POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME

If you are battling to stand up without feeling dizzy or faint, then you might be struggling with Postural Orthostatic Tachycardia Syndrome. POTS is becoming increasingly acknowledged as one of the most commonly under-diagnosed health conditions to affect women of childbearing age.

New statistics reveal that many with POTS battle for years without receiving the help they need. Understanding the symptoms and subtypes of POTS can help to get a swift diagnosis and adequate treatment. The following article briefly reviews what is currently known about POTS, including symptoms, possible causes and management.

What is POTS?

POTS stands for Postural Orthostatic Tachycardia Syndrome. It is a condition that refers to the reduced ability of the heart and circulatory system to adjust when shifting to a standing position.^[1] Those with POTS typically experience a higher-than-average heart rate when standing up or straightening the posture, which often causes light-headedness or dizziness as the main symptom. This is known as orthostatic intolerance, with the word orthostasis referring to standing. POTS is recognized as one of the most common forms of autonomic dysfunction and orthostatic intolerance (aside from hypotension).

The elevated heart rate (tachycardia) indicative of POTS is thought to be the result of autonomic nervous system dysfunction. POTS may be a primary standalone disease or a secondary manifestation attributable to another health condition. A diagnosis necessitates a heart rate of 30 or more beats per minute within 10 minutes of standing or tilting the head to an upright position, in the absence of hypotension. While light-headedness is frequent, recent research has revealed that POTS is, in fact, a complex multifactorial condition that can affect multiple systems of the body.

POTS Prevalence is Severely Underestimated

The global prevalence of POTS is thought to be roughly 0.2-1%. In recent years, these statistics have been questioned due to the high degree of misdiagnoses and the lack of physician awareness about the condition. Some studies have shown that POTS prevalence may be as high as 10% in military personnel and just over 6% in vulnerable adolescents. Post COVID pandemic, the prevalence of POTS is seeing a substantial rise in numbers as it is becoming frequently associated with long-haul covid^[2]. The overwhelming majority of those with POTS are premenopausal women of childbearing age (typically between 15 and 25 years), outnumbering others with the condition by 5 to 1 on average. 

A lack of awareness about POTS is central to its underestimated prevalence and frequent misdiagnosis, which has been shown to average up to 75% in some surveys. It has been shown that those with POTS can average 4 years to receive a proper diagnosis, which often entails visits to multiple physicians and several misdiagnoses along the way. It has been ascertained that current approaches are inadequate for diagnosing POTS, especially in children and teens, who are known to be more vulnerable to orthostatic intolerance. Health conferences have been held with leading experts to address the current gap with regard to POTS and its diagnosis; however, it will take some time before adequate measures can be instituted.^[3]

Symptoms

POTS presents with an elevated heart rate after posture adjustment, especially when transitioning from sitting to standing. Symptoms may be noticeably worse during the day and at various times of the menstrual cycle.

Common symptoms include:

• Dizziness or light-headedness
• Fatigue or weakness
• Reduced ability to think or focus
• Headaches
• Heart palpitations
• Chest pain
• Nausea
• Bloating
• Sleep disruption
• Profuse or impaired sweating

As POTS results from dysfunctional autonomic control, symptoms can vary widely, be atypical, and often difficult to diagnose. POTS may additionally contribute to the severity of other health conditions by profoundly impacting cardiovascular well-being.

Types of POTS and Possible Causes

Due to a lack of conclusive research, there is currently no known cause for POTS. It is generally accepted that POTS can result from any factors that reduce sufficient blood flow to and from the extremities, most of which revolve around cardiovascular function.

POTS Subtypes. As POTS is a distinctly human (bipedal) condition, animal trials fail to contribute much valuable information, which has considerably slowed down endeavors to understand the condition. Human studies performed on POTS patients have indicated several potential causes. These have begun to delineate distinct POTS profiles amongst patients, which may also overlap across patient samples.

