What Causes POTS?

POTS symptoms can occur due to many different abnormalities in the body. Some disorders associated with POTS symptoms have been identified. Many of the causes of POTS still remain unknown. It can be difficult to distinguish between the causes and effects of this disorder, which further complicates matters.  

There are a multitude of disorders that can produce POTS-like symptoms. It is important that physicians attempt to find possible causes of a patient's orthostatic intolerance, as many secondary disorders are treatable. Some of the entities that may be contributing to one's orthostatic intolerance include: 

Adrenal disorders, such as Addison's disease,can produce symptoms that mimic POTS. 

Anemia patients sometimes exhibit the symptoms of POTS (Nand, Mohan, Khosla & Kumar, 1989). Some patients may have folic acid deficiency, which is contributing to their anemia and POTS symptoms. 

POTS patients may have a form of hidden anemia where the standard tests, such as hemoglobin and hematocrit, are relatively normal even though the patient has a severe anemia (Raj, Biaggioni, Yamhure, Black, Paranjape, Byrne & Robertson, 2005). A formal radioisotope dilution assessment of blood volumes was required to discover the red blood cell volume deficit documented in a 2005 study of POTS patients (Raj, et. al, 2005). The authors of this study state that it is possible a deficit in erythropoietin production might play a pathophysiological role in POTS, although this is not yet clear.

Angiotensin II has been found to be increased in some people with postural orthostatic tachycardia syndrome. The results from one study imply impaired catabolism of Angiotensin II through the angiotensin-converting enzyme 2 pathway. Vasoconstriction in POTS may result from a reduction in Ang-(1-7) and an increase in angiotensin II (Stewart, Ocon, Clarke, Taneja & Medow, 2009).

The angiotensin II type I receptor gene may be responsible for some orthostatic disorders.The NIH has researched vascular responsiveness in subjects with polymorphisms of the angiotensin II type I receptor gene. Angiotensin II is a hormone that constricts blood vessels by attaching to a protein on the blood vessels. People can have a variety of forms of this protein. Researchers have looked for differences in the gene that makes this protein to determine if these genetic differences have any effect on blood pressure.

Autoimmune disorders,such as Guillain-Barre (Singh, Jaiswal, Misra & Srivastava, 1987) and lupus are suspected of causing POTS symptoms in some individuals. 

Researchers have discovered an antibody to neuronal nicotinic acetylcholine receptors of autonomic ganglia (Vernino, Low, Fealey, Stewart, Farrugia & Lennon, 2000).  Some people with POTS have an antibody titer test that is positive to this antibody. Patients with orthostatic intolerance, anhidrosis, constipation, urinary dysfunction, sicca syndrome and pupillary dysfunction had higher antibody titers than subjects that did not (Gibbons & Freeman, 2009). Patients with the highest levels of these ganglionic-receptor-binding antibodies have the most severe autonomic dysfunction. Physicians have discovered that antibody levels lower as some patients improve, which suggests a cause and effect relationship. Patients interested in being tested for the ganglionic antibody should have their physician contact:

Mayo Medical Laboratories
1-800-533-1710
mml@mayo.edu

Cardiac atrophy has been pinpointed as the cause of orthostatic intolerance in astronauts. Research has shown that astronauts' hearts actually shrink and stiffen due to the reduced blood volume caused by microgravity (Mitka, 2002). Researchers want to find out if the cardiac atrophy is entirely reversible, and if the loss of mass can reach a point where it leads to catastrophic consequences (Healthline Scripts: Cardiac Atrophy, 1998). This finding may have implications for people who develop orthostatic intolerance due to being bedridden. Whether or not the finding can be applied to a percentage of patients who develop orthostatic intolerance for other reasons has yet to be proven. 

Cardiac disease can cause POTS symptoms. Most physicians are quick to rule cardiac disease out.

Cardiac electrophysiologic property abnormalities may be occurring in some POTS patients. Data from one study suggests abnormalities of atrioventricular conduction and ventricular repolarization in some patients with POTS (Singer, Shen, Opfer-Gehrking, McPhee, Hilz, & Low, 2003). The investigating physicians of this study concluded that these findings may reflect intrinsic cardiac electrophysiologic abnormalities or may be secondary due to abnormalities of cardiac autonomic innervation.

