Can the parasternal long axis plane replace the apical four-chamber plane in diagnosing mitral valve prolapse?

Since the mitral anulus is now known to be saddle-shaped, use of the qualitative motion of the mitral valve (MV) leaflets in the apical four-chamber plane to diagnose mitral valve prolapse (MVP) may be unsound, in that superior systolic displacement of the MV leaflets would occur in normal subjects, as well as in patients with MVP. It has therefore been suggested that the parasternal long axis (PLAX) plane should be used to diagnose MVP. To test the feasibility of this approach, the authors examined the predictive accuracy of PLAX prolapse and other isolated echocardiographic abnormalities versus a multivariate decision tree approach. PLAX prolapse, which was significantly associated with marked (greater than 0.7 cm) apical four-chamber prolapse, mitral regurgitation, the presence of a thick mitral valve, and low relative body weight, was 100% specific for MVP but only 44% sensitive. Similarly, marked apical four-chamber prolapse was 100% specific but only 53% sensitive. Apical four-chamber prolapse, if gauged only qualitatively as present or absent, was 94% sensitive but only 50% specific. By contrast, the decision tree classified all 32 initial patients correctly, and in a second, test set, selected 6 additional patients; these 6 patients had many of the clinical features of MVP. These observations suggest that: (1) if prolapse is seen in the PLAX plane, the patient does have MVP; on the other hand, lack of prolapse in this plane does not exclude the diagnosis of MVP and (2) the apical four-chamber plane, used qualitatively, does not reliably distinguish patients with MVP from those without MVP.