Origin and Properties of the Electrocardiogram T-Wave
The ventricle exhibits gradients in repolarization time in both transmural and apicobasal directions. These gradients, caused by the varying strengths of cellular ionic currents in the different regions, affect the morphology of the electrocardiographic T wave. Abnormal gradients, observed clinically by alterations in the ECG, can increase susceptibility to arrhythmias, and therefore the characteristics of both gradients as well as their roles in manifesting the T wave must be understood. The UCLA rabbit ventricular action potential model is based on experimental data from rabbit ventricular myocytes along with reported ion channel properties. To recreate the repolarization gradients in the ventricle, alterations were made to the conduction of repolarizing currents, IKr and Ito,f in the single cell model to simulate the different APDs observed in-situ. The resulting cells were then incorporated into a 3D ventricle model. Simulations were performed with varying presence and direction of repolarization gradients, and an in-silico ECG was calculated. It was found that transmurally, APD epi must be shorter than APD endo and apicobasally, APD base must be shorter than APD apex to give a correct ECG.