Tsunetoyo Namba

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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(More)
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(More)
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(More)
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(More)
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(More)
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(More)
Spatial heterogeneity in the refractoriness of the ventricular myocardium due to a regionally prolonged refractory period has often been observed in patients with cardiovascular disease as the substrate for functional reentrant tachyarrhythmias. The present study sought to determine how functional reentrant activity could occur due to the spatial(More)
INTRODUCTION It is unclear how the patterns of wavelet propagation during ventricular fibrillation (VF) vary between structurally different tissues. We hypothesized that the structural complexities of septal tissue influence the maintenance of reentrant wavelets in the ventricle. METHODS AND RESULTS Endocardial activation patterns during VF were analyzed(More)
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(More)
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(More)