General Considerations

• Rheumatic disease causes mitral stenosis in 99.8% of cases

• Acute rheumatic fever (ARF) → pancarditis

• Mitral valve most commonly involved valve

• Followed by mitral and aortic together

• Then by aortic alone

• Acute phase → cardiomegaly

• Mitral regurgitation is valvular lesion of ARF
• As acute phase subsides, fibrosis alters leaflet or cusp structure

• Results in cuspal or leaflet thickening along valvular margins of closure

• Mitral orifice becomes smaller → two circulatory changes

  • To maintain LV filling across narrowed valve, left atrial pressure goes up

  • Blood flow across mitral valve is decreased which decreases cardiac output

Mitral Valve Areas

• Normal mitral valve orifice 4-6 sq cm in adults

• When reduced to <2 sq cm, LA pressure increases

• Gradient across mitral valve is hallmark of mitral stenosis

• About 20 mm Hg in mitral stenosis

MS and MR

• Rheumatic mitral stenosis occurs with varying degrees of mitral regurgitation

• When MS is severe, MR is relatively unimportant

Mitral Valve Calcification

• Calcium usually deposited in clumps on valve leaflets

• Heavier calcific deposits in men than women

• Calcification of mitral annulus does not signify presence of mitral valve disease

• Occurs in older women as a degenerative process

Effect of MS on Heart

• Left atrium hypertrophies and dilates 2° pressure and volume load

• Atrial fibrillation and mural thrombosis follow

• Left ventricle is “protected” by stenotic valve

• Usually normal in size and contour

Effect of MS on Lungs

• Increased pulmonary venous and capillary pressure

• Chronic edema of alveolar walls → fibrosis

• Pulmonary hemosiderin is deposited in lungs

• Pulmonary ossification may occur

• Pulmonary arterial hypertension develops

  • First passively

  • Then 2° muscular hypertrophy and hyperplasia → increased pulmonary vascular resistance

Effect of MS on Right Ventricle

• RV hypertrophies in response to increased afterload

• Eventually RV fails and dilates

• Causes dilation of tricuspid annulus → tricuspid regurgitation

Mitral Stenosis-Other Causes

• Congenital Mitral Stenosis

  • Exists as isolated abnormality 25% of time

  • Coexists with VSD 30% of time

  • Coexists with another form of left ventricular outflow obstruction 40% of time—SHONE’S Syndrome

  • Shone’s Syndrome

    • Parachute mitral valve

    • Supravalvular mitral ring

    • Subaortic stenosis

    • Coarctation of aorta

  • Infective endocarditis

    • Large vegetations occurring on previously normal mitral valve may produce MS

• Carcinoid Syndrome

  • Carcinoid of lung allows for prolonged exposure of mitral valve to serotonin

  • May result in stiff, stenotic mitral valve

• Fabry’s Disease

  • Deposition of aramide trihexoside thickens and decreases mobility of mitral leaflets

• Hurler’s Syndrome

  • Deposition of mucopolysaccharide thickens and decreases mobility of mitral leaflets

• Whipple’s Disease

  • Same as gut lesions in mitral leaflets

• LA Myxoma

  • Most common form of primary cardiac tumor

  • 86% of myxomas are found in left atrium

  • 90% of myxomas are solitary

  • Usually occur around fossa ovalis

Imaging Findings

• Cardiac Findings

  • Usually normal or slightly enlarged cardio-thoracic ratio

  • Straightening of left heart border

  • Convexity of left heart border 2° to enlarged atrial appendage--only in rheumatic heart disease

  • Small aortic knob from decreased cardiac output

  • Double density of left atrial enlargement

  • Rarely, right atrial enlargement from tricuspid insufficiency

• Calcifications

• Calcification of mitral valve--not annulus--seen best on lateral film at fluoroscopy

• Rarely, calcification of the left atrial wall 2° fibrosis from long-standing disease

• Rarely, calcification of pulmonary arteries from PAH

• Pulmonary Findings

• Cephalization

• Elevation of left mainstem bronchus (especially if 90° to trachea)

• With severe, chronic disease enlargement of the main pulmonary artery from pulmonary arterial hypertension

• Echocardiographic Findings

• In 90%, M-mode study will demonstrate flattening of E-F slope

• Decreased diastolic excursions of mitral leaflets

• Concordant anterior movement of anterior and posterior leaflets during systole

• If left atrium > 5cm, increased incidence of

• Atrial fibrillation

• Left atrial thrombus

• Systemic embolization

• Angiographic Findings

• Ventriculography in 30 to 40° RAO projection usually used

• Severity of lesion determined hemodynamically by simultaneously measuring

• Pulmonary capillary wedge pressure

• Left ventricular inflow tract pressure and cardiac output

• Calcified, hypokinetic and domed mitral leaflets

• Enlargement of left atrium

• Left ventricle is small with a reduced ejection fraction

• Mitral valve leaflets appear thickened and nodular and may appear to attach directly to the papillary muscle

• Scarring and retraction of the chorda tendina