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BACKGROUND: We aimed to describe the morphology of the border zone of viable myocardium surrounded by scarring in patients with Chagas heart disease and study their association with clinical events. METHODS: Adult patients with Chagas heart disease (n=22; 55% females; 65.5 years, SD 10.1) were included. Patients underwent high-resolution contrast-enhanced cardiac magnetic resonance using myocardial delayed enhancement with postprocessing analysis to identify the core scar area and border zone channels number, mass, and length. The association between border zone channel parameters and the combined end-point (cardiovascular mortality or internal cardiac defibrillator implantation) was tested by multivariable Cox proportional hazard regression analyses. The significance level was set at 0.05. Data are presented as the mean (standard deviation [SD]) or median (interquartile range). RESULTS: A total of 44 border zone channels (1[1-3] per patient) were identified. The border zone channel mass per patient was 1.25 (0.48-4.39) g, and the extension in layers of the border zone channels per patient was 2.4 (1.0-4.25). Most border zone channels were identified in the midwall location. Six patients presented the studied end-point during a mean follow-up of 4.9 years (SD 1.6). Border zone channel extension in layers was associated with the studied end-point independent from left ventricular ejection fraction or fibrosis mass (HR=2.03; 95% CI 1.15-3.60). CONCLUSIONS: High-resolution contrast-enhanced cardiac magnetic resonance can identify border zone channels in patients with Chagas heart disease. Moreover, border zone channel extension was independently associated with clinical events.

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Background: Vasovagal syncope (VVS) is the most common cause of syncope. Some stages of its pathophysiological mechanisms remain unclear. Vasoactive substances such as nitric oxide metabolites (NOx) and endothelin (ET) may be involved during acute orthostatic stress. Objective: To analyze plasma changes in NOx and ET and heart rate variability (HRV) in the supine positions (T1) and during the head-up tilt test (HUTT) (T2), in patients with VVS (case group) and control group. Methods: Thirty-seven patients (17 in the case group and 20 in the control group), matched for age and sex (mean aged 31.8 years) underwent HUTT with simultaneous HRV recording and venipuncture. Blood samples were collected during phases T1 and T2 and the analysis was performed without knowledge of the HUTT result. Results: In the total sample, there was an increase in NOx values (P = .014), however there was no increase in ET values from phase T1 to phase T2. Patients with VVS tended to increase plasma NOx values (P = .057) and had significantly higher plasma values compared to ET (P = .033) between phases T1 to T2. In the control group, there was no significant change in the values of these vasoactive substances. Regarding HRV, there were a decrease in the component HF (high frequency) and increased of the LF (low frequency)/HF ratio during HUTT. Conclusions: There was an increase in ET during HUTT occurred only in the case group. These patients are more likely to have an imbalance between antagonistic vasoactive biomarkers during orthostatic stress.

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PURPOSE OF REVIEW: Among the most common causes of cardiac syncope are arrhythmias and ischemic heart disease, both of which can coexist. The purpose of this review is to discuss the main causes of cardiac and vascular syncope related to atherosclerosis, its epidemiological and clinical aspects, warning signs, and initial approach. RECENT FINDINGS: Cardiac syncope may have a frequency of up to 34% in elderly people. Atherosclerosis-related causes of cardiac and vascular syncope may be due to cardiac arrhythmia and/or structural impairment of the heart or arteries. Late ventricular tachycardia and late-onset high-grade atrioventricular block associated with myocardial ischemia may occur with syncope, which is related to higher mortality. Besides ventricular dysfunction, concentric remodeling is also a prognostic factor. In calcific degenerative aortic stenosis, syncope carries a worse prognosis than the other cardinal signs. Cardiac syncope has a high recurrence and mortality rate. There are red flag alerts that must be considered in risk stratification.

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ABSTRACT Background: We aimed to describe the morphology of the border zone of viable myocardium surrounded by scarring in patients with Chagas heart disease and study their association with clinical events. Methods: Adult patients with Chagas heart disease (n=22; 55% females; 65.5 years, SD 10.1) were included. Patients underwent high-resolution contrast-enhanced cardiac magnetic resonance using myocardial delayed enhancement with postprocessing analysis to identify the core scar area and border zone channels number, mass, and length. The association between border zone channel parameters and the combined end-point (cardiovascular mortality or internal cardiac defibrillator implantation) was tested by multivariable Cox proportional hazard regression analyses. The significance level was set at 0.05. Data are presented as the mean (standard deviation [SD]) or median (interquartile range). Results: A total of 44 border zone channels (1[1-3] per patient) were identified. The border zone channel mass per patient was 1.25 (0.48-4.39) g, and the extension in layers of the border zone channels per patient was 2.4 (1.0-4.25). Most border zone channels were identified in the midwall location. Six patients presented the studied end-point during a mean follow-up of 4.9 years (SD 1.6). Border zone channel extension in layers was associated with the studied end-point independent from left ventricular ejection fraction or fibrosis mass (HR=2.03; 95% CI 1.15-3.60). Conclusions: High-resolution contrast-enhanced cardiac magnetic resonance can identify border zone channels in patients with Chagas heart disease. Moreover, border zone channel extension was independently associated with clinical events.

