In some examples, determining a health status includes using an implantable medical device configured for subcutaneous implantation and comprising at least one optical sensor. Processing circuitry of a system comprising the device may determine, for a patient, a current tissue oxygen saturation value based on a first signal received from the at least one optical sensor and a current pulsatile oxygen saturation value based on a second signal received from the at least one optical sensor. The processing circuitry may further compare the current tissue oxygen saturation and current pulsatile oxygen saturation values to corresponding baseline values, determine corresponding heart failure and pulmonary statuses of the patient based on the comparisons, and determine the health status of the patient based on the statuses.
