What is a normal pressure gradient for the aortic valve?

From the Guidelines

A normal gradient for an aortic valve is typically less than 10 mmHg for the mean gradient and less than 20 mmHg for the peak gradient. These values represent the pressure difference between the left ventricle and the aorta during systole when blood flows through the aortic valve. In clinical practice, a mean gradient of 10-20 mmHg suggests mild aortic stenosis, 20-40 mmHg indicates moderate stenosis, and greater than 40 mmHg represents severe aortic stenosis, as indicated by the 2021 ACC/AHA guideline for the management of patients with valvular heart disease 1. The gradient increases as the valve becomes narrower due to calcification, fibrosis, or congenital abnormalities, causing the heart to work harder to pump blood through the restricted opening. Echocardiography is the standard method for measuring these gradients, using Doppler techniques to assess blood flow velocities across the valve. Understanding these normal values is essential for clinicians to properly diagnose and monitor aortic valve disease progression and determine when intervention might be necessary.

Some key points to consider when evaluating aortic valve gradients include:

• The severity of aortic stenosis is classified based on the mean gradient, with severe stenosis typically defined as a mean gradient ≥40 mmHg 1.
• The peak gradient is also an important measure, with a peak gradient ≥4 m/s indicating severe stenosis 1.
• The valve area, calculated using the continuity equation, is another important measure of aortic stenosis severity, with a valve area ≤1.0 cm² indicating severe stenosis 1.
• The presence of symptoms, such as exertional dyspnea or decreased exercise tolerance, is also an important consideration in the evaluation of aortic stenosis, as indicated by the 2021 ACC/AHA guideline 1.

Overall, the evaluation of aortic valve gradients is a critical component of the diagnosis and management of aortic stenosis, and clinicians should be familiar with the normal values and the classification of stenosis severity based on these values.

From the Research

Aortic Valve Gradient

• A normal gradient for an aortic valve is generally considered to be less than 5 mm Hg, as stated in the study 2.
• However, the study 2 also found that a mean aortic valve gradient of 10-15 mm Hg or an aortic flow >2.0 m/s should be considered for routine follow-up, as these values can indicate the development of aortic stenosis.
• The study 3 defines severe aortic stenosis as a mean aortic valve gradient (mAVG) exceeding 40 mm Hg, in addition to an aortic valve area (AVA) of < 1.0 cm2.
• Other studies, such as 4, have also used a mean aortic valve gradient of 40 mm Hg as a cutoff for severe aortic stenosis, and have found that higher gradients are associated with improved outcomes after transcatheter aortic valve replacement (TAVR).

Gradient Ranges

• The study 2 stratified participants into three groups based on mean gradients: < 5 mm Hg, 5-9.9 mm Hg, and 10-14.9 mm Hg.
• The study 3 found that the mean systolic flow (MSF) rate at which mAVG tended to exceed 40 mm Hg varied by AVA, with critical AVA (< 0.6 cm2) having an MSF rate of 120 ml/s, severe AVA (0.6-0.79 cm2) having an MSF rate of 183 ml/s, and moderately severe AVA (0.8-0.99 cm2) having an MSF rate of 257 ml/s.
• The study 4 found that every 10 mm Hg increase in mean AVG was associated with a 20% reduction in mortality after TAVR, suggesting that higher gradients may be associated with improved outcomes.