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This article contains a review of some of the most important studies in the field of arrhythmias and cardiac electrophysiology that have been reported in publications during the last year. They were selected because of their clinical relevance and because they made a positive contribution to the continuing technological development of the invasive procedures used in cardiac electrophysiology.

Introduction and Objectives: The aim was to investigate the clinical effectiveness of using antiarrhythmic drugs after electrical cardioversion in patients without structural heart disease, including their effect on the maintenance of sinus rhythm., Methods: In total, 528 patients with persistent atrial fibrillation but without significant structural heart disease who underwent successful electrical cardioversion at 96 Spanish hospitals were followed up for 1 year. Patients were assessed at 1, 3, 6 and 12 months. The use and effectiveness of antiarrhythmic drugs for preventing the recurrence of persistent atrial fibrillation was evaluated., Results: Some 80% of patients were receiving antiarrhythmic drugs at discharge, most frequently amiodarone. No specific clinical factor was associated with greater use of antiarrhythmics. Overall, 37% of patients were in sinus rhythm at all follow-up assessments. At the 1-year assessment, 59% of patients who remained in sinus rhythm were still taking antiarrhythmic drugs. Multivariate Cox regression analysis identified weight (hazard ratio [HR]=1.01 per kg; P=.04) and no antiarrhythmic treatment (HR=1.59; P=.001) as being independently associated with the recurrence of persistent atrial fibrillation. Amiodarone tended to be better than other antiarrhythmic drugs., Conclusions: In routine clinical practice, the large majority of patients without structural heart disease received antiarrhythmic drugs, most frequently amiodarone, after successful electrical cardioversion. Drug use was the principal factor associated with the maintenance of sinus rhythm at 1 year.

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.

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.

In the present manuscript the information concerning electrical therapy of atrial fibrillation (AF) to prevent its development and to control its consequences (excluding ablation which will be covered in separate manuscripts of this series) is reviewed. Both presently conventional approaches and those undergoing investigation will be considered, under three general headings. Electrical stimulation to prevent the development of AF. Based on non controlled studies comparing VVI stimulation with other modalities that include stimulation of the atria, it was suggested that atrial stimulation could prevent AF recurrences in patients with sinus node dysfunction. This concept has been questioned in recent studies. In contrast, the hypothesis that specific ways of atrial stimulation (stimulation at sites other than the high right atrium, multisite simultaneous or with certain "delays" atrial stimulation) may be more efficacious is presently under enthusiastic assessment. Electrical stimulation to control ventricular response. Despite the evidence that ventricular stimulation may contribute to regularization and rate control during AF, its quantitative value seems to be scarce and, thus, is not of regular use in practice. Automatic implantable atrial defibrillator. Both animal experiments and clinical studies have demonstrated that the atria can be defibrillated using intracavitary electrodes with less than 3 joules in most cases, and without risk of inducing ventricular tachyarrhythmias as long as shocks are synchronized to the R wave and the preceding R-R interval is not short. Although an implantable atrial defibrillator is already undergoing clinical evaluation, the subject of tolerability of patients to shocks for non malignant arrhythmias is still controversial, since even low energy shocks seem to be painful.

This report describe a 69-year old woman with a congenital aneurysm of the non-coronary sinus of Valsalva ruptured in the right atrium, causing severe hemodynamic derangement of the right ventricle. The site of the communication between the aneurysm and the receiving chamber was accurately diagnosed by two-dimensional color flow Doppler imaging which provided more valuable preoperative information than conventional aortography.