóstico correto é fundamental para a instituição da terapia adequada. O reconhecimento dos principais sinais e sintomas clínicos associados à interpretação criteriosa do eletrocardiograma são peças determinantes do sucesso terapêutico. Neste artigo serão abordadas as principais arritmias supraventriculares e ventriculares, no que diz respeito à sua apresentação clínica, critérios eletrocardiográficos, conduta imediata e em longo prazo. Vale enfatizar que a arritmologia atual oferece inúmeras opções terapêuticas efetivas e curativas para a grande maioria dos pacientes.

Effects of combined sildenafil-nitric oxide donor on defibrillation efficacy.

BACKGROUND: A previous study demonstrated that supra-therapeutic concentration of sildenafil citrate attenuates defibrillation efficacy. However, the effect of combined sildenafil and NTG administration on defibrillation efficacy is not known. OBJECTIVE: The present study investigated whether sildenafil administration at the therapeutic level increases the defibrillation threshold (DFT) when combined with NTG. MATERIAL AND METHOD: Twenty-four pigs (20-25 kg) were randomized into four groups. After the control DFT was obtained, a stock solution of 50-mg (group 1, therapeutic concentration) and 100-mg (group 2, supratherapeutic concentration) of sildenafil, and 100-mL of saline (groups 3 and 4) were infused at 2 mL/min. Then, NTG was administered in groups 1-3 at 5 microg/min, with an increment of 5 microg/min every 5 min. The DFT was determined again after NTG was infused for 20 minutes. RESULTS: In group 1, the DFT (402 +/- 33V, 11 +/- 2J) was not different from the control (404 +/- 28V, 11 +/- 2J). In group 2, the DFT (521 +/- 18V, 19 +/- 1J) was higher (p < 0.004) than that in the control group (444 +/- 31V, 14 +/- 2J). Saline did not alter the DFT either individually or in combination with NTG. CONCLUSION: Supratherapeutic dose of sildenafil-NTG combination significantly increased the DFT (17% of peak voltage, 37% of total energy). This effect on DFT appears to be driven by sildenafil and not NTG.

The Effect of Cryoinjury on Ventricular Tachycardia in the Swine Right Ventricle

This study was performed to assess the influence of the cryoinjury on the dynamics of wavefronts and to determine whether they can convert ventricular fibrillation (VF) to ventricular tachycardia (VT) in fibrillating right ventricular (RV) of swines using an optical mapping system. A cryoinjury with a diameter of 12 mm was created on the epicardium of perfused RV of swines (n = 6) and optical mapping were taken from baseline until 10 minutes after the cryoinjury. Out of 35 cryoinjuries, the images were possible to be interpreted in 32. The optical action potential could not be observed in either the cryoinjury or peri-injury sites at 1 and 3 minutes, was observed in only the cryoinjury site at 5 minutes, and recovered in both sites at 10 minutes. The cycle length of the tachycardia was 135.9 +/- 23.6 msec at baseline, 176.2 +/- 79.3 msec at 1 minute, 187.6 +/- 97.9 msec at 3 minutes, 185.5 19.2 msec at 5 minutes, and 152.1 +/- 64.1 msec at 10 minutes. The cycle lengths at 1, 3, and 5 minutes after the cryoinjury were significantly more prolonged than that at baseline (p = 0.001, p = 0.006, p = 0.016). After the cryoinjury, the VF changed to VT in 9 (28.0%), and terminated in 2 (6.3%). These changes were observed mainly within 5 minutes after cryoinjury. The cryoinjury had anti-fibrillatory effects on the tissue with VF. This phenomenon was related to a decreasing mass and stabilizing wavefronts.

Implante de desfibrilador: a propósito de um limiar de desfibrilação elevado / Defibrillator implant: aiming at a high defibrillator threshold

Este artigo tem por finalidade orientar a conduta nos casos de pacientes com taquicardia ventricular sustentada e disfunção grave, encaminhados para implante de desfibrilador, situação cada vez mais frequente. Discute-se a possibilidade de utilizar alternativas cirúrgicas para solucionar situações em que os limiares de desfibrilação permanecem altos durante os testes realizados no momento do implante

Electrophysiological concept of ventricular defibrillation mechanism.

