Mid diastolic murmer with presystolic accentuation is seen in -

In MITRAL STENOSIS The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to, the cardiac apex. 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. The duration of this murmur correlates with the severity of the stenosis in patients with preserved CO. In patients with sinus rhythm, the murmur often reappears or becomes louder during atrial systole (presystolic accentuation). ( Harrison&;s principle of internal medicine,18th edition,pg no. 1931)