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Los mecanismos de mantenimiento y finalizacion de la fibrilacion ventricular (FV) son poco conocidos. El objetivo del estudio es comparar las caracteristicas espectrales de la senal electrica de la FV sostenida y no sostenida en pacientes portadores de desfibrilador implantable. Se incluyo a 51 pacientes con al menos un episodio de FV sostenida (de mas de 5 s y que precisara choque) y no sostenida (de mas de 3 s y terminacion espontanea) registrados por el dispositivo en configuracion monopolar. Se realizo un analisis espectral de los primeros 3 s de cada episodio. La frecuencia dominante fue mayor en las FV sostenidas (4,6 ± 0,7 frente a 4,3 ± 0,6 Hz en las no sostenidas; p = 0,01), y los demas parametros fueron similares. Durante los primeros 3 s, si bien las caracteristicas espectrales son parecidas, hay diferencias utilizables en algoritmos de deteccion precoz de FV no sostenida.

Introduction and objectives Mathematical models of cardiac electrical activity may help to elucidate the electrophysiological mechanisms involved in the genesis of arrhythmias. The most realistic simulations are based on reaction-diffusion models and involve a considerable computational burden. The aim of this study was to develop a computer model of cardiac electrical activity able to simulate complex electrophysiological phenomena but free of the large computational demands required by other commonly used models. Material and method A cellular automata system was used to model the cardiac tissue. Each individual unit had several discrete states that changed according to simple rules as a function of the previous state and the state of the neighboring cells. Activation was considered as a probabilistic process and was adjusted using restitution curves. In contrast, repolarization was modeled as a deterministic phenomenon. Cell currents in the model were calculated with a prototypical action potential that allowed virtual monopolar and bipolar electrograms to be simulated at any point in space. Results Reproducible flat activation fronts, propagation from a focal stimulus, and reentry processes that were stable and unstable in two dimensions (with their corresponding electrograms) were obtained. The model was particularly suitable for the simulation of the effects observed in curvilinear activation fronts. Fibrillatory conduction and stable rotors in two- and three-dimensional substrates were also obtained. Conclusions The probabilistic cellular automata model was simple to implement and was not associated with a high computational burden. It provided a realistic simulation of complex phenomena of interest in electrophysiology.

The Telecommunications Engineering degree contains the study and understanding of a wide range of knowledge areas, like signal theory and communications, computer networks, and radio propagation. This diversity makes it hard for students to integrate different concepts, which is essential to tackle real and practical problems that involve different subjects. As a response to this need of integration, a group of professors at Rey Juan Carlos University carried out an educational project based on Problem Based Learning (PBL), called the Wireles4x4 Project. In this project, groups of students build a complete system to autonomously drive a radio controlled car, involving different technologies such as wireless communications, positioning systems, power management, and system integration. The results show that the participating students improve not only their specific knowledge on the involved issues, but also their capability of integrating different subjects of the degree and the skills for autonomous learning.

The mechanisms responsible for the maintenance and termination of ventricular fibrillation (VF) are poorly understood. The aim of this study was to compare the spectral characteristics of the electrical signal during sustained and non-sustained VF in patients with an implantable cardioverter-defibrillator. The study included 51 patients who had had at least one episode of sustained VF (ie, duration >5 s and requiring shock administration) and non-sustained VF (ie, duration >3 s and spontaneously terminated) that were recorded by the device set in a unipolar configuration. Spectral analysis of the first 3 s of each episode was performed. The dominant frequency was higher in sustained VF (4.6 [0.7] Hz) than in non-sustained VF (4.3 [0.6] Hz; P=.01), while the other parameters were similar. Although the spectral characteristics of sustained and non-sustained VF were similar, differences were observed during the first 3 s that could be used in algorithms for the early detection of non-sustained VF.

Previous studies indicate that the carboxyl terminal of connexin43 (Cx43CT) is involved in fast transjunctional voltage gating. Separate studies support the notion of an intramolecular association between Cx43CT and a region of the cytoplasmic loop (amino acids 119–144; referred to as “L2”). Structural analysis of L2 shows two α-helical domains, each with a histidine residue in its sequence (H126 and H142). Here, we determined the effect of H142 replacement by lysine, alanine, and glutamate on the voltage gating of Cx43 channels. Mutation H142E led to a significant reduction in the frequency of occurrence of the residual state and a prolongation of dwell open time. Macroscopically, there was a large reduction in the fast component of voltage gating. These results resembled those observed for a mutant lacking the carboxyl terminal (CT) domain. NMR experiments showed that mutation H142E significantly decreased the Cx43CT-L2 interaction and disrupted the secondary structure of L2. Overall, our data support the hypothesis that fast voltage gating involves an intramolecular particle-receptor interaction between CT and L2. Some of the structural constrains of fast voltage gating may be shared with those involved in the chemical gating of Cx43.

