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

El colágeno de la reestenosis post angioplastia con stent: ¿se origina en la íntima o en la adventicia? / Origin of collagen in restenosis post stenting: intima or adventitia?

Background: Restenosis post stenting is due to the deposit of extracellular matrix, mainly collagen in the neointima. Controversy exists regarding if collagen is generated locally or by immigration from the adventitia. Aim: To study the fibrocellular response after stent implantation in rabbit iliac arteries. To observe, by immunohistochemistry and in situ hybridization, if collagen type I mRNA is expressed in the neointima, in the media or in the adventitia. Material and methods: Thirty eight white rabbits (New Zealand) of 4 kg received an hypercholesterolemic diet during 1 month. After this period, in all but 6 of them, an angioplasty with stent implantation was performed via right carotid artery in both iliac arteries, using a 1:1.3 relationship regarding the reference vessel. Angiograms were performed at day 0, 4, 21, and 40, followed by paraffin fixation of the injured segments, immunohistochemistry for a-actin and in situ hybridization to detect procollagen type I (a1R1) mRNA. Results: No hybridization was observed in non injured arteries or at day 0 (n= 6). Expression of a1R1 mRNA was observed in the neointima starting at day 4 after stenting (n= 8). At day 21 (n= 8) hybridization of procollagen type I was not only observed in the neointima, but also in the media, which became equally intense in both areas. At day 40 (n= 6) hybridization was observed similarly in the media and adventitia. Conclusions: In this model, hybridization of procollagen type I started in the neointima, then involved the media and finally the adventitia. This finding might be useful for designing therapies to be delivered locally at the end of an angioplasty to prevent collagen deposition in the neointima

Isquemia miocárdica reversible en el hipotiroidismo: comunicación de un caso / Reversible myocardial ischemia associated to hypothyroidism: report of one case

A silent, reversible myocardial ischemia with normal coronary angiography and reversible with thyroid hormone substitution, has been recently described in hypothyroid patients. We report a 49 years old male with an abnormal exercise electrocardiogram detected in a preventive medical examination. He had laboratory evidence of hypothyroidism and a history of two years of asthenia and progressive coarsening of the voice. The Thallium myocardial perfusion study, showed an alteration of coronary flow during exercise in the septum and lower wall of the left ventricle. Thyroid hormone substitution was started and three months later, a coronary angiography was normal. After six months a repeated Thallium perfusion study and exercise electrocardiogram were informed as normal

Hipertensión arterial refractaria y uso de drogas anticonvulsivantes: caso clínico / Resistant hypertension and anticonvulsant drugs: report of 1 case

Resistant arterial hypertension is uncommon when there is good compliance to antihypertensive therapy and secondary causes have been ruled out. We report a 41 years old male that suffered hypertensive encephalopathy and received prophylactic anticonvulsant therapy showing progressive raise of arterial pressure levels. Renovascular hypertension, aldosteronism and pheochromocytoma were discarded and, in spite of combined use of antihypertensive drugs, he did not achieve normal blood pressure. When phenytoin was discontinued, blood pressure temporarily normalized. Carbamazepine was started and blood pressure raised again. lt fell when this medication was discontinued. Antiepileptic agents could induce drug metabolizing system and thus reduce the effects of antihypertensive medications

Tratamiento de la insuficiencia cardíaca avanzada mediante trasplante de corazón / Heart transplantation as a treatment for advanced heart failure

Background: Heart transplantation currently provides the most effective treatment for advanced heart failure. However, medical therapy for this condition has also improved, heart donors are scarce and the cost of the procedure is high. Therefore the indications and management of these patients need reevaluation. Aim: To analyze the results of 24 patients submitted to heart transplantation for end-stage heart failure needing repeated hospitalizations and i.v. inotropes for compensation. Patients and methods: The group was comprised by 21 men and 3 women with a mean age of 36.8 years, mean left ventricular ejection fraction 19ñ4.5 percent, mean systolic pulmonary artery pressure 48ñ13 mmHg (24-70) and mean pulmonary vascular resistance 2.6 Wood Units (1-5). Fourteen patients (58 percent) had a previous median sternotomy. Immunosupression did not include induction therapy and steroids were discontinued early...

