<prompt> Severity of mitral stenosis is assessed byLoud opening snapLength of murmurLoud S1Splitting S2  <response>: Ref Harrison 19 th ed pg 1540 In general, 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. 