Experiencia de 36 años con marcapasos implantables: un análisis histórico / A 36 year experience with implantable pacemakers

Background: The implantation of pacemakers improves cardiac function and quality of life, in particular with dual chamber DDD and DDDR modes. Aim: To evaluate our clinical experience and results on pacemaker implantation, from 1963 to 1998. Material and methods: Computerized data collected from 2,445 consecutive paced patients was reviewed. A total of 3,554 operative procedures were performed, including 412 procedures for complications and 697 pacemaker replacement. Patient survival was determined from clinical records, inquiry to pacemaker manufacturers and death certificates from Servicio de Registro Civil e Identificaci-n de Chile (Chilean Civil and Identification Registry). Results: Use of dual chamber (DDD and DDDR) pacemakers increased progressively up to 74 percent from 1988 to 1998. Complication rate was 42 percent in the 1963-1976 study period, it decreased to 10.6 percent in the 1977-1987 study period, and to 5.6 percent by 1988-1998. Only two patients died during surgery in the study period (0.08 percent). In the 1977-1987 period, pacemakers lasted 10.6 years. Survival rates were 52 percent at ten years, 33 percent at 15 years, and 21 percent at 20 years, with a median survival of 11.7 years, and 7.24 years in patients over 80 years old. Conclusions: Transvenous permanent pacing can be accomplished today with a low complication rate, mainly due to better technology and surgical procedures

Actividad rítmica espontánea en vasos de placenta humana: ¿un marcapaso fisiológico en los vasos sanguíneos? / Spontaneous rhythmic contractions of human umbilical vessels, evidences for a physiological pacemaker in blood vessels?

Background: Placental vessels are not innervated. Therefore the vasomotor activity and vascular tone is not regulated by the nervous system. Aim: To assess the existence of pacemaker mechanisms related to rhythmic motor activity of blood vessels. Material and methods: Isometric contractions of rings from umbilical and chorionic vessels of term human placentas were monitored. Results: Recordings of the circular layer of chorionic and umbilical vessels revealed rhythmic spontaneous contractions with a frequency of 1,4ñ0,05 cycles/min, the duration of each cycle was 42,8ñ0,24 s (n=12). The amplitude of contractions was larger in veins than in arteries, predominating in umbilical vein biopsies, proximal to the fetus. Both the frequency and the amplitude of contractions were relatively constant during the first 30 min. However, after an hour, the frequency declined while the amplitude increased. The absence of the endothelium neither modified the frequency nor the amplitude of the rhythmic activity. Blockage of voltage dependent sodium channels or calcium channels did not alter the frequency of spontaneous contractions, although their magnitude was reduced. Glibenclamide, an ATP-dependent K+ channel blocker or the blockade of gap junctions ablated the frequency and amplitude of spontaneous contractions. Conclusions: We propose that rhythmic contractions are triggered by pacemaker cells located in the circular layer of the smooth muscle of blood vessels and spread via gap junctions; they likely contribute to the control of blood flow

Ablación por radiofrecuencia de extrasistolía ventricular aislada sintomática en corazón sano / Radiofrequency catheter ablation in symptomatic premature ventricular depolarizations in patients without heart disease

Introduction: Premature ventricular depolarizations (PVDs) in patients without heart disease, are a frequent clinical problem that can cause important symptoms. Most commonly, this benign arrhythmia responds to treatment with antiarrhythmic drugs. However, occasionally PVDs are refractory to pharmacological treatment but they can be eliminated with radiofrecuency catheter ablation. Aim: To show our experience with four patients in whom we used this method. Material and method: We studied three men and a woman, twelve to forty six years old. All of them were symptomatic, their EKG and echocardiogram were normal and they had been treated with several drugs without response. In three of them the PVDs had left bundle-branch block morphology with inferior axis; the other patient had right bundle-branch block morphology with superior axis. The origin of the PVDs was determined using pace mapping. Results: Two of the patients had spontaneous PVDs; in the other two isoproterenol infusion was used to induce them. In three patients the origin of the PVDs was located in right ventricular outflow and in the other in the anterolateral region of the left ventricle. None had sustained atrial or ventricular arrhythmia. In all of them PVDs were eliminated. A patient presented a second morphology that could not be treated. None of the patients had complications and they were discharged within the next 24 hours. Three noted symptomatic improvement and after 18 months, only one had a probable recurrence of the arrhythmia. Conclusions: radiofrecuency catheter ablation can be successfully used to eliminate PVDs in severely symptomatic and drug-resistant patients

