One increasingly recognized autonomic nervous system (ANS) disorder is postural orthostatic tachycardia syndrome or POTS. It occurs in those recovering from COVID-19, which makes it a perfect example post-infectious, immunity and inflammation (I-Cubed). POTS causes seemingly causes cardiac symptoms such as rapid palpitations, lightheadedness, chest discomfort, and shortness of breath, as well as non-cardiac symptoms including brain fog, headache, nausea, tremulousness, generalized weakness, and blurred or tunnel vision. People with POTS complain of non-specific gastrointestinal symptoms of abdominal pain, nausea and irritable bowel syndrome, and urinary complaints including bladder symptoms. It is associated with involves poor vascular tone, which limits the ability of the blood vessels in the legs to move blood upward toward the heart and head against gravity when you suddenly stand upright from a lying or sitting position, but symptoms can even be present lying flat at night due to a high resting heart rate.
While stress can make POTS feel worse, it is not stress-induced; rather the underlying biological dysfunction simulates stress. The essential difference is that people with POTS do not suffer from a primary emotional disorder; they are suffering from a hard to diagnose medical event. If you are an individual with POTS, you may have an unknown source of anxiety and stress resulting from altered ANS dysfunction. In a sense, you are hard wired to have an accelerated pulse rate, even when stress is not a factor.
Screening for ANS disorders like POTS starts with measurement of heart rate (HR) and systolic blood pressure (SBP) to 5 minutes of head up tilting (HUT) or prolonged standing, which will indicate the correct diagnosis and differentiate it from orthostatic hypotension. To simply understand the three different types of abnormal HUT table test, I use an objective cutoff of <100 millimeter of mercury (mm Hg) as the definition of hypotension, and >100 beats per minutes (bpm) as the definition of tachycardia. When both SBP and HR increase to >100 (mmHg and bpm) with HUT (or standing), this indicates POTS. When both the BP and HR fall to <100 this indicates uncompensated orthostatic hypotension. Rather, if SBP falls to <100 mmHg and HR increases to > 100 bpm, this is indicates compensated orthostatic hypotension.
Each of these disorders are treated differently, however a general rule is the importance of adequate hydration, dietary salt, and exercise as tolerated. Those with low SBP (<100) at rest should be offered proamatine (Midodrine) and fludrocortisone (Florinef) to directly increase blood pressure and indirectly reduce bothersome tachycardia. However, individuals with POTS are treated with a beta-blocker. All individuals should be screened by a physician for potentially harmful medications that can cause or worsen ANS symptoms such as amphetamines, which can speed up the HR, and SSRI anti-depressants, which can aggravate symptoms of hypotension due to direct effect on the ANS.