Patent ID: 8165676

Claim:
An implantable medical device, comprising: a light source emitting light comprising a first light wavelength corresponding to a blue to ultraviolet light spectrum and a second wavelength corresponding to a red to infrared light spectrum; a light detector receiving light emitted by the light source and scattered by a volume of body tissue, the light detector emitting a first signal correlated to the received light having the first light wavelength and a second signal correlated to the received light having the second wavelength; a processor configured to: receive the first signal and the second signal from the light detector; determine a divergence between the first signal and the second signal; and determine patient condition in response to the divergence; and further comprising an electrode for sensing cardiac electrical signals, wherein the processor receives the cardiac electrical signals and detects a heart rhythm in response to the cardiac electrical signals, and wherein the processor determines the patient condition further based at least in part, on the heart rhythm.