From the Guidelines
The upper limit of normal for aortic stenosis as measured by echocardiography is a mean pressure gradient of less than 40 mmHg and an aortic valve area of greater than 1.0 cm². According to the most recent guidelines 1, the definition of severe aortic stenosis is consistent among guidelines, and it is defined by a mean gradient ≥40 mmHg and valve area <1.0 cm².
Key Points to Consider
- The assessment of the severity of stenotic valve disease should combine the evaluation of valve area with flow-dependent indices such as mean pressure gradient and maximal flow velocity 1.
- The echocardiographic criteria for the definition of severe valve stenosis include a mean gradient >40 mmHg and valve area <1.0 cm² for aortic stenosis 1.
- The guidelines recommend an integrative approach including echocardiographic, CT aortic valve calcium score, and clinical variables to assess the severity of paradoxical low-flow low-gradient AS 1.
Clinical Implications
- Higher velocities and pressure gradients indicate more severe obstruction to left ventricular outflow, which can lead to symptoms like syncope, angina, and heart failure when severe.
- The timing of aortic valve replacement (AVR) is recommended in the presence of symptoms, very severe AS, reduced left ventricular function, or elevated brain natriuretic peptides 1.
Diagnostic Approach
- Echocardiography is the key technique used to confirm the diagnosis of valvular heart disease and assess its severity and prognosis 1.
- Three-dimensional echocardiography and transoesophageal echocardiography can be useful in assessing anatomical features and monitoring the results of surgical valve repair or percutaneous procedures 1.
From the Research
Aortic Stenosis Severity Parameters
The upper limit of normal for aortic stenosis as measured by echocardiography can be determined using parameters such as aortic valve area (AVA) and mean pressure gradient (MPG).
- The study 2 found that a mean pressure gradient (MPG) of 22 mmHg and an aortic valve area (AVA) of 1.15 cm² correspond to a peak aortic valve velocity (Vmax) of 3 m/sec.
- For a Vmax of 4 m/sec, the corresponding MPG and AVA values are 39 mmHg and 0.90 cm², respectively 2.
- More severe cases, with a Vmax of 5 m/sec or 5.5 m/sec, are associated with MPG values of 60 mmHg or 65 mmHg, and AVA values of 0.76 cm² or 0.68 cm², respectively 2.
Diagnostic Challenges
The diagnosis of aortic stenosis can be challenging, particularly in cases with low-gradient aortic stenosis (LGAS) 3, 4, 5.
- LGAS is characterized by an AVA of less than 1.0 cm², but a mean pressure gradient of less than 40 mmHg 3, 5.
- Stress echocardiography can be useful in diagnosing LGAS, particularly in patients with symptomatic LGAS and low stroke volume or low ejection fraction 3, 4, 5.
Reference Values
The study 6 provides reference values for aortic valve area (AVA) in a large population.
- The average AVA was found to be 2.6 ± 0.7 cm² in patients with normal valves and 2.3 ± 0.7 cm² in patients with aortic sclerosis 6.
- The study also found that AVA values below the cutoffs for moderate or severe aortic stenosis can be found in patients without the disease, highlighting the risk of overestimating aortic stenosis when relying solely on flow-corrected indices 6.