MITRAL STENOSIS

Causes - rheumatic heart disease (isolated mitral stenosis in 25% of all cases of rheumatic h.d., mixed mitral stenosis and regurgitation in 40 % of all cases of rheumatic h.d., two third of patients - women);

in about 50% of patients with mitral stenosis the rheumatic fever may be unrecognised;

viral carditis - very rare cause of mitral stenosis;

two thirds of cases occur in women;

Pathophysiology:

- the mitral valve orifice

• - normally about 5 cm² (in diastole)

• - moderate stenosis (approx 2cm²) - patients remain asymptomatic

• - 1cm or less in severe mitral stenosis

- in mitral stenosis cardiac output may be maintained by rise pressure in LA, pulmonary venous and capillaries - it results in the loss of lung compliance and the development of exertional dyspnoea

• - mild stenosis - atrial pressure rises only on exercise

• - severe stenosis - raised atrial pressure is reqiured to maintain CO even at rest

- the raised atrial pressure - enlarged diameters of LA (LA dilatation in 80% os cases) - atrial fibrillation (sometimes the first sign of clinical deterioration) - loss of atrial contraction contricute to diminished ventricular filling

- risk of atrial thrombosis and systemic thromboembolism (particulary those with AF)

- sudden onset of atrial fibrillation - sudden increase in pulmonary venous pressure - sometimes pulmonary oedema

- the long-termed mitral stenosis and more gradual rise in pressure - the increased pulmonary vascular resistance, which protects against pulmonary oedema

- right ventricular hypertrophy and pulmonary hypertension (results from : passive back-pressure, arterioral constriction, obliterative changes in pulmonary vessels)

SYPMTOPMS (most common in the third or fourth decade of life)

1. Exertional dyspnoea, nocturnal dyspnoea, cough, hemoptysis

2. Leg, ankle oedema, abdominal swelling (right ventricular failure)

3. Symptoms of acute pulmonary oedema (AF, pregnancy)

4. Symptoms secondary to arterial (rare venous) emboli

5. Symptoms of diminished CO (fatique, tiredness)

Asymptomatic mitral stenosis - the phisical signs of mitral stenosis are found before symptoms develop

SIGNS

1. Atrial fibrillation

2. Mitral facies

3. Auscultation

• Loud first heard sound (the stenotic valve prolonges atrial emptying, leaflets remain open at the onset of diastole and are closed suddenly)

• Opening snap (the opening snap gets colser to the second sound as the stenosis becomes more severe, may be inaudible if the valve is heavily calcified)

• Mid-diastolic murmur (the turbulent flow causes the low pitched diastolic murmur, and often a thrill; murmur is accentuated by exercise and during atrial systole-presystolic accentuation; il is heard best at the cardiac apex with the petients in the left lateral decubitus position)

4. Signs of raised pulmonary capillary pressure (crepitations, pulmonary oedema, effusions)

5. Signs of pulmonary hypertension (abnormal pulsation felt to the left of the sternum, due to either to righ ventricular hypertrophy or to forward displacement of the heart by dilated LA; loud the pulmonary component of the second heart sound; tricuspid regurgitation secondary to right ventricular dilatation causes the systolic murmur and systolic waves in the venous pulse)

INVESTIGATIONS

1. The ECG:

• The left atrial hypertrophy - P mitrale (the bifid P waves) or atrial fibrillation

• Right ventricular hypertrophy (the earliest sign - reduction in the size of the usual QS complex in the lead V1)

2. CXR:

• enlarged left atrium

• signs of pulmonary venous hypertension (enlargement of the upper pulmonary veins, horizontal linear shadows in the costophrenic angles)

3. Echocardiography: thickened immobile cusps, enlarged size of the left atrium, reduced valve area, reduced rate of diastolic filling

4. Cardiac catheterisation: pressure gradient between LA and LV

Category: Cardiology Notes