How is pathophysiology of MS?

Normal adults Mitral valve is 4-6 cm2, in obstruction <2cm2 blood flows from LA to LV if elevated LA pressure (hemodynamic hallmark of MS). <1.5cm2 severe MS need LA pressure 25mmHg to maintain normal CO. Elevated pulmonary artery pressure reduces pulmonary compliance thus exertional dyspnea, which is precipitated by clinical event increasing blood flow in orifice elevating LA pressure. For assessment transvalvular pressure gradient and flow rate should be measured, isolated MS LV EDP and EF are normal, influences are important at level of PAP