The present disclosure relates to a method of assessing heart function and a system for assessing heart function. In detail, the present disclosure relates to a measuring a change in oxygenation or blood flow in the heart of the subject in response to a breathing maneuver and comparing the change in oxygenation or blood flow to a control. The change in oxygenation may be measured by segmenting an image of a heart, determining the signal intensity of a region of interest in a segment of the image and comparing the signal intensity to a control. An abnormal change in oxygenation blood flow or signal intensity in the heart compared to the control is indicative of reduced heart function. The disclosure further relates to a system for diagnosing heart disease which comprises an imaging device and processor configured to assess heart function.
