Hakki Formula

AVA = Cardiac Output (L/min) / √Peak-to-Peak Pressure Gradient (mmHg).

The Gorlin equation is $AVA = rac{CO}{HR imes SEP imes 44.3 imes sqrt{Delta P}}$. Hakki noted that for many patients, the product of $HR imes SEP imes 44.3$ (Heart Rate × Systolic Ejection Period × 44.3) is approximately 1.0, allowing for the drastic simplification of the math.

The Hakki/Gorlin formulas measure the hemodynamic (effective) valve area, which may be smaller than the anatomic area measured by planimetry on Echo or CT.