Pressure-volume analysis is provided in medical diagnostic ultrasound imaging. The heart of a patient is scanned multiple times during a given cycle. B-mode and flow information are obtained for various times. The flow information is used to estimate pressure over time. A reference pressure, such as from a cuff, may be used to calibrate the pressure waveform. The B-mode information is used to determine a heart volume over time, such as a left ventricle volume over time. The heart volume over time and pressure over time are plotted, providing a pressure-volume loop. The pressure-volume loop is determined non-invasively with ultrasound.