Mitral Regurgitation
Acute MR (papillary rupture, endocarditis) = surgical emergency with flash pulmonary edema. Chronic MR is insidious, EF is misleadingly preserved. EF 60% in severe MR = significant dysfunction.
Overview
Acute vs Chronic
| Feature | Acute MR | Chronic MR |
|---|---|---|
| Causes | Papillary rupture (post-MI), endocarditis, chordae rupture | Myxomatous (MVP), rheumatic, functional (LV dilation) |
| Presentation | Flash pulmonary edema, cardiogenic shock | Asymptomatic years → dyspnea |
| Treatment | EMERGENCY SURGERY | Surgery when criteria met |
EF in MR is misleading. LV ejects into low-pressure LA → EF artificially preserved. EF 60% in severe MR = significant dysfunction. Don’t wait for 40%.
Acute vs Chronic MR, Detailed Comparison
| Feature | Acute MR | Chronic MR |
|---|---|---|
| LA size | Normal (no time to dilate) | Enlarged (compensatory dilation) |
| LA pressure | Markedly elevated → pulmonary edema | Only mildly elevated (compliant LA absorbs volume) |
| LV size | Normal | Dilated (eccentric hypertrophy from volume overload) |
| Murmur | May be soft/absent (equalization of pressures) or decrescendo | Holosystolic, blowing, radiates to axilla |
| Hemodynamics | Cardiogenic shock, pulmonary edema | Gradual decompensation over years |
| CXR | Flash pulmonary edema, normal heart size | Cardiomegaly, chronic congestion |
| Urgency | Surgical emergency. Stabilize with nitroprusside/IABP | Elective surgery when criteria met |
Acute MR pearl: A patient with sudden flash pulmonary edema + normal-sized heart on CXR + new murmur = acute MR until proven otherwise. Most commonly post-MI (papillary muscle rupture, typically 3–7 days after inferior MI affecting posteromedial papillary muscle).
MR Severity Grading
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Regurgitant volume (mL/beat) | <30 | 30–59 | ≥60 |
| Regurgitant fraction (%) | <30 | 30–49 | ≥50 |
| EROA (cm²) | <0.20 | 0.20–0.39 | ≥0.40 |
| Vena contracta (cm) | <0.3 | 0.3–0.69 | ≥0.7 |
| Color jet area | Small, central | Moderate | Large (>40% LA area) or wall-hugging eccentric jet |
Eccentric jets are deceptive. Wall-hugging (Coanda effect) jets appear smaller on color Doppler than their true severity. Always use quantitative measures (EROA, regurgitant volume) rather than relying on color jet area alone.
Primary vs Secondary MR
| Feature | Primary (Degenerative) MR | Secondary (Functional) MR |
|---|---|---|
| Pathology | Intrinsic valve disease (leaflets, chordae, papillary muscles) | Normal valve; MR from LV dilation/dysfunction |
| Common causes | Myxomatous/MVP, rheumatic, endocarditis, radiation | Ischemic cardiomyopathy, dilated cardiomyopathy |
| Treatment | Mitral valve repair (preferred) or replacement | Optimize GDMT first; MitraClip if persistent COAPT, 2018 |
Workup
Workup
- TTE (severity, LV size/function), TEE for surgical planning
- ECG: Afib common
- CXR, BNP
- Cardiac cath pre-op
Management
Surgery Indications (Chronic Primary MR)
| Indication | Action |
|---|---|
| Symptomatic severe MR | Surgery (repair > replacement) |
| Asymptomatic + EF ≤60% | Surgery |
| Asymptomatic + LVESD ≥40mm | Surgery |
| Secondary MR + HFrEF | MitraClip if on optimal GDMT COAPT 2018 |
| Asymptomatic + new AF | Consider surgery (Class IIa) |
| Asymptomatic + pulm HTN | PASP >50 mmHg at rest, consider surgery (Class IIa) |
Repair > Replacement. Mitral valve repair has lower operative mortality, better LV function preservation, and avoids lifelong anticoagulation. Repair success rates >95% at experienced centers for degenerative MR (posterior leaflet prolapse). Always refer to a surgeon with high repair volume.
