- Mitral stenosis (MS) impedes blood flow from the lungs and left atrium into the left ventricle.
- Rheumatic heart disease is the most common etiology.
- MS may result from calcium deposition in the mitral annulus and leaflets, from congenital valvular malformation, or from connective tissue disorders.
- Left atrial myxoma or cor triatriatum may mimic MS.
- Prosthetic mitral valves (particularly bioprosthetic valves) may become stenotic late after implantation.
- Significant MS results in elevation of left atrial, pulmonary venous, and pulmonary capillary pressures, with consequent pulmonary congestion.
- The degree of pressure elevation depends on the severity of obstruction, flow across the valve, diastolic filling time, and presence of effective atrial contraction.
- Factors that normally augment flow across the mitral valve, such as tachycardia, exercise, fever, and pregnancy, result in a marked increase in left atrial pressure and may exacerbate HF symptoms.
- Left atrial enlargement and fibrillation may result in atrial thrombus formation, which contributes to the high incidence (20%) of systemic embolization in patients with MS who are not anticoagulated.
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- Pulmonary congestion, such as dyspnea, cough, and occasionally hemoptysis are prominent.
- Physical signs of pulmonary venous congestion and right heart volume and pressure overload often are present.
- A loud S1, early diastolic opening snap, and rumbling diastolic murmur are present on auscultation.
Imaging and Diagnostic Studies
- The diagnosis and severity of MS can be confirmed by two-dimensional and Doppler echocardiography.
- Transesophageal echocardiography (TEE) can also be used to confirm the diagnosis, define the anatomy more fully, and provide diagnostic information in patients in whom transthoracic echocardiography is suboptimal.
- Cardiac catheterization is indicated in patients in whom there is a likelihood of concomitant coronary artery disease and in whom echocardiographic studies are either technically suboptimal or nondiagnostic.
- Factors that increase left atrial pressure, including tachycardia and fever, should be identified and alleviated.
- Vigorous physical activity should be avoided in patients with moderate to severe MS.
- Diuretics are the mainstay of therapy for pulmonary congestion and edema.
- Atrial fibrillation may not be well tolerated.
- Anticoagulant therapy is indicated for patients with MS and atrial fibrillation (because of the high thromboembolism risk), prior embolic event, or known atrial thrombi. Heparin therapy should be instituted at the onset of atrial fibrillation, followed by long-term warfarin therapy.
- When the patient is hemodynamically stable, the ventricular response rate to atrial fibrillation can be controlled using digoxin, calcium channel antagonists, or Î²-adrenergic antagonists.
- Synchronized direct current cardioversion should be performed if hemodynamic compromise (hypotension, pulmonary dema, and angina) occurs.
- An attempt to restore and maintain sinus rhythm may be beneficial. It should be preceded by anticoagulation therapy for at least 3 weeks to minimize the risk of systemic embolization on resumption of normal sinus rhythm.
- A TEE should be performed to evaluate the left atrium for presence of thrombi in patients who require cardioversion prior to completion of a full course of anticoagulation.
- After conversion to sinus rhythm has been accomplished, antiarrhythmics may be beneficial to maintain sinus rhythm.
- Infective endocarditis prophylaxis is indicated.
- Continuous prophylaxis against recurrent rheumatic fever is indicated in young patients, patients at high risk for streptococcal infection (parents of young children, schoolteachers, medical and military personnel, and those in crowded living conditions), and those who have had acute rheumatic fever within the previous 10 years.
- Patients with severe symptoms or pulmonary hypertension and significant MS (valve area <1 cm2/m2) should undergo commissurotomy or mitral valve replacement (MVR).
- Patients with mild to moderate symptoms may improve with diuretics and can be followed with clinical evaluations and serial echocardiograms.
- A single systemic thromboembolic event does not necessarily mandate MVR.
- However, the recurrence rate of systemic thromboembolism in patients with MS is high, even with systemic anticoagulation, and MVR should be strongly considered.
- Percutaneous balloon mitral valvuloplasty can reduce the mitral valve pressure gradient and improve cardiac output. This procedure is an alternative to surgery and carries acceptable morbidity and mortality in selected patients without severe MR or severe valvular calcification.