Introduction and objectives. The magnitude of the change in heart rate during the first few minutes of the head-up tilt test has been used to predict the test’s result. The aim of this study was to investigate whether the heart rate increase during the head-up tilt test potentiated with nitroglycerin is related to the development of syncope. Patients and method. The study included 158 consecutive patients with syncope, with stable sinus rhythm, and without structural cardiac disease who were undergoing a head-up tilt test with nitroglycerin. The heart rate increment induced by the tilt maneuver and by nitroglycerin administration was calculated, and its relationship to clinical variables and to the test’s results was analyzed. Results. The head-up tilt test gave positive results in 117 patients (74%). The heart rate was 68.7 (11.3) bpm in the decubitus position and 85.1 (15.4) bpm during the first 6 min of tilting. There was strong inverse correlation between the heart rate increase induced by tilting and age (r=‐0.63; P

Publicado en la Revista Española de Cardiología 2005;58(1):41-47. Introduction and objectives. Mathematical models of cardiac electrical activity may help to elucidate the electrophysiological mechanisms involved in the genesis of arrhythmias. The most realistic simulations are based on reaction-diffusion models and involve a considerable computational burden. The aim of this study was to develop a computer model of cardiac electrical activity able to simulate complex electrophysiological phenomena but free of the large computational demands required by other commonly used models. Material and method. A cellular automata system was used to model the cardiac tissue. Each individual unit had several discrete states that changed according to simple rules as a function of the previous state and the state of the neighboring cells. Activation was considered as a probabilistic process and was adjusted using restitution curves. In contrast, repolarization was modeled as a deterministic phenomenon. Cell currents in the model were calculated with a prototypical action potential that allowed virtual monopolar and bipolar electrograms to be simulated at any point in space. Results. Reproducible flat activation fronts, propagation from a focal stimulus, and reentry processes that were stable and unstable in two dimensions (with their corresponding electrograms) were obtained. The model was particularly suitable for the simulation of the effects observed in curvilinear activation fronts. Fibrillatory conduction and stable rotors in two- and three-dimensional substrates were also obtained. Conclusions. The probabilistic cellular automata model was simple to implement and was not associated with a high computational burden. It provided a realistic simulation of complex phenomena of interest in electrophysiology. Introducción y objetivos. La utilización de modelos matemáticos de activación y propagación del impulso ha mejorado la comprensión de diversos mecanismos electrofisiológicos involucrados en la génesis de las arritmias. Las simulaciones más realistas se basan en los modelos de reacción-difusión e implican una carga computacional muy elevada. El objetivo del estudio es desarrollar un modelo de activación eléctrica cardíaca por ordenador que permita simular fenómenos electrofisiológicos complejos y que no requiera la carga computacional necesaria en otros modelos habitualmente empleados. Material y método. Se ha modelado el tejido cardíaco como un autómata celular, cada uno de cuyos elementos adopta estados discretos en función de su estado previo y del de las células vecinas siguiendo unas reglas sencillas. La activación se contempla como un proceso probabilístico y se ajusta mediante el fenómeno de restitución, mientras la repolarización se modela como un proceso determinista. Finalmente, las corrientes celulares se calculan utilizando un potencial de acción prototipo, lo que permite simular los electrogramas virtuales monopolares y bipolares en cualquier punto del espacio. Resultados. Se ha conseguido reproducir frentes planos de activación, propagación de un estímulo focal y reentradas estables e inestables en 2 dimensiones, con sus electrogramas correspondientes. El modelo es particularmente adecuado para simular los fenómenos asociados a la curvatura de los frentes, y permite reproducir la conducción fibrilatoria y los rotores estables en 2 y 3 dimensiones. Conclusiones. Aunque el modelo de autómata celular probabilístico desarrollado es sencillo y no requiere cargas computacionales elevadas, es capaz de simular de forma realista fenómenos complejos de gran interés en electrofisiología. Teoría de la Señal y Comunicaciones

Introduccion y objetivos. El incremento acentuado de la frecuencia cardiaca en los primeros minutos de la prueba de basculacion ha sido utilizado como predictor del resultado final de esta, en protocolos sin potenciacion farmacologica o con isoproterenol. El objetivo del estudio es evaluar si este incremento se relaciona con la aparicion de sincope durante la prueba de basculacion potenciada con nitroglicerina. Pacientes y metodo. Analisis retrospectivo de 158 pacientes consecutivos sometidos a prueba de basculacion potenciada con nitroglicerina por sincope, sin cardiopatia y en ritmo sinusal. Se calculo el incremento de la frecuencia cardiaca secundario a la basculacion y el debido a la nitroglicerina, relacionandolos con las variables clinicas y el resultado de la prueba. Resultados. La prueba de basculacion fue positiva en 117 pacientes (74%). La frecuencia cardiaca paso de 68,7 ± 11,3 lat/min en decubito a 85,1 ± 15,4 lat/min en los primeros 6 min posbasculacion. El incremento de frecuencia presento una fuerte correlacion negativa con la edad (r = ­-0,63; p < 0,001), pero no se relaciono significativamente con el resultado (16,8 ± 9,3 lat/min en el grupo con prueba positiva frente a 14,9 ± 11,3 en el negativo; p = 0,3). El aumento de la frecuencia cardiaca inducido por la nitroglicerina (27,3 ± 12,6 y 26,7 ± 13,4 lat/min, respectivamente; p = 0,8) tampoco predijo el resultado del test durante la fase farmacologica. Conclusiones. Los incrementos de frecuencia cardiaca en los primeros minutos despues de la basculacion y la administracion del farmaco se relacionan fundamentalmente con la edad y no tienen utilidad para predecir el resultado de la prueba de basculacion potenciada con nitroglicerina.