Causes Problems for Most POTS Patients
Orthostatic intolerance is defined as the inability to tolerate upright position due to increased symptom load which is generally relieved by lying down. Many people without postural orthostatic tachycardia syndrome (POTS) feel orthostatic intolerance when they are sick with COVID or the flu – new symptoms appear when they stand up to head to the bathroom. POTS is a form of orthostatic intolerance.
Here are the symptoms of orthostatic intolerance that are common in people with POTS:
Head
Heart
Digestive System
General
Several factors related to blood flow in the body determine whether you develop orthostatic intolerance.
The autonomic nervous system helps control many involuntary bodily functions, including heart rate and blood pressure. These are controlled independently and can keep adequate blood flow to the heart and brain regardless of body position in healthy individuals. When the autonomic nervous system malfunctions, as it does in POTS, then blood flow toward the heart is decreased, causing an increase in both heart rate and force of contraction.
The sympathetic nervous system releases norepinephrine and epinephrine to increase both heart rate and blood pressure. In order to increase blood pressure, the blood vessels constrict, making their diameter smaller. When the blood volume, muscle pumps and autonomic nervous system are normal, orthostatic intolerance does not develop. But when blood flow to the heart and head decreases, then orthostatic intolerance can occur.
When you move from sitting to standing, there is a change in the pull of gravity on your body. When you stand up, gravity pulls the blood in your body down toward your legs and feet and away from your heart and brain. The response of the body to this change of position differs based on blood volume, intact muscle pumps, and function of the autonomic nervous system.
Healthy person
Person with POTS
We use this phenomenon to quickly and easily diagnose POTS: the standing test.
Standing Test
1. Lay on your back for 5 minutes and be as still as possible. While still laying down, take the pulse and write it down.
2. Stand up still as possible for 2 minutes without leaning or flexing leg muscles. Take the pulse while still standing. If there is no significant change in pulse, continue standing up to 10 minutes, taking the pulse every 2 minutes.
If the heart rate is greater than 120 beats per minute at any point while standing, POTS might be indicated. For adults age > 19, an increase in heart rate of 30+ beats per minute may indicate POTS. For children and teens age <19, an increase in heart rate of 40+ beats per minute is consistent with POTS.
You can use the Stand Test for POTS app to track changes in heart rate during this test. If you have an automatic blood pressure cuff at home, you can use it to monitor blood pressure and pulse for you. It is normal to have a decrease in blood pressure by up to 20/10 mmHg when standing.
Want to learn more? Listen to Episode 7 of The POTScast where Dr. Cathy Pederson discusses orthostatic intolerance.