In an effort to clarify the genesis of the opening snap (OS) of mitral stenosis (MS), the frequency versus
amplitude spectra of OS of 30 patients were obtained using the FFT algorithm together with mono- and twodimensional
échocardiographie parameters. Each echo parameter was correlated with the relative energy contained
in each of the 20-Hz bands in which the normalized average spectrum of OS of each subject was divided. Out of these
echo parameters, only left atrial volume, mitral valve area, septal and posterior left ventricular diastolic slopes
showed significant correlations with the phonocardiographic signal. Besides the role of the valvular apparatus, the
size of the left atrium seems to be the most important factor. The left atrium with the blood it contains appears to
represent the mass of a mass-spring system which is maximally decelerated rendering manifest the forces generating
the vibrations when the stenotic valve suddenly blocks the blood flow.