A simulation of qrs-t wave based on the transmembrane action potential of myocardial cell

The QRS-T wave was simulated by a mathematical model of electrical heart activity, and quantitative relationship was investigated between the T wave polarity and the ventricular gradient. A rectangular solid model was constructed for this study, which was composed of the working myocardium and the excitation conduction system uniformly distributed on the endocardial surface. The propagations of both depolarization and repolarization processes can be determined mathematically in this model for a given ventricular gradient and values of conduction velocities of the conduction system and the working myocardium. The electrical potentials at given points in a homogenous infinite volume conductor were calculated as the sum of the time-varying dipoles in each 1 mm cubic block (60, 000 blocks in total), which was calculated on the basis of transmembrane action potentials. The present model reproduced the characteristic patterns of the QRS complex and T wave seen in clinical electrocardiograms, and disclosed that the ventricular gradient more than 20 ms/cm as the difference of the duration of action potentials between the endocardial and epicardial surfaces can produce the positive-polarity T wave in the left precordial leads, although the T wave polarity is much influenced by the conduction velocities of the myocardium and the conduction system as well as the ventricular gradient.