Mitral valvular stenosis is characterized by the reduction of mitral orifice area (normally has 4-6 cm2), which is a dam in blood flow from the left atrium to the left ventricle during diastole. Almost all types of mitral stenosis appear as a complication of rheumatic fever. In rheumatic mitral stenosis are characteristic the following pathological changes:
- Valvular narrowing, by the join of the corners;
- Fibrosis, thickening and calcification of the valve;
- Thickening of the pillars and cordages.
Reduction of mitral orifice area determine left atrial dilatation, thickening of the pulmonary veins and pulmonary capillaries, dilation and proliferation of intima and media of pulmonary artery and dilatation and hypertrophy of the right ventricle and right atrium. Mitral Stenosis has hemodynamic consequences in both downstream and upstream:
- Downstream occur: decreased cardiac output, which lowers the coronary flow;
- Upstream, the pressure increases in:
- Left atrium, with its hypertrophy and dilation, which favor the occurrence of arrhythmias (atrial fibrillation);
- Pulmonary vein, where the blood stagnates;
- Pulmonary capillary, causing the occurrence of effort dyspnoea, acute pulmonary edema, chronic interstitial edema and pulmonary sclerosis;
- Pulmonary artery, causing its expansion;
- Right atrium and right ventricle, causing their dilatation and hypertrophy with the installation of right heart failure;
Depending on the degree of narrowing, mitral stenosis is classified in:
- Large mitral stenosis (between 2.5 cm2 and 1.5 cm2);
- Moderate mitral stenosis (between 1.5 cm2 and 1cm2);
- Severe mitral stenosis (less than 1 cm2).
Mitral stenosis mainly affects women, the symptoms became evident between 25 and 30 years. Symptoms depend on the degree of stenosis, the left atrial dilatation and pulmonary stasis. Symptomatology is evident when the surface of mitral hole is less than 1.5 cm2:
- Dyspnoea, the most common symptom may be mild and intermittent (occurs only in situations that increase cardiac output, such as effort and fever), chronic and severe or even permanent, paroxysmal, which is favored by factors such as exercise, excitement, sexual intercourse , labor, menstrual period and pregnancy;
- Dry, persistent cough, caused by compression of the dilated left atrium on the bronchi;
- Palpitations, as expression of compensatory tachycardia occurred during exercise or as expression of arrhithmias;
- Pain in the left interscapular region;
- Dysphagia due left atrial compression over the esophagus;
- Fatigue in the legs.