[Totally subcutaneous defibrillator]. / El cardiodesfibrilador totalmente subcutáneo.

The implantable cardioverter-defibrillators (ICD) is a therapy for the prevention of sudden cardiac death. Complications with implant have been associated mainly with transvenous lead insertion. Difficulties in achieving venous access can occasionally result in failed ICD implantation. Lead failures remains a major limitation and often require removal. This procedure is associated with important morbidity and mortality. To eliminate the need for venous access, Bardy et al. designed an entirely subcutaneous ICD system. The subcutaneous ICD consists of a 3-mm tripolar parasternal electrode positioned parallel to the left of the sternal midline and guided exclusively by anatomical landmarks without fluoroscopy. The pulse generator is positioned over the sixth rib between the midaxillary line and the anterior axillary line. The device delivers a maximum of only 80-J shocks. Ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two tests to ensure a margin of safety. A demand pacing at 50 beats per minute is available for 30 seconds after a shock. These studies are preliminary but the system will need to be employ in a long-term, randomized, prospective, multicenter clinical trials.

El cardiodesfibrilador totalmente subcutáneo / Totally subcutaneous defibrillator

El implante de un cardiodesfibrilador (CDI) se ha transformado hoy, en un procedimiento similar al de un marcapasos. Sin embargo, persisten inconvenientes relacionados principalmente a las vías vasculares en pacientes que portarán el equipo por muchos años, y también merecen una consideración especial los niños y jóvenes, algunos con anomalías de formación del sistema venoso. En tal sentido, puede resultar de utilidad el equipo desarrollado por Bardy y colaboradores para un implante totalmente subcutáneo, incluso sin necesidad de fluoroscopia, ya que el mismo se realiza por marcas anatómicas. El electrodo tripolar se ubica en el tejido celular subcutáneo paralelo al borde esternal izquierdo, y luego paralelo a la quinta o sexta costilla, el generador a la altura de la línea axilar. El equipo puede efectuar una descarga máxima de 80 Joule (J), pero se admite 65J para tener un margen de seguridad adecuado. La tolerancia de los pacientes fue buena. Las pruebas realizadas hasta el presente muestran factibilidad y buenos resultados. Sin duda son necesarios estudios más amplios, aleatorizados, multicéntricos y prospectivos.

The implantable cardioverter-defibrillators (ICD) is a therapy for the prevention of sudden cardiac death. Complications with implant have been associated mainly with transvenous lead insertion. Difficulties in achieving venous access can occasionally result in failed ICD implantation. Lead failures remains a major limitation and often require removal. This procedure is associated with important morbidity and mortality. To eliminate the need for venous access, Bardy et al. designed an entirely subcutaneous ICD system. The subcutaneous ICD consists of a 3-mm tripolar parasternal electrode positioned parallel to the left of the sternal midline and guided exclusively by anatomical landmarks without fluoroscopy. The pulse generator is positioned over the sixth rib between the midaxillary line and the anterior axillary line. The device delivers a maximum of only 80-J shocks. Ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two tests to ensure a margin of safety. A demand pacing at 50 beats per minute is available for 30 seconds after a shock. These studies are preliminary but the system will need to be employ in a long-term, randomized, prospective, multicenter clinical trials.

Efeito dos aparelhos iPod e MP4 sobre o funcionamento dos marcapassos / Effect of equipment on the iPod and MP4 pacemakers

Los equipos iPods (Apple) pueden producir interferencias electromagnéticas sobre los generadores de marcapasos. Este estudio investigó el efecto de iPod (Apple) y MP4 sobre marcapasos implantados a fin de detectar interferencia electromagnetica. Se estudiaron 72 pacientes, 39 hombres com edad media 75 + - 12 años (24-92 años) implantados con marcapasos. Las posibles interferencias fueron estudiadas durante las maniobras en encendido y apagado y cuando los Ipod se colocaban a 5 cm de la zona de implante durante 5 a 10 minutos. El técnico registraba...

