High frequency components (HFC) of ECG are often observed in patients with myocardial infarctions and other cardiomyopathies. However the genesis of HFC is still unknown. We supposed that these HFC are caused by time-dependent distortions of excitation fronts passed through the scattered myocardial necroses in the myocardium. In order to validate this supposition, we performed computer simulations using a square-shaped two-dimensional myocardium whose activities and conduction properties were reproduced by Luo-Rudy model and bidomain model, respectively. Micro-necroses were realized as conductive regions, and quasi-ECG were obtained by integrating the electromotive force density, which is assumed to be proportional to the spatial gradient of the membrane potential distribution, over the myocardium. Power spectrum density analyses were performed on the quasi-ECG during QRS periods. As the result, it is suggested that the micro-necroses actually cause HFC, and the highest frequency is equal to the inverse of the passing time of the excitation fronts around the micro-necroses.
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