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Right ventricular outflow tract (RVOT) ventricular tachycardias (VT) occur in the absence of structural heart disease and are called idiopathic ventricular arrhythmias. These arrhythmias are thought to be produced by adenosine-sensitive, cyclic AMP mediated, triggered activity and are commonly observed in adolescents and young adults. In the ECG, they appear with a wide QRS complex, a left bundle branch block morphology and, usually, an inferior QRS axis. In the last few years, there has been an increasing number of reports suggesting the possibility of a curative treatment of RVOT VT by means of catheter ablation. This paper reviews the rate of cure of such arrhythmias by discussing the effects of catheter ablation on symptoms, arrhythmia detection, possibility of induction, and short- and long-term follow-up studies.

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BACKGROUND: The cardiac depolarization-repolarization process (D-REPP) may differ among various modes of cardiac pacing depending on the paced chamber(s) and lead position. We intended to assess the effect of different modes of cardiac pacing (left, right and biventricular) on the D-REPP as expressed in QRS, QT, peak-to-end of the T wave (PETW) and PETW/QT intervals and their dispersion. These intervals were compared during pacing and sinus rhythm. METHODS: We studied 31 patients without structural heart disease and with normal ventricular function who underwent right, left and biventricular pacing. Simultaneous 12-leads were recorded and electronic calipers were used for measurement of the QRS, QT, corrected QT (cQT), PETW, and PETW/QT ratio. RESULTS: cQT duration, PETW, standard deviation of the PETW, PETW/QT, and QRS duration were shorter during sinus rhythm. Isolated stimulation of the right or the left ventricle produced a similar increase in all the intervals and did not display significant differences in terms of cQT duration, PETW, PETW/QT, or QRS duration. Biventricular pacing produced a significant increase in cQT, QRS, PETW and PETW/QT, but these values were shorter than those obtained during isolated right or left ventricular stimulation. CONCLUSION: In subjects without structural heart disease, cardiac pacing produces a significant increase of the D-REPP. No differences were found when comparing right or left univentricular pacing. Biventricular stimulation induces less perturbation of the D-REPP.

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UNLABELLED: Radiofrequency (RF) ablation is a curative treatment for many different types of cardiac arrhythmias but its application has been more limited in the paediatric population. We here describe RF paediatric ablation experience at a 400-bed University Hospital in a western Venezuelan province and compare it with the results reported in other countries. METHODS: One hundred and fifty five patients under 18 years of age who where submitted to RF ablation between 1994 and 2007 were included. The patients were 12.8+/-3.4 year-old (rank: 3-17 years); 59% were female. Nine patients were submitted to more than one procedure. AV nodal re-entrant tachycardia and atrio-ventricular re-entrant tachycardias mediated by accessory pathways made up 83% of the ablations. The overall success rate was 91.5%. In the AV nodal re-entrant tachycardia and atrial flutter, success rate almost reached 100%. Ablation was successful in 93% of the patients with the Wolff-Parkinson-White syndrome. The overall complication rate was 5% with 0.6% of major complications and 0% death rate. The results were comparable to those recently reported by the cooperative paediatric ablation registry in the United States of America and by a large hospital in Taiwan. CONCLUSION: RF ablation is a curative therapy with a high success rate and very low complication rates in the paediatric population at the Cardiovascular Research Institute of the University Hospital of The Andes in Venezuela.

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An 18-year-old girl had been suffering from palpitations for 3 years. After a normal and asymptomatic pregnancy, she became highly symptomatic with more than 6 tachycardia paroxysms a week, many of them requiring emergency hospitalizations because of hemodynamic collapse. The electrophysiological evaluation revealed dual A-V nodal pathways and the presence of 4 accessory pathways (3 in the left A-V ring: lateral, posterior, and posteroseptal, 1 right posteroseptal) with 5 types of atrioventricular tachycardia and atrial flutter. The 4 accessory pathways and the slow A-V nodal pathway were successfully ablated, and the patient has been asymptomatic for 12 months without taking antiarrhythmic drugs.

