[Biphasic low-energy internal cardioversion in atrial fibrillation induced during electrophysiologic study]. / Cardioversión eléctrica interna con baja energía y curva bifásica en fibrilación auricular inducida durante el estudio electrofisiológico.

INTRODUCTION: Atrial fibrillation is observed in 10% of electrophysiological studies. Previous studies have shown the efficacy of biphasic low energy internal cardioversion to restore sinus rhythm. We studied the efficacy and safety of low-energy internal cardioversion and the biphasic curve, in sustained atrial fibrillation (>15 min) during electrophysiologic procedures. MATERIALS AND METHODS: From January 1997 to August 1998, 320 patients underwent an electrophysiological study. An internal cardioversion was done on those patients who developed sustained atrial fibrillation. We delivered biphasic shocks between electrodes-catheters positioned in the right atrium and the coronary sinus. Increasing energy was applied until restoration of sinus rhythm or a maximum of 10 joules were achieved with no result. A right ventricle electrode was used to synchronize the V wave and for temporary pacing. RESULTS: Thirty one episodes of sustained atrial fibrillation were observed in 26 patients (1,23 episodes/patient) and a mean of 2,58 internal cardioversions were applied per every patient. Sinus rhythm was restored in twenty three patients. The mean energy delivered was 4.1 joules. The mean time for the recovery was 3,200 ms. Temporary pacing was used in 16% of the patients for up to 1 minute. No AV blocks were observed. CONCLUSIONS: Internal cardioversion successfully restored sinus rhythm in 88.5% of the patients who presented sustained atrial fibrillation (88.5%). Temporary pacing was necessary for the treatment of postsinus shock pauses.

[Chronic atrial flutter: an infrequent manifestation of sick sinus syndrome. Clinical case]. / Flutter auricular crónico: una manifestación infrecuente de enfermedad del nódulo sinusal. Caso clínico.

We report a 41 years old female, previously operated of an atrial septal defect, presenting with a persisting atrial flutter. Sinus node dysfunction became evident during an electrophysiological study at the moment of interrupting the flutter with electrical stimulation. The patient was treated with his bundle ablation and implantation of a definitive pacemaker. After one year of follow up, she is devoid of symptoms.

[Ventricular reentry tachycardia within the bundle branches. Report of 3 cases]. / Taquicardia ventricular por reentrada de rama a rama: presentación de tres casos.

Vientricular tachycardia due to reentry within the bundle branches occurs in the presence of left ventricular dilatation and conduction alterations in the His-Purkinje system. A macro-reentry is formed by the His bundle, left and right bundles and ventricular myocardium. The anatomical substrate of this arrhythmia is ventricular dilatation. However, it may appear in healthy hearts. Alterations of intraventricular conduction are reflected by a prolongation of PR interval and bundle branch block in the surface EKG and prolongation of HV interval in the endocavitary registry. During tachycardia, His activation precedes ventricular activation. We report three patients aged 55, 58 and 78 years old with a dilated cardiomyopathy and ventricular tachycardia due to reentry within the bundle branches. All had a left bundle branch block and a prolonged HV internal. The arrhythmia was induced during the study in two patients. All were subjected to radiofrequency fulguration of the right branch of the His bundle. After fulguration, two remained with a pattern of complete right bundle branch block and one with a complete intermittent AV block. All three are free of arrhythmic events.

[Radiofrequency ablation of right accessory pathways]. / Fulguración con radiofrecuencia de haces paraespecíficos derechos.

