Flow-mediated dilation

https://longcovidatlas.org/glossary/flow-mediated-dilation

In plain language

What it is

A test of vessel-lining health: a cuff briefly blocks blood flow in the arm, then releases it, and a healthy artery widens a lot afterward.

Why it matters

Lower dilation means more impairment, and it can be abnormal when standard tests look normal.

Think of it like

Squeeze a garden hose, let go, and watch how well it springs back open.

For specialists

Formal definition

An ultrasound measure of endothelium-dependent vasodilation in the brachial artery following reactive hyperemia.

Mechanism

Reflects nitric-oxide-mediated dilation; reduced FMD indicates impaired endothelial function.

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