Virtual Heart: Modeling Of Anatomy And Electrophysiology

By setting electrophysiology, dynamics, fluid mechanics of blood, nerves and chemical biological control together within an extremely complex integrated system, virtual heart modeling can be used to simulate the structure and function of the real heart, which is a technical work with high degree of difficulty and complexity. At present, most pathologists study the mechanism of the heart from micro-level, such as physiological cardiac cells, genes, proteins, molecules, while the majority of the experiments can only reflect in single-cell or partial identity, which can not be used to well explain how the cardiac abnormalities in micro-pathological level evolved into the macro-pathological level, and clinical cardiac experts, however, pay more attention to the overall comprehension of macro cardiac performance characteristics, less concern the micro-origined cause of the heart diseases. Their decisions of the diagnosis and treatment on complex heart disease are largely depend on experience. The virtual heart model is the effective means of connection between the micro and macro level heart research. Based on virtual heart model, doctor can study the physiological and pathological quantitative changes of myocardial conveniently in micro level and also test how the micro changes develop into the overall macro-change, which can contribute to improve the diagnosis and treatment of heart disease and the development of innovative medicines. In recent years, with the rapid development of biomedical engineering and other disciplines, there are a lot of new methods and new theories are introduced in these fields. The introduction of these methods and theories to virtual heart modeling areas can help us set up more complex and sophisticated model and sequentially in-depth understand the laws and the nature of cardiovascular system, which can eventually contribute to promote the further developing of forward and inverse problem of heart modeling studies.In this paper, we will focus on the mathematical modeling of the anatomical structure and electrophysiology of the heart. Based on the original LFX virtual heart model, the first generation of virtual heart model of Zhejiang University, with comprehensive application of the Virtual Human technology, image processing, signal processing, parallel computing, three-dimensional scientific visualization and other technical means, we try to solve the key biological computing problems and set up the new generation of Cardiome-CN virtual heart electrophysiology model, which performance indicators is on the top of the international similar models and the related technology has an important influence on promoting the development of Cardiome project. The design and implementiaon of the parallel algorithms for ionic-channel based and bidomain model equations of myocardial excitation propagation can also be used for reference of other large-scale development of bio-computing technology. In this paper, the main research work and findings include:1. Based on medical image data, physiological data samples, virtual human project dataset, we construct the database of virtual heart anatomical structure, including rabbit, dog, and human heart models. For the human heart model as an example, the spatial resolution of data structure is 0.33mm, which contains a complete atrial and ventricular structure, stratification of ventricular wall, myocardial fiber orientation, conduction pathway settings, organizations such as the definition of functional classification of heart tissue, etc. The calculation method, visualization grid of these models was also set up. The constructed human virtual heart model is one of the best virtual heart models in the world with detailed anatomy structure.2. Based on experimental data of ion channels in cardiac myocytes, we pioneeringly set up the first cardiac myocyte action potential model library of dogs, human in the domestic, which contain the pacemaker cells, atrial myocytes, ventricular myocytes and other heterogeneous models with a complete cycle of calcium and excitation-contraction coupling mechanism. We carried out in-depth research on calculation and analysis for cell model. By using of non-standard finite difference method (NSFD) and operator DVODE, we accelerate cell model computational speed and sum up the expansion of the static and dynamic analysis methods, enriching the model means. The cell models have been used for simulation of heart failure, short-QT syndrome, Brugada syndrome-related diseases.3. Based on MPI and OpenMP parallel computing protocol library, we design and implement parallel algorithms of the bidomain model, and use them to simulate the anisotropic spread of the cardiac excitation propagation. By coupling ionic channel cell model and bidomain reaction and diffusion model, we setup the one-dimensional structural conduction models to the three-dimensional anatomical conduction models and simulate the normal heart tissue conduction sequences. Then, we study the mechanism of reentrant arrhythmia by using these conduction models, which is international advanced level in the field of domestic virtual organ modeling.4. Based on real physiological structures, a virtual human heart model, Cardiome-CN, has been constructed. This model can be used to simulate myocardial ischemia, a variety of arrhythmias, genetic variation, and ionic channel function diseases.5. Based on the US virtual human project data, we build both male and female human torso models. Together with the Cardiome-CN model, we simulate the cardiac electric field distribution and body surface potential, calculate electrocardiogram and vectorcardiogram, study the the cellular mechanism of ECG morphological characteristics in arrhythmia condition.In the future, virtual heart models have great potential applications not only in the biomedical field, bu also in clinical services, including interventional treatment, the individual custom database information and so on. Especially for the clinical diagnosis needs of atrial fibrillation, ventricular fibrillation and other arrhythmias diseases, the virtual heart model can help to enhance the application value of transcatheter interventional ablation techniques. Although it can not realize the real-time reconstruction of individual cases at the present, with the improvement of the calculation ability, the individual customized virtual heart model for clinical therapy application must become a reality in the future.