MitraClip (Transcatheter Edge-to-Edge Repair) Criteria
| Criterion | COAPT Eligibility |
|---|---|
| MR severity | Moderate-severe to severe (EROA ≥0.3 cm², regurgitant volume ≥45 mL) |
| Symptoms | NYHA II–IVa despite optimal GDMT |
| LVEF | 20–50% |
| LVESD | ≤70 mm |
| GDMT | Must be on maximally tolerated guideline-directed medical therapy |
| Anatomy | Suitable valve morphology for clip placement (assessed by TEE) |
| Heart Team | Deemed prohibitive or high surgical risk |
COAPT vs MITRA-FR: COAPT, 2018 showed benefit; MITRA-FR, 2018 did not. Key difference: COAPT enrolled patients with disproportionate MR (severe MR relative to LV size), while MITRA-FR included proportionate MR (LV too dilated for clip to help). Ensure MR severity is disproportionate to LV dilation before referring for MitraClip.
Medications
Medical Therapy
| Drug | Role |
|---|---|
| ACEi/ARB | Afterload reduction. Reduces regurgitant fraction |
| Diuretics | Volume management |
| GDMT (HF pillars) | For secondary MR with HF |
| Nitroprusside | Acute severe MR bridge to surgery (ICU only) |
On Rounds
Why is EF misleading in MR?
LV ejects into both aorta AND low-pressure LA → inflated EF. EF 60% with severe MR = significant dysfunction (normal heart would be >70%). Surgery threshold is EF ≤60%, not 40%.
What is the COAPT trial?
MitraClip (transcatheter repair) reduced HF hospitalization and mortality in secondary MR with persistent symptoms despite optimal GDMT. Must optimize HF meds first.
Why is repair preferred over replacement for primary MR?
Mitral valve repair preserves the subvalvular apparatus (chordae + papillary muscles), which is critical for LV function. Repair has lower operative mortality (~1% vs 5–10%), better long-term LV function, no need for lifelong anticoagulation (unlike mechanical replacement), and lower risk of prosthetic valve endocarditis. Posterior leaflet prolapse has >95% repair success rate at experienced centers.
What papillary muscle is more commonly involved in ischemic MR, and why?
The posteromedial papillary muscle is far more commonly affected because it has a single blood supply (from the PDA, a branch of the RCA or LCx). The anterolateral papillary muscle has dual blood supply (LAD + LCx) and is therefore protected from single-vessel ischemia. This is why acute MR from papillary rupture most often occurs after inferior MI.
How do you differentiate primary from secondary MR on echo?
Primary MR: structural valve abnormality visible, flail leaflet, prolapse, perforation, vegetation. Jet direction often eccentric. Secondary (functional) MR: valve leaflets appear structurally normal but with restricted closure due to LV dilation/dysfunction, look for tethering, incomplete coaptation, and central regurgitant jet. LV is dilated with wall motion abnormalities.
What is the Coanda effect and why does it matter in MR assessment?
The Coanda effect describes how an eccentric MR jet adheres to the LA wall and appears smaller on color Doppler than its true severity. Wall-hugging jets are common in flail leaflets and prolapse. This leads to underestimation of MR severity by color jet area. Always use quantitative measures (EROA, regurgitant volume, vena contracta) when you see an eccentric jet, rather than relying on visual jet area.
What are the key differences between COAPT and MITRA-FR trials?
Both studied MitraClip in secondary MR, but reached opposite conclusions. COAPT (positive): enrolled patients with disproportionate MR, severe MR (EROA ≥0.3) with only moderate LV dilation (LVESD ≤70mm). MITRA-FR (negative): enrolled patients with proportionate MR, MR severity matched the degree of LV dilation.
When should you use nitroprusside or IABP in acute MR?
Acute severe MR with hemodynamic instability requires urgent afterload reduction as a bridge to emergency surgery. Nitroprusside (ICU, arterial line monitoring): reduces SVR → more blood goes forward through aorta, less regurgitates into LA. IABP: augments diastolic coronary perfusion + reduces afterload during systole, ideal bridge in post-MI papillary rupture. Neither is definitive treatment, surgery is the only cure.
