Objective    To evaluate the value of real-time three dimensional transthoracic echocardiography in diagnosing mitral valve prolapse.     Methods    Thirty-four patients with mitral valve prolapse with moderate mitral regurgitation were examined by real-time three dimensional transthoracic echocardiography preoperatively. The categories of mitral pathological change and compartmental localization were judged and recorded

and were compared with surgical findings. Carpentier’s nomenclature was applied to the mitral valve anatomic localization of real-time three dimensional echocardiography and surgery. Three anterior leaflet scallops were defined as A1

A2 and A3

and 3 posterior leaflet scallops were defined as P1

P2 and P3. The surgeons recorded the pathology of mitral valve prolapse

ruptured chordae

and the location of scallop lesions in each leaflet scallop.     Results    The shape and spatial structure of the anterior and posterior leaflets was clearly displayed using real-time three dimensional transthoracic echocardiography

and the mitral valve and its chordae tendineae were observed through left atrium view and left ventricular view. Compared with surgery findings

the accuracy rate of real-time three dimensional transthoracic echocardiography in diagnosing mitral valve prolapse was 100% qualitatively

94.1%(32/34) in diagnosing the categories of mitral pathological change

and 91.2% (31/34) in localizing the diseased region with the anterior and posterior mitral valve.     Conclusion    Real-time three dimensional transthoracic echocardiography can clearly display the pathological shape of the mitral valve prolapse

accurately localize the diseased region

and provide reliable evidence to design surgical procedure plans. It has essential value in diagnosing mitral valve prolapse.