La importancia de la reprogramación en la vida útil y costo de implante de los marcapasos bicamerales / The importance of adjusting parameters for the duration and cost of dual chamber pacemakers

Antecedentes: realizamos un estudio prospectivo de 236 pacientes sometidos a implante de marcapaso DDD bicameral. Los parámetros nominales de implante permiten márgenes de seguridad de estimulación más que suficientes. Las mejoras en la tecnología de marcapasos y electrodos han permitido reducir los umbrales de captura y, por lo tanto, la programación de los parámetros de salida. Dichos cambios pueden significar una reducción en el consumo de la batería a largo plazo, produciendo una mayor durabilidad del generador. Métodos y resultados: se estudió 236 pacientes consecutivos implantados con marcapasos Pacesetter DDD para determinar el impacto de la reprogramación en la durabilidad y costo del implante del marcapaso. Se excluyó a 36 pacientes, 19 murieron, 13 no tuvieron suficientes controles y 4 fueron reprogramados a modo VVI. Los 200 pacientes restantes completaron al menos 18 meses de seguimiento y se les implantó generadores capaces de medir umbrales de estimulación crónico, ancho de pulso, impedancia y energía de la batería. Comparamos la durabilidad estimada basada en la energía de la batería bajo parámetros de implante nominales, con aquella basada en los parámetros obtenidos tras la reprogramación durante el seguimiento. La estimación de durabilidad fue de 6,89 años bajo parámetros nominales y de 10,5 años bajo parámetros de programación final (p<0,001). Conclusiones: la reprogramación podría aumentar la durabilidad y reducir el costo de implante de los marcapasos. En nuestro estudio la reprogramación aumentó la durabilidad del marcapaso en 3,6 años y ocasionó una reducción promedio en sus costos de 330 dólares por año

Flutter auricular crónico: una manifestación infrecuente de enfermedad del nódulo sinusal: caso clínico / Chronic atrial flutter as an infrequent manifestation of sick sinus syndrome: report of 1 case

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

Marcapasos bicamerales: resultados inmediatos y alejados / Short and long terms results of dual chamber pacemaker use

Background: Continuous improvement of dual chamber DDD pacemakers, electrode stability and programmed sequential stimulation changed the prognosis of patients implanted with these devices. Aim: To report our experience with the use of dual chamber pacemakers. Material and methods: One hundred seventy six patients (116 male), aged 13 to 91 years old, who received a dual chamber pacemaker implant, are reported. Patients were followed for a mean of 2.6 years. Results: Indications for DDD pacemaker were complete atrioventricular block in 43 percent, sick sinus syndrome in 32 percent, paroxysmal A-V block in 24 percent. All pacemakers were Siemens-Pacesetter and were provided with an automatic sensing and threshold device. J shaped atrium electrodes were used in 78 percent of patients and screw-in electrodes in 22 percent. Post operative complications were displacement of atrial electrode in 8 patients, of ventricular electrode in 6 patients, infection in two patients and a hematoma in one. Chronic parameters, measured after six months, were within expected ranges and allowed a good reprogramming of pacemakers. Long term programming aimed to reduce battery depletion, enhance device performance and improve hemodynamic conditions. Normal sequential stimulation was achieved in 154 patients (87 percent), 14 (85) patients died of cardiovascular disease not related to pacemaker function. Eight patients were in atrial fibrillation and were reprogrammed to VVI and DDI modes. Conclusions: DDD pacemakers are reliable and afford symptomatic relief in a broad spectrum of patients

Angina inestable: resultados inmediatos y a un año del tratamiento con angioplastía coronaria transluminal percutánea / Immediate and late results of transluminal coronary angioplasty in patients with unstable angina

Background: Unstable angina is characterized by angina at rest, angina of recent onset or accelerating angina. It is caused by a fissure or ulceration of an atheromatous plaque leading to thrombi formation and coronary spasm. Aim: To report the immediate and late results of coronary angioplasty in patients with unstable angina. Patients and methods: Eight hundred twenty eight patients were subjected to coronary arteriography between January 1994 and June 1996. Of these, 242 were subjected to a transluminal coronary angioplasty, 245 patients were subjected to surgical revascularization and 341 patients were treated without revascularization. Results: A total of 323 stenotic lesions (1.3 lesions per patient) were subjected to angioplasty. Angiographic success was obtained in 93 percent of patients. Angiographic success and lack of major complications such as death, infarction of the need for surgery, was obtained in 90 percent of patients. Five patients (2.1 percent) had a non fatal infarction and five required emergency surgery. Hospital mortality was 1.2 percent. During the year of follow up, 15 percent required a new revascularization, 3.3 percent had a non fatal infarction and 3.3 percent died. Conclusions: Coronary angioplasty had a 90 percent immediate success and 78 percent of patients were free of ischemic events after one year of follow up

Aterectomía rotacional (rotablator) en la angioplastía coronaria percutánea transluminal / Rotational atherectomy (rotablator) for percutaneous transluminal coronary angioplasty