Clinical Examples
📋 Case 1, Acute MR Post-MI (Papillary Rupture)
Patient: 66M, day 5 post-inferior STEMI (delayed presentation, no reperfusion). Sudden onset severe dyspnea with pink frothy sputum.
Vitals: HR 125, BP 78/52, RR 32, SpO2 82% on NRB.
Exam: New harsh holosystolic murmur at apex radiating to axilla. Bilateral crackles to apices. JVD. Cold, clammy extremities.
CXR: Flash pulmonary edema with normal heart size (classic for acute MR).
Bedside echo: Flail posterior mitral leaflet with severe eccentric MR jet, ruptured posteromedial papillary muscle head. LVEF 40%.
Management:
- Intubation for respiratory failure
- IABP placed for hemodynamic support (afterload reduction + coronary perfusion augmentation)
- Nitroprusside drip initiated with arterial line monitoring
- Emergent CT surgery consultation, mitral valve replacement (repair often not feasible with ruptured papillary muscle)
- Intraoperative finding: necrotic posteromedial papillary muscle with complete rupture
Teaching point: Papillary rupture is a mechanical complication of MI occurring 3–7 days post-infarct. The posteromedial papillary muscle (single blood supply from PDA) is affected far more often than anterolateral. Normal heart size on CXR + flash pulmonary edema = acute MR. This is a surgical emergency with ~75% mortality without surgery.
📋 Case 2, Chronic Severe MR with Declining EF
Patient: 54F with known myxomatous mitral valve prolapse and severe MR, followed with serial echos. Previously LVEF 68%, LVESD 36mm. Latest echo: LVEF 58%, LVESD 42mm. Patient reports mild exertional dyspnea (NYHA II).
Echo details: Posterior leaflet prolapse (P2 segment), EROA 0.52 cm², regurgitant volume 72 mL, vena contracta 0.8 cm. Moderate LA dilation. New onset AF on ECG.
Decision analysis:
- Three independent triggers for surgery: (1) Symptoms (NYHA II dyspnea), (2) EF ≤60% (now 58%), (3) LVESD ≥40mm (now 42mm)
- Additionally: new AF is a Class IIa indication
- P2 prolapse is the most favorable anatomy for repair (>98% success rate)
Management: Referred for mitral valve repair (not replacement) at a high-volume center. Successful posterior leaflet repair with annuloplasty ring. Post-op echo: trivial residual MR, EF 52% (expected transient drop after eliminating low-resistance LA pathway).
Teaching point: Do not wait for EF to drop to 40%, EF ≤60% in severe MR already represents significant dysfunction. Multiple triggers were present here. P2 prolapse is the ideal repair scenario. Repair at high-volume centers (>25 repairs/year) has superior outcomes.
📋 Case 3, Functional MR in Heart Failure
Patient: 71M with ischemic cardiomyopathy (prior LAD stent), LVEF 28%, on maximally tolerated GDMT (sacubitril/valsartan, carvedilol, spironolactone, dapagliflozin, hydralazine/ISDN). Persistent NYHA III symptoms despite 6 months of optimized therapy.
Echo: Dilated LV (LVESD 58mm), severe functional MR with central jet. Leaflets structurally normal but tethered with incomplete coaptation. EROA 0.35 cm², regurgitant volume 50 mL.
Assessment:
- Secondary MR from LV dilation, valve is structurally normal
- Already on maximal GDMT with CRT-D in place
- COAPT criteria met: EROA ≥0.3, LVEF 20–50%, LVESD ≤70mm, persistent symptoms on optimal therapy
- STS score high risk for open surgery
- MR appears disproportionate to LV dilation (COAPT phenotype, not MITRA-FR)
Management: Proceeded with MitraClip (transcatheter edge-to-edge repair). Post-procedure: MR reduced to mild, NYHA improved to II, no HF hospitalization at 1-year follow-up. COAPT, 2018
Teaching point: In secondary MR, always optimize GDMT first (including CRT if indicated). MitraClip is reserved for patients with persistent symptoms despite maximal therapy who meet COAPT criteria. The key is ensuring MR is disproportionate to LV size.
