valve area

Valve area is simply how big the opening is when a valve is fully open — the size of the doorway through which blood must pass. It is usually expressed in square centimetres, and it is one of the most important numbers for judging how severe a stenosis is.

The logic is intuitive: the smaller the opening, the harder it is for blood to get through. A normal aortic valve opens to roughly 3–4 cm²; as it narrows, the area shrinks, and a value below about 1 cm² generally signals severe aortic stenosis. A normal mitral valve opens to about 4–6 cm², with severe mitral stenosis below roughly 1.5 cm².

Valve area is estimated non-invasively by echocardiography, either by directly tracing the opening or by calculating it from blood flow and velocity (the continuity equation), and sometimes by other formulas. Because each method has assumptions and pitfalls, clinicians read valve area alongside other measures — the pressure gradient and flow velocity — and in the context of symptoms rather than relying on any single number.

Thresholds are guides, not absolutes; severity grading integrates several measurements and clinical findings, which is a task for cardiology assessment.