# How Is the Aortic Valve Area Index Calculated?

By Valerie Becker

Calculating the aortic valve area index is a critical component of assessing the severity of aortic stenosis. This index is used to determine if a patient requires surgery or other interventions. In this article, we will explore how the aortic valve area index is calculated.

Firstly, let’s understand what the aortic valve area is. The aortic valve area is the opening through which blood flows from the left ventricle to the aorta.

In patients with aortic stenosis, this opening becomes narrowed due to calcium build-up on the valve leaflets. As the opening narrows, it becomes harder for blood to flow through it, leading to increased pressure in the left ventricle and reduced blood flow to the body.

To calculate the aortic valve area index, we need to measure both the valve area and patient’s body surface area (BSA). The BSA can be calculated using various formulas based on height and weight measurements.

The most common method used to measure the aortic valve area is echocardiography. This non-invasive test uses ultrasound waves to produce images of the heart and its valves. During an echocardiogram, measurements are taken of the velocity of blood flow across the narrowed valve and its diameter.

Once we have these measurements, we use them in an equation known as Gorlin formula to calculate the aortic valve area (AVA). The formula is as follows:

AVA = (CO / HR) x (44.3 / peak gradient)

Where CO represents cardiac output, HR represents heart rate, and peak gradient represents maximum pressure difference across the narrowed valve.

After calculating AVA, we then divide it by BSA to obtain the aortic valve area index (AVAI). This value helps us determine whether or not intervention such as surgery or transcatheter aortic valve replacement (TAVR) should be considered.

It’s important to note that while the aortic valve area index is a valuable tool for assessing the severity of aortic stenosis, it should not be used in isolation. Other factors such as symptoms, exercise tolerance, and left ventricular function should also be considered.

In conclusion, the aortic valve area index is crucial in determining the severity of aortic stenosis and whether or not intervention is necessary. By measuring both the valve area and patient’s BSA and using the Gorlin formula, we can obtain this important value.