As MS worsens, left atrial pressure increases forcing the mitral valve open earlier in diastole. Thus, in severe MS, the opening snap occurs earlier as does the initial decrescendo part of the murmur.

The mobility of the valve leaflets is a major factor influencing the intensity of M1 component of the first heart sound (S1). In mild to moderate mitral stenosis, the increased left atrial pressure causes the mobile portions of the mitral valve leaflets to be more widely separated, thus resulting in an accentuated M1 sound. In severe to critical mitral stenosis, the valve leaflets are so calcified and immobile that the M1 sound is diminished or absent.

Mitral stenosis results in a uniquely shaped, low-pitched diastolic murmur best heard at the cardiac apex. The opening of the mitral valve produces an "opening snap" due to the high LA pressures, which is immediately followed by a decrescendo murmur as blood flows passively from the left atrium to the LV through the stenosed mitral valve creating turbulence. Immediately before the S1 sound, active LV filling occurs when the left atrium contracts and forces more blood through the stenosed mitral valve creating a late diastolic decrescendo murmur. In the presence of atrial fibrillation, the active LV filling phase does not take place and the latter part of the MS murmur disappears.