How Do You Find the Dimensionless Index With the Aortic Valve?

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By Monica Bates

The dimensionless index (DI) is a valuable tool used to assess the severity of aortic stenosis. It is a non-invasive and cost-effective method that uses echocardiography to determine the ratio of the left ventricular outflow tract (LVOT) velocity to the peak aortic jet velocity. This article will guide you through the process of finding the dimensionless index with the aortic valve.

Step 1: Measure the LVOT velocity
To find the DI, you first need to measure the LVOT velocity. This can be done using Doppler echocardiography, which measures blood flow through the heart using sound waves.

The LVOT is located in the left ventricle, just below the aortic valve. To measure its velocity, place a Doppler sample volume at its base and take a measurement.

Step 2: Measure peak aortic jet velocity
The next step is to measure peak aortic jet velocity. This can also be done using Doppler echocardiography by placing a sample volume just downstream from the aortic valve and measuring blood flow as it passes through.

Step 3: Calculate DI
Once you have measured both velocities, you can calculate DI by dividing LVOT velocity by peak aortic jet velocity:

DI = LVOT Velocity / Peak Aortic Jet Velocity

A normal DI value ranges between 0.25-0.50. If DI is less than 0.25, it suggests severe stenosis, while higher than 0.50 suggests mild or no stenosis.

Tips for accurate measurement:
– Ensure that measurements are taken from multiple angles to obtain an accurate result.
– Use proper equipment and settings to minimize errors.
– Make sure that there are no obstructions or leakage near either site of measurement.


The dimensionless index is a useful tool in assessing the severity of aortic stenosis. It is a simple and cost-effective method that can be done non-invasively using Doppler echocardiography.

By measuring LVOT velocity and peak aortic jet velocity, you can easily calculate the DI value and determine the severity of the condition. Remember to take accurate and multiple measurements to obtain reliable results.