Mitral Regurgitation (MR)

• • Fibrous annulus of mitral valve (MV) is thin, incomplete ring of fibrous tissue

  • Most MVs have anterior and posterior leaflets, attached by thin fibrous chordae tendineae to papillary muscle

  • Closed during systole via action of papillary muscle contraction, open during diastole when LA pressure higher than LV pressure

  • Etiology includes:

  • -Rheumatic heart disease

    -Idiopathic MV calcification

    -Mitral valve prolapse (MVP)

    -Infective endocarditis

    -Ischemic MR

  • Postinfarction papillary muscle rupture: 0.1% of coronary artery disease; congestive heart failure with new murmur days after myocardial infarction

  • MR results in LA hypertension, resulting in pulmonary congestion, dyspnea, pulmonary hypertension, RV failure

  • LV is subjected to chronic volume overload causing LV failure (unlike mitral stenosis)

Epidemiology

• • Causes of valve disease include:

  • -Rheumatic carditis (most common)

    -Valve collagen degeneration

    -Infection

  • Less common causes include:

  • -Collagen-vascular disease

    -Tumors

    -Carcinoid

    -Marfan syndrome

  • Valvular heart disease: 89,000 hospital discharges in 1998

  • 40% of MR caused by rheumatic disease

  • Risk factors of idiopathic MV calcification include:

  • -Hypertension

    -Aortic stenosis

    -Diabetes

    -Chronic renal failure

  • MVP is present in 3-4% of general population; 5% of patients with MVP have significant MR

  • Infective endocarditis accounts for 5% of MR cases

  • 3% of patients with severe coronary disease have ischemic MR; affects posterior leaflet primarily

Symptoms and Signs

• • Exertional dyspnea, orthopnea, fatigue

  • Symptoms do not correlate with degree of MR

  • Hemoptysis

  • Atrial fibrillation (75% of severe cases)

  • Malaise, fever, chills in this setting: consider infective endocarditis

  • Angina is rare

  • Apical impulse displaced to left, palpable thrill at apex

  • High pitched holosystolic murmur radiating to axilla and back

Laboratory Findings

• • ECG: LV hypertrophy; if sinus rhythm P mitrale may be present

Imaging Findings

• • Chest film

  • -LA and LV enlargement

    -RV enlargement

    -Pulmonary edema

    -Kerley B lines

  • Transesophageal echocardiography identifies site of regurgitation jet

  • Cardiac catheterization demonstrates LA v waves, elevated LV pressure

  • Cardiac index < 2.0 L/min/m2, wide AV oxygen difference indicate severe impairment

• • Evaluate for endocarditis

  • Evaluate for secondary LV dysfunction

• • 3 determinants of clinical severity:

  • 1. Degree of regurgitation

    2. LV function

    3. Etiology of valve disease

• • Preload reduction (diuretics), afterload reduction (ACE inhibitors): Helps in increase forward output, decrease regurgitation

  • Operation: Repair vs replacement

  • Virtually all MVP can be repaired (posterior leaflet reconstruction and annuloplasty)

  • Ischemic regurgitation: Ring annuloplasty + coronary artery bypass grafting

  • Rheumatic disease, valve calcification, or endocarditis: Prosthetic valve replacement

Surgery

Indications

• • Symptomatic heart failure (NYHA class II or greater)

  • Asymptomatic, ejection fraction (EF) < 60%, end-systolic dimension > 45 mm, pulmonary hypertension exists, or new atrial fibrillation