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UNLABELLED: Assuming that blood pressure control could induce a shortening of the inter-atrial conduction time and prevent atrial fibrillation occurrence, we studied the inter-atrial conduction time in hypertensive patients with left ventricular hypertrophy. METHODS: Sixty-eight (26 male) 58.34+/-8.08-year-old patient participated in the study. All were in sinus rhythm and had abnormal blood pressure (163+/-18/95+/-9 mm Hg). Their cardiac mass index was increased (151+/-43 g/m(2) SC) and their left atrial dimension was normal (3.67+/-0.54 cm). The inter-atrial conduction time was measured in the echocardiogram from the beginning of the electrocardiographic P wave to the beginning of the A wave in the mitral Doppler signal and was corrected for heart rate. Heart rhythm disturbances were monitored clinically and by means of a Holter. Most patients were treated with angiotensin antagonists. RESULTS: It was found that arterial blood pressure decreased significantly after treatment and that the P-A interval was significantly reduced (71.4+/-14.5 vs. 63.9+/-11.5 ms). During the follow-up, no patient complained of arrhythmia symptoms or exhibited atrial fibrillation in the Holter recording. CONCLUSION: In this selected group of patients with hypertensive heart disease (left ventricular hypertrophy), an effective blood pressure control was accompanied by a significant decrease in the inter-atrial conduction time. It is possible that these effects prevent atrial fibrillation.

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OBJECTIVE: To determine whether an algorythm designed at our Electrophysiology Unit could facilitate the electrocardiographic diagnosis of tachyarrhythmias. METHODS: Twenty two first-year cardiology residents, general practitioners and last-year medical students attended an electrophysiology course. One hundred ECG of tachyarrhythmic patients were distributed to the participants who were then randomly divided into 2 groups. Group A analyzed the ECG with the help of the algorythm, whereas Group B analyzed them without it. Results were compared to those obtained by an electrophysiologist. RESULTS: Group A diagnosis coincided with that of the electrophysiologist in 41% of the cases. In Group B the concordance reached 64% (p = 0.0000013). There was no between-group difference regarding the type and number of uninterpreted ECG. CONCLUSIONS: The decision tree increases diagnostic accuracy in less expert hands. This could in turn entail an improvement in the therapeutic measures applied to the study of arrhythmias.

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BACKGROUND: Patients with myocardial infarction and left ventricular dysfunction are at risk for sudden death. This research was conducted to determine the applicability and safety of a bedside programmed stimulation protocol to determine the risk for sudden death in these patients. METHODS: Four hundred and twelve patients with acute myocardial infarction were studied. Left ventricular ejection fraction was evaluated by means of an echocardiogram. Ventricular arrhythmia, late potentials and heart rate variability were determined by means of Holter recordings. Fifty patients (60 +/- 14-year-old; 85% male) presented a left ventricular ejection fraction lower than 0.40 (0.36 +/- 0.10) associated with late potentials, low heart rate variability or ventricular arrhythmia greater than Lown I. After a central venous access was placed under fluoroscopy guidance and ECG monitoring, a quadripolar catheter was advanced to the right ventricular apex to perform programmed ventricular stimulation with up to three extrastimuli. The patients were followed-up to determine in-hospital morbidity and/or mortality. RESULTS: No patient suffered complications. Ventricular tachycardia or ventricular fibrillation was induced in six patients. All of them received amiodarone and in five an automatic cardioverter-defibrillator was implanted. After a 22 +/- 6 month follow-up, five patients had received appropriate discharges from the implanted device and none had suffered from arrhythmic sudden death. CONCLUSION: Bedside programmed stimulation is a safe and useful means for sudden death risk stratification in post myocardial infarction patients. It moreover presents the advantage of being cheaper than conventionally used procedures.

