Cause of loud S1 with mitral stenosis

This schematic representation shows the transition between left atrial (LA) and left ventricular (LV) pressures at end-diastole in the normal heart (A) and in a patient with mitral stenosis (B). In B, a significant pressure gradient remains at end-diastole. Note that at low LA pressures, the rate of LV pressure development (dP/dt) is much slower than when crossover occurs at higher LA pressures. Hence, the rate of mitral valve closure is increased in mitral stenosis, the principal cause of a loud S1.