M-mode echocardiography in supine and standing position in control subjects and patients with auscultatory evidence of mitral valve prolapse but negative supine echocardiography: does sensitivity improve?

Approximately 10-20% of patients with auscultatory evidence of mitral valve prolapse (MVP) have "false negative" echocardiograms. Pharmacological maneuvers do not significantly improve the sensitivity and may cause side effects. It is well known that auscultatory features of MVP change and not uncommonly can be heard only in the standing position. Therefore M-mode echo was performed in both supine and standing positions in 10 normal control subjects and 25 patients of comparable age and sex who had auscultatory evidence of MVP but negative echo in supine position. All 10 control subjects had normal echo in both supine and standing positions. No instance of false positive MVP was noted. Of the 25 patients with "false negative" supine echo, 5 showed evidence of MVP (3 pansystolic and 2 late systolic) in standing position. Based on these results the following conclusions were reached. In normal individuals the MVE remains uninfluenced by change in posture. There is modest (20%) improvement in sensitivity of detecting MVP when M-mode echo is performed in standing position in addition to supine position. Change in posture is preferable to the use of pharmacological maneuver to improve the sensitivity of detecting MVP because it is physiological, devoid of any cost, and does not produce side effects. M-mode echo in standing position or two-dimensional echo in supine position can be used to confirm the diagnosis of MVP in those patients who have "false negative" and/or nondiagnostic supine echo in the presence of auscultatory features of midsystolic click and mid- or late-systolic murmurs.