What are the recommended measurements and treatment options for severe mitral regurgitation?

Measurements for Severe Mitral Regurgitation

For severe mitral regurgitation, use vena contracta width ≥7 mm or effective regurgitant orifice area (EROA) ≥40 mm² as your primary quantitative thresholds, integrating multiple echocardiographic parameters rather than relying on any single measurement. 1, 2

Primary Quantitative Measurements

Vena Contracta Method

• Measure vena contracta width in multiple views (apical 4-chamber and 2-chamber); severe MR is defined as ≥7 mm 1, 2
• Calculate the mean if measurements differ between views (e.g., if 6 mm in one view and 10 mm in another, mean = 8 mm indicates severe MR) 1
• This method works reliably for both central and eccentric jets 1
• Intermediate values (3-7 mm) require confirmation with additional quantitative methods 1

PISA Method (Proximal Isovelocity Surface Area)

• EROA ≥40 mm² indicates severe primary (organic) MR 1, 2
• Regurgitant volume (RVol) ≥60 mL/beat confirms severe primary MR 1, 2
• Regurgitant fraction ≥50% supports severe MR diagnosis 2
• Use color M-mode to assess temporal variation of MR flow throughout systole, as EROA can be highly variable 1
• Set aliasing velocity near 40 cm/s with baseline shifted toward the MR jet for simplified calculation (EROA = r²/2) 1

Lower Thresholds for Secondary (Functional) MR

• EROA ≥20-30 mm² defines severe secondary MR 1, 2
• RVol ≥30-45 mL/beat in low-flow conditions indicates severe secondary MR 1, 2
• These lower thresholds reflect that secondary MR severity is disproportionate to LV size and function 1

Supporting Qualitative Parameters

Color Doppler Assessment

• Do not rely solely on jet area, as color Doppler underestimates very severe regurgitation and eccentric jets are difficult to assess qualitatively 1
• Jet momentum flux relates to peak velocity squared, not just jet size 1
• Large central jet occupying >40% of left atrial area or wall-hugging eccentric jet suggests severe MR 1

Pulmonary Vein Flow

• Systolic flow reversal in more than one pulmonary vein indicates severe MR 1, 2
• Normal pulmonary vein pattern argues against severe MR 1

Mitral Inflow Pattern

• E-wave velocity ≥1.2 m/s with restrictive filling pattern suggests severe MR 1
• A-wave dominant mitral inflow is not compatible with severe MR 1

Continuous Wave Doppler

• Dense, triangular CW signal throughout systole supports severe MR 1
• Peak velocity helps estimate left atrial pressure: LAP = systolic BP - peak MR gradient 1

Cardiac Chamber Assessment

Left Ventricular Dimensions

• In acute severe MR, LV and LA dimensions are normal or only mildly increased 1
• In chronic severe primary MR, expect LV end-diastolic diameter >65 mm or end-systolic diameter >51 mm (end-systolic volume >140 mL) 1
• Normal LV and LA size in an asymptomatic patient excludes chronic severe MR 1

Left Atrial Enlargement

• Significant LA dilation supports chronic severe MR 2
• Acute severe MR presents with normal LA size but elevated LA pressure 1

Advanced Imaging When Echocardiography Is Inadequate

Transesophageal Echocardiography (TEE)

• Perform TEE when transthoracic echocardiography provides insufficient information, for pre-surgical planning, or when MR severity remains uncertain 1, 2
• TEE is essential for guiding transcatheter interventions 1
• TEE may be necessary to accurately determine valve anatomy in acute settings 1

Cardiac Magnetic Resonance (CMR)

• Use CMR when distinction between moderate and severe MR is indeterminate by echocardiography or when echocardiographic and clinical findings are discordant 1, 2
• CMR provides more reproducible quantitative measurements of RVol, regurgitant fraction, and LV volumes 1
• CMR planimetry of regurgitant orifice shows good agreement with PISA method by echocardiography 3

Critical Pitfalls to Avoid

Integration of Multiple Parameters

• Never rely on a single measurement; integrate vena contracta, EROA, RVol, regurgitant fraction, pulmonary vein flow, and chamber dimensions 1, 2
• Internal inconsistency among measurements should prompt additional imaging with TEE or CMR 1

Temporal Variation in Secondary MR

• Recognize that secondary MR severity is dynamic and changes with loading conditions, blood pressure, volume status, and heart rate 4, 5
• Positive pressure ventilation and sedation significantly reduce apparent MR severity 1
• Always reassess severity after optimizing medical therapy before making intervention decisions 4, 5

Non-Holosystolic MR

• Biphasic or early systolic MR (common in secondary MR) leads to overestimation when using single-frame EROA measurements 1
• Use velocity-time integral of the CW Doppler signal to convert EROA to RVol when MR is not holosystolic 1

Eccentric Jets and Acute MR

• Eccentric jets impinging on the atrial wall lose energy and appear smaller than their actual severity 1
• In acute severe MR, a modest regurgitant volume into a non-compliant LA causes severe pulmonary congestion despite smaller measurements 1

Clinical Correlation

• Murmur intensity does not correlate with MR severity; acute severe MR may present with a low-intensity murmur due to elevated LA pressure 2
• Physical examination findings (late-peaking murmur, clear lungs, no diastolic filling sound) help distinguish mild-moderate from severe MR 1

Surveillance Protocol

• Moderate MR: clinical evaluation every 6-12 months with annual echocardiography 4, 2, 5
• Severe MR: clinical evaluation every 6 months with annual echocardiography 4, 2, 5
• Consider exercise echocardiography when exercise-induced symptoms are present to assess dynamic worsening 4, 2