- Mitral stenosis (MS) is characterized by incomplete opening of the mitral valve during diastole, which limits antegrade flow and yields a sustained diastolic pressure gradient between the left atrium (LA) and the left ventricle (LV).
- Due to the widespread use of antibiotics, the incidence of rheumatic heart disease (and MS) has decreased in the developed world.
- Predominant cause of MS; two-thirds of patients are females; may be associated with mitral regurgitation (MR).
- Rheumatic fever can cause fibrosis, thickening, and calcification, leading to fusion of the commissures, leaflets, chordae, and/or papillary muscles.
- Other causes: systemic lupus erythematosus (SLE), rheumatoid arthritis, congenital, substantial mitral annular calcification, oversewn or small mitral annuloplasty ring; “functional MS” may occur with obstruction of the LA outflow due to tumor (particularly myxoma), LA thrombus, or endocarditis with a large vegetation.
Physiologic states that either increase the transvalvular flow (enhance CO) or decrease diastolic filling time (via tachycardia) can increase symptoms at any given valve area. Pregnancy, exercise, hyperthyroidism, atrial fibrillation (AF) with rapid ventricular response, and fever are examples in which either or both of these conditions occur. Symptoms are often first noticed at these times. MS causes increased pressure in the LA, which then dilates as a compensatory mechanism to minimize the increase in pressure. A dilated and fibrosed atrium develops, predisposing to atrial arrhythmias and clot formation. A sustained increase in pulmonary venous pressures is transmitted backward to cause PH and, with time, increased pulmonary vascular resistance and right ventricular pressure overload and dysfunction.
After a prolonged asymptomatic period, patients may report any of the following: dyspnea, decreased functional capacity, orthopnea and/or paroxysmal nocturnal dyspnea, fatigue, palpitations (often due to AF), systemic embolism, hemoptysis, chest pain, and/or signs and symptoms of infective endocarditis.
Findings on physical exam will depend on the severity of valve obstruction and the associated adaptations that developed; they may include:
- Opening snap (OS) caused by sudden tensing of the valve leaflets; the A2-OS interval varies inversely with the severity of stenosis (shorter interval = more severe stenosis).
- Mid-diastolic rumble: low-pitched murmur heard best at the apex with the bell of the stethoscope; the severity of stenosis is related to the duration of the murmur, not intensity.
- Signs of right-sided HF and PH.
P mitrale (P-wave duration in lead II ≥0.12 seconds indicating LA enlargement [LAE]), AF, right ventricular hypertrophy
- LAE, enlarged right atrium/right ventricle and/or enlarged pulmonary arteries
- Calcification of the mitral valve (MV) and/or annulus
- Assess etiology of MS.
- Assess leaflets and subvalvular apparatus to determine candidacy for percutaneous mitral balloon commissurotomy (PMBC).
- Determine MV area and mean transmitral gradient.
- Estimate pulmonary artery systolic pressure and evaluate right ventricular size and function.
- Assess presence or absence of clot and severity of MR in patients being considered for percutaneous mitral balloon valvuloplasty.
- Evaluate MV morphology and hemodynamics in patients with MS for whom TTE was suboptimal.
- Cardiac catheterization
- Indicated to determine severity of MS when clinical and echocardiography assessment are discordant
- Reasonable in patients with MS to assess the cause of severe PH when out of proportion to the severity of MS as determined by noninvasive testing; can also assess the reversibility of PH
- Severe MS
- Valve area ≤1.5 cm2 (very severe MS ≤1.0 cm2)
- Usually accompanied by LAE and often PH
- Diuretics and low-salt diet for HF symptoms.
- Secondary prevention of rheumatic fever is indicated for rheumatic MS.
- AF (occurs in 30–40% of patients with severe MS).
- Therapy is mostly aimed at rate control (negative dromotropic agents) and prevention of thromboembolism; rhythm control is rarely successful.
- AHA/ACC Guidelines—class I indications for anticoagulation for prevention of systemic embolization in patients with MS:
- MS and AF (paroxysmal, persistent, or permanent)
- MS and a prior embolic event, even in sinus rhythm
- MS with LA thrombus
Other Nonoperative Therapies
- AHA/ACC recommendations for intervention:
- Symptomatic patients with severe MS (valve area ≤1.5 cm2) (stage D) and favorable valve anatomy in the absence of an LA clot or moderate to severe MR (class I)
- Asymptomatic patients with very severe MS (valve area ≤1.0 cm2) (stage C) and favorable valve anatomy in the absence of a LA clot or moderate to severe MR (class IIa)
- Asymptomatic patients with severe MS (stage C) and favorable valve anatomy in the absence of a LA clot or moderate to severe MR who have new-onset AF (class IIb)
- Balloon inflation separates the commissures and fractures some of the nodular calcium in the leaflets, yielding an increased valve area.
- It compares favorably with surgical mitral commissurotomy (open or closed) and is the procedure of choice in experienced centers in patients without contraindications.
- AHA/ACC recommendations for intervention (repair, commissurotomy, or replacement)
- Severely symptomatic patients (NYHA class III/IV) with severe MS (valve area <1.5 cm2; stage D) who are not high risk for surgery and who are not candidates for or failed previous PMBC (class I).
- Concomitant MV surgery is indicated for patients with severe MS (valve area <1.5 cm2; stage C or D) undergoing other cardiac surgery.
- Chapter 6: Pericardial and Valvular Heart Disease
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