US Patent 7925347 Assessment of cardiac output by implantable medical device

An implantable medical device calculates cardiac output on a repeated basis based on acquired cardiac information that relates to one or more parameters of the Fick equation, including venous oxygen saturation, arterial oxygen saturation, estimated oxygen consumption and hemoglobin information. In some aspects, the estimated oxygen consumption may be based on the activity of a patient. For example, respiratory-related information and/or temperature related information may be used to determine the activity level of the patient. In addition, trends relating to heart function may be identified based on cardiac output calculations that are generated over time.