Description, Physiology & Onset
Hyperadrenergic POTS is a subtype of POTS that affects about 10% of patients with dysautonomia symptoms due to orthostatic intolerance. (Grubb et al, 2011) The mechanism differs from other types in so far as it is caused by centrally driven sympathetic activation. In other words, symptoms are caused directly from an ANS malfunction, rather than the ANS malfunction being a response to another cause. This results in patients having increased norepinephrine (adrenaline) in circulation and a rise in systolic blood pressure upon standing.
Two additional characterizations of hyperPOTS go hand-in-hand - hypovolemia and the reduction in the activity of the enzyme renin and aldosterone. When a person with hyperPOTS is upright, there is a loss of plasma blood volume into the surrounding tissue (hypovolemia). In people without hyperPOTS, there is a normal reduction in urinary sodium levels when upright. This mechanism doesn't happen effectively in a person with hyperPOTS and this contributes to the severity of the reduced blood volume upon standing. In addition, the plasma enzyme renin plays a major role in the regulation of blood pressure, thirst, and production of urine. When standing, the activity of renin and aldosterone is greatly reduced in a person with hyperPOTS.
The third major characteristic is the elevated norepinephrine and epinephrine levels in a person with hyperPOTS. Adrenaline is a neurotransmitter, a substance communicating within the nervous system and it is active in the synapse, the junction between nerves. When present, it causes activation of the sympathetic nervous system, causing an increase in HR and/or BP, commonly known as the “fight-or-flight response” which causes excitement, tremors, etc. The increase of norepinephrine can be activated by different mechanisms, the ANS produces too much adrenaline ( centrally mediated hyperadrenergic activation ), the excess adrenaline does not get cleaned out of the synapse once no longer needed ( Norepinephrine Transporter Deficiency ) or autoimmune antibodies against cholinesterase receptors. (Vanderbilt)
The onset of hyperadrenergic POTS is largely the same as other forms of POTS, with the onset of symptoms following precipitating events such as viral infection, pregnancy or trauma, including surgery. Another cause found in hyperadrenergic POTS is MCAS ( mast cell activation syndrome ). In this case, the circulating vasodilator produces reflex sympathetic activation which causes symptoms like flushing and orthostatic intolerance ( the inability to compensate for the upright posture ). (Vanderbilt)
Diagnosis
The criteria for diagnosis shares many factors with POTS; including the presence of symptoms for 6 months or longer, a Head-Up Tilt Table Test (HUTT) shows tachycardia of 30 BPM or above 120 BPM in the presence of orthostatic intolerance within the first 10 minutes of upright posture. Patients are diagnosed with the hyperadrenergic form of POTS based on an increase in their SBP ( the higher number ) of at least 10 mmHg upon standing or during the HUTT with concomitant tachycardia or serum norepinephrine levels of above 600 pg/ml when upright. (Grubb, et al, 2011)
Symptoms
The symptoms of hyperadrenergic POTS are often shared with other types of POTS but also can be specific to this type of POTS: anxiety, tremors, orthostatic hypertension, and cold hands and feet being specific to this type. Other symptoms include fatigue, palpitations, dizziness and presyncope, syncope, excessive sweating, nausea/ diarrhea/ bloating, excessive stomach acid, increased urine output upon standing. Similar symptoms can be caused by pheochromocytoma ( a benign tumor on the adrenal gland ), so the presence of this must be ruled out before the diagnosis can be made. (Grubb et al, 2011)
Treatment
In addition to increased fluid intake and compression garments, it can be helpful to increase salt intake, but caution is needed when hypertension is present. Twenty (20) minutes of mild aerobic exercise ( in fresh air when possible ) 3 times a week has been proven effective. A fine balance of activity and rest periods can prevent hyperadrenergic symptoms and can promote healthy sleep patterns.(Grubb et al, 2011)
There are many medications that have been effective in symptom improvement, however, there are no FDA approved drugs for the treatment of this type of POTS. The treatment is highly individual, which means some meds will help one patient but not the other. This can create a frustrating process of trial-and-error but often will lead to the discovery of the right combination.
Some of the medications that have been found helpful are:
- Adderall, Ritalin
- Florinef
- Clonidine
- Beta-blockers (especially the combination of Carvelidol and Labetaiol)
- Midodrine
- SSRI/SNRI
- Modafinil
- Methyldopa
One of the more significant findings in the treatment of hyperPOTS is the general observation that centrally acting sympatholytics (Clonidine, Methyldopa & others) and beta-blockers seem to work better to manage symptoms in people with hyperPOTS than patients with neuropathic POTS. (Grubb, et.al)
Prognosis
Hyperadrenergic POTS is often chronic and can be progressive. Some patients are disabled and unable to work while others are able to function with limitations. It has been shown that treatment is challenging since often the symptoms change or increase over time and medications may need to be adjusted or changed.
It is important to note that most research into POTS and subgroups of POTS recognize the inherent problems associated with trying to narrow down the specific subtype. One of the most difficult problems is that the abnormalities seen in different subtypes are not mutually exclusive from other abnormalities. For example, a person with the norepinephrine levels indicative of hyperPOTS may also have QSART levels pointing to neuropathic POTS. Therefore, most physicians specializing in the treatment of POTS disorders focus on the specific abnormal findings instead of focusing on categorizing the subtype. (Vanderbilt) (Grubb)
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Resources:
Blair P. Grubb, Khalil Kanjwal, Bilal Saeed, Beverly Karabin, Yousuf Kanjwal
Clinical presentation and management of patients with hyperadrenergic postural orthostatic tachycardia syndrome. A single center experience, Cardiology Journal, 2011, Vol 18 No. 5
https://journals.viamedica.pl/cardiology_journal/article/view/21202/16806
Vanderbilt University
Autonomic Dysfunction Center
Italo Biaggioni, David Robertson, Cyndya Shibao, Amanda Peltier, and additional faculty members, et al.
Hyperadrenergic Subgroup and POTS subtype: Does it really matter?https://ww2.mc.vanderbilt.edu/adc/38938
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