In an implantable heart monitoring device and method, particularly for monitoring diastolic dysfunction, a control circuit (a) detects the heart rate, (b) derives information correlated to the stroke volume of the heart at the detected heart rate, and (c) stores the detected heart rate and the derived information correlated to the stroke volume in a memory. The control circuit automatically implements (a), (b) and (c) at a number of different occasions for a number of different, naturally varying heart rates, so that the memory contains information indicating the stroke volume as a function of the heart rate.
