Hakki Formula: A simplified calculation for Aortic Valve Area (AVA) used primarily in the cardiac catheterization lab as an alternative to the Gorlin equation.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Quick estimation of Aortic Valve Area (AVA) during cardiac catheterization.
As a bed-side or "sanity-check" calculation to verify more complex Gorlin equation results.
In patients with standard heart rates (60–100 bpm) where more complex time-averaging constant is unnecessary.
Section 2
Formula & Logic
The Formula
AVA = Cardiac Output (L/min) / √Peak-to-Peak Pressure Gradient (mmHg).
A Simplified Gorlin
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.
Section 3
Pearls/Pitfalls
Limitations
The Hakki formula under-performs in patients with significantly high or low heart rates (bradycardia or tachycardia), as the assumption that $HR imes SEP approx 1$ no longer holds true. In these cases, the full Gorlin equationmust be used.
Echo vs. Cath
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.
Section 4
Evidence Appraisal
Original Proposal
A simplified formula for establishing aortic valve area.
Hakki AH et al. • Am J Cardiol.. 1981;47(3):618-20. Demonstrated high correlation (r = 0.96) between the simplified formula and the original Gorlin method.
