Mitral regurgitation is systolic flow from the left ventricle into the left atrium when the mitral leaflets fail to coapt. On transthoracic echo, color Doppler locates the jet, but severity is graded with an integrative ASE-style approach: vena contracta, PISA-derived effective regurgitant orifice area (EROA), regurgitant volume, supporting spectral Doppler, and chamber size. The goal is to separate trace mitral regurgitation from mild and severe disease and to avoid the technical errors that inflate or shrink the jet.
Confirm the Mechanism First
Primary MR is a leaflet, chordal, or papillary problem: prolapse, flail, rheumatic restriction, perforation, or cleft. Jets are often eccentric and opposite the diseased leaflet. Secondary MR reflects ventricular tethering or atrial annular dilation. Mechanism tells you whether a wall-hugging jet can still be severe and which cutoffs to emphasize. Thin leaflets with a dilated ventricle or atrium should not be labeled degenerative on color appearance alone.
Color Flow for Trace and Mild Mitral Regurgitation
Color is the screen, not the grade. Use parasternal long axis and apical two-, three-, and four-chamber views, a narrow sector, Nyquist near 50 to 60 cm/s, and gain just below noise. A tiny, brief, central jet with normal leaflets is trace mitral regurgitation (sometimes reported as mitral valve trace regurgitation) and is usually physiologic. Mild mitral regurgitation is typically a small central jet, vena contracta under 0.3 cm, a faint incomplete continuous-wave (CW) envelope, and no pulmonary-vein systolic reversal. Eccentric Coanda jets look smaller than their orifice. Flail, multiple jets, a dense CW signal, or a dilated left atrium should trigger quantification rather than a color-only label of mild mitral valve regurgitation.
How to Quantify Severity
Use at least two quantitative methods plus supportive signs. When numbers disagree, hunt for a technical cause. Lab technique is covered in a course on mitral regurgitation mechanisms and quantification.
Vena contracta
Zoom coaptation in parasternal long axis or a well-aligned apical view. Measure the narrowest jet neck at or just downstream of the orifice in mid-systole, perpendicular to flow. Commonly cited ranges:
- Less than 0.3 cm: mild
- 0.3 to 0.69 cm: moderate
- 0.7 cm or greater: severe
Vena contracta is less load-sensitive than jet area. It is unreliable with multiple jets or a crescentic orifice, which is typical of secondary MR.
PISA, EROA, and regurgitant volume
Shift the color baseline in the jet direction to an aliasing velocity of about 30 to 40 cm/s so a hemisphere is clear. Measure radius from the aliasing shell to the orifice. For holosystolic jets, use mid-systole. EROA equals 2πr² times aliasing velocity divided by MR peak CW velocity. Regurgitant volume equals EROA times the MR velocity-time integral.
Commonly cited ranges for chronic primary MR:
- Mild: EROA less than 0.20 cm², regurgitant volume less than 30 mL, regurgitant fraction less than 30%
- Moderate: values between the mild and severe cutoffs
- Severe: EROA 0.40 cm² or greater, regurgitant volume 60 mL or greater, regurgitant fraction 50% or greater
In secondary MR, an EROA of 0.20 cm² or a regurgitant volume of 30 mL is often hemodynamically important because the orifice is crescentic and driving velocity may be lower. Do not copy primary cutoffs onto a tethered valve without comment. Examples are reviewed in case studies of primary mitral regurgitation and case studies of secondary mitral regurgitation.
Supportive Doppler and chambers
- CW jet: faint and incomplete favors mild; dense and triangular favors severe or acute MR
- Mitral inflow: A-wave dominant argues against severe chronic MR; E velocity greater than about 1.2 m/s supports severe chronic MR
- Pulmonary veins: systolic reversal in more than one vein is specific for severe MR if the jet is not isolated to that vein
- Chambers: chronic severe MR enlarges the left atrium and, over time, the left ventricle. Normal size makes chronic severe MR unlikely except in acute regurgitation
Checklist for Trace, Mild, and Severe MR
- Trace: tiny central jet, normal leaflets, no chamber enlargement
- Mild: small central jet, vena contracta less than 0.3 cm, EROA less than 0.20 cm², regurgitant volume less than 30 mL, incomplete CW jet, no systolic pulmonary-vein reversal
- Severe primary: vena contracta 0.7 cm or greater, EROA 0.40 cm² or greater, regurgitant volume 60 mL or greater, dense CW jet, pulmonary-vein systolic reversal, dilated left atrium with left ventricular volume load, or flail
- Severe secondary: lower EROA and volume values may still be important; integrate tenting, annular dilation, ventricular function, and pulmonary pressures
Pitfalls That Skew Severity
- Color gain and Nyquist errors: too much gain or a low Nyquist inflates the jet; too little gain or a high Nyquist shrinks it
- Coanda jets hug the wall and look smaller than central jets of equal orifice
- Late-systolic MR in mitral valve prolapse: mid-systolic PISA overestimates EROA if the jet is not holosystolic
- Noncircular or multiple orifices make a single PISA radius and vena contracta misleading
- Acute MR and loading: pulmonary edema can accompany a modest jet and normal chambers; hypertension enlarges the color jet, so record cuff pressure
When parameters conflict, return to mechanism, repeat vena contracta, and confirm a hemispheric PISA shell. Poor windows or a highly eccentric jet warrant transesophageal echocardiography, not higher color gain.
Accurate grading of mitral regurgitation supports clinical judgment, follow-up intervals, and referral timing under current guidelines. IAME offers accredited ultrasound CME courses, including an update on mitral regurgitation, for structured case review.
Frequently Asked Questions
What are the symptoms of moderate to severe mitral regurgitation?
Common symptoms include exertional dyspnea, fatigue, orthopnea, palpitations, and edema. Acute severe MR may present with pulmonary edema, yet some patients with severe regurgitation remain asymptomatic and are identified by chamber remodeling on echo.
What kind of sound does a mitral regurgitation murmur make?
The classic murmur is high-pitched, blowing, and holosystolic at the apex, often radiating to the axilla. Jet direction can send the murmur to the back or base, and intensity does not reliably track severity.
Does mitral valve prolapse get worse with age?
Prolapse may remain stable, but some patients progress as leaflets thicken, chords elongate or rupture, or the annulus dilates. New flail, rising EROA, or progressive atrial and ventricular enlargement should prompt closer surveillance under current valvular guidance.
How should mild or trace mitral regurgitation be interpreted?
Trace mitral regurgitation with normal leaflets and chambers is usually physiologic and does not, by itself, warrant valve intervention. Mild mitral regurgitation still needs a mechanism note and follow-up if leaflets are abnormal, the ventricle is remodeling, or symptoms are unexplained; individual management belongs with the treating clinician and current guidelines.
