Mitral regurgitation

Definition

Mitral regurgitation (MR) is incomplete closure of the mitral valve with systolic backflow of blood from the left ventricle into the left atrium. In primary (organic) MR the valve apparatus itself is diseased; in secondary (functional) MR an otherwise normal valve becomes incompetent because of ventricular or atrial disease.

Classification

• By course: acute or chronic.
• By mechanism: primary (e.g. prolapse, rheumatic) or secondary; secondary ventricular (ischemic or non-ischemic) or atrial-functional in atrial fibrillation with an enlarged atrium.
• Severe MR (echocardiography): vena contracta above 7 mm, effective regurgitant orifice area above 0.40 cm², regurgitant volume above 60 ml, regurgitant fraction above 50 %.
• Moderate MR: vena contracta 3–7 mm, effective regurgitant orifice area 0.20–0.40 cm², regurgitant volume 30–60 ml, regurgitant fraction 30–50 %.

Aetiopathogenesis

• Acute MR: ischemic papillary muscle dysfunction or rupture, infective endocarditis with chordal rupture, acute rheumatic fever, myxomatous chordal rupture, acute ventricular dilatation in myocarditis or ischemia, failure of a prosthetic mitral valve.
• Primary chronic MR: most often mitral valve prolapse or rheumatic heart disease; less commonly connective tissue disorders, congenital cleft mitral valve and radiogenic heart disease.
• Secondary chronic MR: ventricular dilatation displaces the papillary muscles outwards, the leaflets are tethered and no longer coapt (after myocardial infarction or in cardiomyopathy); atrial-functional due to annular dilatation in chronic atrial fibrillation.
• Pathophysiology: in chronic MR the left atrium enlarges; the ventricle dilates with eccentric hypertrophy and initially compensates until it decompensates. Consequences are atrial fibrillation with thromboembolism and an increased risk of endocarditis. Acute MR can cause pulmonary edema and cardiogenic shock.

Clinical features

• Acute MR: symptoms of acute heart failure (dyspnea, fatigue, weakness, edema) up to cardiogenic shock; specific signs of MR may be absent.
• Chronic MR: initially asymptomatic; later dyspnea, fatigue, orthopnea and palpitations (often due to atrial fibrillation); rarely first presentation as endocarditis.
• Inspection and palpation: brisk apical impulse; with ventricular dilatation sustained, enlarged and displaced downwards and to the left; diffuse precordial lift in severe MR; possibly a palpable thrill.
• Auscultation: holosystolic murmur, best heard at the apex in the left lateral position, radiating to the left axilla; soft (occasionally loud) first heart sound; third heart sound with a dilated ventricle and severe MR. The murmur becomes louder with handgrip and squatting, softer on standing and with the Valsalva maneuver.

Diagnosis

• Echocardiography: Doppler to detect regurgitant flow and pulmonary hypertension; two- or three-dimensional assessment of leaflet morphology and motion, cause and severity, annular calcification and the size and function of ventricle and atrium. Typical: eccentric jet in primary MR, central jet in secondary MR with global dysfunction or in atrial-functional MR.
• Acute severe MR: may not be obvious on color Doppler; acute heart failure with hyperdynamic left ventricular function raises suspicion.
• ECG: left atrial enlargement, left ventricular hypertrophy with or without ischemia; usually sinus rhythm in acute MR.
• Chest X-ray: pulmonary edema in acute MR; in chronic MR enlargement of atrium and ventricle, pulmonary congestion.

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Mitral Regurgitation
2. StatPearls: Mitral Regurgitation

Cross-references