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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.

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The persistence of inflammatory processes in the myocardium in varying degrees of chronic Chagas heart disease has been poorly investigated. We hypothesized that edema could occur in patients with chronic chagasic cardiomyopathy and corresponds to the persistence of inflammatory processes in the myocardium. Eighty-two Chagas disease (CD) seropositive patients (64.6% females; age = 58.9 ± 9.9) without ischemic heart disease or conditions that cause myocardial fibrosis and dilation were considered. Late gadolinium enhancement (LGE) and T2-weighted magnetic resonance imaging of edema were obtained and represented using a 17-segment model. Patients were divided into three clinical groups according to the left ventricular (LV) ejection fraction (EF) as G1 (EF > 60%; n=37), G2 (35% > EF < 60%; n=33), and G3 (EF < 35%; n=12). Comparisons were performed by the Fisher or ANOVA tests. Bonferroni post hoc, Spearman correlation, and multiple correspondence analyses were also performed. Edema was observed in 8 (9.8%) patients; 2 (5.4%) of G1, 4 (12.1%) of G2, and 2 (16.7%) of G3. It was observed at the basal inferolateral segment in 7 (87.5%) cases. LGE was observed in 48 (58.5%) patients; 16 (43.2%) of G1, 21 (63.6%) of G2, and 11 (91.7%) of G3 (p < 0.05). It was observed in the basal inferior/inferolateral/anterolateral segments in 35 (72.9%) patients and in the apical anterior/inferior/lateral and apex segments in 21 (43.7%), with midwall (85.4%; n=41), subendocardial (56.3%; n=27), subepicardial (54.2%; n=26), transmural (31.2%; n=15), and RV (1.2%; n=1) distribution. Subendocardial lesions were observed only in patients with LVEF < 35%. There was no involvement of the mid-inferolateral/anterolateral segments with an LVEF > 35% (p < 0.05). Deteriorations of the LV and RV systolic functions were positively correlated (r s =0.69; p < 0.05) without evidence of LGE in the RV. Edema can be found in patients with chagasic cardiomyopathy in the chronic stage. In later stages of cardiac dilation with low LVEF, the LGE pattern involves subendocardium and mid locations. Deteriorations of RV and LV are positively correlated without evidence of fibrosis in the RV.

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Resumen Actualmente hay un porcentaje importante de autopsias que quedan sin un diag nóstico concluyente del fallecimiento, especialmente cuando este evento letal se produce súbitamente. El análisis genético se ha ido incorporando recientemente al campo de la medicina forense, sobre todo en aquellos pacientes que han fallecido de forma repentina, y donde no se identifica causa concluyente del fallecimiento tras una autopsia médico-legal completa. En estos casos las enfermedades eléctricas primarias son las principales responsables del fallecimiento. Hasta la fecha se han descrito más de 40 genes asociados a afecciones arritmogénicas causantes de muerte súbita cardiaca. Las principales enfermedades arritmogénicas son el síndrome de QT largo y la taquicardia ventricular; estudios genéticos post-mortem no solo permiten llevar a cabo un diagnóstico de la causa del fallecimiento, sino que también permiten una traslación clínica hacia los familiares, focalizado en la identificación precoz de individuos en riesgo de síncope, así como adopción de medidas terapéuticas personalizadas para la prevención de un episodio arrítmico letal.

Abstract Currently, there are a significant percentage of autopsies left without a conclusive diagnosis of death, especially when this lethal event occurs suddenly. Genetic analysis has been recently incorporated into the field of forensic medicine, especially in patients with sudden death and where no conclusive cause of death is identified after a complete medical- legal autopsy. Inherited arrhythmogenic diseases are the main cause of death in these cases. To date, more than 40 genes have been associated with arrhythmogenic disease, and causing sudden cardiac death has been described. The main arrhythmogenic diseases are Long QT Syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia, Brugada Syndrome, and Short QT Syndrome. These post-mortem genetic studies, not only allow a diagnosis of the cause of death, but also allow a clinical translation in relatives, focusing on the early identification of individuals at risk of syncope, as well as adopting personalised therapeutic measures for the prevention of a lethal arrhythmic episode.