Another study suggested a primary sinus node abnormality could be present in a subset of POTS patients (Singer, Shen, Opfer-Gehrking, McPhee, Hilz & Low, 2002). Abnormal rate-dependent P-wave axis behavior has been observed in a small subset of POTS patients. This could be interpreted as a primary sinus node abnormality. However, several publications caution against ablating POTS patients.

A Mayo clinic study reported short-term success in five of seven ablated patients with inappropriate sinus tachycardia and postural orthostatic tachycardia features (Shen, Low, Jahangir, Munger, Friedman, Osborn, Stanton, Packer, Rea & Hammill, 2001). However, long-term outcomes were disappointing in these patients. None of the patients experienced complete eradication of symptoms. A follow-up evaluation showed no vast improvement in symptoms, despite better heart rate control. A later publication states "in our laboratory, sinus node modification, total sinus node ablation, or atrioventricular nodal ablation is not recommended for patients with inappropriate sinus tachycardia who have autonomic evidence of postural orthostatic tachycardia" (Shen, 2002).

Ablations have reportedly been detrimental to some POTS patients who were misdiagnosed as having inappropriate sinus tachycardia. After the apparently successful elimination of their "sinus tachycardia", they were left with profound orthostatic hypotension (Grubb & Karas, 1999).

Cervical stenosis is a condition in which the spinal canal is too narrow, causing compression of the spinal cord and nerve roots. It was once reported that POTS patients with cervical stenosis may benefit from craniovertebral decompression (Rosner, D'Amour & Rowe, 1999). A few patients have reported a decrease or resolution in POTS symptoms after undergoing surgery to correct this condition. Yet other patients have not had any decrease in POTS symptoms after undergoing surgery to correct cervical stenosis. Some physicians are convinced that cervical stenosis can cause POTS, others debate the relationship.

Chemical exposure may cause POTS symptoms in some individuals. Researchers at Johns Hopkins University have tested Gulf War vets to see if they have neurally mediated hypotension or POTS. The study aimed to find out if environmental factors such as pesticides, vaccinations or infections are associated with having POTS.

Chiari malformation is a condition in which the cerebellar tonsils protrude down into the spinal cord. This can restrict the flow of cerebral spinal fluid. The symptoms of Chiari are similar to those of POTS. A number of Chiari patients have reported being diagnosed with POTS. Some of these patients proclaim a decrease or resolution in POTS symptoms after undergoing surgical correction of their Chiari malformation. Other POTS patients with Chiari malformation have not experienced any benefits from corrective surgery. Some physicians are convinced that Chiari malformation is a cause of POTS, others doubt the relationship.

Physicians from the NIH and The Chiari Institute believe their is a connection between Ehlers-Danlos syndrome, POTS and Chiari 1 malformation. Read More

Diabetes can produce the symptoms of POTS (Llamas, Garcia, Gaos, Jimenez, Villavicencio, Cueto & Arriaga, 1985). There are different types of diabetes, including diabetes insipidus, that are associated with POTS symptoms. Read more 

Ehlers-Danlos Syndrome (EDS), a connective tissue disorder,is found in some POTS patients. Physicians propose that these syndromes occur together due to abnormal connective tissue in dependent blood vessels in those with EDS, which permits veins to distend excessively in response to ordinary hydrostatic pressures (Rowe, Barron, Calkins, Maumenee, Tong & Geraghty, 1999). Simply put, this connective tissue abnormality allows excessive amounts of blood to pool in these patients' lower limbs when they stand up.

There are a variety of types of Ehlers-Danlos syndrome. Classical and type III EDS were originally reported in orthostatic intolerance patients (Rowe et al., 1999). Many POTS patients with EDS have type III (Grubb, 2002).

The classical form of Ehlers-Danlos syndrome (types I and II) is characterized by soft, hyperextensible skin; easy bruising; poor wound healing; thin, atrophic scars; hypermobile joints; varicose veins and prematurity of affected newborns (Wenstrup & Hoechstetter, 2001). Mutations in type V collagen are a major cause of the classical type of Ehlers-Danlos syndrome.

