In this study particle image velocimetry (PIV) is used to measure and visualise the blood flow through a leaking mitral heart valve. The results are compared with the results from Doppler echocardiography and computational fluid dynamics (CFD). Using CAD, five-axis milling and Rapid Prototyping Machining (RPM) technology, a hydraulic in vitro flow model was developed and constructed which is compatible with flow investigation with 2D normal speed PIV and 2D Doppler echocardiography. The same CAD model was used to conduct the CFD analysis. PIV results compared successfully with Doppler echo and CFD results, both in the upstream converging region and downstream the turbulent regurgitated jet zone. These results are expected to improve the assessment of mitral valve regurgitation severity with Doppler echocardiography in clinical practice.