A device for non-invasively measuring at least one parameter of a cardiac blood vesselin a patient is provided. The device comprises at least one light source that emitslight in the 400 nm to 1000 nm wavelength range at least one photodetector adaptedto receive light emitted by the light source and generate an output based on thereceived light, wherein said light is reflected from or transmitted through tissueof the patient, the output of said photodetector being correlated with a parameterof the blood vessel and at least one probe for facilitating delivery of lightfrom the light source to an external tissue site on the patient in the proximity ofthe cardiac blood vessel and receipt of light by the photodetector. A system andmethods of monitoring/measuring cardiac parameters utilizing the device and/orsystem are also provided.
