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To investigate complex electrophysiological behaviour (such as reentrant cardiac arrhythmias) in the setting of the complex anatomy of the heart, the use of a simplified model is computationally more effective. In this study, the Rogers-modified FitzHugh-Nagumo model was further modified to allow control of action potential upstroke velocity, conduction velocity, action potential duration and refractory...
Cardiac rhythm is irregular with heart rate varies from time to time. Heart rate variation (HRV) is clinically relevant and indicative of a pathological condition. However, the mechanisms underlying the HRV are still controversial and stochastic nervous modulation may be a major responsible factor. In this study, we implemented a computer simulation study to investigate a causative link between stochastic...
Volume rendering of 3D anatomical and medical data would be valuable in medical diagnosis and surgical planning. In this paper, we investigated the visualization of the segmented heart obtained by the cross-sectional data from the Visible Human Project, and proposed an accelerated rendering method to speed up the original ray-casting rendering method. To provide a satisfactory visualization quality...
Slow conduction through the Purkinje-ventricular junction (PVJ) is thought to result in conduction block and ultimately re-entry under certain pathological conditions. The relationships between tissue structure, conduction velocity and the safety of conduction at such junctions however, are unknown. We developed an electrophysiologically detailed 3D model of the PVJ and varied the Purkinje fibre thickness...
Atrial fibrillation (AF) is commonly associated with rapid excitation of the atria, but mechanisms of its initiation are unknown. Intracellular Ca2+ dynamics has been shown to affect cell restitution properties and, as a result, patterns of rapid reentrant excitation in ventricles at early stages of ventricular fibrillation. We study effects of the intracellular Ca2+ concentration changes on restitution...
Experimentally observed differences in the action potential (AP) properties - primarily, refractoriness - between the left (LA) and right (RA) atria are believed to be important in maintaining atrial fibrillation (AF). However, relationships between the underlying ionic differences in the LA and RA cells, as well as their impacts on the tissue refractoriness and susceptibility to AF are unknown. We...
We postulated that atrial fibrillation (AF) induced electrical remodelling in electrically heterogeneous human atria facilitates chronic AF. A modern biophysically detailed mathematical model of human atrial action potential was modified to incorporate electrophysiological properties of different cell types present within the atria. The heterogeneous cell models were then further modified to incorporate...
The diversity and complexity of cardiac tissues makes it very challenging to visualize 3D cardiac magnetic resonance image (MRI) data. In this paper, we proposed an adaptive volume data preprocessing approach, and used a semi-automated transfer function for volume rendering of the pre-processed cardiac MRI data. To improve the quality of 3D cardiac MRI data, we first used a three-dimensional median...
The idea of this research is to determine how long in advance can we predict the onset of paroxysmal atrial fibrillation (PAF) from the HRV data. Having established such methods with great confidence it is possible to avert the PAF onset using pacing techniques, thus reliving patient pains.
Idiopathic short QT (SQT) syndrome is a recently identified, genetically heterogeneous condition characterized by abbreviated QT intervals and an increased susceptibility to arrhythmia and sudden death. In this computer simulation study, we identify the mechanisms by which cellular electrophysiological changes in the SQT syndrome associated with V307L KvLQT1 (KCNQ1) gene mutation (the gene coding...
Remarkable differences in action potential properties between the Purkinje fibre and ventricular cells may lead to abnormalities in excitation conduction through the Purkinje-ventricular junction (PVJ) and arrhythmogenic behaviour. We develop a family of electrophysiologically detailed computer models for rabbit epicardial, midmyocardial and endocardial ventricular myocytes, as well as the rabbit...
We computationally evaluated the functional roles of atrial fibrillation induced electrical remodelling (AFER) on human atrial electrical excitations at cellular, tissue and whole organ levels. Our results show that AFER produced a dramatic reduction in action potential duration, slowing down of intra-atrial conduction, decrease in tissuepsilas temporal vulnerability, but remarkable increase in tissuepsilas...
In both human and animal mammals, the pacemaker of the heart, the sinoatrial node (SA node), deteriorates with age. The main features of the aged SA nodes are a slow pacemaking rate and possible SA node-atrium conduction exit block or arrest of SA node pacemaking (i.e., termination of the SA node pacemaker activity). The mechanisms underlying the age-related dysfunction of the heart are unclear. In...
We have developed a three-dimensional computational wedge model of canine cardiac ventricular wall electro-physiology that incorporates biophysically detailed, spatially heterogeneous excitation, and high-resolution geometry and fibre orientation. Isolated cell model electrophysiological characteristics reproduce the experimentally observed characteristics under control conditions, and under conditions...
Sinoatrial (SA) node, the pacemaker of the heart, is a structurally and functionally complex tissue. The role of this complexity in initiation and conduction of the pacemaker activity is not fully understood. Computer modeling provides a powerful alternative way to experiment in studying complex cardiac phenomena. In this work we combine histological, immunochemical, electrophysiological data with...
Atrial arrhythmias (flutter and fibrillation) are characterised by rapid and irregular activation of atrium. There are two possible mechanisms: abnormal spontaneous electrical activity of ectopic foci and multiple reentrant wavelets. In this study, we developed a biophysically detailed computer model of virtual human atrium to study the interaction between the two major arrhythmic origins. Depending...
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