In plain language
What it is
A form of orthostatic intolerance where the heart races on standing, often with dizziness and fog.
Why it matters
It is common in long COVID and overlaps heavily with vascular and autonomic problems.
Think of it like
Stand up and your body's autopilot overcorrects, revving the engine to keep blood to your brain.
For specialists
Formal definition
Postural orthostatic tachycardia syndrome: a sustained heart-rate rise of at least 30 beats per minute on standing without orthostatic hypotension.
Mechanism
Associated with autonomic neuropathy, hypovolemia, and in some cases autoantibodies to adrenergic receptors.