Method and apparatus for determining right ventricular ejection fraction from high fidelity thermodilution curves

A method of determining right heart ejection fraction comprising injecting a cold indicator into the right ventricle or locations in the heart upstream thereof during an injection period and allowing the indicator to be diluted with blood and flow to the pulmonary artery whereby the temperature of the fluid in the pulmonary artery falls and then rises, measuring the temperature of the fluid in the pulmonary artery at least during the time that the temperature in the pulmonary artery is rising, measuring a prebolus temperature of the blood in the pulmonary artery prior to the time that the cold indicator reaches the pulmonary artery, establishing a post bolus baseline temperature which is lower than said prebolus baseline temperature, comparing at least some of the measured temperatures during the time that the temperatures of the fluid in the pulmonary artery are rising to the post bolus baseline temperature to establish temperature differentials, and using at least some of the temperature differentials to determine ejection fraction.