1. What is Dimensionless Index?

The Dimensionless Index (DI) is a ratio used to assess the severity of aortic stenosis by comparing the velocity-time integral of the left ventricular outflow tract (VTI_LVOT) to the velocity-time integral of the aortic valve (VTI_AV). It provides a unitless measure of stenosis severity.

2. How Does the Calculator Work?

The calculator uses the Dimensionless Index equation:

Where:

• \( VTI_{LVOT} \) — Velocity-time integral of left ventricular outflow tract (cm)
• \( VTI_{AV} \) — Velocity-time integral of aortic valve (cm)

Explanation: The ratio compares the flow velocity before and across the stenotic aortic valve, with lower values indicating more severe stenosis.

3. Importance of Dimensionless Index

Details: Dimensionless Index is particularly useful in low-flow, low-gradient aortic stenosis and provides a reliable measure of stenosis severity that is less dependent on flow conditions than absolute velocity measurements.

4. Using the Calculator

Tips: Enter both VTI_LVOT and VTI_AV values in centimeters. Ensure measurements are obtained from proper Doppler echocardiographic views for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the clinical significance of Dimensionless Index values?
A: DI < 0.25 suggests severe aortic stenosis, while DI > 0.25 typically indicates non-severe stenosis.

Q2: When is Dimensionless Index particularly useful?
A: It's especially valuable in low-flow states, paradoxical low-flow low-gradient aortic stenosis, and when echocardiographic windows are suboptimal.

Q3: How does DI compare to other aortic stenosis indices?
A: DI correlates well with aortic valve area and provides complementary information to peak velocity and mean gradient measurements.

Q4: What are the limitations of Dimensionless Index?
A: Accuracy depends on proper Doppler alignment and may be affected by concomitant valvular lesions or significant arrhythmias.

Q5: Can DI be used for serial monitoring?
A: Yes, DI can be used to track disease progression over time, though consistent measurement techniques are essential.