The four main POTS subtypes are briefly discussed below:

• Neuropathic POTS. This POTS subtype is characterized by reduced sympathetic nervous activity in the lower limbs, resulting in lowered vasoconstriction and a tendency for blood to pool in the extremities upon standing. Some studies suggest that peripheral nerve damage may be implicated in causing neuropathic POTS, bearing associations with viral infections, autoimmune disease and neuropathy. Other features of this type include reduced sweating in the feet, diminished reflex times in the lower limbs and reductions in lower limb norepinephrine levels. These patients are at a higher risk for developing chronic pain disorders.
• Hyperadrenergic POTS. As the name suggests, this form of POTS is characterized by excessive sympathetic nervous activity. Norepinephrine activity is increased in the postural muscles, resulting in blood pressure fluctuations or a hypertensive response towards standing up or straightening the neck. In addition to tachycardia and hypertension, these patients may also sweat profusely and may experience symptoms in response to any form of physical activity or emotional triggers. Hyperadrenergic POTS onset is associated with chronic use of medications that inhibit norepinephrine, mast cell activation syndrome, hyperthyroidism, rare autoimmune diseases and catecholamine-secreting tumors.
• Hypovolemic POTS. Low blood plasma volume (hypovolemia) is linked with promoting POTS and forms one of the subtypes. As many as 70% of those with POTS are seen to have reduced red blood cell counts pertaining to low plasma levels. This is thought to be the result of unbalanced body fluid dynamics, which may be due to the lower levels of renin and aldosterone observed amongst some patients with POTS. Dehydration and various gastrointestinal disorders have also been implicated in POTS onset.
• Cardiovascular Deconditioning in POTS. Changes in the size and functioning of the heart are common among those with POTS. It is unclear whether these changes occur prior to or as a result of POTS. Those with the condition often present with smaller left ventricles and a decreased ability for the heart to pump blood. Physical inactivity, chronic fatigue and bedrest, as well as other cardiovascular conditions, can promote and exacerbate these changes, giving rise to chronic POTS.

Potential Risk Factors

Several factors are known to precede POTS and may increase the risk. These include:

• Female Gender. It is not presently understood why POTS displays such a high degree of female predominance. Preliminary evidence suggests that female hormones and their cyclic fluctuations may contribute towards increased vasodilation, arterial looseness, water retention and a loss of circulatory control that culminates in tachycardia. This is especially pertinent in puberty, during which the prevalence of POTS and hormonal fluctuation is at its highest in women. ^[4] POTS is also associated with a higher risk for reproductive disorders in women, indicative of hormonal imbalances.^[5] The smaller size of the female heart may also be a prominent contributing factor.
• Genetics. There are no distinct genes associated with POTS. However, related states of disease and other risk factors, such as a predisposition for chronic headaches, may run in families. Ehlers-Danos syndrome is a rare genetic disease frequently associated with POTS due to loss of connective tissue integrity and resultant cardiovascular impairments.
• Comorbid Conditions. It is common for POTS to present as a comorbidity or as secondary to another condition. Cardiovascular disease and other metabolic conditions may contribute to circulatory changes that can increase the risk for POTS. Depression, fibromyalgia, and chronic fatigue, as well as reproductive and anxiety disorders, may also serve as POTS risk factors.
• Autoimmunity. Autoimmune diseases are the most common conditions frequently associated with POTS. Those with autoimmune diseases tend to display heightened immune and sympathetic nervous system activity, similar to some patients with POTS. A small number of studies have shown that many with POTS (yet not all) often displayed higher levels of autoimmune antibodies against receptors that regulate adrenergic and autonomic nervous signaling.^[6] Due to these similarities, autoimmunity may become an established cause of POTS in the future.
• Infectious Illness. Chronic illness may induce dehydration and affect cardiovascular or neurologic function, thus increasing the risk of developing POTS. Viral infections are commonly implicated, including influenza, Epstein-Barr virus and COVID-19. Tick-borne diseases and co-infections are also noted to induce POTS.^[7]
• Medications. Medications that interfere with autonomic functioning, vasodilation or osmolarity may exacerbate symptoms of POTS and serve as risk factors. These include norepinephrine reuptake inhibitors, monoamine oxidase inhibitors, tricyclic antidepressants, diuretics and potent vasodilators.
• Trauma. POTS onset has been linked to all forms of trauma, including prolonged severe stress, traumatic events, injury (particularly brain injury and a history of concussion) and surgery.
• Other Factors. High heat exposure, overexertion, heavy metal exposure and other types of acute poisoning have all been suggested as risk factors for POTS. All of these factors have the ability to interfere with fluid balance and blood flow, as well as increase physiological stress and the risk for tachycardia. Prolonged reclining, bed rest and physical inactivity may also be problematic as they detract from circulation, postural control, autonomic regulation and cardiovascular health.

