Mitral Regurgitation

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

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

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

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 a progressive increase in the LVESD or a decrease in the EF

• This latter was based on information that LV function is more likely to return to normal when the LVEF was > 64% and the LVESD was < 3.7 cm

Calculated regurgitant orifice areas > 40 mm² by echocardiogram are considered severe

Surgical valve repair

• Preferred in mitral prolapse and in some with endocarditis

• Essentially all patients who undergo valve repair also get mitral annular rings placed

• Also used in patients with cardiomyopathy

Mitral valve replacement uses mechanical or bioprosthetic valves

Novel percutaneous approaches to mitral valve repair include

• Transseptal stitching of leaflets (Evalve procedure)

• Coronary sinus crimping

• Other measures to reduce annular size

Functional mitral regurgitation may improve with biventricular pacing; some patients may require surgical intervention or percutaneous repair