Clinical features associated with EDS III include soft skin and large and small joint hypermobility (Wenstrup & Hoechstetter, 2001). Skin may be stretchy but scarring tends to be normal. POTS patients with EDS III are often hypermoblie/hyperflexable, double jointed, pale, female and tend to have blond hair and blue eyes (Grubb, 2002). The genetic basis for EDS III is unknown.

A wide variety of medical complications may occur with the classical and hypermobile types of EDS. Mitral valve prolapse can occur in all types of EDS and delayed gastric emptying has been observed in type III (personal observations, Wenstrup & Hoechstetter, 2001). A significant number of individuals with both the classical form and the hypermobile form have dilation and/or rupture of the ascending aorta (Wenstrup & Hoechstetter, 2001). Hiatal hernia has been widely reported in adults with EDS (Steinman, Royce & Superti-Furga, 1993). As previously stated, premature rupture of the membranes in pregnancy (primarily classical type) and poor wound healing (particularly with severe classical type) may occur. Other complications include a mild to moderate increase in peripartum bleeding, joint dislocations, chronic pain (most common in the hypermobile type), surgical complications and intraoperative problems (more common in the classical than hypermobile type), diverticulitis, problems associated with fragile skin (particularly with the classical type) and motor delay (Wenstrup & Hoechstetter, 2001).

One study on patients with "joint hypermobility syndrome", a disorder similar if not identical to EDS III, showed that 78% had signs of dysautonomia, such as orthostatic hypotension, postural orthostatic tachycardia syndrome and uncategorized orthostatic intolerance (Gazit, Nahir, Grahame, & Jacob, 2003). These patients also had evidence of a-adrenergic and B-adrenergic hyperresponsiveness. The authors of this study note that patients with the joint hypermobility syndrome have apparently intact vagal control of heart rate with disturbed sympathetic function. They further state that "the sympathetic dysregulation associated with joint hypermobility syndrome may have several explanations, such as peripheral neuropathy, blood pooling in the lower limbs, impaired central sympathetic control, or deconditioning due to muscle disuse through pain or fear of pain".

Another study of one hundred and seventy women with joint hypermobility syndrome concluded that non-musculoskeletal symptoms are common in patients with joint hypermobility syndrome, and that individuals with these symptoms may express more fatigue, anxiety, migraine, flushing, night sweats, and poor sleep than their peers (Hakim & Grahame, 2004). Read more

Electrical injury has reportedly occurred prior to the development of POTS in a couple of cases (Kanjwal, Karabin, Kanjwal & Grubb, 2009).

Gastric bypass surgery may cause orthostatic intolerance in some individuals.

Lesions of the autonomic nervous system might be causing POTS in some individuals. Research shows that animals become dysautonomic by selectively lesioning postganglionic sympathetic neurons (Carson, Appalsamy, Diedrich, Davis & Robertson, 2001).

Lipodystrophy a rare metabolic disorder, has been associated with POTS symptoms (Bernstein, Pierson, Ryan & Crespin, 1979).

Liver disease may contribue to orthostatic intolerance. Compensated Cirrhosis is a condition in which the liver is damaged but is able to compensate for it. This condition coincides with hypovolemia and vasodilation. POTS, as well as peripheral blood pooling and decreased arterial tone, has been found in some patients (Hartleb, Rudzki, Karpel, Becker, Waluga, Boldys, Nowak & Nowak, 1979). 

Mast-cell activation disorders may play a role in the development of POTS in some individuals. Some patients with orthostatic intolerance suffer from episodes of flushing, palpitations, shortness of breath, chest discomfort, headache, lightheadedness, hypotension or hypertension and occasionally syncope (Jacob & Biaggioni, 1999). Exercise may trigger an attack (Shibao, Arzubiaga, Roberts, Raj, Black, Harris & Biaggioni, 2005). Patients may complain of increased fatigue, sleepiness, increased urination and/or diarrhea after an attack (Jacob & Biaggioni, 1999). Symptoms of orthostatic intolerance often worsen after an episode. An increase in urinary methylhistamine, a marker of mast-cell activation, can be found in these patients.