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Introducción: La determinación de la variabilidad espontánea del intervalo de ciclo de las taquicardias ventriculares es fundamental para interpretar los efectos de tratamientos y para programar dispositivos anti-taquicardia. Objetivo: Estudiar la variabilidad espontánea del intervalo de ciclo de las taquicardias ventriculares producidas por re-entrada. Métodos: Incluimos 22 pacietes (12 varones) de 52 ± 18 años de edad, en quienes se introdujeron 121 taquicardias ventriculares monomórficas sostenidas. Las taquicardias inducidas en un mismo paciente tenían la misma morfología y eran producidas por re-entrada. Resultados: En promedio, las taquicardias ventriculares tenían un intervalo de ciclo de 318 ± 39 milisegundos (mseg). La desviación típica del promedio de los intervalos de ciclo de las taquicardias ventriculares de igual morfología inducidas en cada paciente (variación inter-taquicardia) 10,91 ± 9,63 mseg. La diferencia promedio entre el R-R mínimo (variación inter-taquicardia) fue de 26,15 mseg. La variación intra-taquicardia (desviación típica de los 10 ciclos que fueron promediados) fue de 5,78 ± 2,40 mseg (2,58 - 15,05). El sexo, la etiología y la edad no determinaron diferencias en la frecuencia cardíaca durante la taquicardia. Conclusión: En este grupo de pacientes, las taquicardias ventriculares de re-entrada originadas en un mismo circuito en un mismo paciente muestran poca variación del intervalo de ciclo. Esta estabilidad relativa debe tenerse presente al considerar efectos terapéuticos, programar dispositivos anti-taquicardia y estudiar los factores relacionados con variabilidad misma. Palabras Clave: Taquicardia ventricular, intervalo de ciclo, variabilidad.

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BACKGROUND: Little is known about the correlation between the inter-atrial conduction time (IACT) measured at the electrophysiology laboratory and the interval measured from the beginning of the electrocardiographic P wave to the initiation of the A wave in the mitral Doppler signal (P-A interval). HYPOTHESIS: IACT can be assessed by means of echo-Doppler. METHODS: We studied 21 patients who were referred to our arrhythmia clinic for evaluation of supraventricular tachycardia. During the electrophysiological study, the IACT was measured from the first rapid deflection of the A wave recorded with the high right atrial catheter to the A wave recorded with the coronary sinus catheter. An independent observer measured the P-A interval. Both the electrophysiological and echo-Doppler measurements were corrected for heart rate. RESULTS: P-A interval was slightly longer than IACT (83.36 +/- 23.91 vs 80.77 +/- 24.11 msec; p = 0.042), but a very good correlation was found between both measurements (r2 = 0.94). CONCLUSIONS: IACT can be non-invasively assessed by measuring the P-A interval.

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BACKGROUND: Little is known about the correlation between the inter-atrial conduction time (IACT) measured at the electrophysiology laboratory and the interval measured from the beginning of the electrocardiographic P wave to the initiation of the A wave in the mitral Doppler signal (P-A interval). HYPOTHESIS: IACT can be assessed by means of echo-Doppler. METHODS: We studied 21 patients who were referred to our arrhythmia clinic for evaluation of supraventricular tachycardia. During the electrophysiological study, the IACT was measured from the first rapid deflection of the A wave recorded with the high right atrial catheter to the A wave recorded with the coronary sinus catheter. An independent observer measured the P-A interval. Both the electrophysiological and echo-Doppler measurements were corrected for heart rate. RESULTS: P-A interval was slightly longer than IACT (83.36 +/- 23.91 vs 80.77 +/- 24.11 msec; p = 0.042), but a very good correlation was found between both measurements (r2 = 0.94). CONCLUSIONS: IACT can be non-invasively assessed by measuring the P-A interval.