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Currently, there are a significant percentage of autopsies left without a conclusive diagnosis of death, especially when this lethal event occurs suddenly. Genetic analysis has been recently incorporated into the field of forensic medicine, especially in patients with sudden death and where no conclusive cause of death is identified after a complete medical-legal autopsy. Inherited arrhythmogenic diseases are the main cause of death in these cases. To date, more than 40 genes have been associated with arrhythmogenic disease, and causing sudden cardiac death has been described. The main arrhythmogenic diseases are Long QT Syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia, Brugada Syndrome, and Short QT Syndrome. These post-mortem genetic studies, not only allow a diagnosis of the cause of death, but also allow a clinical translation in relatives, focusing on the early identification of individuals at risk of syncope, as well as adopting personalised therapeutic measures for the prevention of a lethal arrhythmic episode.

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La displasia arritmogénica del ventrículo derecho es una cardiopatía de origen genético, su importancia radica en la capacidad de generar muerte súbita en pacientes en la tercera y cuartadécada de la vida, después de grandes esfuerzos por aumentar la sensibilidad y mejorar la capacidad diagnóstica continúa siendo un importante problema de salud pública. Los desfibriladores implantables han demostrado aumentar la supervivencia de quienes presentan arritmias letales asociadas, sin embargo, debido al carácter progresivo de la enfermedad un interrogante de importancia es cómo tratar a los pacientes con terapias apropiadas y frecuentes de estos dispositivos, la ablación por radiofrecuencia es una respuesta terapéutica seria a este dilema. En la actualidad disponemos de técnicas de ablación que combinan los métodos de la imagen TC cardiaca, la resonancia cardiaca, los mapas electroanatómicos y algunas herramientas de la electrofisiología convencional que permiten realizar ablaciones sin la inducción de arritmias ventriculares de forma sostenida y durante el ritmo sinusal, de modo similar el mejor entendimiento de la patogenia introdujo el uso de técnicas híbridas endo y epicárdica, la suma de cada uno de estos avances ha aumentado la tolerancia durante el procedimiento, ha mejorado los resultados en las etapas agudas postablación y en los seguimientos a mediano plazo, hoy los márgenes de seguridad y eficacia para esta técnica se incrementan, siendo de primera línea en diferentes situaciones de relevancia en esta compleja enfermedad.

Arrhythmogenic right ventricular dysplasia (ARVD) is a genetic disease associated with sudden cardiac death, affecting subjects in the 3rd and 4th decade of life. Despite great efforts made in order to improve its early diagnosis, ARVD remains as a major public health problem in Europe and America. Currently, risk stratification of sudden cardiac death in patients with ARVD remains challenging. Over the last decade implantable defibrillators have been shown to increase survival of patients with structural heart disease and risk factors for sudden cardiac death. However, there is no consensus about how to treat patients with recurrent appropriate implantable defibrillators therapies. Recent studies have shown that radiofrequency ablation is an effective treatment for patients with recurrent episodes of ventricular tachycardia. Specifically, substrate ablation techniques have been shown to be especially useful in the case of ARVD, as these techniques allow performing ablation during sinus rhythm. Additionally, emerging tools as electroanatomic navigation, CT or MRI have provided further knowledge of the pathogenesis of ARVD, allowing the development of novel therapeutic approaches. In this review epidemiologic, pathogenic, diagnostic and therapeutic features of ARVD are discussed, with special focus on the treatment of ventricular arrhythmias associated with ARVD.

