Postural orthostatic tachycardia syndrome (POTS)

Postural orthostatic tachycardia syndrome, better known as POTS, has to do with something we all do every day without thinking: standing up. In POTS, the heart speeds up too much when a person stands. That's tachycardia, a pulse that's too fast. POTS is a common condition, and it's a type of autonomic dysregulation, meaning a problem with how the autonomic nervous system makes its adjustments. That's the part of the nervous system that runs on autopilot, without you having to decide anything. POTS also comes with orthostatic intolerance: symptoms that show up while standing and can ease once you lie down.

Here's what happens inside the body. When someone stands up, gravity pulls downward, and some of the fluid inside the blood vessels moves out into the surrounding tissues. As a result, each heartbeat sends out less blood; that amount is called stroke volume. In POTS, the sympathetic nervous system, the part of that autopilot that steps on the heart's gas pedal, overreacts, and even so, stroke volume stays low. Picture a water pump that pushes out less than it should with every stroke: someone keeps pressing the button to make it pump faster, but each stroke still comes up short. That sped-up pumping is the tachycardia.

Besides the fast pulse, standing up can bring on dizziness, fainting, and palpitations, which means feeling your heartbeat pounding or racing in your chest. And POTS often starts after a pregnancy, major surgery (in other words, a big operation), trauma, or a viral infection.