Background: The use of Rotablator in percutaneous transluminal coronary angioplasty attempts to reduce the atheromatous plaque abrading it and fragmenting the pariental calcium of the artery. Aim: To report our experience with the use of Rotablator: Patients and methods: Rotational atherectomy was performed in 189 patients aged 60.8 ñ 11 years (154 men). The clinical indication for the procedure was chronic angina in 22 percent, unstable angina in 44 por ciento, myocardial infarction in 21 percent, silent angina in 7 percent and re-stenosis in 6 percent. One bundred seventy seven patiens were followed for a mean of 15.9 ñ 6.3 months. Results: Two hundred thirty six stenoses in 215 coronary arteries were treated with a 98.7 percent angiographic success rate. One patient had a Q infarction and no patient died or required emergency surgery. Fourteen patients had rises in CK MB enzymes (non Q infarction). Thee patients had a pseudoaneurism and three had bleedings that required transfusion. Of the followed patients, 33 had a clinically suspected re-stenosis, that was angiographically confirmed in 23. Cardiac mortality was 2.3 percent. Seventy nine percent of patients had an evolution without angina or coronary events. Conclusions: Percutaneous transluminal coronary angioplasty with the use of Rotablator had a high immediate success rate and a low incidence of complications. The clinical evolution of patients has been favorable with a low incidence of mortality and ischemic events

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

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

Edema pulmonar no-cardiogénico relacionado con la hidroclorotiazida / Non-cardiogenic pulmonary edema related to hidrochlorothiazide

A 54 years old female patient with a mitral valve prolapse and a rheumatic arthritis with steroids was admitted with dysnea and hypotension, that started 30 min after taking a pill containing enapril and hydroclorothiazide. Hemodynamic monitoring with a Swan-Ganz catheter showed a pulmonary capillary pressure of 5 mm Hg, a systemic vascular resistance of 887 (dyn sec)/cm5 and a cardiac output of 10 1/min. Tha patient had a history of adverse reactions to thiazides and responded to volume replacement, dopamine and steroids

Ventilación mecánica no invasiva intermitente: utilidad en el tratamiento de la insuficiencia cardíaca crónica avanzada / Non invasive intermittent mechanical ventilation: utility in the treatment of advanced chronic cardiac failure

The higher respiratory work and less inspiratory muscle strength of patients with cardiac failure may contribute to dicrease their functional capacity. To assess the effects of non invasive intermittent mechanical ventilation on clinical parameters, peropheral perfusion, cardiac and inspiratory muscle function. Patients with chronic cardiac failure, functional cpacity III-IV were subjected to 6 sessions of nasal non invasive intermittent ventilation during 4 hours or to simulated ventilation (controls). Fifteen ventilated patients and 6 controls completed the protocol. Ventilated patients improved the mahler transition score for dysnea by 4ñ1.6 points. They also improved their aerobic capacity, increasing the exercise duration from 10.9ñ4 to 12.7ñ5 min and their maximal oxygen consumption from 14.6ñ4 to 16.4ñ5.7 ml/kg/min. These patients also decreased their O2 and CO2 ventilatory equivalents. Maximal inspiratory pressure increased from 67.9ñ23.6 to 80.19ñ21.4 cm H2O, sustained maximal inspiratory pressure increased from 101.4ñ48 to 133ñ53 cm H2O and maximal endurance increased from 132ñ52 to 162ñ58 g in ventilated patients. None of these variables was modified in control patients. No changes were observed in renal function, blood volume, arterial gases, spirometry or plasma catecholamine levels in any group. Intermittent nasal ventilation or other measures to improve inspiratory muscle function may be beneficial for patients with severe cardiac failure

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

Fulguración con radiofrecuencia de la vía nodal lenta: experiencia en 30 casos consecutivos / Radiofrequency fulguration of the slow nodal pathway: experience in 30 consecutives cases

Atrioventricular nodal reentry tachycardia (AVNRT) is one of the most 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 here 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 37ñ3.7 years. All patients had symptomatic tachycardia and six had history of syncope. Electrophysiological studies revealed AVNRT in all patients, in addition, 2 patients had a left accesory pathway. Slow pathway ablation was performed with Mansfield 7 F catheter, guided by both fluoroscopic positioning and endocardial signals. A mean of 13 burst were applied. In the 30 patients conduction though the slow pathway was interrupted and thus tachycardia was no longer inductible. 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 15.7ñ2.5 months and are asymptomatic in the absence of antiarrhythmic therapy