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BACKGROUND: In developing economies, there are patients in whom pacemaker implantation is delayed because they cannot afford one. Reused devices have been a solution. To address concerns about safety, a cohort of consecutive patients implanted with a reused pacemaker was compared with a control group. METHODS AND RESULTS: A cohort of 603 consecutive patients from 2000 to 2010 was studied in an ambispective noninferiority study. The study group patients (n=307) received resterilized pacemakers, and the control group patients (n=296) received a new pacemaker. A combined end point of 3 major outcomes-unexpected battery depletion, infection, and device dysfunction-was analyzed. A total of 85 pacemakers had to be explanted, 31 in the control group (10.5%) and 54 in the study group (17.6%; relative risk, 1.68; 95% confidence interval, 1.1-2.5; P=0.02). Forty-three reached the primary end point, 16 in the control group (5.5%) and 27 in the study group (7.2%; relative risk, 1.3; 95% confidence interval, 0.70-2.45; P=0.794). In terms of individual outcomes, 5 new pacemakers (1.7%) and 11 resterilized pacemakers (3.6%) had unexpected battery depletion (relative risk, 2.12; 95% confidence interval, 0.75-6; P=0.116); 3.7% new pacemakers and 3.2% reused pacemakers had a procedure-related infection (relative risk, 0.87; 95% confidence interval, 0.38-2.03; P=0.46); and 1 pacemaker in the study group malfunctioned. CONCLUSIONS: Pacemaker reuse is feasible and safe and is a viable option for patient with bradyarrhythmias. Other than the expected shorter battery life, reuse of pacemaker generators is not inferior to the use of new devices.

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A 34-week premature neonate presented with drug-refractory permanent junctional incessant tachycardia and haemodynamic compromise. The patient underwent successful radiofrequency catheter ablation using a single-catheter approach. The child remains in sinus rhythm, without pharmacological treatment, 2 years after the procedure.

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We are in the midst of a rapidly evolving era of technology-assisted medicine. The field of telemedicine provides the opportunity for highly individualized medical management in a way that has never been possible before. Evolving medical technologies using cardiac implantable devices (CIEDs) with capabilities for remote monitoring permit evaluation of multiple parameters of cardiovascular physiology and risk, including cardiac rhythm, device function, blood pressure values, the presence of myocardial ischaemia, and the degree of compensation of congestive heart failure. Cardiac risk, device status, and response to therapies can now be assessed with these electronic systems of detection and reporting. This document reflects the extensive experience from investigators and innovators around the world who are shaping the evolution of this rapidly expanding field, focusing in particular on implantable pacemakers (IPGs), implantable cardioverter-defibrillators (ICDs), devices for cardiac resynchronization therapy (CRT) (both, with and without defibrillation properties), loop recorders, and haemodynamic monitoring devices. This document covers the basic methodologies, guidelines for their use, experience with existing applications, and the legal and reimbursement aspects associated with their use. To adequately cover this important emerging topic, the International Society for Holter and Noninvasive Electrocardiology (ISHNE) and the European Heart Rhythm Association (EHRA) combined their expertise in this field. We hope that the development of this field can contribute to improve care of our cardiovascular patients.

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We are in the midst of a rapidly evolving era of technology-assisted medicine. The field of telemedicine provides the opportunity for highly individualized medical management in a way that has never been possible before. Evolving medical technologies using cardiac implantable devices with capabilities for remote monitoring permit evaluation of multiple parameters of cardiovascular physiology and risk, including cardiac rhythm, device function, blood pressure values, the presence of myocardial ischaemia, and the degree of compensation of congestive heart failure. Cardiac risk, device status, and response to therapies can now be assessed with these electronic systems of detection and reporting. This document reflects the extensive experience from investigators and innovators around the world who are shaping the evolution of this rapidly expanding field, focusing in particular on implantable pacemakers, implantable cardioverter defibrillators, devices for cardiac resynchronization therapy (both with and without defibrillation properties), loop recorders, and hemodynamic monitoring devices. This document covers the basic methodologies, guidelines for their use, experience with existing applications, and the legal and reimbursement aspects associated with their use. To adequately cover this important emerging topic, the International Society for Holter and Noninvasive Electrocardiology and the European Heart Rhythm Association combined their expertise in this field. We hope that the development of this field can contribute to improve care of our cardiovascular patients.

