[Anesthesia and cardiac electrophysiology (Part I)]. / Anestesia y electrofisiología cardiaca (Parte I).

Cardiac arrhythmias are a common complication of surgery and anesthesia. They are more likely to occur in patients with heart disease and the presence of a transitory imbalance can supply the underlying substrate for reentry, triggered activity, or abnormal automaticity. The physiologic impact of a given arrhythmia depends on its duration, on ventricular response, and on the underlying cardiac disease. Optimal management of arrhythmias in the anesthetized patient will depend on knowledge of the trigger mechanisms, the effects of anesthetic drugs on cardiac electrophysiology, and situations that favor arrhythmias. The anesthesiologist must cope with a plethora of problems related to the patient's clinical state and the trauma of surgical manipulation. Experience with electrocardiography and the application of various devices (pacemakers, cardioverters, implantable defibrillators) and knowledge of the pharmacodynamics and pharmacokinetics of new intravenous drugs will be essential for patient management. The purpose of the present review is to provide the anesthesiologist with an overview of current views on the diagnosis and management of arrhythmias during anesthesia.

Anestesia y electrofisiología cardiaca (Parte I) / Anesthesia and cardiac electrophysiology (Part I)

Las arritmias cardiacas representan una complicación frecuente de la cirugía y de la anestesia. Ocurren de forma más habitual en pacientes con patología cardiaca y la p esencia de una alteración transitoria puede proporcionar el sustrato necesario para que se desencadene una entrada, una actividad "triggered" o un automatismo anormal. El impacto fisiológico de una determina- da arritmia dependerá de su duración, respuesta ventricular y de la enfermedad cardiaca subyacente. El manejo óptimo de las arritmias en el paciente anestesia- do está condicionado por el conocimiento de los mecanismos desencadenantes, de los efectos de los fármacos empleados en la anestesia en la electrofisiología cardiaca y de las causas que favorecen las arritmias. El anestesió- logo se enfrenta en el curso perioperatorio a un gran número de problemas relacionados con el estado clínico del paciente y la agresión que presenta el acto quirúrgico. La experiencia en electrocardiografía, así como en el uso de dispositivos específicos (marcapasos, cardioversión, desfibriladores implantables) y el conocimiento de fármacos nuevos de uso intravenoso, junto a su farmacodinamia y farmacocinética, es esencial para el manejo del paciente. El propósito de esta revisión es proporcionar al anestesiólogo una aproximación a los conceptos actuales del diagnóstico y manejo de las arritmias durante la anestesia

Cardiac arrhythmias are a common complication of surgery and anesthesia. They are more likely to occur in patients with heart disease and the presence of a transitory imbalance can supply the underlying substrate fore entry, triggered activity, or abnormal automaticity. The physiologic impact of a given arrhythmia depends on its duration, on ventricular response, and on the underlying cardiac disease. Optimal management of arrhythmias in the anesthetized patient will depend on knowledge of the trigger mechanisms, the effects of anesthetic drugs on cardiac electrophysiology, and situations that favor arrhythmias. The anesthesiologist must cope with a plethora of problems elated to the patient's clinical state and the trauma of surgical manipulation. Experience with electrocardiography and the application of various devices (pacemakers, cardioverters, implantable defibrillators)and knowledge of the pharmacodynamics and pharmacokinetics of new intravenous drugs will be essential for patient management. The purpose of the present review is to provide the anesthesiologist with an overview of current views on the diagnosis and management of arrhythmias during anesthesia

[Ventricular arrhythmias induced by appropriate antibradycardia pacing in patients with implantable defibrillators]. / Inducción de arritmias ventriculares por estimulación antibradicardia apropiada en pacientes portadores de desfibrilador automático.

INTRODUCTION AND OBJECTIVES: The induction of ventricular arrhythmias by appropriate antibradycardia ventricular pacing in patients with implantable cardioverter defibrillators has been reported in only a few cases. The aim of this study was to assess the incidence, characteristics and management of these episodes. METHODS: The follow-up records of 180 patients with implantable cardioverter defibrillators with intracardiac electrogram storage were reviewed. Pacing induced episodes were defined as those occurring immediately after an appropriate paced stimulus in a patient with sporadic paced beats. We assessed the number and type of episodes, mode of onset, therapy administered and the efficacy of different prevention measures. RESULTS: Pacing induced episodes were found in 9 patients (5%). Seven received device administered therapy which was effective in all cases. One to 95 episodes were observed per patient, of which 138 were monomorphic ventricular tachycardias and 20 polymorphic ventricular tachycardia/ventricular fibrillation episodes. All were induced by a paced ventricular beat after a post-extrasystolic pause or after long RR intervals during atrial fibrillation. Pacing induced arrhythmias were prevented by changing the pacing rate or hysteresis in 3 out of 6 patients and by decreasing the stimulus energy in 3 out of 3. Antibradycardia pacing function was disabled in 4 patients. CONCLUSIONS: Ventricular arrhythmias induced by appropriate antibradycardia ventricular pacing are relatively common in patients with implantable cardioverter defibrillators. Effective prevention can be achieved in most cases by changing the pacing rate or the pacing stimulus energy, however in selected cases the antibradycardia function may be disabled.

