The chest X-ray usually shows a generally small heart with an enlarged left atrium. Pulmonary venous hypertension is usually also present. Late in the course of the disease a calcified mitral valve may be seen on a penetrated or lateral view. The signs of pulmonary oedema or pulmonary hypertension may also be apparent when the disease is severe.
In sinus rhythm the ECG shows a bifid P wave due to delayed left atrial activation. This doublehumped P wave is best seen in leads II, V3 and V4. A biphasic P wave with a large late negative component is seen in lead VI. However, atrial fibrillation is frequently present. As the disease progresses, the ECG features of right ventricular hypertrophy (right axis deviation and perhaps tall R waves in lead V,) may develop.
The movement of the valve cusps and the rate of diastolic filling of the left ventricle may be measured-severe mitral stenosis produces immobility of the valve cusps and slow filling of the ventricles. The echocardiogram appearances are usually sufficient to allow surgical management to be considered; trans oesophageal echocardiography is particularly useful in this situation. CW Doppler is used to estimate peak mitral transvalvular gradient and the valve area. The presence of tricuspid regurgitation can be used to estimate pulmonary arterial pressure.
This is only required if an adequate echocardiogram is impossible to obtain or if coexisting cardiac problems (e.g. mitral regurgitation or coronary artery disease) are suspected. The typical findings in mitral stenosis are a diastolic pressure that is higher in the left atrium than in the left ventricle. This gradient of pressure is usually proportional to the degree of the stenosis.
Mild mitral stenosis may need no treatment other than prompt therapy of attacks of bronchitis. Although infective endocarditis in pure mitral stenosis is uncommon, antibiotic prophylaxis is advised. Early symptoms of mitral stenosis such as mild dyspnoea can usually be treated with low doses of diuretics. The onset of atrial fibrillation requires treatment with digoxin and anticoagulation to prevent atrial thrombus and systemic embolization. If pulmonary hypertension develops or the symptoms of pulmonary congestion persist despite therapy, surgical relief of the mitral stenosis is advised. There are four operative measures.
Trans-septal balloon valvotomy
This is a relatively new technique whereby a catheter is introduced into the right atrium via the femoral vein. The interatrial septum is then punctured and the catheter advanced into the left atrium and across the mitral valve. A balloon is passed over the catheter to lie across the valve, and then inflated briefly to split the valve commisures. The procedure is performed under local anaesthesia in the cardiac catheter laboratory. As with other valvotomy techniques, significant regurgitation may result necessitating valve replacement (see below). This procedure is not suitable for heavily calcified or regurgitant valves.
This operation is advised for patients with mobile, noncalcified and non-regurgitant mitral valves. The fused cusps are forced apart by a dilator introduced through the apex of the left ventricle and guided into position by the surgen’s finger inserted via the left atrial appendage. Cardiopulmonary bypass is not needed for this operation. Closed valvotomy may produce a good result for 10 or more years. The valve cusps often re-fuse and eventually another operation may be necessary.
This operation is often preferred to closed valvotomy. The cusps are carefully dissected apart under direct vision. Cardiopulmonary bypass is required. Open dissection reduces the likelihood of causing traumatic mitral regurgitation.
Mitral valve replacement
Replacement of the mitral valve is necessary if:
• Mitral regurgitation is also present
• There is a badly diseased or badly calcified stenotic
valve that cannot be reopened without producing significant regurgitation Artificial valves may work successfully for more than 20 years. Anticoagulants are generally necessary to prevent the formation of thrombus, which might obstruct the valve or embolize.