How this calculator works
Continuity compares LVOT stroke volume with mitral inflow VTI and is unreliable with important regurgitation or shunting. The empirical pressure half-time equation uses 220 ms·cm². For a linear E-wave deceleration slope, pressure half-time is approximately 0.29 of deceleration time. Altered ventricular or atrial compliance and recent valvotomy can invalidate the half-time method. The result is an estimate for information only and is not medical advice.
Formula
MVA = π(D_LVOT/2)² × VTI_LVOT/VTI_MV. MVA(cm²) = 220/PHT(ms). PHT ≈ 0.29 × DT; MVA = 220/(0.29 × DT).
Worked example
PHT 220 ms gives 1 cm²; PHT 110 ms gives 2 cm². A 2 cm LVOT with VTI 20 cm and mitral VTI 50 cm gives 1.2566 cm².
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Frequently asked questions
Is 220 a unitless constant?
No. Its use assumes half-time in milliseconds and area in square centimetres.
Why can methods disagree?
They rely on different assumptions about flow conservation, chamber compliance and Doppler measurements.
Is deceleration time the same as pressure half-time?
No. For the assumed linear slope, half-time is about 29% of the full deceleration time.