Reduction of right ventricular pacing with advanced atrioventricular search hysteresis: results of the PREVENT study.

Background: Right ventricular pacing predisposes to the development of heart failure and atrial fibrillation. Automatic atrioventricular search hysteresis (AVSH) is a commonly used strategy to decrease the percentage of right ventricular pacing (%VP) in patients without permanent AV block, but the results have not been optimal.

Methods: The randomized, crossover PREVENT study evaluated whether an enhanced AVSH with two new features can reduce %VP compared with standard AVSH.

Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: incidence, electrophysiological characteristics, and results of radiofrequency ablation.

Aims: To investigate the incidence, electrophysiological properties, and ablation results for left atrial (LA) tachycardia as a sequel to the circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF).

Methods And Results: Sixty-seven patients with AF underwent CPVA. Sustained LA tachycardia developed in 21/67 (31%) patients and in 16/21 symptomatic patients 55 LA tachycardias (3.

Catheter ablation of left atrial focal tachycardia guided by electroanatomic mapping and new insights into interatrial electrical conduction.

Background: Experience in catheter ablation of left atrial (LA) focal tachycardia and information about interatrial electrical connections during LA focal tachycardia are limited.

Objectives: The purpose of this study was to describe our experience in electroanatomic mapping-guided catheter ablation of LA focal tachycardia and to investigate interatrial electrical connections during LA focal tachycardias.

Methods: Thirty-three patients undergoing catheter ablation for LA focal tachycardia guided by electroanatomic mapping were reported.

Acute and long-term results of slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia--an analysis of the predictive factors for arrhythmia recurrence.

Background: Predictors of atrioventricular nodal reentrant tachycardia (AVNRT) recurrence after radiofrequency ablation including the importance of residual slow pathway conduction are not known. The aim of this study was to report the acute and long-term results of slow pathway ablation in a large series of consecutive patients with AVNRT and to analyze the potential predictors of arrhythmia recurrence with a particular emphasis on the residual slow pathway conduction after ablation.

Methods: The study included 506 consecutive patients with AVNRT (mean age 52.

C825T polymorphism of the G-protein beta3 subunit gene and atrial fibrillation: association of the TT genotype with a reduced risk for atrial fibrillation.

Background: A polymorphism consisting of a C825T substitution in the G-protein beta(3) subunit gene (GNB3) has been associated with enhanced human atrial inward rectifier potassium currents regarding the TT genotype. Therefore, we investigated a possible impact of the GNB3 C825T polymorphism on atrial fibrillation in an association study.

Methods: Two hundred ninety-one consecutive patients admitted to our center with atrial fibrillation (age, 58 +/- 10 years) and 292 consecutive control patients without atrial tachyarrhythmias (59 +/- 11 years) were genotyped for the C825T polymorphism.

Incidence of antitachycardia therapy suspension due to magnet reversion in implantable cardioverter defibrillators.

Electromagnetic interference may result in transient or persistent suspension of antitachycardia therapies in ICDs. The incidence of such events has not been assessed so far. Patient charts were retrospectively analyzed for the occurrence of temporary suspension of antitachycardia therapies as it is stored in the Holter of St.

Exaggerated electrodermal startle responses after intracardiac shock discharges in patients with implanted cardioverter defibrillators.

Objective: We studied whether repetitive intracardiac shock discharges of implantable cardioverter defibrillators (ICDs) provoke an enduring enhancement of startle responses.

Methods: The study population comprised 134 patients with an ICD. Among those, 67 patients had experienced shock delivery.

Circumferential mapping and electric isolation of pulmonary veins in patients with atrial fibrillation.

Information about the clinical efficacy and complications of the circumferential mapping and isolation of the pulmonary veins (PVs) in patients with atrial fibrillation (AF) is still limited. The present study included 75 patients (mean age 58 +/- 11 years, 20 women) with paroxysmal (n = 69) or persistent AF (n = 6). Mapping of PVs was performed with a circumferential mapping catheter.

Radiofrequency ablation of cardiac arrhythmias using a three-dimensional real-time position management and mapping system.

A recently developed three-dimensional real-time position management system (RPM) uses an ultrasound ranging technique that enables multiple distance measurements between two reference catheters and a mapping catheter each equipped with ultrasound transducers. In addition to three-dimensional representation of the catheters and ablation sites it displays real-time movements of catheters (including the tip and shaft). A recently released version of the system enables additional geometry reconstruction of the heart chamber and activation mapping.

Direct and indirect catheter-to-catheter carbonization caused by high power radiofrequency delivery via a large tip ablation electrode.

We report two cases of directly and indirectly induced catheter carbonizations by radiofrequency application via a large tip ablation catheter. We assume that during a large tip high power delivery of more than 50 watts, an adjacent, smaller-sized, low resistance electrode produces a local increase in the intensity of the current field that is sufficient to elevate the tissue temperature above 100 degrees C. Due to the potential risk of embolism, this may have an impact on ablation procedures in the left atrium and ventricle using similar mapping configurations.

Psychophysiological correlates of peritraumatic dissociative responses in survivors of life-threatening cardiac events.

