Diastolic function is monitored within a patient based on dynamic cardiogenic impedance as measured by a pacemaker or other implantable medical device. In one example, the device uses ventricular cardiogenic impedance values to detect E-wave parameters representative of passive filling of the ventricles. Atrial cardiogenic impedance values are used to detect A-wave parameters representative of active filling of the ventricles. Diastolic function is then assessed or evaluated based on the E-wave and A-wave parameters. Various functions of the implantable device are then controlled based on the assessment of diastolic function, such as by adjusting atrioventricular delay parameters to improve diastolic function. In some examples, the detection of E- and A-wave parameters is achieved by aligning impedance signals to atrial activation, and separately to ventricular activation, during asynchronous VOO pacing or while artificially inducing a 2:1 block.