# How Is the Aortic Valve Dimensionless Index Calculated?

By Eric Wilson

The aortic valve dimensionless index (AVDI) is a measure used to assess the function of the aortic valve in patients with heart disease. It is a non-invasive way to determine the severity of stenosis, or narrowing, of the aortic valve.

The AVDI is calculated by dividing the velocity of blood flow across the aortic valve by the velocity of blood flow in the left ventricular outflow tract (LVOT). Let’s take a closer look at how this calculation is done.

## Step 1: Measuring Blood Flow Velocity

The first step in calculating the AVDI is to measure blood flow velocity across the aortic valve and in the LVOT using echocardiography. This is typically done using Doppler ultrasound imaging. The technician will place an ultrasound probe on the patient’s chest and use sound waves to create images of the heart.

### Aortic Valve Velocity Measurement

To measure blood flow velocity across the aortic valve, the technician will use color Doppler imaging and pulse wave Doppler. Color Doppler imaging shows blood flow direction and speed using different colors on an ultrasound image. Pulse wave Doppler measures blood flow velocity at a specific point in time.

### LVOT Velocity Measurement

To measure blood flow velocity in the LVOT, pulse wave Doppler is used again. The technician will place an ultrasound probe just below the aortic valve and measure blood flow velocity as it leaves the left ventricle.

## Step 2: Calculating AVDI

Once both velocities have been measured, they can be used to calculate the AVDI using this formula:

AVDI = Vaortic / VLVOt

Where Vaortic is blood flow velocity across the aortic valve and VLVOt is blood flow velocity in the LVOT.

### Interpreting AVDI Results

The AVDI is a dimensionless index, which means that it has no units of measurement. It ranges from 0 to 1, with higher values indicating more severe aortic stenosis. A value of 0.25 or less is considered normal, while a value greater than 0.5 indicates severe aortic stenosis.

## Conclusion

The AVDI is an important tool for assessing the function of the aortic valve in patients with heart disease. By measuring blood flow velocity across the aortic valve and in the LVOT, doctors can calculate the AVDI and determine the severity of stenosis. With this information, they can develop an appropriate treatment plan for their patients.