Echocardiographic Valvular Assessment
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Direct answer
Quantifying a valve lesion means grading stenosis by maximum velocity, mean gradient and calculated area, and regurgitation by jet size, vena contracta, effective regurgitant orifice and supportive signs — never by colour-jet eyeballing alone. Severe aortic stenosis is velocity above 4 m/s, mean gradient above 40 mmHg, or area below 1.0 cm², with the area derived from the continuity equation: LVOT area times LVOT velocity-time integral divided by the aortic valve VTI. Severe mitral regurgitation declares itself with a vena contracta of 0.7 cm or more, an EROA of 0.4 cm² or more, or systolic flow reversal in the pulmonary veins; severe aortic regurgitation adds a pressure half-time under 200 ms and holodiastolic flow reversal in the descending aorta. Mitral stenosis area comes from planimetry or the pressure half-time formula, 220 divided by PHT in milliseconds.
What you must remember
- Aortic stenosis triad: Vmax over 4 m/s, mean gradient over 40 mmHg, AVA under 1.0 cm² = severe; moderate roughly 3-4 m/s, 20-40 mmHg, 1.0-1.5 cm²; the continuity equation AVA = (π × LVOT radius² × VTI LVOT)/VTI aortic.
- Mitral stenosis numbers: planimetry is the reference method; severe is area 1.0 cm² or less or mean gradient over 10 mmHg; pressure half-time method: MVA = 220/PHT (ms); Wilkins score sums mobility, thickness, calcification and subvalvular change (each 0-4) to judge balloon suitability.
- Severe mitral regurgitation: vena contracta at least 0.7 cm, EROA at least 0.4 cm², regurgitant fraction at least 50 per cent, flail leaflet or coaptation defect, and systolic blunting or reversal in pulmonary venous flow.
- Severe aortic regurgitation: vena contracta at least 0.6 cm, jet width to LVOT diameter 65 per cent or more, pressure half-time under 200 ms, holodiastolic flow reversal in the descending aorta, regurgitant fraction at least 50 per cent, plus a hyperdynamic dilated LV.
- Continuity discipline: measure the LVOT diameter in mid-systole exactly where the pulsed Doppler samples — the error-squaring step — and align the sample without touching the stenotic jet.
- Low-flow low-output trap: a patient with EF under 40 may show velocity and gradient below the severe cut-offs with an area under 1.0 cm² — dobutamine stress echo separates true severe stenosis from pseudo-severe.
- Prosthetic valve grammar: gradients must be compared with the expected range for that valve size and position, not generic numbers; a rising gradient over serial studies outranks any single measurement.
The continuity equation, worked through
A 72-year-old with a crescendo-decrescendo murmur: trace the CW jet across the aortic valve — Vmax 4.3 m/s, mean gradient 44 mmHg, already severe. Confirm with area: LVOT diameter 2.0 cm, so LVOT area = π × 1² = 3.14 cm². Pulsed Doppler in the LVOT gives a VTI of 20 cm; the aortic jet VTI is 105 cm. AVA = (3.14 × 20)/105 = 0.60 cm² — severely stenosed, all three modalities agreeing. Now the same patient decompensates a year later with an EF of 30 per cent, Vmax has "improved" to 2.9 m/s and the mean gradient "fallen" to 26 mmHg — the valve did not improve; the ventricle stopped generating enough force. The step of last resort is dobutamine challenge: velocity and gradient that climb proportionally with flow confirm severe stenosis; an area that stays fixed while gradients stay flat exposes a primary cardiomyopathy with incidental moderate stenosis.
Where students slip
Colour jets are read as volume: a wall-hugging eccentric jet looks small whatever the volume — the vena contracta and support signs carry the verdict, never colour area. The LVOT diameter is measured casually, yet squaring it squares its error; half a millimetre of carelessness moves the area materially. Pressure half-time is used for mitral stenosis in patients with abnormal left atrial compliance or aortic regurgitation, both of which invalidate the 220 formula, and for prosthetic mitral valves where its assumptions also fail. In atrial fibrillation, gradients are sampled beat-to-beat across similar R-R intervals, not averaged blindly, since cycle length swings the numbers. Indian exam papers also expect named supportive signs — presystolic flow reversal in severe AR is a favourite viva answer.
Frequently asked questions
How is aortic valve area calculated by the continuity equation?
LVOT cross-sectional area (from π times the squared radius) multiplied by the LVOT velocity-time integral, divided by the aortic jet VTI. Accurate LVOT diameter measurement is critical because its error is squared.
What echo criteria define severe mitral regurgitation?
Vena contracta of 0.7 cm or more, effective regurgitant orifice area of 0.4 cm² or more, regurgitant fraction of 50 per cent or more, a flail leaflet, or systolic reversal in pulmonary venous flow.
When is the pressure half-time method used for mitral valve area?
MVA = 220/PHT in milliseconds is applied in mitral stenosis when planimetry is difficult. It is unreliable with abnormal atrial compliance, significant aortic regurgitation, or immediately after balloon valvuloplasty.
What is low-flow low-gradient aortic stenosis and how is it resolved?
A depressed ventricle generates sub-threshold velocity and gradient despite a small valve area. Low-dose dobutamine distinguishes true severe stenosis (gradients and velocity rise with flow, area stays small) from pseudo-severe stenosis.
Which signs support severe aortic regurgitation beyond jet size?
Pressure half-time under 200 ms, holodiastolic flow reversal in the descending aorta, jet width exceeding 65 per cent of the LVOT, and a hyperdynamic dilated left ventricle — corroborating signs outrank the colour map.