A method for evaluating diastolic function of a heart includes measuring a volumetric flow of blood through the heart and determining volume change rates during a diastolic flow period. A diastolic index is formulated from a combination of volume change rates and features of the volumetric change and is weighted by the index for evaluating the weighted feature at a heightened sensitivity against a preselected value. The index weighting provides a measure of diastolic filling performance specific to the weighting parameter. As a result, guidance is provided in evaluating volume changes in heart failure patients, cardiac diastolic performance, medication/titration for diastolic performance, an athletic training program, and cardiac reserve. Guidance is also provided for improving exercise capacity in patients with diastolic dysfunction without requiring the patient to be evaluated during exertion.