Mast-cell activation results in the release of the vasodilator histamine, which may contribute to symptoms of POTS. Other mast cell mediators, such as plasma prostaglandin 2, may contribute to symptoms as well. Urinary histamine is often measured in the evaluation of flushing, but it is less specific than methylhistamine and not useful in the diagnosis of mast-cell activation (Shibao et al., 2005). Patients should be instructed to collect urine for a 4-hour period immediately after a severe spontaneous flushing episode. Urinary methylhistamine is usually normal between episodes in patients with mast-cell activation disorders, although the patients may experience chronic fatigue and orthostatic intolerance between episodes, which can lead to a disabling condition (Shibao et al., 2005).

Beta blockers should be used with caution, if at all, in those with mast-cell activation disorders (Shibao et al., 2005). Beta blockers may trigger mast-cell activation.

Mitochondrial disease is sometimes found in patients who present with autonomic dysfunction. Read more

Neuropathy may be involved in the development of POTS in some individuals. One study showed that POTS may be, in part, a manifestation of autonomic cardiac neuropathy (Haensch, Lerch, Schlemmer, Jigalin & Isenmann, 2009). Sympathetic denervation of the legs might be the cause of POTS in some patients as well. 

Nitric Oxide deficit may play a role in POTS symptoms. Nitric Oxide (NO) is a very simple molecule whose job it is to control blood vessel size with changes in blood flow, changes in blood vessels during inflammation and blood vessel leakiness (Stewart, 2005). Some POTS patients have a deficit of nitric oxide (Stewart, Taneja, Glover & Medow, 2008.). This deficit may relate to the nitric oxide synthase molecule called nNOS, but it also has a compelling relationship with the hormone angiotensin-II.Together angiotensin-II and  NO may help to regulate sympathetic nerve activity in the brain and also in certain peripheral nerves (such as the splanchnic circulation). Moreover, angiotensin-II can result in increased oxidative stress which can itself reduce NO (Dr. Julian Stewart, personal communication, November 28, 2007).

Researchers have found that NO levels can be increased by blocking the most important receptor for angiotensin-II. This may lead to treatments in the future in select groups of POTS patients.

Norepinephrine transporter deficiency is thought to cause POTS in some patients. These patients have an abnormality in the clearance of norepinephrine from the synaptic cleft. The body normally recycles norepinephrine. The protein that recycles norepinephrine doesn't work well in people with the norepinephrine transporter deficiency (Grubb, 2002). Excessive amounts of norepinephrine is spilled over. These people soon become depleted of norepinephrine if the neuron is continually stimulated (Grubb, 2002). They go from having excessive amounts of norepinephrine to having no norepinephrine, at which point they crash. Read More

Other researchers have reportedly discovered hypermethylation of the norepinephrine transporter (NET) gene promoter in POTS patients (Esler, Alvarenga, Pier, Richards, El-Osta, Barton, Haikerwal, Kaye, Schlaich, Guo, Jennings, Socratous & Lambert, 2006) In these patients, the gene for the protein that transports norepinephrine (NET) is turned off because its promoter is turned off. Further studies are being conducted to determine whether hypermethylation of the NET gene promoter is a mechanism or cause of POTS.

The nutcracker phenomenon has reportedly produced POTS symptoms in some individuals. Nutcracker phenomenon (NC) is the congestion of the left renal vein due to its compression by the aorta and the superior mesenteric artery (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The main and common findings of one study on pediatric NC patients were chronic fatigue associated with orthostatic hypotension and/or postural tachycardia (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The authors of this study point out that "the originally reported symptom of NC is renal bleeding. However, reported 'renal bleeding' patients, including ours, have no complaints of chronic fatigue and our 'chronic fatigue' (NC) patients have no renal bleeding". Some of these patients did report fibromyalgia type pain. Some patients had proteinuria, others had no urinary abnormalities. 

