Modelling cardiac repolarisation for the study of the T wave: effect of repolarisation sequence

The electrocardiogram is of major importance in the diagnosis of heart disease. Cardiac repolarisation is the result of the return to a resting state of myocardial cells, and is detected on the surface 12-lead ECG as the T wave. The exact mechanisms responsible for the T wave shape are not completely understood. In this work, using our computer model of left ventricular repolarisation, we investigated the effect of different action potential duration gradients on the T wave in order to understand which are the most important in determining T wave shape. Three different repolarisation sequences (no base to apex epicardial gradient, no posterior to septal wall gradient and no epicardial gradient) were simulated and the T waves on the 12-lead ECG were computed and compared with those resulting from a normal repolarisation sequence. Results show that T wave shape is little affected by the specific repolarisation sequence, although its polarity in the 12 leads is dependent upon it. We found that including only the epicardium to endocardium gradient, the most common T wave polarity pattern across the 12 leads was generated, while eliminating the posterior to septal wall gradient produced abnormal T wave inversion in leads V4 and V5. This suggests that the epicardium to endocardium gradient is the most important for producing the T wave shape. These results are in agreement with experimental evidence.