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Background: Highly trained athletes are at increased risk of atrial fibrillation (AF) and flutter. Atrial dilatation and dysfunction might be the underlying substrate for the increased risk. The aim of the present study was to relate atrial size and deformation in a selected group of highly trained athletes and patients with paroxysmal atrial fibrillation (PAF). Methods: 20 professional male hand-ball players, 18 patients with PAF and 20 healthy age-matched, non-sportive males were compared. All subjects underwent a transthoracic echocardiogram with evaluation of left atrial (LA) dimensions. Left atrial strain (LASa) and strain rate (LASRa) derived from speckle tracking were used to evaluate LA deformation post atrial contraction. Results: LA volumes were significantly larger in athletes and PAF patients compared to controls (36 + 1.7 ml/m2; 36 ± 2.3 ml/m2 and 24 + 1 ml/m2, respectively, p < 0.01;). LASa and LASRa during active atrial contraction were decreased in PAF patients compared to athletes and controls (-10.6 ± 0.2 %; -12.2 ± 0.4 % and -14.5 ± 0.5 %, p < 0.01 for LASa and -1.2 ± 0.08 sec-1; -1.5 ± 0.12 sec-1; -1.7 ± 0.13 sec-1, p= 0.04 for LASRa respectively). Athletes with LA volume > 40 ml/m2 (n=7) showed reduced LASa compared to athletes with LA volume < 40 mL/m2 (-10.3 ± 0.4% versus -13.0 ± 0.5%, p < 0.01). PAF patients had LASa values similar to those of subjects with normal LA volume. Conclusion: Athletes with increased LA volume exhibit lower strain parameters compared to subjects with PAF. It is postulated that measurement of LA strain may be used to predict development of AF in highly trained athletes.

Introducción: Atletas de alto rendimiento tienen un riesgo aumentado de desarrollar fibrilacion auricular (FA) y flutter. La dilatación y disfunción auricular podrían ser el sustrato subyacente para este incremento en el riesgo. El objetivo fue analizar y relacionar el tamaño y deformación auricular en un grupo seleccionado de atletas y en pacientes con FA paroxística. Métodos: Se incluyeron 20 jugadores de balón-mano profesionales y 20 controles sedentarios, pareados por edad y sexo, junto a 18 pacientes con FA paroxística. En todos los sujetos se realizó un estudio ecocardiográfico bidimensional con evaluación de las dimensiones y de la deformación (post contracción auricular) por strain (Sa) y strain rate (SRa) de la aurícula izquierda (AI). Resultados: El volumen AI fue significativamente mayor en atletas y pacientes con FA respecto de los controles (36 + 1,7 ml/m2; 36 ± 2,3 ml/m2 y 24 + 1 ml/m2, p < 0,01; respectivamente). El SaAI y SRaAI durante la contracción auricular estaban disminuidos en los pacientes con FA paroxística respecto de atletas y controles (-10,6 ± 0,2 %; -12,2 ± 0,4 % y -14,5 ± 0,5 %, p < 0,01 para SaAI y -1,2 ± 0,08 sec-1; -1,5 ± 0,12 sec-1; -1,7 ± 0,13 sec-1, p= 0,04 para SRaAI, respectivamente). Los atletas con un volumen AI > 40 ml/m2 (n=7) mostraron valores reducidos de SaAI comparados con atletas con un volumen AI < 40 mL/m2 (-10,3 ± 0,4% versus -13,0 ± 0,5%, p < 0,01) y éstos fueron similares a los pacientes con FA (-10,3 ± 0,4% versus -10,6 ± 0,2%, p= 0,6). Conclusiones: Una proporción de atletas con dilatación AI presentan evidencia de disfunción contráctil de la AI, caracterizado por valores de strain disminuidos que son similares a los de pacientes con FA paroxística. Esto podría corresponder a un sustrato para el desarrollo posterior de arritmias auriculares en estos atletas.

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BACKGROUND: Differential diagnosis of wide QRS complex tachycardias using the 12-lead ECG may be difficult in many clinical settings. OBJECTIVE: The purpose of this study was to determine the value of ECG lead II, specifically, the duration at its beginning, defined as R-wave peak time (RWPT), in differentiating ventricular tachycardia (VT) from supraventricular tachycardia (SVT) in patients with wide QRS complex tachycardia. METHODS: Two hundred eighteen ECGs showing wide QRS complex tachycardias were evaluated. Two cardiologists blinded to the diagnosis measured RWPT duration at lead II (from the isoelectric line to the point of first change in polarity), and results between VT and SVT were compared, with the findings of electrophysiologic study used as the gold standard. RESULTS: One hundred sixty-three VTs had a significantly longer RWPT at DII (76.7 +/- 21.7 ms vs 26.8 +/- 9.5 ms in 55 SVT, P = .00001). Receiver operating characteristic curve identified RWPT > or =50 ms at lead II as having greater specificity and sensitivity in discriminating VT from SVT. Area under the curve was 0.97 (95% confidence interval 0.95-0.99), positive likelihood ratio was 34.8, and kappa coefficient (kappa) was 0.86. Bivariate analysis identified higher age in VT patients (60.7 vs 50.1 years, P < or =.01) and wider QRS complex duration at lead II in VT patients (169.4 vs 128.3 ms, P <.0001). QRS width at DII was not superior to RWPT in diagnosing VT. CONCLUSION: RWPT > or =50 ms at DII is a simple and highly sensitive criterion that discriminates VT from SVT in patients with wide QRS complex tachycardia.