Monitoring
| Parameter | Frequency |
|---|---|
| Echo | q6–12mo severe; q1–2y moderate |
| AF surveillance | ECG at visits |
Summary
Summary
Acute MR
Papillary muscle rupture or endocarditis. Surgical emergency with flash pulmonary edema: the left atrium has had no time to dilate, so the regurgitant volume transmits straight to the lungs. A new murmur with shock days after an MI is papillary rupture until echo says otherwise.
Primary vs Secondary
Primary: the valve is diseased (prolapse, flail, endocarditis, rheumatic, radiation) and surgery is the treatment. Secondary: the valve is normal and the ventricle is the problem, so GDMT comes first.
The EF Trap
EF is misleadingly preserved in MR, because the ventricle ejects partly into a low-pressure atrium rather than against systemic afterload. An EF of 60% in severe MR already signals significant dysfunction; waiting for a low EF means operating late on an irreversibly damaged ventricle.
When to Operate
Symptomatic severe MR → surgery. Asymptomatic with EF ≤ 60% or LVESD ≥ 40 mm → surgery, because both mark early decompensation. New atrial fibrillation also tips the decision. Repair beats replacement, so refer to a center that repairs.
MitraClip, and Who It Helped
For secondary MR already on optimal GDMT. COAPT, 2018 was positive while MITRA-FR, 2018 was not: COAPT enrolled disproportionate MR, severe regurgitation with a less dilated ventricle, which is the phenotype that benefits.
Workup
TTE for severity and LV size and function; TEE for mechanism and whether the valve is repairable, which decides where the patient is referred. ECG for AF, which is common. BNP, and cath before surgery.
Biggest Pitfall
Following an asymptomatic patient too long. Symptoms and EF both lag the damage, so serial echo against the LVESD and EF thresholds above is what catches the moment to operate.
📄 One Pager
Text version
CARDIOLOGY · One Pager
Mitral Regurgitation
Acute MR is a surgical emergency with flash pulmonary edema and a normal-sized heart; chronic MR is silent for years while a falsely reassuring EF hides real LV dysfunction.
Severity Grading (Severe MR)
- Regurgitant volume ≥60 mL/beat (mild <30, moderate 30–59).
- Regurgitant fraction ≥50% (mild <30, moderate 30–49).
- EROA ≥0.40 cm² (mild <0.20, moderate 0.20–0.39).
- Vena contracta ≥0.7 cm (mild <0.3, moderate 0.3–0.69).
- Color jet: large (>40% of LA area) or a wall-hugging eccentric jet.
- Workup: TTE for severity and LV size/function, TEE for surgical planning, ECG (AF is common), CXR, BNP, and cardiac cath pre-op.
Acute vs Chronic, Primary vs Secondary
- Acute MR causes: papillary rupture post-MI, endocarditis, chordae rupture. LA is normal size with markedly elevated pressure, so it presents as flash pulmonary edema and cardiogenic shock.
- Chronic MR causes: myxomatous (MVP), rheumatic, functional from LV dilation. The compliant dilated LA absorbs the volume, so patients stay asymptomatic for years before dyspnea.
- Acute murmur may be soft or absent (pressures equalize) or decrescendo; chronic is holosystolic, blowing, radiating to the axilla.
- Primary (degenerative) MR: intrinsic valve disease (myxomatous/MVP, rheumatic, endocarditis, radiation). Treatment is repair, preferred over replacement.
- Secondary (functional) MR: structurally normal valve, MR driven by LV dilation or dysfunction (ischemic or dilated cardiomyopathy). Optimize GDMT first, MitraClip if MR persists.
- Papillary rupture timing: typically 3–7 days after inferior MI, hitting the posteromedial papillary muscle.
Management, Step by Step
1
Acute severe MR is a surgical emergency. Sudden flash pulmonary edema with a normal-sized heart on CXR plus a new murmur is acute MR until proven otherwise. Get emergent CT surgery involved.
2
Stabilize with afterload reduction as a bridge, not a cure: nitroprusside in the ICU with an arterial line (drops SVR so more blood goes forward through the aorta and less regurgitates into the LA), and IABP (augments diastolic coronary perfusion while reducing systolic afterload), ideal in post-MI papillary rupture.
