Mitral Stenosis

·         Rheumatic disease causes mitral stenosis in 99.8% of cases

·         Acute rheumatic fever (ARF) → pancarditis

o       Mitral valve most commonly involved valve

o       Followed by mitral and aortic together

o       Then by aortic alone

·         Acute phase → cardiomegaly

o       Mitral regurgitation is valvular lesion of ARF

o       As acute phase subsides, fibrosis alters leaflet or cusp structure

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

·         Mitral Valve Calcification

o       Calcium usually deposited in clumps on valve leaflets

o       Heavier calcific deposits in men than women

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

§         Occurs in older women

·         Mitral orifice becomes smaller → two circulatory changes

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

o       Blood flow across mitral valve is decreased which m cardiac output

·         Mitral Valve Areas

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

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

o       Gradient across mitral valve is hallmark of mitral stenosis

§         About 20 mm Hg in mitral stenosis

·         MS and MR

o       Rheumatic mitral stenosis occurs with varying degrees of mitral regurgitation

o       When MS is severe, MR is relatively unimportant

·         Effect of MS on Heart

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

o       Atrial fibrillation and mural thrombosis follow

o       Left ventricle is “protected” by stenotic valve

§         Usually normal in size and contour

·         Effect of MS on Lungs

o       Increased pulmonary venous and capillary pressure

o       Chronic edema of alveolar walls → fibrosis

o       Pulmonary hemosiderin is deposited in lungs

o       Pulmonary ossification may occur

·         Effect of MS on Lungs

o       Pulmonary arterial hypertension develops

o       First passively

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

·         Effect of MS on Right Ventricle

o       RV hypertrophies in response to increased afterload

o       Eventually RV fails and dilates

o       Causes dilation of tricuspid annulus → tricuspid regurgitation

·         Mitral Stenosis-Other Causes

o       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

o       Parachute mitral valve

o       Supravalvular mitral ring

o       Subaortic stenosis

o       Coarctation of aorta

o       Infective Endocarditis

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

o       Carcinoid Syndrome

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

§         May result in stiff, stenotic mitral valve

o       Fabry’s Disease

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

o       Hurler’s Syndrome

§         Deposition of mucopolysaccharide thickens and decreases mobility of mitral leaflets

o       Whipple’s Disease

§         Same as gut lesions in mitral leaflets

o       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

·         X-Ray Findings of MS

o       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

o       X-Ray Findings of MS

§         Cardiac Findings

·         Small aortic knob from decreased cardiac output

§         Double density of left atrial enlargement

§         Rarely, right atrial enlargement from tricuspid insufficiency

Frontal chest x-ray shows normal-sized heart
with enlarged left atrium

·         X-Ray Findings of MS-Calcifications

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

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

o       Rarely, calcification of pulmonary arteries from PAH

·         X-Ray Findings of MS-Pulmonary Findings

o       Cephalization

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

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

·         Mitral Stenosis-Echocardiographic Findings

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

o       Decreased diastolic excursions of mitral leaflets

o       Concordant anterior movement of anterior and posterior leaflets during systole

·         Mitral Stenosis-Echocardiographic Findings

o       If left atrium > 5cm, increased incidence of

o       Atrial fibrillation

o       Left atrial thrombus

o       Systemic embolization

·         Mitral Stenosis-Angiographic Findings

o       Ventriculography in 30 to 40° RAO projection usually used

o       Severity of lesion determined hemodynamically by simultaneously measuring

o       Pulmonary capillary wedge pressure

o       Left ventricular inflow tract pressure and

o       Cardiac output

·         Mitral Stenosis-Angiographic Findings

o       Calcified, hypokinetic and domed mitral leaflets

o       Enlargement of left atrium

o       Left ventricle is small with a reduced ejection fraction

·         Mitral Stenosis-Angiographic Findings

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

o       Scarring and retraction of the chorda tendina

 

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