[Complex implantation of an automatic defibrillator-cardioverter through a left superior vena cava]. / Implantación compleja de desfibrilador-cardioversor automático a través de una vena cava superior izquierda.

We describe the case of a 19-year-old girl with a left superior vena cava and a surgically corrected complete atrioventricular canal defect. After an inhospital sudden death an automatic defibrillator-cardioverter was implanted through her left superior vena cava. During the postoperative course, multiple inappropriate discharges caused by myopotential oversensing indicated the relocation of the electrode and, finally, insertion of two epicardial leads by a left submammarian thoracotomy approach, produced an optimal result.

[Radiofrequency catheter ablation for atrial tachycardia]. / Ablación con catéter mediante radiofrecuencia de taquicardias auriculares.

INTRODUCTION: Radiofrequency catheter ablation of atrial tachycardia guided by bipolar activation mapping has been reported in the last years. This article reports the use of radiofrequency catheter ablation for the treatment of atrial tachycardia using simultaneous bipolar and unipolar activation mapping at our institution. METHODS: Nine patients (7 male and 2 female, mean age 37.2 +/- 24.1 years), were selected for radiofrequency catheter ablation of drug refractory atrial tachycardia. Mapping procedure included an investigation of the local earliest bipolar and unipolar activity and unipolar morphology analysis. RESULTS: Atrial tachycardia was successfully ablated in 7 patients (78%) with an average number of 6.8 +/- 3.1 RF pulses. Procedure related complications and tachycardia follow-up recurrences were not observed in any patient. Bipolar local activation time was significantly shorter at successful than at unsuccessful ablation sites (-30 +/- 21.1 ms vs -18.3 +/- 20.6 ms; p = 0.01). No difference was observed in unipolar local activation time between successful and unsuccessful sites (-22.5 +/- 26.2 ms vs -19.8 +/- 21.5 ms; p = 0.56). Accurate localization of the successful ablation site by unipolar electrogram analysis was not feasible because a "QS" pattern was found at both 21 unsuccessful and 2 successful ablation sites. Finally, a fast slope of the negative deflection of the unipolar electrogram was found at 2 out of 45 unsuccessful and 3 out of 6 successful ablation sites. CONCLUSIONS: Radiofrequency catheter ablation of atrial tachycardia is feasible without complications in most patients. Bipolar activation mapping accurately localizes the successful ablation site. A "QS" pattern is not predictive of successful radiofrequency application.

[Radiofrequency catheter ablation of ventricular tachycardias in patients with postinfarction scars]. / Ablación con catéter mediante radiofrecuencia de taquicardias ventriculares en pacientes con cicatriz postinfarto.

Radiofrequency catheter ablation has recently emerged as a therapeutic option for ventricular tachycardia in postinfarction patients. However, the indications for its use and the mapping procedure remain controversial. The most common arrhythmogenic circuit found fits an "8" shape model. This model incorporates a slow conducting central area, separated from the surrounding myocardium by conduction blocking areas and with entrance and exit sites. This circuit has classically been confined in the left ventricle. However, recently successful radiofrequency catheter ablation of ventricular tachycardia has been reported from the right ventricle. Several markers for adequate positioning of the ablation catheter have been reported: local presystolic activity, isolated mid diastolic potential, transient entrainment with concealed fusion, match between electrogram-QRS and stimulus-QRS intervals, match between first postpacing interval and tachycardia cycle length and tachycardia electrocardiographic reproduction by pace-mapping. Procedure related complications are rare and the success rate is around 70%. Nevertheless, currently this technique should be limited to postinfarction patients with ventricular tachycardia meeting certain requisites.

[Mechanism and location of typical atrial flutter. Information drawn from experimental models and clinical electrophysiology]. / Mecanismo y localización del flutter auricular típico. Información obtenida de los modelos experimentales y de la electrofisiología clínica.

Several experimental models have been proposed to explain the electrocardiographic and electrophysiological characteristics of atrial flutter. In animal models based on anatomical obstacles, intercaval crush or Y like shaped lesion located in the right atrium, it has been possible to induce sustained atrial arrhythmias in which the entrainment criteria could be demonstrated. Additionally these tachycardias presented an atrialwave morphology similar to the F waves of type 1 or typical atrial flutter. Flutter type 2 could better be explained by models based on functional reentry like the leading circle. Typical atrial flutter in human, saw teeth morphology in inferior ECG leads, is though to be a circus movement located in the right atrium, as deduced of the analysis of activation sequence, resetting and entrainment phenomena from right and left atrium. Moreover the successful results of RDF ablation procedures confirm this idea. Nevertheless the delimitation of the anatomical boundaries of the reentry pathway remains inconclusive.

[Radiofrequency catheter ablation of ventricular tachycardia in patients without apparent structural cardiopathy]. / Ablación con catéter mediante radiofrecuencia de taquicardias ventriculares en pacientes sin cardiopatía estructural aparente.

