An implantable medical device that includes an optical sensor for providing a signal corresponding to light attenuation by a volume of blood perfused tissue, a control module coupled to the optical sensor controlling the light emitted by the optical sensor, a monitoring module receiving an optical sensor output signal and measuring light attenuation, a tissue electrode for stimulating the volume of blood perfused tissue, a pulse generator coupled to the tissue electrode for delivering electrical stimulation to the volume of blood-perfused tissue, and a processor coupled to the cardiac electrode and the monitoring module and configured to detect an arrhythmia in response to the depolarization signals, compute a tissue oxygenation measurement and control the pulse generator to deliver electrical stimulation to the volume of blood-perfused tissue in response to detecting the arrhythmia, and detect a hemodynamic status of the arrhythmia in response to at least one of a detected rate of tissue oxygenation decline and a detected rate of tissue oxygenation recovery.