BACKGROUND: Accessory pathways are muscular connections between auricles and ventricles, present in different points of mitral and tricuspid annuluses. These pathways participate in 50% of paroxysmal supraventricular tachycardias and the definitive cure of the arrhythmia is their ablation. AIM: To report our experience in patients with right accessory pathways. PATIENTS AND METHODS: Fifty consecutive patients treated between 1990 and 1996 are reported. Eight had a history of syncope, two had a diagnosis of Ebstein disease and 36 had a pre-excitation in the surface electrocardiogram. RESULTS: Fifty four accessory pathways were identified, since four patients had two pathways. Twenty four pathways were posteroseptal, 15 were lateral, 9 were medioseptal and 6 were anteroseptal. One patient had also a nodal reentry tachycardia. Fulguration was attempted in 39 patients and it was finally successful in 32. Three patients required more than one session. There were six relapses and all were successfully ablated in a second session. A mean of 28 radiofrequency applications were done (range 1-76), mean laboratory time was 6 hours and mean radioscopy time was 70 min. Four patients had a transient atrioventricular conduction blockade. CONCLUSIONS: Radiofrequency ablation of accessory pathways has a high degree of success and a low rate of complications.

[Late effects of radiofrequency fulguration: report of five cases]. / Efectos tardíos post fulguración con radiofrecuencia: experiencia clínica en 5 casos.

Radiofrequency fulguration is the definitive treatment of several supraventricular and ventricular arrhythmias. During radiofrequency application, the conduction in a specific zone is interrupted as a consequence of cellular necrosis and edema. The disappearance of edema, minutes or hours after the procedure, allows the reappearance of conduction and arrhythmias. On the other hand, the definitive lesion is larger than the one caused acutely, due to the progression of the scar. We report five patients, in whom there was an apparent failure of the fulguration, since at the end of the procedure there was conduction in the fulgurated zone, the tachycardia was inducible or pre excitation and arrhythmias reappeared during the follow up. All five were subjected to a new electrophysiological study and in all, fulguration had been effective. We conclude that these late effects of fulguration are due to the slow progression of fibrosis, that continues days or weeks after the procedure.

[Idiopathic tachycardia originated in left ventricle]. / Taquicardia ventricular idiopática originada en el ventrículo izquierdo.

BACKGROUND: Idiopathic ventricular tachycardia occurs in patients with no structural heart disease and may originate in left of right ventricle. AIM: To report our experience with this condition. PATIENTS AND METHODS: We report six patients (five male), aged 35 years old as a mean, with idiopathic left ventricular tachycardia that were subjected to conventional electrophysiological studies with atrial and ventricular stimulation programs and radiofrequency fulguration, between December 1993 and May 1996. RESULTS: The mean lapse of disease was 24 months and five patients received antiarrhythmic medications previously. All tachycardias had a morphology with an image of right bundle branch block. Radiofrequency fulguration was done after obtaining a satisfactory pace mapping of at least 11 of the 12 superficial EKG derivations. The procedure was successful in five patients and two had a relapse. One of the relapsed patients was successfully fulgurated again. CONCLUSIONS: Radiofrequency fulguration for idiopathic ventricular tachycardias is a safe and effective therapeutic procedure.

[Cardiovascular effects of AV interval shortening with electrical stimulation in dilated cardiomyopathy]. / Efectos cardiovasculares del acortamiento del intervalo AV mediante estimulación eléctrica del corazón en miocardiopatía dilatada.

BACKGROUND: A temporal alteration between atrial and ventricular contraction, in which the last one would be abnormally retarded, could exist in patients with dilated cardiomyopathy. This alteration could have adverse hemodynamic effects. AIM: To study the hemodynamic modifications caused by an artificial shortening of AV interval in patients with dilated cardiomyopathy. PATIENTS AND METHODS: Nine patients with dilated cardiomyopathy were studied. Hemodynamic and tissular perfusion values, echocardiographic and radioisotopic ventricular function parameters were measured before and after six hours of AV interval shortening with electrical stimulation of the heart. RESULTS: After electrical stimulation, cardiac output increased from 3.38 +/- 0.8 to 3.87 +/- 0.79 l/min (p< 0.05). Pulmonary capillary pressure decreased from 23.8 +/- 8.9 to 19.8 +/- 9.2 mm Hg (p = NS). There were no significant changes in ventricular function parameters or in systemic and pulmonary pressures. CONCLUSIONS: Electrical shortening of AV interval in patients with dilated cardiomyopathy increases cardiac output but does not change ventricular function parameters.

