The role of fibroblasts in complex fractionated electrograms during persistent/permanent atrial fibrillation: implications for electrogram-based catheter ablation.

Rationale: Electrogram-based catheter ablation, targeting complex fractionated atrial electrograms (CFAEs), is empirically known to be effective in halting persistent/permanent atrial fibrillation (AF). However, the mechanisms underlying CFAEs and electrogram-based ablation remain unclear.

Objective: Because atrial fibrosis is associated with persistent/permanent AF, we hypothesized that electrotonic interactions between atrial myocytes and fibroblasts play an important role in CFAE genesis and electrogram-based catheter ablation.

Transmural dispersion of repolarization determines scroll wave behavior during ventricular tachyarrhythmias.

Background: Ventricular tachyarrhythmia is the leading cause of sudden cardiac death, and scroll wave re-entry is known to underlie this condition. Class III antiarrhythmic drugs are commonly used worldwide to treat ventricular tachyarrhythmias; however, these drugs have a proarrhythmic adverse effect and can cause Torsade de Pointes or ventricular fibrillation. Transmural dispersion of repolarization (TDR) has been suggested to be a strong indicator of ventricular tachyarrhythmia induction.

Abnormal restitution property of action potential duration and conduction delay in Brugada syndrome: both repolarization and depolarization abnormalities.

Aims: This study sought to examine the action potential duration restitution (APDR) property and conduction delay in Brugada syndrome (BrS) patients. A steeply sloped APDR curve and conduction delay are known to be important determinants for the occurrence of ventricular fibrillation (VF).

Methods And Results: Endocardial monophasic action potential was obtained from 39 BrS patients and 9 control subjects using the contact electrode method.

A procedural method for modeling the purkinje fibers of the heart.

The Purkinje fibers are located in the ventricular walls of the heart, just beneath the endocardium and conduct excitation from the right and left bundle branches to the ventricular myocardium. Recently, anatomists succeeded in photographing the Purkinje fibers of a sheep, which clearly showed the mesh structure of the Purkinje fibers. In this study, we present a technique for modeling the mesh structure of Purkinje fibers semiautomatically using an extended L-system.

Identification of local myocardial repolarization time by bipolar electrode potential.

Purpose: The aim of this study was to investigate whether bipolar electrode potentials (BEPs) reflect local myocardial repolarization dynamics, using computer simulation.

Methods: Simulated action potential and BEP mapping of myocardial tissue during fibrillation was performed. The BEP was modified to make all the fluctuations have the same polarity.

Spiral wave control by a localized stimulus: a bidomain model study.

Introduction: It has been reported that electrical stimulation can control spiral wave (SW) reentry. However, previous research does not account for the effects of stimulus-induced virtual electrode polarization (VEP) and the ensuing cathode-break (CB) excitation. The aim of the present study was to examine the interaction of VEP with SW reentry in a bidomain model of electrical stimulation and thus provide insight into the mechanistic basis of SW control.

Mechanisms of myocardial capture and temporal excitable gap during spiral wave reentry in a bidomain model.

Background: Recent studies have demonstrated that regional capture during cardiac fibrillation is associated with an elevated capture threshold. It is typically assumed that the temporal excitable gap (capture window) during fibrillation reflects the size of the spatial excitable gap (excitable tissue between fibrillation waves). Because capture threshold is high, virtual electrode polarization is expected to be involved in the process.

Vortex cordis as a mechanism of postshock activation: arrhythmia induction study using a bidomain model.

Introduction: The ventricular apex has a helical arrangement of myocardial fibers called the "vortex cordis." Experimental studies have demonstrated that the first postshock activation originates from the ventricular apex, regardless of the electrical shock outcome; however, the related underlying mechanism is unclear. We hypothesized that the vortex cordis contributes to the initiation of postshock activation.

Differences in sympathetic and vagal effects on paroxysmal atrial fibrillation: a simulation study.

The incidence of paroxysmal atrial fibrillation (AF) is affected by circadian variations in the vago-sympathetic balance. It is well known that both sympathetic and vagal effects increase the onset of paroxysmal AF, due to the shortened action potential duration. However, the reason why the vagally-mediated paroxysmal AF is maintained more than the adrenergically-mediated paroxysmal AF has remained unclear.

Widening of the excitable gap and enlargement of the core of reentry during atrial fibrillation with a pure sodium channel blocker in canine atria.

Background: This study aimed to assess the effects of pilsicainide, a pure sodium channel blocker, on electrophysiological action and wavefront dynamics during atrial fibrillation (AF).

Methods And Results: In a newly developed model of isolated, perfused, and superfused canine atria (n=12), the right and left endocardia were mapped simultaneously by use of a computerized mapping system. AF was induced with 1 to 5 micromol/L acetylcholine.

Afterdepolarizations promote the transition from ventricular tachycardia to fibrillation in a three-dimensional model of cardiac tissue.

Recent experimental results regarding the action potential duration restitution curve have explained the transition from ventricular tachycardia (VT) to fibrillation (VF) in terms of spiral wave (SW) meandering and breakup. However, it remains unclear whether VF always has a steep restitution curve. The present study was designed to test the hypothesis that afterdepolarizations occur at excitable gaps during VF and affect the SW dynamics, even if the restitution curve is gentle.