Techniques are provided for use in controlling rate-adaptive pacing within implantable medical devices such as pacemakers or implantable cardioverter-defibrillators (ICDs). In one example, a force-frequency relationship is determined for the heart of the patient, which is representative of the relationship between
cardiac stimulation frequency and myocardial contractile force. To this end, various parameters are detected for use as surrogates for contractile force, including selected systolic pressure parameters and cardiogenic
impedance parameters. Rate-adaptive pacing is then controlled based on the detected force-frequency relationship to, for example, deactivate rate-adaptive pacing if the slope and / or abscissa of the force-frequency relationship indicates significant
contractility dysfunction within the patient. In other examples, rather than deactivating rate-adaptive pacing,
control parameters are adjusted to render the rate-adaptive pacing less aggressive. In still other examples, trends in the slope and / or abscissa of the force-frequency relationship are monitored to detect
contractility dysfunction and / or
heart failure and titrate medications accordingly.