Diagnosing a patient's cardiac health through the use of parameter change analysis involves a system that includes an implantable cardiac device to sense a parameter related to a patient's heart. The system further includes a parameter change detection sub-system configured to derive a trend of the parameter over time and to detect changes to the trend. The trend and detected changes can then be used to diagnose changes in the patient's cardiac health. Results of the diagnosis are stored and presented to a care physician.