Sudden cardiac death is a major health problem in most industrialized countries around the world including Thailand. It is mainly caused by ventricular fibrillation (VF). Currently, defibrillation is the only effective clinical treatment of this fatal arrhythmia. Although defibrillation mechanism has been investigated extensively for many decades, its definite mechanism is still debated. It is known that understanding the basic mechanism of defibrillation is essential to develop better treatment of VF: In the present article, seven hypotheses commonly proposed as the mechanism of ventricular defibrillation are reviewed. Since research in the field of defibrillation mechanism is dynamic, the present review is to update the information to clinicians and basic investigators on the mechanism of defibrillation available to date.

Muerte súbita: parte I / Sudden death: part I

La muerte súbita es probablemente el problema más grave que enfrenta la cardiología moderna, tanto por el gran número de casos que se producen anualmente como por su impacto socioeconómico. En el adulto está ligada en más del 80 por ciento de los casos a la cardiopatía coronaria, siendo en ella factores de peor pronóstico, la mala función ventricular, la presencia de arritmias ventriculares y la hipertrofia ventricular izquierda. La muerte súbita es un problema complejo en el que intervienen varios factores: inestabilidad eléctrica, miocardio vulnerable y una serie de condiciones moduladoras, varias de ellas relacionadas con el sistema simpático. En general es producida por una arritmia ventricular, siendo la fibrilación ventricular la más frecuente, le siguen en orden de frecuencia, la bradiarritmia o asistolía de la cual prácticamente los pacientes no se recuperan nunca y finalmente la taquicardia ventricular que es de mejor pronóstico, pero desgraciadamente la más infrecuente

Paro circulatorio por fibrilación ventricular (1ª parte) / Circulatory arrest due to ventricular fibrillation (Part I)

La velocidad y la amplitud de las ondas fibrilatorias son una expresión, en cierta manera, de las condiciones funcionales del miocardio y de su grado de oxigenación. Se reconocen tres tipos de ondas fibrilatorias. A) Fibrilación convulsiva o gruesa: con ondas fibrilatorias de alta frecuencia (>150/minuto y entre 0,5 y 1 mV de amplitud). Observando directamente al corazón, el órgano se sacude violentamente como si convulsivara. B) Fibrilación trémula o fina: la frecuencia sigue siendo alta (>100/minuto) pero de menor amplitud y las ondas recorren en forma anárquica la superficie de la pared ventricular. Esta fase es consecuencia del gran consumo de oxígeno de la fase anterior. Dura de 3 a 5 minutos. C) Fibrilación hipotónica o lenta: las ondas fibrilatorias son anchas, de baja amplitud y baja frecuencia. (>100/minuto), el corazón luce cianótico, dilatado e hipotónico. Puede durar entre 5 y 15 minutos hasta que el corazón para totalmente en asistolia. Un corazón globalmente hipóxico difícilmente se fibrile en forma espontánea. El corazón debe ser desfibrilado durante las fases de fibrilación rápida. La desfibrilación es un intento de despolarizar globalmente a todo el corazón mediante una descarga eléctrica, y con ello producir una asistolia de breve duración durante la cual el corazón tiene la oportunidad de reanudar su actividad normal a partir de la activación espontánea del marcapaso natural, es decir, el nodo sinusal, y arrancar con ritmo sinusal. Estudios anteriores con descargas de baja energía (175-200 joules para un adulto) no lograron demostrar beneficio alguno de choques iniciales inferiores a 2 j/kg y choques en rápida sucesión de 3 a 4 j/kg (apróximadamente 200 a 400 joules de energía). Según el protocolo de la American Heart Association, el paciente debe ser desfibrilado con dos primeros choques de 2 a 3 j/kg. en rápida sucesión. Y si éstos fracasan deberá recibir un tercero de 4 j/kg. Los tres choques deben hacerse en rápida sucesión (no todos los autores concuerdan con este criterio), sin intervención medicamentosa intermedia y sin levantar las paletas del lugar, para evitar modificaciones en la impedancia transtorácica y lesiones de la piel (eritema, edema) en otras regiones del tórax. En el texto se analiza también el efecto de los medicamentos habitualmente utilizados en la reanimación cardíaca, sus indicaciones e inconvenientes.

