In the aim to clarify the magnitude and features of alterations in left ventricular function observed in patients with mitral valve prolapse syndrome (MVPS), we studied 41 patients with MVPS with M-mode echocardiography and computerized reading of recordings (with particular regard to the diastolic phase), and compared them with a control group of 15 healthy subjects matched for age and sex. Routine morphological and functional echocardiographic parameters were evaluated and, in addition, peak rates of movement of left ventricular endocardia, of wall thicknesses change and of cavity dimensions variations were obtained. Finally, a detailed analysis of various diastolic phases have been performed, according to the method proposed by Hanrath et al. There were no significant statistical differences in the morphological echocardiographic parameters (ventricular diameters, wall thicknesses) between the two groups. Patients with MVPS showed (compared to the control group) a significant increase in the peak rate of posterior wall endocardium movement during systole (1.64 +/- 0.42 vs 1.29 +/- 0.30, p less than 0.01) and a reduction of peak rate of interventricular septum thickening (1.21 +/- 0.36 vs 1.45 +/- 0.46, p less than 0.05). The comparison of all other systolic function parameters did not show statistical differences. As far as diastolic phase is concerned, no significant differences were found in the analysis of the peak velocities. However, evaluation of the diastolic phases demonstrated, in MVPS group, a significantly shorter slow filling period, both in absolute value (185.88 +/- 78.91 vs 303.15 +/- 117.58, p less than 0.001) and in percent of the whole diastole (37.42 +/- 11.88 vs 52.50 +/- 10.61, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)