A hemodynamic status of a patient is determined in an implanted medical device (IMD) by observing a perturbation of the patient's heart, measuring heart rate turbulence resulting from the perturbation, and quantifying the heart rate turbulence to determine the hemodynamic status. The perturbation may be naturally-occurring, or may be generated by the implantable medical device. The patient's response to heart rate turbulence may also be used to provide a response to the patient, such as providing an alarm and/or administering a therapy. Heart rate turbulence may also be used to tune and/or optimize a device parameter such as A-V or V--V pacing intervals.