Fulguración con radiofrecuencia de taquicardia ventricular por displasia arritmogénica de ventrículo derecho / Radiofrequency ablation in patients with right ventricular arrhythmogenic dysplasia

La taquicardia ventricular del tracto de salida de ventrículo derecho (TVD) es causa del 70 por ciento de las taquicardias ventriculares idiopáticas. Entre octubre de 1995 y agosto de 1997, siete pacientes (4 hombres), con edad promedio de 35 años (6-60), fueron sometidos a estudio electrofisiológico (EEF) y fulguración con radiofrecuencia (FRF) por TVD. El tiempo promedio de evolución de los síntomas fue de 21 meses. Los 7 pacientes tenían palpitaciones y 2 síncope. Ninguno tenía cardiopatía estructural de base y todos habían fracasado el tratamiento farmacológico. Durante el EEF, en tres pacientes la TV se inició espontáneamente, en cuatro con estimulación ventricular e isoproterenol y en uno con estimulación auricular. Para la FRF se avanzó un catéter vía vena femoral derecha, y bajo visión radioscópica, se mapeó el tracto de salida del ventrículo derecho con técnica de pace mapping. La FRF tuvo éxito en los 7 pacientes. Hubo una recidiva a los 92 días, con refulguración exitosa. El promedio de aplicaciones de radiofrecuencia fue de 10 (rango de 1 a 19). El tiempo promedio de laboratorio fue de 4,6 ñ 0,6 horas, con un tiempo de radioscopia de 27 ñ 5 min. No hubo complicaciones ni recidivas de las TVDs. Conclusión: la FRF es una alternativa terapéutica eficaz y segura para pacientes con TVD

Efectos tardíos post fulguración con radiofrecuencia: experiencia clínica en 5 casos / Late effects of radiofrecuency fulguration: report of 5 cases

Radiofrecuency fulguration is the definitive treatment of several supraventricular and ventricular arrythmias. During radiofrecuency 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 arrythmias. On the other hand, the definitive lesion is larger than the one caused acutely, due to the progression of the scar. We report four 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 arrythmias reappeared during the follow up. All four were subjected to a new eletrophysiological 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

Torsión de las puntas y marcapaso endocavitario ventricular de demanda / Torsade de pointes and demand endocavitary pacemaker: report of one case

We report a 81 years old female with a severe aortic insufficiency, treated with diuretics and antidepressants admitted due to recurrent syncopal episodes. During the first syncopal episode, an atrioventricular block was detected and an endocavitary demand pacemaker implanted. Two years later, she had a new syncope without evidences of pacemaker failure. The EKG during pacemaker rhythm showed a prolonged QT interval. During hospital monitoring, she presented a self limited polymorphic ventricular tachycardia (Torsade de pointes). Consequently, the pacemaker was programmed at a greater frequency, and the QT interval shortened from 0.73 to 0.56 sec. Thereafter, the patient no longer had tachycardia or syncopal episodes, after one year of follow up

Taquicardia ventricular por reentrada de rama a rama: presentación de tres casos / Ventricular tachycardia due to reentry within the bundle branches: report of three cases

Ventricular 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 intenval 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

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

Background: Accessory pathways are muscular connections between auricles and ventricles, present in different points of mitral and tricuspid annuluses. These pathways participate in 50 percent 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: 50 consecutive patients treated between 1990 and 1996 are reported. Eight had a history of syncope, two had a diagnosis of Epstein 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 conductor blockade. Conclusions: Radiofrequency ablation of accessory pathways has a high degree of success and a low rate of complications