Chagas disease: state-of-the-art of diagnosis and management.

Chagas' disease or American trypanosomiasis, is a potentially lethal parasitic zoonosis prevalent and endemic only in Latin America, caused by the flagellate protozoa Trypanosoma cruzi. It has 3 different stages, acute, indeterminate and chronic phase, with the chance of an etiological approach in the first stage and pharmacological and non-pharmacological treatment in the chronic phase. There are five main clinical forms of chronic chagasic cardiomyopathy: indeterminate, arrhythmogenic (predominantly dromotropic and extrasystolic), with ventricular dysfunction, thromboembolic and mixed forms. There are several diagnostic tests at the different stages, however, the ECG is the method of choice in longitudinal population studies in endemic areas because it is simple, with a low cost and a good sensitivity. Microscopic examination or parasitological diagnosis in the acute phase or immunodiagnostic tests are used to confirm the disease. The antiarrhythmic drug amiodarone, the most frequently prescribed agent for symptomatic ventricular arrhythmia treatment of Chagas' disease patients, has also recently been shown to have antifungal activity. Cardiac device implantation is very common, and chronic Chagas disease patients require pacemaker implantation at a younger age in contrast with patients with other cardiac pathologies. In summary, Chagas disease is a social disease, endemic in Latin America and shows different prevalence rates in Latin American countries.

Novos tratamentos famacológicos para a fibrilação atrial / New pharmacological treatments of atrium fibrillation

Quando se fala em fibrilação atrial, a maior preocupação sempre está relacionada às suas complicações, principalmente fenômenos tromboembólicos provocando acidente vascular cerebral...

Riesgo de muerte y miocardiopatía dilatada / Risco de morte e cardiopatia dilatada / Death risk and dilated cardiomyopathy

La miocardiopatía dilatada idiopática tiene alta incidencia en la población general, con mayor prevalencia en el hombre, y la muerte, súbita o por insuficiencia cardíaca, ocurre en plena etapa productiva. El adecuado tratamiento medicamentoso disminuyó la morbimortalidad en tanto el implante del cardiodefibrilador logró disminuir también la muerte arrítmica y se lo emplea con éxito para la prevención secundaria. Sin embargo no han podido definirse aún los marcadores de riesgo para la prevención primaria. Las drogas antiarrítmicas y especialmente la amiodarona se ensayaron en estudios como el GESSICA, CHF-STAT, CAT, AMIOVIRT, SCDHeFT, pero no se pudo demostrar eficacia total para la prevención. Se analizó la presencia de síncope como marcador clínico pero tampoco fue determinante para indicar el implante de un cardiodefibrilador. El problema se centró en el estudio de las arritmias con los registros Holter de 24 hs, la prolongación y dispersión del intervalo QT. La intervención de la disfunción autonómica se analizó mediante la variabilidad de la frecuencia cardíaca o el estudio del baroreflejo. La presencia de potenciales tardíos mediante el empleo de la electrocardiografía de alta resolución sirvió para señalar anormalidades anatómicas que se expresaban con la aparición de postpotenciales. Un estudio dinámico como el análisis del microvoltage de la onda T, los estudios electrofisiológicos invasivos y la resonancia magnética nuclear si bien aportan datos significativos es mayor su valor como predictores negativos que positivos. El cardiodefibrilador implantable demostró su utilidad para prevenir la muerte pero es necesario extremar los estudios para la elección del paciente en riesgo evitando el implante innecesario que entraña morbilidad y un costo elevado que nuestras economías y aquellas que ni aún los países desarrollados pueden sostener.