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Introducción y objetivos: la miocardiopatía hipertrófica es una enfermedad de origen genético con prevalencia de 1 porciento al 2 porciento. La mitad de los pacientes fallecen por muerte súbita cardiaca, la mayoría por arritmias ventriculares. Todavía no está claro a qué pacientes se les debe implantar un desfibrilador automático. El objetivo de este trabajo es describir una serie de pacientes con implante, los criterios empleados y los resultados obtenidos, así como analizar los predictores de terapia apropiada por el desfibrilador.Métodos: se incluyeron 20 pacientes que recibieron un desfibrilador de tercera generación. En todos se realizó estudio electrofisiológico y seguimiento prospectivo con registro de eventos. En 18 (90 porciento) se hizo estudio genético.

Introduction and objectives: hypertrophic myocardiopathy is a genetic entity with 1% to 2% prevalence. Half patients die of sudden cardiac death, most due to ventricular arrhythmias. There is still no clarity with regard to the patients to whom an automatic defibrillator has to be implanted. The objective of this work is to describe a series of patients with implant, the criteria used and the results obtained, as well as to analyze the predictors of appropriate therapy with the defibrillator. Methods: 20 patients that received a third generation defibrillator were included. Electrophysiological study and prospective follow-up with register of events was performed in all. Genetic study was done in 18 (90%). Results: 55% were men with mean age 40 (11-78) years. Six (30%) received implant for secondary prevention and 14 (70%) for primary prevention; the last ones because of several risk factors. A sustained arrhythmia was induced in 15 (75%) and in 3 (15%) monomorphic sustained ventricular tachycardia. At 22 months of follow-up, 4 (20%) underwent appropriate therapy and 2 (10%) died. Clinical monomorphic ventricular tachycardia (p=0.03) and the induced one (p<0.01) were significant therapy predictors. In 10 (56%) a mutation was identified; in 8 (44%) in the b-myosin gene. Conclusions: monomorphic sustained clinical ventricular tachycardia and the induced one were predictors of the appropriate defibrillator therapy in this series. The stratification based on the risk factors addition is actually a good option for primary prevention. Mutations in the heavy b-myosin chain are also the most frequent in our population.

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INTRODUCTION: PRKAG2 plays a role in regulating metabolic pathways, and mutations in this gene are associated with familial ventricular preexcitation, hypertrophic cardiomyopathy, and atrioventricular conduction disturbances. Clinico-pathologic and experimental data suggest the hypothesis of a glycogen storage disease. OBJECTIVE: To report a unique pattern of clinical features observed in individuals with a mutant PRKAG2 from two unrelated families. METHODS AND RESULTS: We studied two large families and found a total of 20 affected individuals showing a combination of sinus bradycardia, short PR interval, RBBB, intra and infrahisian conduction disturbances often requiring a pacemaker, and atrial tachyarrhythmias. Three individuals died suddenly at a young age. No patient had the Wolff-Parkinson-White (WPW) syndrome, and only two patients (10%) had myocardial hypertrophy. We performed screening of the exons and exon-intron boundaries of PRKAG2. Genetic analysis revealed a missense mutation (Arg302Gln) in the affected individuals from both families. This mutation had been described before and has been associated with the familial form of the WPW syndrome and with a high prevalence of left ventricular hypertrophy. CONCLUSION: PRKAG2 mutations are responsible for a diverse phenotype and not only the familial form of the WPW syndrome. Familial occurrence of right bundle branch block, sinus bradycardia, and short PR interval should raise suspicion of a mutant PRKAG2 gene.

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Sudden death is defined as the death occurring less than one hour before the onset of the patient's symptoms. It is a severe condition considered a public health issue in several countries and in ours, it accounts for 33 000 to 53 000 annual deaths mainly related to ischemic heart disease. The main cause of sudden death are severe ventricular arrhythmias, but determining what patients are at risk for such an episode is complex, that is why risk stratification is usually a low cost-effective intervention. In the present study, we describe different sudden death risk-stratification strategies. Different sudden death treatment strategies regarding general population have different success rates in different countries, nevertheless, among select high risk populations; the best therapy currently available is the automatic implantable cardioverter-defibrillator. We also discuss other treatment options. In Mexico it is deemed necessary to do an important effort for the early detection, prevention and treatment of sudden death in order to limit the consequences of this problem.

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