From the Guidelines
The normal aortic valve area in adults is typically considered to be in the range of 3.0 to 4.0 square centimeters (cm²). This measurement is crucial for assessing the severity of aortic stenosis, a common valvular heart disease. A valve area of less than 2.0 cm² indicates some degree of stenosis, with severe aortic stenosis typically defined as an area less than 1.0 cm² 1. The aortic valve area naturally decreases slightly with age due to fibrosis and calcification, even in healthy individuals.
Key Considerations
- The valve area can be calculated using various methods, including the continuity equation during echocardiography, which is the most common non-invasive assessment technique.
- Understanding the normal valve area provides a baseline for diagnosing valvular disease and determining when intervention might be necessary.
- Severe aortic stenosis is unlikely if cardiac output is normal and there is a mean pressure gradient <40 mmHg, but in cases of low flow, lower pressure gradients may be encountered in patients with severe AS 1.
- The degree of aortic valve calcification is a strong predictor of clinical outcome, and quantitation of aortic valve calcium by CT imaging can be useful in patients with low-flow, low-gradient AS of unclear severity 1.
Clinical Decision Making
- The key measurements for clinical decision-making in patients with AS are the maximum aortic velocity, mean pressure gradient, and valve area.
- An additional measurement that may be useful when there are discrepancies in these measures or in other clinical or imaging data is the ratio of the velocity in the LV outflow tract proximal to the aortic valve and the velocity in the narrowed aortic orifice 1.
- In patients with severe AS and LVEF <50%, dobutamine stress echocardiography may be useful to distinguish severe AS with LV systolic dysfunction from primary myocardial dysfunction with only moderate AS 1.
From the Research
Normal Aortic Valve Area in Adults
The normal aortic valve area in adults can vary depending on several factors, including body size and valve morphology.
- A study published in 2018 2 defined severe aortic stenosis as an aortic valve area (AVA) ≤1.0 cm2.
- Another study from 2021 3 suggested that an AVA indexed to height (H) might be more applicable to a wide range of populations and body morphologies, with a proposed threshold of 0.6 cm2/m for defining severe aortic stenosis.
- A 1996 study 4 found that aortic valve areas determined by transthoracic echocardiography, transesophageal echocardiography, and cardiac catheterization were similar, with a mean area of approximately 1.43-1.47 cm2 for non-stenotic valves.
- A 2012 study 5 identified cutoff values for echocardiographic parameters of severity in patients with aortic stenosis and normal flow, including an AVA of 1.15 cm2 corresponding to a peak aortic valve velocity (Vmax) ≥ 3 m/sec.
Factors Influencing Aortic Valve Area
Several factors can influence the aortic valve area, including:
- Body size: Studies have shown that indexing AVA to body surface area (BSA) or height can provide a more accurate assessment of valve severity 6, 3.
- Valve morphology: The shape and size of the aortic valve can affect its area and function.
- Flow characteristics: The presence of normal or abnormal flow can impact the assessment of valve severity 5.
Diagnostic Thresholds
Diagnostic thresholds for aortic stenosis can vary depending on the method used and the population being studied.
- An AVA ≤1.0 cm2 is commonly used to define severe aortic stenosis 2.
- An AVA/H <0.6 cm2/m has been proposed as a threshold for defining severe aortic stenosis 3.
- Cutoff values for other echocardiographic parameters, such as mean pressure gradient and peak aortic valve velocity, can also be used to assess valve severity 5.