Cardiovascular · Topic 31 of 48

Mitral Regurgitation

Cardiovascular · valvular heart disease

Mitral Regurgitation

Acute MR floods the lungs: reduce afterload, add a balloon pump and send to surgery. Chronic primary MR is repaired once symptoms or LV changes appear.

Key numbers

Primary MR: operate when LVEF ≤ 60%LVEF ≤ 60% · LVESD ≥ 40

Severe MR: regurgitant fraction ≥ 50%EROA ≥ 0.40 cm²

01 · Don't confuseAcute MR: flash pulmonary edema, shock

Acute MR (papillary muscle rupture, or chordal rupture from endocarditis or myxomatous disease) causes sudden pulmonary edema and cardiogenic shock; the murmur may be soft or absent, and sinus rhythm is usual.

02 · DoBridge with nitroprusside and balloon pump

Pending surgery, cut afterload with an IV vasodilator (nitroprusside, nicardipine or nitroglycerin) and an intra-aortic balloon pump: forward stroke volume rises and regurgitant volume falls; hypotension often limits vasodilators.

03 · Defined byPrimary MR: operate when LVEF ≤ 60%

Severe chronic primary MR needs intervention when symptoms appear or the LV starts to fail: LVEF ≤ 60% or LV end-systolic diameter ≥ 40 mm. Mitral valve repair is preferred over replacement.

What it is

Core idea

Primary MR: valve disease; secondary: ventricular diseasePrimary MR is disease of the valve itself (prolapse, rheumatic); secondary (functional) MR comes from a dilated or infarcted LV, or an enlarged atrium in atrial fibrillation, pulling normal leaflets apart.

Presentation

What you'll see

Apical holosystolic murmur radiating to axilla must knowChronic MR: an apical holosystolic murmur radiating to the left axilla, best heard in left lateral decubitus; louder with handgrip or squatting, softer with standing or Valsalva. An S3 suggests severe MR.

Large v waves on the wedge tracingSignificant MR produces prominent systolic c-v waves on the pulmonary capillary wedge pressure tracing.

Diagnosis & monitoring

Work-up

Severe MR: regurgitant fraction ≥ 50%Echo criteria for severe MR: vena contracta ≥ 0.7 cm, effective regurgitant orifice area ≥ 0.40 cm², regurgitant volume ≥ 60 mL, regurgitant fraction ≥ 50%.

Do right now

In this order

First moves

Hyperdynamic LV in acute HF suggests MR

→

Bridge with nitroprusside and balloon pump

→

Acute severe MR: emergency valve surgery

Why each step

Hyperdynamic LV in acute HF suggests MRSevere acute MR can be underestimated on color Doppler; suspect it when acute heart failure occurs with a hyperdynamic left ventricle, and get TEE to define the mechanism or look for endocarditis.

Bridge with nitroprusside and balloon pumpPending surgery, cut afterload with an IV vasodilator (nitroprusside, nicardipine or nitroglycerin) and an intra-aortic balloon pump: forward stroke volume rises and regurgitant volume falls; hypotension often limits vasodilators.

Acute severe MR: emergency valve surgeryAcute severe MR requires emergency mitral repair or replacement, with coronary revascularization at the same operation when ischemia is the cause.

Management

Orders

Secondary MR: optimize heart failure therapy firstTreat secondary MR first with guideline-directed heart failure therapy (ARNI or ARB, carvedilol-type beta-blocker, aldosterone antagonist) plus CRT for LBBB. Vasodilators do not help asymptomatic primary MR with normal LV function.

TEER for symptomatic patients unfit for surgeryTranscatheter edge-to-edge repair suits severe primary MR with NYHA III–IV symptoms in patients who cannot have surgery, and GDMT-refractory secondary MR with LVEF 20–50%, LVESD ≤ 70 mm and PA systolic pressure ≤ 70 mmHg.

Red flags & don'ts

Avoid harm

Papillary rupture follows inferoposterior MI complicationPost-MI papillary muscle rupture usually follows an inferoposterior infarct because the posteromedial muscle has a single blood supply; it presents as abrupt pulmonary edema with a new apical holosystolic murmur.

Chronic MR brings atrial fibrillation: anticoagulate complicationChronic MR enlarges the left atrium, leading to atrial fibrillation and thromboembolism; anticoagulate patients with MR and atrial fibrillation.

Acute or chronic mitral regurgitation?

Commonly confused

Usual cause	Papillary muscle or chordal rupture, endocarditis
Presentation	Sudden pulmonary edema and shock
Murmur	May be soft or absent
Rhythm	Usually sinus
Treatment	Afterload reduction, IABP, emergency surgery

Commonly confused

Tell apart

Tricuspid regurgitation murmur louder with inspirationDistinguish MR from tricuspid regurgitation by respiration: the TR murmur gets louder with inspiration; the MR murmur does not.

More detail

Reference

Show 7 reference facts

If primary MR cannot be repaired, a mechanical prosthesis is preferred (tissue valves wear faster in the mitral position) except in older patients; in secondary MR, replacement beats a downsized annuloplasty ring.

In decompensated MR, valve replacement can markedly depress EF because the ventricle had come to rely on the low-afterload leak into the atrium; surgical risk is high when EF is below 30%.

Once MR is severe, about 8% of asymptomatic patients become symptomatic each year.

Atrial fibrillation, pulmonary hypertension, a flail leaflet or left atrial dilation alone is not an indication for MR intervention; early repair may still be reasonable when surgical risk is low and repair likely.

Loop diuretics relieve exertional and nocturnal dyspnea in chronic MR; digoxin may help symptoms with atrial fibrillation or when surgery is not an option.

During CABG, repair only severe secondary MR; adding repair for moderate ischemic MR did not improve remodeling or survival and caused more adverse events.

Chest x-ray in acute MR shows pulmonary edema with a normal heart size; chronic MR shows left atrial and LV enlargement.

Pearl

Lower the afterload and more blood goes forward: nitroprusside and a balloon pump help acute MR — the same pump that is forbidden in aortic regurgitation.

Sources · Merck Manual Professional — Mitral Regurgitation · Otto CM et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation 2021;143:e72–e227 (full text, STS-hosted PDF) · Merck Manual Professional — Complications of Acute Coronary Syndromes · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).