[Supraventricular paroxysmal tachycardia with ventriculo-atrial dissociation. Report of one case]. / Taquicardia paroxística supraventrictular con disociación ventrículo auricular: a propósito de un caso.

Nodal reentrant supraventricular paroxysmal tachycardia corresponds to a reentry circuit established between fibers with different conduction velocities and refractory periods in the atrioventricular node. These are the slow and fast nodal pathways. That ventricular tissue does not form part of the circuit of this arrhythmia is accepted nowadays, and the involvement of atrial tissue is discussed. We report a 57 years old male with a nodal reentrant tachycardia. In the electrophysiological study he presented an atrial and ventricular dissociation during the tachycardia. These findings allow a better understanding of the electrophysiological substrate of this arrhythmia.

[Radiofrequency catheter ablation in patients with common atrial flutter]. / Fulguración con radiofrecuencia en pacientes con flutter auricular típico.

BACKGROUND: Type 1 atrial flutter is produced by a reentry circuit located in the right atrium that can be interrupted applying radiofrequency in the inferior cava-tricuspid valve isthmus. AIM: To report our experience in the treatment of atrial flutter with radiofrequency ablation. PATIENTS AND METHODS: Nine patients (eight male) whose ages ranged from 6 to 72 years old were studied. Two patients had an operated congenital cardiopathy, two had high blood pressure, one was subjected previously to radiofrequency ablation due to a left paraspecific pathway, one developed a cardiac failure secondary to tachycardia and three did not have evidences of cardiopathy. RESULTS: In two patients, atrial flutter was not interrupted. In the other seven patients, radiofrequency ablation was successful. There were three relapses in the first month after the procedure, of these, two patients were successfully treated again. After a mean follow up of 4.5 months, these patients are asymptomatic and without antiarrhythmic drugs. Analysis of obtained signals, showed that radiofrequency that interrupted atrial flutter always occurred in zones of double potentials. CONCLUSIONS: Radiofrequency ablation is an effective treatment for atrial flutter and the zone of successful ablation is associated to the presence of double atrial potentials.

[Radiofrequency fulguration for supraventricular tachycardia in pediatrics]. / Fulguración por radiofrecuencia de las taquicardias supraventriculares en pediatría.

Supraventricular tachycardias (SVT) are the most frequent cause of tachycardia in children. Its pharmacological treatment has adverse effects, is not curative, and is not always effective. During the last few years radiofrequency ablation (RF-A) has changed the treatment. The purpose of this study is to evaluate our experience in RF-A in children with SVT. Between 1990 and 1995, 92 patients (1 month to 17 years old) underwent electrophysiological study after the diagnosis of SVT. RF-A was attempted in 55 patients with accessory pathways (AP), slow-pathway of the atrioventricular node, or ectopic focus. The site of ablation was decided according to the electrical signals and the catheter position. The success of the RF-A was confirmed by the interruption of the tachycardia, the change in the sequence of activation of the intracardiac signals, the regression of the preexcitation, and the inability to reinduce tachycardia. RF-A was successful in 81% of the patients; 88% in those with a left AP, 56% in those with a right AP, and 100% in those with nodal reentry. Complications were seen in 7% of the patients: 3 with arterial obstruction, one with a minimal pneumothorax, and one with cardiac tamponade. During a follow up of 16.6 months there was no relapse nor late complications. We conclude that RF-A is a safe and effective procedure in pediatric patients with SVT.

[Fulguration with radiofrequency of the slow nodal pathway: experience in 30 consecutive cases]. / Fulguración con radiofrecuencia de la vía nodal lenta: experiencia en 30 casos consecutivos.

