Severity of mitral stenosis Is assessed by -

In MS The first hea sound (S 1 ) is usually accentuated and slightly delayed. The pulmonic component of the second hea sound (P 2 ) also is often accentuated, and the two components of the second hea sound (S 2 ) are closely split. The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to, the cardiac apex. This sound generally follows the sound of aoic valve closure (A 2 ) by 0.05-0.12 s. The time interval between A 2 and OS varies inversely with the severity of the MS. The OS is followed by a low-pitched, rumbling, diastolic murmur, heard best at the apex with the patient in the left lateral recumbent position. In general, the duration of this murmur correlates with the severity of the stenosis in patients with preserved CO. ( Harrison&;s principle of internal medicine,18th edition,pg no. 1931 )