The psychophysiological startle response pattern associated with peritraumatic dissociation (DISS) was studied in 103 survivors of a life-threatening cardiac event (mean age 61.0 years, SD 13.95).

Characterization of paroxysmal and persistent atrial fibrillation in the human left atrium during initiation and sustained episodes.

Introduction: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes.

Methods And Results: The study population consisted of 21 patients (15 men and 6 women; mean age 58+/-9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF.

Biatrial multisite mapping of atrial premature complexes triggering onset of atrial fibrillation.

Pulmonary veins are considered to be the most common origin of the focal activity that triggers the onset of atrial fibrillation (AF). However, little is known about the importance of ectopic activity located outside the pulmonary veins. This study included 45 patients (8 women and 37 men, mean age 55 +/- 12 years) with paroxysmal (n = 25) and persistent (n = 20) AF in whom multisite mapping of the right and left atria was performed using a 64-electrode basket catheter (n = 21) or a noncontact mapping system (n = 24).

Pseudotermination of intermittent atrial fibrillation by a pacemaker algorithm: antitachycardia pacing without capture miscounted as successful termination of fibrillation episodes.

A patient is described with intermittent AF and an implanted pacemaker which provides preventive pacing and overdrive stimulation designated to terminate atrial arrhythmias. The case highlights the possibility of false estimation of therapeutic efficacy and possible proarrhythmic effect of this therapeutic modality.

Activation patterns in the left atrium during counterclockwise and clockwise atrial flutter.

Introduction: Activation of the left atrium (LA) in patients with isthmus-dependent right atrial flutter (AFL) has not yet been studied. The aim of this study was to analyze the activation patterns in the LA in patients with counterclockwise and clockwise AFL.

Methods And Results: The study population consisted of 12 patients (10 men and 2 women; mean age 61+/-13 years) with documented AFL and atrial fibrillation referred for ablation.

Clinical experience with a novel multielectrode basket catheter in right atrial tachycardias.

Background: The complexity of atrial tachycardias (ATs) makes the electroanatomic characterization of the arrhythmogenic substrate difficult with conventional mapping techniques. The aim of our study was to evaluate possible advantages of a novel multielectrode basket catheter (MBC) in patients with AT.

Methods And Results: In 31 patients with AT, an MBC composed of 64 electrodes was deployed in the right atrium (RA).

Internal cardioversion of atrial fibrillation with a single lead configuration in a patient with massive diaphragmatic herniation.

An anatomically related circumstance is reported as indication for the internal low energy cardioversion instead of an external approach. A new single lead electrode configuration is described.

Does radiofrequency catheter ablation induce a deterioration in sympathetic innervation? A positron emission tomography study.

Radiofrequency catheter ablation (RFCA) is an effective treatment for the interruption of accessory bypass tracts in WPW syndrome or the modification of the AV-nodal conduction system in patients with AV-nodal tachycardias. However RFCA may also damage cardiac innervation. The purpose of this pilot study was to assess possible changes in sympathetic innervation after RFCA as evaluated by the cathecholamine analog carbon-11-hydoxyephedrine (HED) positron emission tomography (PET) which allows the visualisation of sympathetic nerve terminals.

Intraoperative recordings of monophasic action potentials with chronically implantable pacemaker leads.

Since the development of fractally coated Iridium electrodes recordings of monophasic action potentials are possible. Intraoperative recordings of MAP from 15 pacemaker implantations were done after positioning the chronically implantable pacemaker leads (Biotronik, Berlin, Germany) in the right ventricle by using five screw-in electrodes and ten anchor electrodes. Intraoperative recordings of MAP are possible with all implanted pacemaker leads.

Frequency dependence in the action of the class III antiarrhythmic drug dofetilide is modulated by altering L-type calcium current and digitalis glucoside.

We investigated how modulation of L-type calcium current affects the class II antiarrhythmic effect of dofetilide. Action-potential duration (APD) was determined in guinea pig papillary muscle by microelectrode techniques at different stimulation frequencies (0.5-3 Hz).

Rate-independent effects of the new class III antiarrhythmic agent ambasilide on transmembrane action potentials in human ventricular endomyocardium.

The electrophysiologic effects of ambasilide, a new class III antiarrhythmic drug reported to be a nonselective blocker of both components (I(Kr) and I(Ks)) of the delayed-rectifier potassium current (I(K)) and other repolarizing potassium currents (I(tol), I(so)), were studied in specimens of left ventricular endomyocardium of human hearts obtained from 10 patients undergoing either heart transplantation (n = 4) or mitral valve replacement (n = 6). We recorded transmembrane action potential (TAP) characteristics at different stimulation frequencies (0.5, 1, 1.

Differential class III antiarrhythmic effects of ambasilide and dofetilide at different extracellular potassium and pacing frequencies.

We studied the effect of two new class II antiarrhythmics, ambasilide and dofetilide, on the action potential duration (APD) of guinea pig right ventricular papillary muscle at different extracellular potassium concentrations ([K+e]) and pacing frequencies. Under normal [K+e], both drugs significantly prolonged APD90 (APD at 90% repolarization) at 0.5 Hz.