Mecanismos involucrados en el efecto antiarritmico y proarritmico del magnesio / Mechanisms involved in the antiarrhythmic and proarrhythmic effects of magnesium

El objetivo fue analizar en perros, los efectos del MgCl2, y del MgSO4 sobre los mecanismos electrofisiológicos que pudieran vincularse con las acciones antiarrítmicas y proarrítmicas de estas soluciones. Se estudiaron previamente los parámetros farmacocinéticos del MgCl2 y del MgSO4; ambos mostraron que el Mg plasmático disminuye exponencialmente (constante beta de O,118 ñ O,013 h-l), t 1/2 de eliminación de 6,02 ñ O,68 h y una Vda de O,259 ñ O,02lxkg-l. Posteriormente se estudiaron dos grupos de animales - Grupo I: dieta normal. Grupo II A: dieta sin Mg + clortalidona + K y Grupo II B: dieta sin Mg + clortalidona + KCI + MgSO4. Se midieron los electrolitos y las variables electrofisiológicas por medio de estimulación ventricular programada. El grupo I mostró que la administración de MgSO4 endovenoso disminuye el Na, el K y el umbral de fibrilación ventricular (UFV) y prolonga el período refractaria efectivo ventricular (PREV). El MgCl2 no modifica el UFV, pero prolonga el PREV, el A-H, el QTc y el PQ. El MgSO4 aumenta la excreción de K urinario en forma significativamente mayor que el MgCl2. La administración de NaCl no alteró las variables electrofisiológicas pero el NaSO4 disminuyó el K plasmático, sin modificar el UFV. El Grupo II A presentó descenso del K y Mg plasmático, linfocitario y miocárdico, disminución del PREV y del UFV y aumento del QTc. A este grupo se le administro en forma aguda: 1) MgSO4 que provocó mayor descenso del UFV y del K plasmático y aumento del PREV y 2) KCI que aumento el K piasmático y el UFV. El grupo II B no modificó los electrolitos ni las variables electrofisiológicas. Se concluye que los efectos antiarrítmicos observados en clínica por la administración de sales de Mg se deberían probablemente a la prolongación del PREV. Sin embargo, la depleción de K inducida por el MgSO4 puede provocar un descenso del UFV, efecto proarrítmico que se podría evitar utilizando MgCl2.

Análise de potenciais tardios em pacientes com arritmias ventriculares malignas / Late potentials analysis in patients with malignant ventricular arrhythmia

PURPOSE--To assess the relationship between late potentials and spontaneous ventricular arrhythmias, organic heart disease, inducibility of arrhythmias at electrophysiological study and ejection fraction. METHODS--The population is comprised by 52 patients (41 men, 11 women with mean age 50 +/- 16 years) with spontaneous clinically documented ventricular tachycardia or ventricular fibrillation. An electrophysiological study was performed with conventional programmed stimulation. Within a week of the test a study of late potentials was also performed. RESULTS--Late potentials were documented in 73 per cent of the patients with ventricular tachycardia and only in 17 per cent of the patients with ventricular fibrillation. Sixty-eight percent of the patients with ischemic cardiopathy presented late potentials and in these, ventricular tachycardia was inducible in 93 per cent . Only one from a group of 7 patients with ventricular arrhythmias and no organic heart disease, presented late potentials. In patients with late potentials, 84 per cent have inducible ventricular tachycardia, but only 26 per cent of patients without late potentials have inducible ventricular tachycardia. The incidence of late potentials was inversely correlated with left ventricular ejection fraction. CONCLUSION--The presence of late potentials was more frequent in patients with ventricular tachycardia than in patients with ventricular fibrillation. The presence of late potentials has a sensibility of 81.5 per cent and a specificity of 78 per cent to detect patients with inducible ventricular tachycardia