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Se han descrito fascículos accesorios postero-septales ubicados dentro de divertículos del seno coronario. Aquí describimos el caso de un paciente que sufría episodios recurrentes de taquicardia supraventricular paroxística causada por un fascículo accesorio oculto localizado en la región anterolateral del anillo mitral. En el paciente también había un divertículo del seno coronario asociado con una vena coronaria aneurismática. En el estudio electrofisiológico, se indujo una taquicardia supraventricular ortodrómica que utilizaba el fascículo accesorio descrito, por lo que se realizó una ablación exitosa del fascículo y la paciente se hizo asintomática. Nuestro caso da prueba de la coexistencia de fascículos accesorios ocultos (ubicados en sitios distantes) y de un divertículo del seno coronario y una vena coronaria aneurismática.

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El tratamiento de las arritmias cardíacas sufrió cambios importantes en la última década. Una de las innovaciones de mayor intéres es la fulguración con radiofrecuencia de focos arritmogénicos. Este trabajo muestra los resultados obtenidos en el Centro de Investigaciones Cardiovasculares de la Universidad de Los Andes (Venezuela) con el uso de fulguración por radiofrecuencia para el tratamiento de arritmias cardíacas. Efectuamos 130 procedimiento en 121 pacientes (81 mujeres) de 34,32 ñ 16,69 años de edad. La fulguración tuvo éxito en el 92 por ciento de los pacientes. Separados en subgrupos, la eficacia fue de 100 por ciento en taquicardia supraventricular (TSV) por reentrada nodal, 90 por ciento en las TSV por fascículo de Kent (incluye woll-parkinson), 70 por ciento en flutter auricular, y 100 por ciento en los casos de fibrilación auricular y taquicardia ventricular. En el 89 por ciento de los pacientes, el estudio electrofisiológico y la fulguración se efectuaron en una sola sesión. No hubo muertes. Se presentaron complicaciones en 6 por ciento de los casos. El promedio de duración del procedimiento fue de 2,7 horas (28 minutos de fluroscopia). La fulguración con radiofrecuencia es un procedimiento seguro y eficaz para curar arritmias cuando se efectúa con una técnica apropiada. Hemos tenido un porcentaje de éxitos y de complicaciones similar al de reputados centros del exterior. Considerados que la fulguración con radiofrecuencia es el tratamiento de elección para las TSV por reentrada nodal y por fascículo accesorios. Es también una modalidad alterna atractiva para el tratamiento de flutter auricular y de formas seleccionadas de taquicardia ventricular y fibrilación auricular

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It has been stated that curare has no direct effect upon the heart because the cardiac muscle is deprived of nicotine receptors. While performing an experimental work, we noticed that when high doses of curare were administered to frogs, a change in cardiac activity occurred. In order to elucidate whether the cardiac effects of curare wee the results of a direct action or a reflex response, we studie the effects of increasing doses of d-tubocurarine on the rate and contractility of 8 isolated and perfused frogs'hearts. After testing the d-tubocurarine effects on the heart rate and contractility, we added either acetylcholine, atropine, atenonol or verapamil in orden to find out whether any change ocurred in the cardiac effects produced byd-tubocurarine. Thirty seven measurements were carriet out and it wasfound that 1) high doses (between 1 and 15 micrograms) of d-tubocurarine produced a highly significant decrease in heart rate an contractility; 2) d-tubocurarine did not avoid the acetycholine effect; 3) atropine, atenonol and verapamil did not interfere with d-tubocurarine effects. We conclude that high doses of d-tubocurarine produce "dosis-dependent" heart rate and contratility reductions. These effects are not mediated by muscarinic receptors beta-1 receptors or the show calcium channels

