Rotors anchored by refractory islands drive torsades de pointes in an experimental model of electrical storm.

Background: Electrical storm (ES) is a life-threatening emergency in patients at high risk of ventricular tachycardia/ventricular fibrillation (VF), but the pathophysiology and molecular basis are poorly understood.

Objective: The purpose of this study was to explore the electrophysiological substrate for experimental ES.

Methods: A model was created by inducing chronic complete atrioventricular block in defibrillator-implanted rabbits, which recapitulates QT prolongation, torsades des pointes (TdP), and VF episodes.

Spatial phase discontinuity at the center of moving cardiac spiral waves.

Background: Precise analysis of cardiac spiral wave (SW) dynamics is essential for effective arrhythmia treatment. Although the phase singularity (PS) point in the spatial phase map has been used to determine the cardiac SW center for decades, quantitative detection algorithms that assume PS as a point fail to trace complex and rapid PS dynamics. Through a detailed analysis of numerical simulations, we examined our hypothesis that a boundary of spatial phase discontinuity induced by a focal conduction block exists around the moving SW center in the phase map.

Inter-arm difference of systolic blood pressure measured by automated double-cuff device is associated with arterial stiffness in patients with hypertension.

Purpose: Inter-arm differences of SBP ≧5 mmHg have been associated with all-cause and cardiovascular mortalities in hypertensive subjects. Inter-arm differences of SBP appears to be mediated by arterial stiffness. We hypothesized inter-arm differences of SBP ≧5 mmHg may be related to higher pulse pressure/stroke volume index, a surrogate marker of arterial stiffness.

Interaction of phase singularities on the spiral wave tail: reconsideration of capturing the excitable gap.

The action mechanism of stimulation toward spiral waves (SWs) owing to the complex excitation patterns that occur just after point stimulation has not yet been experimentally clarified. This study sought to test our hypothesis that the effect of capturing excitable gap of SWs by stimulation can also be explained as the interaction of original phase singularity (PS) and PSs induced by the stimulation on the wave tail (WT) of the original SW. Phase variance analysis was used to quantitatively analyze the postshock PS trajectories.

Association of tricuspid regurgitation within normal range on the development of left ventricular diastolic dysfunction in patients with uncomplicated hypertension.

Aim: Tricuspid regurgitation (TR) with the maximum velocity >2.8m/s has been newly integrated into the diagnostic criteria for left ventricular (LV) diastolic dysfunction. Although the maximum velocity of TR within the normal range (TR < 2.

Ranolazine Facilitates Termination of Ventricular Tachyarrhythmia Associated With Acute Myocardial Ischemia Through Suppression of Late I-Mediated Focal Activity.

Background: Ventricular tachycardia/fibrillation (VT/VF) associated with acute myocardial ischemia is the most common cause of sudden cardiac death, but its underlying mechanisms are incompletely understood. It is hypothesized that late Nacurrent (I) contributes to arrhythmogenic activity in ischemic myocardium.

Methods and results: Langendorff-perfused rabbit hearts with regional ischemia in ventricles were optically mapped.

Partial IK1 blockade destabilizes spiral wave rotation center without inducing wave breakup and facilitates termination of reentrant arrhythmias in ventricles.

It has been reported that blockade of the inward rectifier K(+) current (IK1) facilitates termination of ventricular fibrillation. We hypothesized that partial IK1 blockade destabilizes spiral wave (SW) re-entry, leading to its termination. Optical action potential (AP) signals were recorded from left ventricles of Langendorff-perfused rabbit hearts with endocardial cryoablation.

Calmodulin/CaMKII inhibition improves intercellular communication and impulse propagation in the heart and is antiarrhythmic under conditions when fibrosis is absent.

Aim: In healthy hearts, ventricular gap junctions are mainly composed by connexin43 (Cx43) and localize in the intercalated disc, enabling appropriate electrical coupling. In diseased hearts, Cx43 is heterogeneously down-regulated, whereas activity of calmodulin/calcium-calmodulin protein kinase II (CaM/CaMKII) signalling increases. It is unclear if CaM/CaMKII affects Cx43 expression/localization or impulse propagation.

Detection Algorithm of Phase Singularity Using Phase Variance Analysis for Epicardial Optical Mapping Data.

Objective: Spiral reentry is a recognized cause of tachycardia. Detection and tracking of the spiral core are essential for understanding the spiral wave dynamics. The core of the spiral corresponds to a phase singularity (PS), which can be identified in an optical mapping image by a kernel convolution method.

The renin-angiotensin system promotes arrhythmogenic substrates and lethal arrhythmias in mice with non-ischaemic cardiomyopathy.

Aims: The progression of pathological left ventricular remodelling leads to cardiac dysfunction and contributes to the occurrence of malignant arrhythmias and sudden cardiac death. The underlying molecular mechanisms remain unclear, however. Our aim was to examine the role of the renin-angiotensin system (RAS) in the mechanism underlying arrhythmogenic cardiac remodelling using a transgenic mouse expressing a cardiac-specific dominant-negative form of neuron-restrictive silencer factor (dnNRSF-Tg).

Urinary type IV collagen is related to left ventricular diastolic function and brain natriuretic peptide in hypertensive patients with prediabetes.