3
Chronic primary MR: check the three surgical triggers at every echo, symptoms, EF ≤60%, and LVESD ≥40 mm. Any one of them is enough to operate.
4
Send primary MR for repair, not replacement, to a surgeon with high repair volume. Repair preserves the subvalvular apparatus, has lower operative mortality (~1% vs 5–10%), better long-term LV function, no lifelong anticoagulation, and lower prosthetic endocarditis risk.
5
Secondary MR: maximize GDMT first (including CRT if indicated), then consider MitraClip only if symptoms persist and COAPT criteria are met, because the valve itself is not the primary problem.
Medical Therapy
ACEi / ARBafterload reduction, lowers the regurgitant fraction
Diureticsvolume management for congestive symptoms
GDMT (HF pillars)for secondary MR with heart failure; treats the cause, which is the dilated LV
Nitroprussideacute severe MR bridge to surgery, ICU only with arterial line
Monitoring
- Echo q6–12 months for severe MR, q1–2 years for moderate, because the surgical triggers (EF, LVESD) are echo findings that appear before the patient feels anything.
- ECG at visits for AF surveillance. New AF in asymptomatic severe MR is itself a Class IIa indication for surgery.
- Track LVESD and EF as a trend, not a snapshot. A drift from EF 68% to 58% or LVESD 36 mm to 42 mm is the signal to operate even if the patient feels well.
- Expect a transient EF drop after repair, because eliminating the low-resistance LA pathway unmasks true LV function.
Pitfalls
- Waiting for EF to fall to 40% before operating. The LV ejects into the low-pressure LA so EF is artificially inflated; EF 60% in severe MR already means significant dysfunction (a normal heart would be >70%). The surgical threshold is EF ≤60%.
- Trusting color jet area in an eccentric jet. Wall-hugging (Coanda effect) jets look smaller than they are, so use quantitative measures (EROA, regurgitant volume, vena contracta).
- Missing acute MR because the murmur is quiet. In acute MR, LA and LV pressures equalize, so the murmur can be soft or absent even in cardiogenic shock.
- Reading a normal heart size on CXR as reassuring. In flash pulmonary edema it is the classic tell for acute MR (no time for the LA or LV to dilate).
- Referring MitraClip for the wrong phenotype. Confirm the MR is disproportionate to LV dilation; proportionate MR in a very dilated LV is the MITRA-FR population that did not benefit.
- Defaulting to replacement in degenerative MR. Posterior leaflet prolapse has >95% repair success at experienced centers.
Refer for Intervention When
- Symptomatic severe MR: surgery, repair preferred over replacement.
- Asymptomatic with EF ≤60%: surgery, because the EF has already fallen further than the number suggests.
- Asymptomatic with LVESD ≥40 mm: surgery, the LV is decompensating structurally.
- Asymptomatic with new AF: consider surgery (Class IIa).
- Asymptomatic with pulmonary hypertension, PASP >50 mmHg at rest: consider surgery (Class IIa).
- Secondary MR with HFrEF on optimal GDMT: MitraClip. COAPT eligibility is EROA ≥0.3 cm² or regurgitant volume ≥45 mL, NYHA II–IVa despite optimal GDMT, LVEF 20–50%, LVESD ≤70 mm, suitable anatomy on TEE, and prohibitive or high surgical risk per the Heart Team.
Key Evidence
- COAPT, 2018: MitraClip reduced HF hospitalization and mortality in secondary MR with persistent symptoms despite optimal GDMT. This is what makes "optimize GDMT first" a prerequisite, not a formality.
- MITRA-FR, 2018: no benefit in secondary MR. The difference is the phenotype: COAPT enrolled disproportionate MR (severe MR relative to LV size), MITRA-FR enrolled proportionate MR where the LV was too dilated for a clip to help.
- Why the posteromedial papillary muscle ruptures: it has a single blood supply from the PDA, while the anterolateral has dual supply (LAD plus LCx) and is protected from single-vessel ischemia. That is why acute MR follows inferior MI.
- Repair volume matters: repair success exceeds 95% at experienced centers for degenerative MR (posterior leaflet prolapse), so where you refer changes the operation the patient gets.
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