This invention relates to the healthcare industry and to a novel non-invasive body surface bipolar ECG to monitor the action potential (AP) of the myocardium muscle. The invention uses surface ECG signals to deduce information on the cardiac ion channels, founded on the reconstruction of the epicardial ECG T-wave using a single transfer filter function of the frequency domain. Ion channels conductances obtained are then used to calculate action potential EndAP, EpiAP and MAP of the myocardium. These APs values can in turn be used to calculate post drug transmural dispersion of repolarisation values to giving an indication of possible cardiac arrhythmias. The invention further relates to various apparatus for carrying out the invention, including an array of bipolar electrodes which in use is arranged on the body surface so as to comprise multiples of orthogonally bisecting electrodes.