BACKGROUND AND PURPOSE: It has been suggested that the efficacy of radiofrequency ablation of idiopathic ventricular tachycardia (VT) is dependent on the site of VT origin, with the efficacy being greater for VTs originating from right ventricle. The electrophysiologic characteristic and the results of radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease are reported. Special emphasis was focused to the differences observed in the pace and activating mapping between VTs originating in the right ventricle and those originating from the left ventricle and its possible implications for radiofrequency efficacy. METHODS AND RESULTS: 14 consecutive patients with idiopathic VT (7 women and 7 men, mean age 35 +/- 16 years), 8 originating in the right ventricle (RV) and 6 in the left ventricle (LTV), underwent catheter ablation using radiofrequency energy. The observation of entrainment with fusion in all LV VT suggested that the electrophysiologic mechanism was a reentry, meanwhile the RV VT were due to focal non-reentrant mechanisms. Sites for radiofrequency energy delivery were selected on the basis of pace and activation mapping in all patients less in two patients with incessant VT in whom only activation mapping was performed. 14 VT were mapped. The activation mapping demonstrated isolated presystolic electrograms in the point of origin in all VT arising from the LV. However in RV tachycardias there was continuous activity between presystolic and systolic electrograms, although the prematurity of these electrograms was similar (31 +/- 16 ms vs 33 +/- 9 ms; p = 0.77). Radiofrequency was successful in eliminating 93% of TV (100% RV TV vs 83% LV TV; p = 0.23). No complications were observed. CONCLUSIONS: The results of this study suggest that radiofrequency ablation is highly successful either in right and left ventricles idiopathic tachycardias when pace and activation mapping are used complementary.

[The surgical treatment of sustained ventricular tachycardias. The short- and midterm results in the era of the implantable defibrillator and the heart transplant]. / Tratamiento quirúrgico de las taquicardias ventriculares sostenidas. Resultados a corto y medio plazo en la "era" del desfibrilador implantable y del transplante cardíaco.

BACKGROUND: The surgical treatment of refractory ventricular tachycardia has been shown to be effective. Its use has been limited by a high perioperative mortality. OBJECTIVE: To study the extent to which the introduction of new therapeutic options, i.e. the implantable defibrillator and cardiac transplantation, improves patient selection and results of direct antiarrhythmic surgery. PATIENTS AND METHODS: We analyzed 24 consecutive patients operated upon for ventricular tachycardia (study population). At the same time, 42 patients were treated with implantable defibrillator and 11 patients, with symptomatic ventricular arrhythmias, underwent cardiac transplantation (reference population). RESULTS: The clinical characteristics of the study population (age, functional class, ejection fraction) were significantly different from those of both reference groups. Nine patients (38%) were operated upon because of electrical instability and/or contraindication for other therapeutic options despite of having criteria of high surgical risk. There was one perioperative death (4.2%) and no other early arrhythmic recurrences. Persistence of inducibility occurred in 5 cases (22%). During follow up (35 +/- 22 months) there was a single arrhythmic recurrence. Three patients died of nonarrhythmic causes. Presently, 16 patients are in I or II NYHA functional class. CONCLUSIONS: 1) Direct surgery remains as a useful tool in the treatment of ventricular tachycardia; 2) clinical differences among groups caused by the individual selection of the three therapeutic options preclude comparison of their results, and 3) the introduction of other therapeutic approaches, although resulting in only partial improvement of patient selection, leads to acceptable short and mid-term results of direct antiarrhythmic surgery.

[Determining factors of acceleration in sustained monomorphic ventricular tachycardias in response to bursts of stimuli]. / Determinantes de aceleración en las taquicardias ventriculares monomórficas sostenidas en respuesta a trenes de impulsos.

To analyse the determinants of acceleration of sustained monomorphic ventricular tachycardias in response to bursts of rapid ventricular pacing, we studied 46 consecutive patients with 90 distinct ventricular tachycardias during which one or more burst of rapid pacing were delivered. Tachycardia acceleration was observed in 11 tachycardias in 8 patients. The highest incidence of acceleration was observed in patients with left ventricular dysfunction of non coronary origin. There was a non significant trend towards lower values of left ventricular ejection fraction in patients with acceleration. There were no significant differences between ventricular tachycardias with of without acceleration in respect to: clinical presentation, QRS morphology, tachycardia cycle length and treatment with antiarrhythmic drugs. The shortest cycle of bursts of rapid pacing, was lower in tachycardias with acceleration than in those without it (229 +/- 57 ms vs 283 +/- 67 ms; p = 0.006) and tachycardias with acceleration showed a lower relation between burst cycle length and tachycardia cycle length (69 +/- 9% vs 84 +/- 8%; p < 0.001). The negative predictive value of acceleration was 75% for bursts of rapid pacing with a cycle length > or = 250 ms, and 96% for values of the relation between the burst cycle length and the tachycardia cycle length > or = 70%. This parameter show a very high discriminating value with of without antiarrhythmic drugs effect. Acceleration of sustained monomorphic ventricular tachycardias in response to bursts of rapid pacing depends on, the pacing rate and the relation between pacing rate and tachycardia rate.(ABSTRACT TRUNCATED AT 250 WORDS)