[Prevention of sudden death after myocardial infarction: should the "MADIT" strategy be generally applied? Arguments against]. / Prevención de la muerte súbita postinfarto de miocardio: debe generalizarse la estrategia "MADIT"? Argumentos en contra.

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) suggests that survival in patients with prior myocardial infarction, asymptomatic unsustained ventricular tachycardia and reduced left ventricular function was better among the patients who received implantable cardioverter defibrillator than that in the drug-treatment group. Nevertheless the absence of data about the efficacy and security of the conventional antiarrhythmic treatment weakness its result and clinical applicability.

[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)