The idiopatic dilated cardiomyopathy has high incidence in the general population. More prevalent in men, the sudden cardiac death or that due to deterioration of heart failure are an important social and economical problem. The good medical treatment help to improve the morbimortality and the implant of a cardiodefibrillator diminished the arrhythmic death. It is employed successfully for secondary prevention. There are not good indicators of risk to define the hazard in primary prevention. The antiarrhythmic drugs were evaluated in different trials (GESSICA, CHF-STAT, CAT, AMIOVIRT, SCD-HeFT) but efficacy for total prevention could not be demonstrated. Syncope as a clinical marker was important but not to determine the implant of a cardiodefibrillator. The risk of arrhythmic events was directed to the study of Holter monitoring and the prolongation and dispersion of QT interval. The autonomic dysfunction was analyzed by the heart rhythm variability and the baroreflex response. The presence of postpotentials, studied with the signal averaging ECG, evidence anatomic alterations. The analysis of microvolt T wave alternans, invasive electrophysiologic studies and nuclear magnetic resonance all of them have principally a negative predictor value. The ICD demonstrated the utility to prevent death but it is necessary to improve the method to a better selection of the patient to be implanted as primary prevention. The primary prevention has elevated costs that are difficult to assume in our Latin American economies.

A miocardiopatia idiopática dilatada tem uma alta incidência na população geral. Prevalecendo mais no homem, a morte súbita ou por insuficiência cardíaca, ocorre em plena etapa produtiva. Um tratamento médico adequado ajuda a melhorar a morbimortalidade enquanto que o implante do cardiodefibrilador conseguiu diminuir também a morte arrítmica e se emprega com êxito na prevenção secundária. Entretanto não puderam definir ainda os marcadores de risco para a prevenção primária. As drogas antiarrítmicas e especialmente a amiodarona foram ensaiadas em estudos como o GESSICA, CHF-STAT, CAT, AMIOVIRT, SCD-HeFT, mas não se pôde demonstrar eficácia total para a prevenção. Analisou-se a presença de síncope como marcador clínico, mas não foi determinante para indicar o implante de um cardiodefibrilador. O problema se centrou no estudo das arritmias com os registros Holter de 24 h, a prolongação e a dispersão do intervalo QT. A intervenção da disfunção autonômica se analisou levando em consideração a variabilidade da frequência cardíaca ou o estudo do baroreflexo. A presença de potenciais tardios mediante o uso da eletrocardiografia de alta resolução serviu para marcar anormalidades anatômicas que se expressavam com o aparecimento de post potenciais. Um estudo dinâmico como a análise do micro voltagem da onda T, os estudos eletro fisiológicos invasores e a ressonância magnética nuclear ainda que aportem dados significativosé maior seu valor como prognosticadores negativos que positivos. O cardiodefibrilador implantável demonstrou sua utilidade para prevenir a morte, mas é necessário extremar os estudos na seleção do paciente em risco evitando um implante desnecessário que implica morbilidade e custo elevado que 'Mm nossas economias e nem ainda os países desenvolvidos podem sustentar.

A Latin American registry of implantable cardioverter defibrillators: the ICD-LABOR study.

