Mitral Stenosis

Carlos A. Roldan

Mitral stenosis is the most common valve lesion of rheumatic heart disease.
Isolated mitral stenosis and mixed mitral stenosis and mitral regurgitation (MR) are seen in up to 40% and 30% to 40% of patients with rheumatic heart disease, respectively.
Mitral stenosis is prevalent in developing countries, but it only accounts for ≤10% of left-sided valve disease in United States and Europe (1).
Patients with symptomatic mitral stenosis have significant morbidity (heart failure in 60% to 70%, systemic embolism in 10% to 20%, pulmonary embolism in 10%) and mortality (0% to 15% 10-year survival, and <3-year survival in those with severe pulmonary hypertension) (2).
Therefore, early detection and accurate assessment of the severity of mitral stenosis and its feasibility and timing of valve repair or replacement can significantly alter the prognosis of this disease.
The history and physical examination are important in the detection of mitral stenosis, but they are limited in establishing its severity and suitability for percutaneous valvuloplasty or valve surgery.

Definition

Mitral stenosis results from chronic or recurrent rheumatic valvulitis leading to commissural fusion; thickening, retraction, and frequently calcification of the anterior and posterior mitral leaflets; and thickening, retraction, fusion, and calcification of the chordae tendineae. Consequently, the mitral valve apparatus becomes a funnel-like sleeve; when severe, it looks like a “fish mouth” and loses the ability to open during diastole.
The resulting mitral valve obstruction (a reduction of valve area from 4 to 5 cm² to ≤1.5 cm²) leads to a decrease in left ventricle (LV) filling, an increase in left atrium (LA) to LV gradient, LA hypertension, LA dilatation, pulmonary venous and pulmonary arterial hypertension (due to vasoconstriction, intimal hyperplasia, and medial hypertrophy of the pulmonary arterioles), atrial tachyarrhythmias, and heart failure.

Etiology

Rheumatic fever is the most common cause of mitral stenosis (1,2).
Systemic lupus erythematosus and rheumatoid arthritis are uncommon causes (3,4).
Degenerative severe mitral annular calcification uncommonly results in mitral stenosis (5).
Stenosis of bioprosthetic or prosthetic mitral valves caused by bioprosthetic leaflets degeneration, pannus ingrowth, or thrombosis is uncommon.
Congenital mitral stenosis or parachute mitral valve rarely occurs and is associated with an obstructive mitral valve ring, subaortic stenosis, and coarctation of the aorta (Shone’s complex or anomaly) (6).

Echocardiography

Class I or Appropriate (Score of 7 to 9) Indications for Echocardiography in Patients with Suspected or Known Mitral Stenosis

M-mode, two-dimensional (2D), and real-time three-dimensional (RT3D) transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) and pulsed wave, continuous wave, and color Doppler TTE or TEE are essential in the diagnosis, assessment of morphology and severity, and management of mitral stenosis (7,8,9,10) (Table 7.1).

The integrated use of these echocardiography (echo) techniques accurately characterize the morphology of
the mitral valve and subvalvular apparatus, detect and characterize associated MR and atrial thrombi, identify patients suitable for valvuloplasty or valve replacement, provide guidance during balloon valvuloplasty, and determine the postprocedure mitral valve area, gradients, and degree of MR (8,9,10,11).

Table 7.1 Class I or appropriate (score 7–9) indications for echocardiography in patients with mitral stenosis

Diagnosis of mitral stenosis, assessment of hemodynamic severity (mean gradient, mitral valve area, pulmonary artery pressure), and assessment of right ventricular size and function (2D or RT3D TTE).
Assessment of valve morphology to determine suitability for percutaneous mitral balloon valvotomy (2D or RT3D TTE or TEE).
Two-dimensional or RT3D TEE to evaluate mitral valve morphology and hemodynamics when TTE is suboptimal.
Diagnosis and assessment of concomitant valvular lesions (TTE).
Routine surveillance (≥3 y) of mild mitral stenosis without a change in clinical status or cardiac exam (TTE).
Routine surveillance (≥1 y) of moderate or severe mitral stenosis without a change in clinical status or cardiac exam (TTE).
Re-evaluation of patients with known mitral stenosis with changing symptoms or signs or to guide therapy (TTE).
Assessment of mean gradient and pulmonary artery pressure by exercise Doppler echocardiography in patients with discrepant resting hemodynamics and clinical findings (TTE).
Assessment of changes in hemodynamic severity and ventricular compensation in patients with known mitral stenosis during pregnancy (TTE).
Suspected cardiovascular source of embolus (TEE).
Assessment of atrial thrombus and further definition of the severity of mitral regurgitations before consideration of mitral balloon valvuloplasty (2D or RT3D TEE).
Guidance during percutaneous balloon valvuloplasty (2D or RT3D TEE).
Post intervention (percutaneous valvuloplasty, valve repair, or valve replacement) baseline study for valve function (early) and ventricular remodeling (late) (TTE).
Evaluation of prosthetic mitral valve with suspected dysfunction (stenosis) or a change in clinical status or cardiac exam (TTE).

2D, two-dimensional; RT3D, real-time three-dimensional; TTE, trans-thoracic echocardiography; TEE, transesophageal echocardiography.
All listed indications have a Level of Evidence B or C.
(Adapted from Bonow RO, Carabello BA, Chatterjee K, et al. Practice guideline 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. Circulation. 2008;118:e523–e661; Douglas PS, Garcia MJ, Haines DE, et al. ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 appropriate use criteria for echocardiography. J Am Coll Cardiol. 2011;57:1126–1166.)

M-Mode, Two-dimensional, and Real-time Three-dimensional Echocardiography

Mitral Valve and Subvalvular Apparatus Morphology

Best Imaging Planes

Two-dimensional and RT3D TTE parasternal long- and short-axis views and apical four- and two-chamber views.
Two-dimensional and RT3D TEE transgastric short- and long-axis views and midesophageal four- and two-chamber views.

Key Diagnostic Features

M-Mode

Mitral leaflet thickening/sclerosis with markedly decreased mobility leading to blunting or disappearance of the E to F slope and parallel anterior motion of the leaflets are characteristic (Fig. 7.1A). These abnormalities are caused by commissural fusion and chordal thickening, retraction, and fusion.
The closer the parallel motion of the leaflets, the worse the stenosis. However, if the ultrasound beam is placed above the true valve orifice, the valve opening is overestimated (Fig. 7.1B).

Two-dimensional and Real-time Three-dimensional

Transthoracic Echocardiography