Atrioventricular nodal reentry tachycardia (AVNRT) is one of the most frequent mechanisms of paroxysmal supraventricular tachycardia. In these patients tachycardia is maintained due to anterograde conduction through a slow pathway and retrograde conduction to the atrium via a fast pathway. We present herein our experience in ablation of the slow pathway. Since January 1993, 30 consecutive patients with AVNRT underwent attempted catheter ablation of the slow pathway. Mean age was 35 +/- 3.7 years. All patients had symptomatic tachycardia and six had history of syncope. Electrophysiologic studies revealed AVNRT in all patients, in addition, two patients had a left accessory pathway. Slow pathway ablation was performed with a Mansfield 7 F catheter, guided by both fluoroscopic positioning and endocardial signals. A mean of 13 bursts were applied. In the 30 patients conduction through the slow pathway was interrupted, and thus tachycardia was no longer inducible. Retrograde conduction post ablation was evaluated in 17 of the 30 patients, significant changes were observed in three of them. One patient developed second degree AV block and a permanent pacemaker was implanted. Another patient had recurrence of tachycardia three months post ablation. After a second attempt she is arrhythmia free. Patients have been followed for a mean of 15.7 +/- 2.5 months and are asymptomatic in the absence of antiarrhythmic therapy.

[Junctional reciprocating tachycardia: clinical and electrophysiological characteristics, and the role of fulguration in 5 cases]. / Taquicardia incesante de la unión: características clínicas, electrofisiológicas y rol de la fulguración en 5 casos.

The permanent form is a variety of junctional reciprocating tachycardia that is refractory to medical treatment. The anterograde arm of the circuit is formed by the His Purkinje bundle and the retrograde conduction is through a slow conduction Accessory Atrioventricular Pathway. We report five patients with this type of arrhythmia, subjected to electrophysiological assessment. Their mean age was 37 years, all suffered from palpitations and several medical treatments had failed. During tachycardia, electrocardiogram had a negative P wave in inferior leads and RP interval was bigger than PR interval. Accessory Pathway were located in the right postero-septal region in three patients, in the left postero-septal region in one and in the left lateral in one. Specific bundle fulguration was successfully attempted in four patients, in whom arrhythmias did not recur without medical treatment.

[Arrhythmogenic right ventricular dysplasia. Options of treatment during a 12-year follow-up of a patient]. / Displasia arritmogénica de ventrículo derecho. Opciones de tratamiento durante 12 años de seguimiento en un caso.

The replacement of muscle by fibrous and adipose tissue leads to arrhythmogenic right ventricular dysplasia. We report the clinical features and therapeutic options of a 50 years old male with the disease followed during 12 years. The latter included pharmacological therapy, surgical pseudoaneurysmal resection and radiofrequency fulguration of a second arrhythmogenic focus that appeared 10 after the surgical procedure. The patient remained asymptomatic after each therapy, until the disease progressed again. This follow up is one of the longest reported and documents the disease's clinical presentation, evolution and treatment.

[Radiofrequency fulguration of accessory pathways]. / Fulguración por radiofrecuencia de haces paraespecíficos.

Between August 1991 and August 1993, 75 patients (42 male) with Wolff Parkinson White syndrome (43 concealed) were subjected to radiofrequency ablation of accessory pathways at our institution. 55 had left, 8 postero septal, 2 anteroseptal and 10 right accessory pathways. A retrograde aortic technique with placement of the ablation catheter in close proximity to the mitral annulus was used for most of the patients with left accessory pathways and for some with posteroseptal pathways. The right, anteroseptal and some posteroseptal pathways were ablated using a right heart approach placing the ablation catheter in the tricuspid annulus. Ablation was successful in 61 patients (81%). One subject developed a fatal cardiac tamponade after a transeptal catheterization and was unrelated to the ablation per se. It is concluded that radiofrequency ablation of accessory pathways is a curative procedure for a great majority of patients with Wolf Parkinson White syndrome.

[Multiple pathway tachycardias: electrophysiological properties and fulguration of accessory pathways in 2 cases]. / Taquicardias con circuitos multiples: propiedades electrofisiológicas y fulguración de todas las vías accesorias en dos casos.