Prognosis. POTS is associated with reduced daily functionality, financial burden and a diminished quality of life. The outcome for those with POTS depends on the potential cause and medical history of the patient, with younger patients and those undergoing treatment generally seeing a better prognosis. Those who are suspected to have contracted POTS due to viral infections tend to fully recover within 2-5 years on average. The condition can be lifelong in patients with hyperadrenergic POTS or POTS secondary to another disorder that fails to improve with treatment.^[8]

Prevention. Due to a wide array of possible risk factors and causes, it is not easy to actively reduce the risk of developing POTS. A healthy, active lifestyle that emphasizes cardiovascular fitness, along with proper hydration and symptom awareness, can be helpful. The earlier POTS is detected, the better the outcome.

Current Treatment Options

POTS is not a conventionally diagnosed condition. It can take years to recognize in the absence of a knowledgeable healthcare practitioner. There are no currently known options available that specifically treat POTS. Often a case history is required to devise a precise treatment plan that takes possible causes into consideration in order to effectively manage symptoms. Lifestyle modifications are often implemented before pharmacologic interventions and include gentle exercise, high fluid intake and adequate daily salt consumption.

Exercise Regimens. Gradual exercise that improves cardiovascular well-being, autonomic stability and posture has been noted to help those with POTS improve their symptoms. As intensive exercise may exacerbate POTS severity, gentle workouts are recommended to begin with. Initial routines ought to emphasize activity in non-standing positions (e.g. swimming, stretching in a seated position, etc) that can eventually help to support optimal nervous and postural control.

Supportive Counter Movements. Certain movements and postures can help lower dizziness and improve certain symptoms in those with POTS. Gently stretching or bending forward, keeping the feet elevated at an angle, contracting leg and abdominal muscles before standing, breathing optimally, and making a fist can all help.^[9] Care ought to be taken when shifting positions or straightening posture. When standing, it may help to march a little on the spot before moving forward.

Compression Garments may help some patients with POTS, particularly those subject to neuropathic POTS, where pooling of blood in the legs and syncope (momentary loss of consciousness) are common. In other cases of orthostatic intolerance, compression garments that work on the abdomen appear to be more beneficial than compression stockings alone.

Possible Prescriptions. Healthcare practitioners may prescribe appropriate medications to those with severe POTS, who also have a straightforward medical history that suggests an obvious origin for the condition. Fludrocortisone is a drug that has successfully managed to treat symptoms in select patients by improving alpha-adrenergic signaling and promoting both sodium and water retention. Midodrine may help those with hypovolemia and POTS by enhancing vasoconstriction. Medications known to improve orthostatic intolerance may also be beneficial in the context of POTS therapy. Ivabradine has recently been suggested for POTS due to its ability to safely lower heart rate and treat tachycardia.^[10]

Contraindications. In addition to medications that are known to increase POTS risk, ACE inhibitors, alpha and beta blockers, calcium channel inhibitors and phenothiazines are contraindicated for those with the condition. Some physicians may still prescribe such medications, depending on the patient’s profile.

Conclusion

Postural Orthostatic Tachycardia Syndrome can be a substantially debilitating condition, especially when symptoms go by for years without any intervention. The main symptoms of POTS refer to dizziness and a rapid increase in heart rate upon standing, which is generally ascribed to cardiovascular and autonomic nervous dysfunction resulting in impaired circulation and related symptoms. Diagnosis is often difficult due to there being many POTS manifestations, which further emphasizes the need for public awareness. Women are the most prone to contracting POTS due to female reproductive hormones, higher sensitivity towards fluid perturbations, an increased risk for autoimmunity, and having smaller hearts. Treatment demands being careful of one’s posture, gentle exercise, keeping hydrated, and in severe instances, pharmaceutical intervention.

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