A system for heart performance characterization and abnormality detection processes a heart electrical activity signal in determining multiple first signal characteristic values over multiple heart cycles. A first signal characteristic value substantially comprises a time interval between a peak of a P wave to a peak of a succeeding R wave representing a repolarization time interval in an individual heart cycle and the signal processor uses a peak detector and time detector for identifying the peaks and detecting a time difference between the identified peaks. A comparator compares at least one of the multiple first signal characteristic values or a value derived from the multiple first signal characteristic values with a threshold value to provide a comparison indicator. A patient monitor in response to the comparison indicator indicating a calculated signal characteristic value exceeds the threshold value, generates an alert message associated with the threshold.