I personally think that beta blockers are over-prescribed as a treatment option for hyperadrenergic POTS. They are known to slow heart rate and reduce blood pressure, which on the surface sounds exactly like what we would want. There are many people however that report worsening symptoms while on beta blockers. Some with hyperadrenergic pots even report an increase in blood pressure while on beta blockers. Dr Grubb (one of the leading POTS specialists) has reported this as well.
To
understand the paradoxical effect of beta blockers on some POTS
patients, some background on the sympathetic nervous system is
helpful. The sympathetic nervous system is typically activated by the brain in times of stress. This is the fight or flight response. The brain signals to the adrenal glands to release adrenaline, which causes your heart rate to increase and your blood pressure to rise in order to increase oxygen temporarily to the vital parts of your body that are needed for survival. More specifically, the heart has beta receptors that when activated by adrenaline will increase heart rate and has the side effect of increasing blood pressure because the heart is beating harder and faster. The arteries have alpha receptors that when activated by adrenaline will cause the arteries to constrict in order to increase blood pressure. In addition of anxiety, the sympathetic nervous system can also be activated by a lack of blood flow to the brain. Hyperadrenergic POTS is when the sympathetic nervous system is significantly activated while standing, which is usually caused by to a lack of blood flow to the brain.
Beta blockers work by blocking the beta receptors in the heart. In most people, this causes a drop in heart rate and blood pressure because the heart beats less often which has the side effect of lowering blood pressure. With the beta receptors blocked though, the adrenaline will interact with the alpha receptors in the arteries to raise blood pressure, but not typically as much as it would have been raised by the faster and harder beating heart for the same amount of adrenaline.
For those with hyperadrenergic POTS that report an increase of blood pressure while on beta blockers, I believe that the reason is because more adrenaline ends up being released than would normally be necessary to keep a healthy amount of blood flow to the brain. With the beta receptors blocked, the adrenaline binds to the alpha receptors to raise blood pressure, and the brain will continue to release more and more adrenaline until it gets enough blood.
In this scenario, beta blockers end up having the opposite effect of what you would typically expect.
