Simulation Study Of The Mechanism Of MRI Static Magnetic Fields Influence On ECG-T Wave

Electrophysiological and cellular level study of human cardivascular system influenced by SMF (Static Magnetic Field) is of great importance. It is not only helpful to explore the reason of ECG-T wave change, but also able to provide good references for clinical diagnosis and therapy. Limited by the experimental condition, it is hard to get actual human cardivascular electrophysiological data in SMF. Therefore, the use of alternative methods such as computer simulations can gain some useful information. On the basis of previous simulation studies, we combine magneto-hydrodynamics model with electrophysiological heart model to study the mechanism of ECG-T wave change in SMF.In this thesis, based on magneto-hydrodynamics model and by changing the intensity of SMF, we calculate the volume flow rate of aorta by means of finite element method, and get induced voltage and current figures. Based on ionic-channel model of the cardiac ventricular cell, we simulate different degree of anoxia by changing the permeability of ATP-dependence of L-type calcium channel. I₍K(ATP) springed by acute anoxia and I_Ca(L) change with [ATP]_i are considered. Meanwhile, action potentials ( AP) of epicardial, M cell and endocardial cell at different intensity of SMF are also simulated.Ultrahigh SMF could induce more than 10% reduction of the volume flow rate of the blood in human arota, thus can produce anoxia condition of acute ischemia. Furthermore, we simulate the induced voltages and currents in different intensity of SMF. The cardiac action potential plateau is suppressed and thus shorten the action potential duration (APD), which result in enhanced transmural heterogeneity. The largest of APD decrease is in epicardial cell, and the smallest in endocardial cell. The ECG-T wave alternation is observed in the simulation based on dynamic electrophysiological heart model.The simulation results show that the reduction of the volume flow rate of the blood in arota may induce acute ischemia under ultrahigh SMF, and then it canproduce a significant increase in the ECG T-wave amplitude, which may be an important mechanism for the influence of ultrahigh SMF to ECG T-wave. Other factors such as the effect of dipole source and Lorentz Force or induced current which may affect ECG T-wave in ultrahigh SMF are also discussed.