Pathophysiology
The obstruction to atrial emptying in MS causes an elevation in left atrial and pulmonary venous pressure, leading to reduced lung compliance and breathlessness on exertion.
Reactive pulmonary arterial hypertension causes right ventricular hypertrophy and failure.
Progressive stenosis causes left atrial dilatation and consequent atrial fibrillation, which will further impair the function of the atrium.
Left ventricular filling becomes impaired and cardiac output becomes compromised.
Image: Gross pathology of the heart showing mitral stenosis.