We report two patients (male, 35 and female, 28 years old) with recurrent and refractory tachycardias referred for an electrophysiological study. EKG showed left lateral accessory pathway in both, two tachycardias with identical morphology but with different frequency and activation sequence were detected. One was orthodromic with anterograde conduction by the His-Purkinje budle and retrograde by the accessory pathway and the other with slow nodal anterograde conduction. The accessory pathway was first fulgurated with radiofrequency at the third attempt. Posteriorly, a nodal reentry tachycardia was induced in the first patient and in the second, a double nodal pathway was confirmed. In both, the slow pathway was modified using Jackman's technique, after three and four attempts respectively. After these applications, the induction of tachycardia with programmed atrial or ventricular stimulation, with or without isoproterenol, was not possible. It is concluded that radiofrequency fulguration is a reasonable therapeutic alternative for patients with multiple circuit tachycardias.

Fulguración exitosa de la vía lenta en pacientes con taquicardia con reentrada en el nódulo aurículo-ventrícular / Successful fulguration of the slow pathway in patients with tachycardia by reentry in the atrioventricular node

Entre enero y agosto de 1993 es realizaron 91 estudios electrofisiológicos para determinar el mecanismo de la taquicardia y efectuar eventual fulguración. En 10 pacientes (4 hombres y 6 mujeres), se documentó participación de la vía lenta del nódulo aurículo-ventricular en la taquicardia. La edad promedio fue de 38,7 años (rango 9-58). Ocho pacientes tenían taquicardias por reentrada en el nódulo aurículo-ventrícular (TRNAV) y 2 tenían asociación de taquicardias con participación de haz paraespecífico y TRNAV. La fulguración con radiofrecuencia se realizó ubicando un catéter Mansfield 7F en el ángulo posteroinferior del triángulo de Koch, el que se movilizó hasta obtener una relación A/V de 1/10 en ausencia de His. Se realizaron numerosos intentos de aplicación de radiofrecuencia a 500 KH, buscando obtener taquicardia nodal automática en relación a ella. Se interrumpieron los intentos cuando se documentó incapacidad de inducir TRNAV, ausencia de ecos y curva nodal única. En 8 pacientes se necesitaron 7,2 intentos y en 1 (en que se ensayó catéter diferente) 17 intentos, para bloquear la conducción de la vía lenta, con aplicación de 40 watts por 60 seg. La única complicación presentada fue la aparición transitoria (12 horas) de bloqueo completo de rama derecha, no en relación a la aplicación de la radiofrecuencia. Luego de 2,4 meses promedio (7 meses-15 días) todos los pacientes permanecen libres de arritmia en ausencia de tratamiento antiarrítmico. La fulguración de la vía lenta es un método de bajo riesgo y alta eficacia para curar las taquicardias por reentrada en el nodo aurículo-ventricular

[Block of the slow pathway of the double atrioventricular node: a new technique for treatment of atrioventricular node reentry tachycardia]. / Bloqueo de la via lenta del nódulo aurículo ventricular doble: una nueva técnica para curar taquicardia por reentrada nodal.

The aim of this work is to summarize the first experience in Chile modifying the slow pathway in patients with tachycardias due to atrio-ventricular node reentry. Until now, the only available treatment was the use of antiarrhythmic drugs. The radiofrequency fulguration or cauterization of part of the atrioventricular node has been reported as a treatment for these arrhythmias. The initial technique fulgurated the rapid pathway with a significant risk of atrioventricular block. The modification of the slow pathway has been recently described. We report two patients, 9 and 45 years old, with a history of recurrent tachycardias, refractory to pharmacological treatment. An electrophysiological study demonstrated that the mechanism of their arrhythmias was a nodal reentry. In the same session one of the mapping catheters was changed by a fulguration one and radiofrequency was applied, using a variation of the technique described by Jackman. In both, the slow pathway was modified or blocked with definitive interruption of the nodal reentry circuit and preservation of atrioventricular conduction.