Normal Aortic Valve Hemodynamics
A normal aortic valve without stenosis has a peak velocity below 2.0 m/s and a mean pressure gradient less than 5 mmHg, representing minimal resistance to blood flow during systole. 1
Normal Values
These values represent the normal physiologic pressure difference required to propel blood from the left ventricle into the aorta during normal cardiac output. 1
Clinical Significance and Interpretation
The mean gradient is calculated by averaging instantaneous gradients throughout the entire ejection period using the simplified Bernoulli equation (P = 4V²), where velocity measurements are obtained via continuous-wave Doppler echocardiography. 1
Multiple echocardiographic windows should be interrogated to capture the highest velocity and avoid angle-related underestimation, which is a critical technical consideration. 1
Transition to Pathologic States
Understanding normal values is essential because the transition from normal to pathologic begins at specific thresholds:
- Aortic sclerosis (at risk): Peak velocity <2.0 m/s with valve thickening but no hemodynamic obstruction 2
- Mild aortic stenosis: Peak velocity 2.0-2.9 m/s or mean gradient <20 mmHg 2
- Moderate aortic stenosis: Peak velocity 3.0-3.9 m/s or mean gradient 20-39 mmHg 2
- Severe aortic stenosis: Peak velocity ≥4.0 m/s or mean gradient ≥40 mmHg 2
Important Caveats
Blood pressure status affects velocity and gradient measurements—hypertension can alter peak velocity and mean gradient, so blood pressure should be recorded at every examination and ideally the evaluation should be performed when the patient is normotensive. 2
In research studies of patients without valvular obstruction (peak velocity <2.5 m/s), the mean aortic valve area was 2.6±0.7 cm² in normal valves and 2.3±0.7 cm² in patients with aortic sclerosis, demonstrating that normal values have some variability. 3