Taquicardia ventricular por reentrada de rama a rama: otra arritmia con tratamiento definitivo / Bundle branch reentry ventricular tachycardia: another arrhythmia with a definitive treatment

La taquicardia ventricular por reentrada de rama a rama corresponde a un tipo de taquicardia ventricular monomorfa sostenida que se presenta en pacientes con miocardiopatía dilatada y transtornos de conducción del sistema His-Purkinje. Esta taquicardia produce compromiso hemodinámico y hasta un 75 por ciento de los pacientes debuta con síncope o muerte súbita. Con el desarrollo de la electrofisiología se ha comprendido su mecanismo, y la fulguración con radiofrecuencia permite un tratamiento definitivo mediante interrupción de la conducción por la rama derecha. Presentamos el caso clínico de un paciente con miocardiopatía dilatada de origen valvular, quien presentó taquicardia por reentrada de rama a rama y fue sometido a fulguración con radiofrecuencia

Efectos cardiovasculares del acortamiento del intervalo AV mediante estimulación eléctrica del corazón en miocardiopatía dilatada / Cardiovascular effects of AV interval shortening with heart electric stimulation in 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 ñ 0.8 to 32.87 ñ 0.79 l/min (p < 0.05). Pulmonary capillary pressure decreased from 23.8 ñ 8.9 to 19.8 ñ 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

Diagnóstico diferencial de taquicardias a complejo ancho / Differential diagnosis of tachycardias with widened complex

The differential diagnosis of tachycardias with a widened QRS complex is a frequent problem that cardiologists and emergency room physicians must face. Ventricular tachycardias, supraventrical tachycardias with aberration of ventricular conduction and supraventricular tachycardias conducted by accessory routes (pre-exited or antidromic) are the three mechanisms that cause tachycardias with a widened QRS complex, whose clinical significance and treatments are different. Recently, intracardiac electrophysiological studies allowed the identification of efficient electrocardigraphic criteria to distinguish each of these mechanisms. Several reports have indicated these criteria based on the careful analysis of the surface electrocardiogram

Resultados de fulguración de flutter auricular en doce pacientes consecutivos / Atrial flutter fulguration: results in twelve consecutive patients

El flutter auricular es una arritmia supraventricular que frecuentemente es refractaria al tratamiento farmacológico. En los últimos años se ha desarrollado la técnica de fulguración que permite recuperar ritmo sinusal y suspender fármacos. Presentamos nuestra experiencia de fulguración en flutter auricular en doce pacientes consecutivos. Estos fueron fulgurados entre septiembre 1993 y marzo 1996. En diez de doce pacientes se obtuvo ritmo sinusal post fulguración el que se mantiene al cabo de 11.6 meses (4 a 27 meses). El éxito se asoció a la capacidad de detectar dobles potenciales en la zona de fulguración del piso de la aurícula derecha

Fulguración con radiofrecuencia en pacientes con flutter auricular típico / Radiofrequency fulguration in patients with common atrial flutter

Nine patients (8 males) whose ages ranged from 6 to 72 years old were studied. Two patients had an operated congenital cardiopathy, 2 had high blood pressure, 1 has no subject previously to radiofrequency ablation due to a left paraspecific pathway; 1 developed a cardiac failure secondary to tachycardia and 3 relapses in the first month after the procedure, of these, 2 patients were succesfully treated again. After a mean follow up of 4.5 months, these patients are asymptomatic and without antiarrythmic drugs. Analyzis of obtained signals, showed that radiofrequency that interrupted atrial flutter always occurred in zones of double potentials. Radiofrequency ablation is an effective tretament for atrial flutter and the zone of succesful ablation is associated to the presence of double atrial potentials

Fulguración por radiofrecuencia de las taquicardias supraventriculares en pediatría / Radiofrequency ablation of supraventricular tachycardias in pediatrics

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 mont 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 tachychardia, 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 succesful in 81 percent of the patients; 88 percent in those with a left AP 56 percent in those with a right 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

Características del electrograma local en fulguraciones exitosas de haces paraespecíficos / Characteristics of the local electrogram in successfuly fulgurations of paraspecific bundles