The authors of this study explain the various ways in which NC might affect autonomic function: First, severe congestion in the kidney may cause the expansion of the renal venous bed, which would affect the renin-angiotensin system. Secondly, severe congestion in the adrenal medulla, which is innervated by sympathetic nerves, may disturb a complex set of central neural connections controlling the sympathoadrenal system. On the other hand, overproduction or night retention of catecholamines might be responsible for the various symptoms of pediatric chronic fatigue syndrome (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The nutcracker phenomenon occurs in adults as well as children. Transluminal balloon angioplasty has successfully been used to treat compression of the left renal vein between the aorta and superior mesenteric artery (Takahashi, Sano & Matsuo, 2000). 

The methods used to diagnose nutcracker phenomenon include Doppler US, MRI and three-dimensional helical computed tomography. Dr. Takahashi (personal communication, September 8, 2002) explains the procedures for testing as follows: Conventional ultrasound requires patients to be examined for left renal vein obstruction in 4 positions: supine, semisitting, upright and prone. Nonvisualization of the left renal vein lumen or absence of the left renal vein wall between the aorta and superior mesenteric artery is regarded as signifying left renal vein obstruction. Doppler color flow imaging can be used to locate a blue-colored blood stream flowing to the dorsal direction. This is a collateral vein flowing from the left renal vein into the paravertebral vein. With MRI, oblique coronal images along the left renal vein, and also axial images, are recommended to visualize the collateral veins around the left renal vein. Read more

Nutritional deficiencies can lead to autonomic dysfunction. The B vitamins 1, 3, 6, and 12 have been reportedly linked to dysautonomia symptoms (Autonomic Dysfunction, 2000). Folic acid deficiency (B9) can also cause POTS symptoms.

Other neurological conditions, such as multiple sclerosis, are sometimes associated with autonomic dysfunction.

Parasites can transmit diseases, such as Chagas, that can cause POTS symptoms. Some patients report developing POTS after having Lyme disease. 

Porphyrias have been associated with POTS symptoms (Stewart & Hensley, 1981). Porphyrias are rare, mainly genetic disorders that affect the body's ability to make hemoglobin. They are caused by deficiencies in enzymes involved in the synthesis of heme. Porphyria patients are often overly sensitive to sunlight. 

It is important for physicians to rule out porphyrias before prescribing medication to POTS patients. Some medications that are considered unsafe for porphyria patients are used to treat dysautonomia. Read more

Syringomyelia is a condition in which a cyst grows within the spinal cord. POTS can occur in patients with this condition. Syringomyelia is similar to POTS in that it usually occurs between the ages of 25 and 40, it can have a sudden onset, some patients have Chiari malformation and some patients may experience long periods of stability. The symptoms of syringomyelia can worsen with straining or any activity that causes cerebrospinal fluid to fluctuate. Many POTS patients also report a worsening of symptoms upon straining. Partial sympathetic denervation of the legs in those with syringomyelia might explain the occasional occurrence of postural tachycardia syndrome (NINDS Syringomyelia Information Page, 2001). Read more

Tumors can lead to autonomic dysfunction. Tumors, such as pheochromocytoma and neuroblastoma, can secrete catecholamines that affect the autonomic system. Pelvic ganglioneuroma is another type of tumor that has also been associated with autonomic dysfunction (Gentile, Rainero, Luda & Pinessi, 2001). Tumors can cause compression, which directly affects the autonomic nervous system. Tumors are also capable of having a paraneoplastic effect on the ANS by producing autoantibodies against acetylcholine receptors in the autonomic ganglia (Grubb, Kanjwal & Kosinski, 2006). 

Thyroid disease can cause symptoms that are similar to those of POTS.

Viruses are thought to be the provoking factor in approximately 50% of POTS patients (Low & Schondorf, 1997, p. 279). There are reports of dysautonomia occurring after the Epstein-Barr virus (Itoh, Oishi, Ohnishi, Murai & Imawatari, 1993). Viruses may directly affect the autonomic nervous system or lead to an immune pathogenesis (Grubb, 2000). Roughly one-half of post-viral POTS patients will make a good practical recovery over a 2-5 year period (Grubb, Kanjwal & Kosinski, 2006).

These are but a few of the possible causes of POTS symptoms. More information on causes of autonomic dysfunction can be located at the National Dysautonomia Research Foundation.

References