Patent ID: 8591423

Claim:
A method of determining cardiac output within a patient's heart, the method comprising: sensing an arterial pressure waveform using a pressure sensor located within a pulmonary artery of the patient in order to sense the arterial pressure waveform on a right side of the patient's heart; identifying the systolic portion of the arterial pressure waveform sensed by the pressure sensor; identifying the beginning of a cardiac cycle and correlating the systolic portion of the arterial pressure waveform with the beginning of the cardiac cycle; identifying an estimate of the valve closure time of the pulmonary valve using the arterial pressure waveform, wherein identifying the estimate of the valve closure time of the pulmonary valve includes: determining a first point, the first point comprising a positive-going zero of a second derivative of the arterial pressure waveform; determining a second point, the second point comprising a point of maximum positive value of the second derivative of the arterial pressure waveform; and determining a midpoint in time between the first point and the second point, wherein the midpoint provides the estimate of the valve closure time of the pulmonary valve; estimating the stroke volume using the systolic portion of the arterial pressure waveform and the estimate of the pulmonary valve closure time; and obtaining a measure of cardiac output based at least in part on the estimated stroke volume.