OBJECTIVE: Despite the progress that has been reached in emergency medical systems and resuscitation, sudden cardiac death (SCD) continues to be the major cause of the death, and remains a significant public health problem. In this publication we are reporting our Latin American experience in the secondary prevention of SCD, by means of an ongoing registry involving seven Latin American countries and 770 patients. METHODS: Every individual within the present registry to date has presented with antecedents of aborted sudden death or cardiac arrest due to ventricular tachycardia or ventricular fibrillation. Patients included have fulfilled the Class I indication for implantable cardioverter defibrillator (ICD) and they were implanted with a Biotronik ICD (all models). The study was not sponsored by Biotronik, nor did they have access to the data. A specific protocol was designed for implantation and follow-up of patients. The database was completely registered through the Internet and a personal password was assigned to each group of investigators. The primary end point was death from all causes. Secondary end points were SCD and death due to congestive heart failure (CHF). RESULTS: The etiology of cardiac disease was found to be predominantly coronary artery disease (CAD) 39.7% (306 patients), followed by Chagas disease (ChD), 26.1% (201 patients), and idiopathic dilated cardiomyopathy (DCM), 17% (131 patients). Any remaining pathologies were included as miscellaneous 13.2% (101 patients). In 31 patients (4%) the etiology was unknown. The age did not differ within the principal pathologies, but was significantly older than the miscellaneous group (62.0 +/- 11.3 years vs 48.2 +/- 18.9 years, P < 0.0001). The follow-up period was 27 +/- 25 months (1-113 months) for the whole group. The mortality in functional classes I-II was significantly lower than mortality for functional classes III-IV (relative risk 1.46, CI 95%, P < 0.0001). Mean left ventricular ejection fraction (LVEF) for the whole group was 37.7 +/- 14.3%. Male LVEF was 36.1 +/- 14.1% and female LVEF was 42.2 +/- 13.8% P < 0.0001. During the follow-up period, 130 deaths were reported (global mortality 16.9 +/- 9.7%), out of which 84 (64.6%) were attributed to cardiac causes (10.9 +/- 5.1% of the total population). The annual adjusted cardiac mortality was 5.2 +/- 1.72% (range 3.5-7.0%). Among cardiac deaths the most common cause was progressive heart failure, 48 patients (57%) including 3 patients with pulmonary embolism. The second main cause of cardiac death was SCD, 36 patients (43%), including 4 patients with electrical storm and 3 patients with electromechanical dissociation after multiple shock therapy treatments. CONCLUSIONS: Despite the differences in terms of pathologies between the ICD-LABOR (Latin American bioelectronic ongoing registry) and randomized ICD trials, a parallel evolution in all cause mortality and cardiac mortality was observed. Independent risk factors for mortality included age >70 years, male gender, NYHA III/IV, and ejection fraction <0.30. The etiology of heart disease (Chagas vs Coronary Disease) was not found to be a risk factor.

Which patients with congestive heart failure may benefit from biventricular pacing?

BACKGROUND: Biventricular pacing improves the clinical status and ventricular function in patients with congestive heart failure (CHF) and intraventricular conduction delay. However, patient selection criteria including NYHA functional class, rhythm, PR interval, QRS duration (QRSd), left ventricular ejection fraction (LVEF), left ventricular diastolic diameter (LVDD), and other variables are not clearly defined. OBJECTIVE: To determine which and how many patients referred for an initial cardiac transplantation evaluation may be eligible for biventricular pacing (BP) according to the criteria of recently completed trials of cardiac resynchronization therapy (CRT). METHODS: This was a retrospective review of 200 patients, whose mean age was 51 +/- 13 years (173 men). Sinus rhythm was present in 88% of the patients, 107 had a QRSd > 120 ms, and 38% had left bundle branch block. LVDD was 72.5 +/- 12 mm and LVEF 21.7 +/- 9.3%; 54% had mitral regurgitation. RESULTS: When NYHA class, electrocardiographic, and ventricular function criteria were considered separately, a high proportion of patients appeared to be candidates for CRT: 70.5% were in NYHA functional class III/IV, 34% had QRSd > or = 150 ms, 60% had LVDD > or = 60 mm and 53.5% LVEF < or = 35%. However, the proportions of patients eligible for CRT were different according to the selection criteria of recently completed trials: 18% of the patients with InSync criteria, 13% of the patients with MUSTIC SR criteria, 0.5% with MUSTIC AF criteria, 27% of patients with MIRACLE criteria, and 35% of the patients with CONTAK CD criteria (without considering indications for implantable cardioverter defibrillator). CONCLUSION: In this population-based study, a wide range of patients (13% to 35%) would have been candidates for CRT, according to the selection criteria of different completed trials.

