Mitral Regurgitation

Key Features

• Mitral regurgitation results from

  • Displacement of papillary muscles (dilated cardiomyopathy)

  • Excessive length of chordae or myxomatous degeneration of leaflets (mitral prolapse)

  • Noncontraction of annulus (annular calcification)

  • Scarring (rheumatic fever, calcific invasion)

  • Infection (endocarditis)

• Mitral regurgitation places a volume load on heart (increased preload) and reduces afterload, resulting in enlarged left ventricle (LV) and initial increase in ejection fraction (EF)

• Over time, myocardial contractile function is reduced and EF drops

• The Carpentier classification is used by some experts to categorize the mobility of the mitral leaflets:

  • Type 1 is normal

  • Type II indicates increased leaflet motion (as in prolapse or chordal rupture)

  • Type IIa indicates restricted mitral leaflets in both systole and diastole

  • Type III indicates papillary muscle displacement

  • Type IIIb indicates restricted motion in systole only

Clinical Findings

• Pansystolic murmur at the apex, radiating into the axilla in most patients; murmur does not change in intensity after a premature beat, since the LV to left atrial (LA) gradient is unaffected

• Often associated with an S₃

• Hyperdynamic LV impulse

• Brisk carotid upstroke

• May be asymptomatic for many years (or life)

• When regurgitation develops acutely, left atrial pressure rises abruptly, leading to pulmonary edema if severe

• When regurgitation progresses more slowly, exertional dyspnea and fatigue worsen gradually over many years

• Chronic LA and LV enlargement may result in subsequent atrial fibrillation and LV dysfunction

• Systemic embolization occurs but is relatively unusual compared with other conditions causing atrial fibrillation

Diagnosis

• ECG: LA abnormality or atrial fibrillation and LV hypertrophy

• Chest radiograph: LA and LV enlargement

• Doppler transthoracic echocardiography (TTE)

  • Confirms the diagnosis, etiology and estimates severity by a variety of methods

  • Used for measuring LV function and LV end-systolic and diastolic sizes

  • Should be done at least yearly in patients with severe mitral regurgitation (stage C1) but preserved LV dimensions

• Transesophageal echocardiography (TEE)

  • May reveal the cause and better identify candidates for valvular repair

  • Important in endocarditis

• Coronary angiography is often indicated to determine the presence of coronary artery disease before valve surgery in all men over age 40 years and menopausal women with risk factors

• Exercise hemodynamics with either Doppler TTE or cardiac catheterization may be useful when the symptoms do not fit the anatomic severity of mitral regurgitation

• B-type natriuretic peptide (BNP or pro-NT-BNP) is useful in the early identification of LV dysfunction in the presence of mitral regurgitation

Treatment

• Chronic regurgitation usually requires surgery when symptoms develop or in asymptomatic patients when the LV end-systolic dimension (LVESD) is > 4.0 cm or EF < 60%

• The 2017 update of the valvular guidelines has added a IIa indication for mitral valve surgery when the LVEF is > 60% and the LVESD is still < 4.0 cm

  • The guidelines suggest that mitral valve replacement should be done if serial imaging reveals ...