A method of predicting ventricular arrhythmias includes receiving an electrical signal from a subjects heart for a plurality of heart beats, identifying characteristic intervals and heart beat durations of the electrical signal corresponding to each of the plurality of heart beats to provide a plurality of characteristic intervals with corresponding heart beat durations, representing dynamics of the plurality of characteristic intervals as a function of a plurality of preceding characteristic intervals and durations of corresponding heart beats over a chosen period time, assessing a stability of the function over the chosen period of time, and predicting ventricular arrhythmias based on detected instabilities in the dynamics of the characteristic intervals.
