Heart condition and function can be quantified using repolarization measures and/or repolarization indices derived from a time- frequency transform of an electrocardiogram, e.g., based on points in time associated with the T wave. The electrocardiograms, time- frequency maps derived therefrom, and/or indices obtained by analysis of the time-frequency maps and electrocardiograms may be assembled into a user interface. Further embodiments are described.
