A method for predicting risk of sudden cardiac death through analysis of surface electrocardiographic data includes processing a continuous EKG signal received for a subject over a predetermined time period to identify and extract a plurality of cardiac repolarization phase curves from the EKG signal, assigning each of the cardiac repolarization phase curves into one of a plurality of groups based on a length of the cardiac repolarization phase curve, generating a respective graphical representation for each of the groups in which the cardiac repolarization phase curves assigned to the group are superimposed with one another in the respective graphical representation for the group, and evaluating the graphical representations to assess a risk of sudden cardiac death for the subject based on a classification of cardiac repolarization instability indicated by the graphical representations.
