There are two major haemodynamic disorders in patients with mitral stenosis:
- raised left atrial pressure:
- is not significant until the valve area is less than 25% of normal (1.0 - 1.5 cm sq.)
- causes an increase in left atrial pressure and a diastolic gradient across the mitral valve
- as the pulmonary venous pressure increases, exudation of fluid causes pulmonary oedema with a corresponding rise in pulmonary arterial pressure
- pulmonary hypertension:
- is the result of the long-term increase in left atrial pressure which causes a rise in pulmonary vascular resistance
- is accompanied by intimal and medial thickening of the pulmonary vasculature
- is prominent if the left atrium is small and indistensible
Cardiac output diminishes, especially when dilatation of the right ventricle and tricuspid ring causes tricuspid regurgitation.