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Para evaluar la utilidad del tratamiento antiarrítmico guiado por estudio electrofisiológico (EEF), revisamos el material de nuestra sección de electrofisiología y Arritmias del Centro Cardiovascular de la Universidadde los Andes. Desde septiembre de 1988 hasta enero de 1991 se encontraron 24 pacientes con arritmia ventricular sostenida. El 66 por ciento eran isquémicos, 21 por ciento hipertensos y 13 por ciento sufrían de miocardiopatía dilatada. El motivo del EEF fue la presencia de taquicardia ventricular sostenida (TV) en 9 (37 por ciento), síncope en 6 (25 por ciento), extrasistolia frecuente y compleja en 6 (25 por ciento) y muerte súbita en 3 (13 por ciento). En todos los pacientes con estimulación programada se indujo una TV sostenida y luego fueron sometidos a tratamiento farmacológico guiado por los hallazgos electrofisiológicos. En 13 pacientes la arritmia se transformó en no-inducible (respuesta total (RT)), en 9 la arritmia se hizo más difícil de inducir, más lenta o mejor tolerada (respuesta parcial (RP)) y en 2 pacientes no hubo ninguna respuesta favorable a pesar de que se ensayaron todos los antiarritmicos disponibles (falla (F)). En un seguimiento de 15 ñ 9 meses encontramos 2 muertes súbitas en el grupo F y ninguna en los RT y RP. Hubo tres recurrencias (12,5 por ciento), 2 en los de RP y 1 en los RT. La mortalidad por arritmia o por muerte súbita fue de 8,3 por ciento. Estas cifras de mortalidad se comparan con ventaja con las que se obtienen en otros centros (12 por ciento) donde emplean métodos de tratamiento similares, y superan con creces a las obtenidas cuando el tratamiento se guía por medios no invasivos (35 por ciento). Concluimos en que, en los pacientes que sufren de arritmia ventricular sostenida, el diagnóstico y el tratamiento pueden y deben ser guiados por estudios electrofisiológicos

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Estudiamos los efectos del líquido pericárdico y su contenido de NaCl sobre la amplitud del complejo QRS del electrocardiograma (ECG), en ratas Wistar sometidas a toracotomía y pericardiectomía. Se registró un ECG de control y otro después de secar el epicardio con aire a temperatura ambiente. Bajo registro de ECG, se colocaron sucesivamente, en el epicardio seco 0,3 cc de las siguientes soluciones: dextrosa al 5% y NaCl al 0,45%, 0,9%, 1,35% y 1,8%. Las variaciones de amplitud del QRS se expresaron en porcentajes y se analizaron estadísticamente con prueba de Newman-Keuls, análisis de varianza, de regresión y de correlación. Encontramos que: 1) La desecación del pericardio produjo una disminución de 20% en la amplitud del QRS (p < 0,01). 2) Al humedecer ese órgano con las soluciones, la amplitud del QRS aumentó de inmediato entre 24 y 59% (p < 0,01). 3) El aumento de amplitud del QRS con solución de dextrosa fue menor que con las soluciones de NaCl (p < 0,05). 4) La solución de NaCl al 0,9% fue la que produjo el mayor aumento de amplitud del QRS (p < 0,05). 5) La concentración de NaCl y el aumento de amplitud del QRS tienen una correlación polinomial, parabólica y débil (r = 0,45 con p < 0,1). Los resultados sugieren que la presencia de líquido pericárdico y su contenido de NaCl influyen sobre la amplitud del QRS y que la variación no es simplemente función de la conductividad del líquido pericárdico

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A resposta da pressäo arterial durante a manobra de Valsalva é anormal em pacientes sintomáticos com insuficiência cardíaca e fraçäo de ejeçäo diminuída. Pacientes chagásicos assintomáticos podem apresentar movimentos segmentares anormais da parede ventricular, com fraçäo de ejeçäo normal. Para avaliar a resposta pressórica durante a manobra de Valsalva em relaçäo ao movimento segmentar, foram comparados pacientes chagásicos e indivíduos normais. Trinta e cinco por cento dos pacientes chagásicos com SAC apresentaram resultados anormais, que foram estatisticamente significantes (p < 0,05). A manobra de Valsava pode ser útil na detecçäo de disfunçäo ventricular esquerda incipiente

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