A system comprising a medical device including a processor and a Z-score transformation (ZST) module. The system also includes a display in communication with the processor. The processor is adapted to receive sensor data obtained from at least first and second sensors adapted to produce a time-varying physiologic electrical sensor signal. At least one of the first and second sensors is implantable. The ZST module calculates a ZST for the sensor data received from the first sensor and a ZST for the sensor data received from the second sensor. The display is adapted to display the ZSTs in visual correspondence with each other over time.
