A system and method for monitoring electrical dispersion of the heart is provided including an implantable medical device and associated electrode system for sensing cardiac signals from a combination of two or more local and/or global EGM sensing vectors and/or subcutaneous ECG sensing vectors. Activation and recovery times and the activation-recovery intervals are measured from a selected cardiac cycle for each sensing vector. Dispersion is determined as the differences between activation times, recovery times and/or ARIs measured from each of the sensing vectors. An increase in dispersion indicates a worsening of heart failure and/or an increased risk of arrhythmias. Accordingly, a cardiac therapy may be delivered or adjusted in response to a detected increase in dispersion.