Cardiopatía congénita compleja operada y vena cava superior izquierda: un problema para la colocación de marcapasos definitivo / Surgical complex congenital cardiopathy and left superior vena cava: a problem for the implant of the pacemaker

La decisión de colocación de un marcapasos endocavitario en presencia de una cardiopatía compleja con anomalía del retorno venoso sistémico y pulmonar reparada en presencia de una vena cava superior izquierda (VCSI) puede constituirse en un problema cuando se emplea esta vía para alcanzar el ventrículo derecho. Se presenta el caso de una paciente de 23 años en quien se realizó una cirugía correctora a la edad de 3 años, y se interna para el reemplazo del marcapasos epicárdico. La evaluación completa tanto anatómica como funcional de esta lesión a través del ecocardiograma Doppler color descartó la necesidad de un estudio hemodinámico y facilitó la decisión y el éxito, si bien dificultoso, del implante

Ablación del nódulo atrioventricular con descarga de consensadores y radiofrecuencia / Atrioventricular nodal catheter ablation with condenser discharge and radiofrequency

La ablación del nódulo atrioventricular (AV) en aquellos pacientes com arritmias supraventriculares refractarias a tratamiento farmacológico constituye una alternativa terapéutica que les permite mejorar la calidad de vida. Con este fin se han utilizado dos tipos de energía: corriente directa y radiofrecuencia. El objetivo del presente estudio fue evaluar la tasa de éxito primario y hacer el seguimiento a largo plazo de la ablación del nódulo AV comparando dos tipos de energía: descarga de condensadores y radiofrecuencia. Se realizó ablación del nódulo AV en 80 pacientes: 40 por descarga de condensadores (Grupo I) com una media de seguimiento de 76 + 49 meses y 40 por radiofrecuencia (Grupo II) con un seguimiento medio de 28.1 + 20.8 meses. Se logró bloqueo AV completo luego del primer procedimiento en el 45 por ciento de los pacientes y se observó modificación del nódulo AV en el 50 por ciento del Grupo I. En el 100 por ciento del Grupo II se logró bloqueo AV completo. Tres pacientes del Grupo I (7.5 por ciento) tuvieron arritmias auriculares rápidas durante el seguimiento. Dos de ellos recibieron medicación y 1 un nuevo procedimiento ablativo. En el Grupo II 1 paciente (2.5 por ciento) requirió un segundo procedimiento. En cuanto a las complicaciones no hubo diferencias entre los dos grupos tanto en las tempranas como a largo plazo, com registro de una muerte súbita en cada grupo. La ablación selectiva del nódulo AV con radiofrecuencia en pacientes com arritmia supraventricular refractaria es un método tan seguro como el utilizado previamente (descarga de condensadores) con la ventaja de una tasa de éxito primario cercana al 100 por ciento.

Electrocardiograma de señal promediada de la onda P en individuos sanos / P-wave signal averaged ECG in normal subjects

El electrocardiograma de señal promediada de la onda P puede ser una herramienta útil para identificar pacientes con mayor riesgo de padecer episodios de fibrilación auricular. Para establecer valores de referencia se estudiaron 40 voluntarios mediante ECG convencional y electrocardiograma de señal promediada de onda P, en el cual se usó un filtro de 29 Hz y el ruido residual fue < 0,3 µ V. Se expresan los valores hallados para la duración de la onda P en el filtrado de las derivaciones ortogonales X, Y, Z y en el módulo, así como el RMS-20, RMS-30 y RMS-40

Ablación con radiofrecuencia de una taquicardia por reentrada nodal atípica en una niña de 3 años / Radiofrequency catheter ablation of typical atrioventricular nodal reentrant tachycardia in a child

La presencia de una taquicardia supraventricular paroxística incesante puede llevar a una miocardiopatía dilatada secundaria, siendo ésta una de las indicaciones de ablación por radiofrecuencia. Una niña de 3 años con una taquicardia por reentrada nodal atípica complicada con miocardiopatía fue sometida a una ablación de la vía lenta, siendo el procedimiento exitoso, con recuperación rápida de la función ventricular y sin recidiva de la taquicardia