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DISORDERS OF THE HEART (Mitral Valve Disease (MITRAL STENOSIS…

- - - - area of mitral valve orifice
        
        norm adult: 4–6 cm2
        
        significant obstruction: < ~2 cm2
        
        severe MS: <1.5 cm2; LA P of ~25 mmHg required to maintain normal CO
      - assess severity of obstruction hemodynamically
        
        transvalvular pressure gradient
        
        flow rate; depends on
        
        CO
        
        heart rate: :arrow_up: --> :arrow_down: diastole proportionately more than systole + :arrow_down: time available for flow across the valve; tachycardia augments transvalvular P gradient and elevates further LA pressure.
      - Cardiac Output
        
        severe MS: normal or almost so at rest, but rises subnorm during exertion
        
        very severe MS (<1 cm2): subnormal at rest + may fail to rise / may even decline during activity
      - Pulmonary Hypertension
        
        results from
        
        interstitial edema in walls of small pulmonary vessels
        
        passive backward transmission of elevated LA P
        
        organic obliterative changes in pulmonary vascular bed
        
        pulmonary arteriolar constriction (“second stenosis”) triggered by LA and pulmonary venous hypertension (reactive pulmonary hypertension)
        
        Severe pulmonary hypertension--> RV enlargement, secondary tricuspid regurgitation (TR), and pulmonic regurgitation (PR), as well as right-sided heart failure
    - - other less common etiologies: congenital mitral valve stenosis, cor triatriatum, mitral annular calcification w/ extension onto the leaflets, SLE, rheumatoid arthritis, L A myxoma, and infective endocarditis w/ large vegetations
      - leading cause: rheumatic fever
        
        others: lesser degrees of MS may accompany mitral regurgitation (MR) and aortic valve disease
        
        in 40%: Pure or predominant MS
        
        chronic infla--> diffuse thickening of valve leaflets w/ formation of fibrous tissue and/or calcific deposits; mitral commissures fuse, chordae tendineae fuse and shorten, valvular cusps become rigid--> narrowing at apex of funnel-shaped (“fish-mouth”) valve;
        
        Although initial insult is rheumatic, later changes may be exacerbated by a nonspecific process resulting from trauma to the valve due to altered flow patterns; Calcification of stenotic mitral valve immobilizes leaflets and narrows orifice further. Thrombus formation and arterial embolization may arise from calcific valve itself, but in patients w/ atrial fibrillation (AF), thrombi arise more frequently from dilated L A, particularly from within L A appendage.