La ablación por radiofrecuencia de haces paraespecíficos es un aterapia muye efectiva para el tratamiento de las taquicardías paroxíticas supraventriculares. Con el objeto de evaluar la utilidad del electrograma local en la identificación del sitio correcto para efecturar la ablación por radiofrecuencia, se analizaron las características de éstos en 20 pacientes con haces paraespecíficos fulgurados exitosamente. 16 pacientes tenían un haz paraespecífico izquierdo (10 ocultos), 2, haz paraespecífico anteroseptal y 1, un haz paraespecífico lateral derecho. En 15 pacientes la fulguración se realizó durante taquicardia paroxítica supraventricular y en 5, durante ritmo sinusal. En los 20 electrogramas analizados, el hallazgo más frecuente fue el de complejos fusionados. Se registró un probable electrograma de Kent en 3 pacientes fulgurados en taquicardia y en 4 pacientes fulgurados en ritmo sinusal. Pensamos que ninguna de las características del electrograma local tiene un valor predictivo alto para precisar el sitio de la fulguración exitosa

Taquicardia auricular ectópica: fulguración exitosa con radiofrecuencia / Ectopic atrial tachycardia: successfully fulguration with radiofrequency

La taquicardia auricular es una causa de taquicardia paroxística supraventricular que puede originarse en relación a un circuito de reentrada intraauricular o por la existencia de uno o múltiples focos de automatismo anormal. Esta última forma de taquicardia se denomina como taquicardia auricular ectópica (TAE) y se caracteriza porque suele ser resistente a tratamiento antirrítmico y porque en caso de tener carácter incesante puede llevar a insuficiencia cardíaca. En los últimos años se han desarrollado diversas alternativas de tratamiento no farmacológico. En la presente publicación presentamos el caso clínico de una mujer con TAE derecha que fue fulgurada con radiofrecuencia en forma exitosa

Taquicardia incesante de la unión: características clínicas, electrofisiológicas y rol de la fulguración en 5 casos / Permanent form of junctional tachycardia: clinical and electrophysiological characteristics and fulguration role in 5 cases

The permanent form is a variety of functional 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 accesory 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. Accesory 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 succesfully attempted in four patients, in whom arrythmias did not recur without medical treatment

Variantes electrofisiológicas de la taquicardia incesante / Electrophysiological variations of incesant tachycardia

La taquicardia incesante puede ser causada por diferentes mecanismos electrofisiológicos. Desde 1986, hemos estudiado 13 pacientes con taquicardia incesante, 9 hombres y 4 mujeres (edad promedio 35a). Diez pacientes habían recibido múltiples antiarrítmicos y 4 habían desarrollado insuficiencia cardíaca secundaria a taquicardia. Se efectuó estudio electrofisiológico en 11 pacientes, encontrando: 1) haces accesorios con conducción lenta y decremental en 5 pacientes. Se encontró un haz derecho posteroseptal en 3, un haz izquierdo posterolateral en 1 y un haz izquierdo posteroseptal en 1. La ablación por radiofrecuencia fue exitosa en 4 de estos 5 pacientes. 2) la taquicardia auricular ectópica fue el mecanismo de la arritmia en 4 pacientes. Se efectuó una resección quirúrgica exitosa del foco auricular en 1 paciente y ablación del his en otro. Fracasó la ablación por radiofrecuencia del foco auricular en un paciente. 3) Reentrada nodal atípica existió en 2 pacientes que fueron tratados con antiarrítmicos, cuando carecíamos de radiofrecuencia. 4) Un foco ectópico del his existía en un niño de 1 mes de edad, cuya arritmia se encuentra parcialmente controlada con drogas. 5) Un paciente tenía una taquicardia incesante atípica debida a un haz accesorio lento con intervalos A-H y H-V prolongados. Un intento de ablación con corriente continua se complicó de hemopericario que se trató con cirugía y la arritmia respondió posteriormente a antiarrítmicos. Por tanto, el estudio electrofisiológico es valioso en pacientes con taquicardia incesante y conduce a tratamiento exitoso con ablación por radiofrecuencia en muchos de ellos