A method determines cardiac output or stroke volume by receiving signal data representing multiple parameters of a patient concurrently acquired over a particular time period and comprising at least one of, (a) a parameter derived from an ECG waveform of the patient, (b) a parameter derived from a blood pressure signal of the patient, (c) a parameter derived from signal data representing oxygen content of blood of the patient and (d) a parameter derived from a patient cardiac impedance value. A selected parameter of the multiple concurrently acquired parameters is used in calculating a heart stroke volume of the patient comprising volume of blood transferred through the blood vessel in a heart cycle, in response to, a combination of a weighted summation of values of the selected parameter over the particular time period. Data representing the calculated heart stroke volume is provided to a destination device.
