Continuity Equation AVA Calculation — EECC MCQ

Correct answer: D — AVA = (π × (LVOT diameter/2)² × LVOT VTI) / AV VTI = (3.14 × 1.0² × 22) / 80 = 0.86 cm², consistent with severe AS (AVA ≤1.0 cm²)

The continuity equation is the standard method for calculating AVA by echocardiography, based on the principle of conservation of mass (flow through the LVOT = flow through the AV): AVA = (LVOT area × LVOT VTI) / AV VTI. LVOT area = π × (D/2)² = 3.14 × 1.0² = 3.14 cm². AVA = (3.14 × 22) / 80 = 69.08 / 80 = 0.86 cm². This AVA ≤1.0 cm² is consistent with severe AS. The LVOT diameter measurement is the main source of error (small errors are squared), which is why the dimensionless index (LVOT VTI/AV VTI = 22/80 = 0.275, <0.25 threshold borderline) is useful as it avoids the LVOT diameter measurement. The 2025 ESC VHD Guidelines recommend systematic echo assessment using multiple parameters (Vmax, mean gradient, AVA, DI) for AS grading.

Reference: ESC/EACTS (2025): VHD Guidelines; ASE/EACVI Echo Guidelines