1. What is the Aortic Valve Continuity Equation?

The continuity equation estimates aortic valve area (AVA) using the principle of conservation of flow. It compares the flow through the left ventricular outflow tract (LVOT) with the flow through the aortic valve (AV) to determine valve area.

2. How Does the Calculator Work?

The calculator uses the continuity equation:

Where:

• \( LVOT\ Area \) — Cross-sectional area of the left ventricular outflow tract (cm²)
• \( VTI\ LVOT \) — Velocity-time integral of the LVOT flow (cm)
• \( VTI\ AV \) — Velocity-time integral of the aortic valve flow (cm)

Explanation: The equation is based on the principle that the stroke volume through the LVOT must equal the stroke volume through the aortic valve.

3. Importance of AVA Calculation

Details: Accurate AVA estimation is crucial for diagnosing aortic stenosis severity and determining appropriate treatment strategies.

4. Using the Calculator

Tips: Enter LVOT area in cm², VTI LVOT in cm, and VTI AV in cm. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal aortic valve area?
A: Normal AVA is 3-4 cm². Severe aortic stenosis is typically defined as AVA <1.0 cm².

Q2: How is LVOT area determined?
A: LVOT area is calculated from the LVOT diameter (π × (LVOT diameter/2)²) measured in parasternal long-axis view.

Q3: What are typical VTI values?
A: Normal LVOT VTI is typically 18-22 cm, while aortic valve VTI varies with stenosis severity (higher in severe stenosis).

Q4: Are there limitations to this method?
A: Accuracy depends on proper measurement technique and assumes circular LVOT geometry. Errors in diameter measurement are squared in area calculation.

Q5: When should this calculation be used?
A: This is the standard method for quantifying aortic stenosis severity in echocardiography when Doppler alignment is optimal.