Aim: Urinary type IV collagen is an early biomarker of diabetic nephropathy. Concomitant prediabetes (the early stage of diabetes) was associated with left ventricular (LV) diastolic dysfunction and increased brain natriuretic peptide (BNP) in hypertensive patients. We hypothesized that urinary type IV collagen may be related to these cardiac dysfunctions.

The role of gap junctions in stretch-induced atrial fibrillation.

Aims: The aim of this study was to investigate the role of gap junctions in atrial fibrillation (AF) by analysing the effects of a gap junction enhancer and blocker on AF vulnerability and electrophysiological properties of isolated hearts.

Methods And Results: The acute atrial stretch model of AF in the isolated rabbit heart was used. Sustained AF (SAF) was induced by a burst of high-frequency stimulation of the Bachmann's bundle.

Importance of gradients in membrane properties and electrical coupling in sinoatrial node pacing.

The sinoatrial node (SAN) is heterogeneous in terms of cell size, ion channels, current densities, connexins and electrical coupling. For example, Nav1.5 (responsible for INa) and Cx43 (responsible for electrical coupling) are absent from the centre of the SAN (normally the leading pacemaker site), but present in the periphery (at SAN-atrial muscle junction).

Utility of cystatin C as a marker for the severity of aortic regurgitation in hypertensive patients.

Background: Cystatin C, a cathepsin inhibitor, is involved in the remodeling of human aortic valve and left ventricle (LV).

Objective: Cystatin C may be related to the severity of aortic regurgitation (AR).

Methods: We measured cystatin C and CRP in hypertensive patients with mild-to-moderate AR (n=120) and in those without AR (n=128).

Acute regional left atrial ischemia causes acceleration of atrial drivers during atrial fibrillation.

Background: The mechanisms by which acute left atrial ischemia (LAI) leads to atrial fibrillation (AF) initiation and perpetuation remain unclear.

Objective: To investigate the electrophysiological mechanisms of AF perpetuation in the presence of regional atrial ischemia.

Methods: LAI (90-minute ischemia) was obtained in isolated sheep hearts by selectively perfusing microspheres into the left anterior atrial artery.

Growth rate distribution of NH4Cl dendrite and its scaling structure.

Scaling structure of the growth rate distribution on the interface of a dendritic pattern is investigated. The distribution is evaluated for an NH4Cl quasi-two-dimensional crystal by numerically solving the Laplace equation with the boundary condition taking account of the surface tension effect. It is found that the distribution has multifractality and the surface tension effect is almost ineffective in the unscreened large growth region.

Single camera system for multi-wavelength fluorescent imaging in the heart.

Optical mapping has been a powerful method to measure the cardiac electrophysiological phenomenon such as membrane potential(V(m)), intracellular calcium(Ca(2+)), and the other electrophysiological parameters. To measure two parameters simultaneously, the dual mapping system using two cameras is often used. However, the method to measure more than three parameters does not exist.

Atrial selectivity in Na+channel blockade by acute amiodarone.

Aims: Na(+) channel blockers are often used to treat atrial fibrillation (AF), but may sometimes cause ventricular contractile dysfunction. However, amiodarone, a multi-channel blocker with Na(+) channel block, causes less contractile dysfunction. In this study, we tested the hypothesis that Na(+) channel block by amiodarone is selective in atrial myocytes (AM) compared with ventricular myocytes (VM).

Cardiovascular events increased at normal and high-normal blood pressure in young and middle-aged Japanese male smokers but not in nonsmokers.

Objective: To clarify whether the impact of normal and high-normal BP (BP) per se on cardiovascular disease (CVD) and all-cause death differs depending on smoking status.

Methods And Results: A prospective observational cohort study (median follow-up period: 7.5 years) was performed among 25,077 healthy nondiabetic Japanese men aged 20-61 years (mean age 37.

Inhibition of intercellular coupling stabilizes spiral-wave reentry, whereas enhancement of the coupling destabilizes the reentry in favor of early termination.

Spiral-wave (SW) reentry is a major organizing principle of ventricular tachycardia/fibrillation (VT/VF). We tested a hypothesis that pharmacological modification of gap junction (GJ) conductance affects the stability of SW reentry in a two-dimensional (2D) epicardial ventricular muscle layer prepared by endocardial cryoablation of Langendorff-perfused rabbit hearts. Action potential signals were recorded and analyzed by high-resolution optical mapping.

Thyroid hormone within the normal range is associated with left ventricular mass in patients with hypertension.

Thyroid hormone amplifies hypertrophy of cardiac myocytes. The heart is influenced by the minimal changes of thyroid hormone levels. We hypothesized that thyroid hormone within the normal reference range may be associated with left ventricular (LV) mass in hypertensive subjects.

Pharmacological blockade of IKs destabilizes spiral-wave reentry under β-adrenergic stimulation in favor of its early termination.

We tested a hypothesis that an enhancement of I(Ks) may play a pivotal role in ventricular proarrhythmia under high sympathetic activity. A 2-dimensional ventricular muscle layer was prepared in rabbit hearts, and action potential signals were analyzed by optical mapping. During constant stimulation, isoproterenol (ISP, 0.