Reviews

Evaluating and managing postural tachycardia syndrome

Author and Disclosure Information

Release date: May 1, 2019
Expiration date: April 30, 2020
Estimated time of completion: 1 hour

Click here to start this CME/MOC activity.

ABSTRACT

Postural tachycardia syndrome (POTS) is a disorder of the autonomic nervous system with many possible causes, characterized by an unexplained increase in heartbeat without change in blood pressure upon standing. Associated cardiac and noncardiac symptoms can severely affect quality of life. Therapy, using a combined approach of diet and lifestyle changes, plus judicious use of medications if needed, can usually improve symptoms and function.

KEY POINTS

  • Several POTS subtypes have been recognized, including hypovolemic, neuro­pathic, and hyperadrenergic forms, overlapping with Ehlers-Danlos syndrome, mast cell activation, and autoimmune syndromes.
  • Treatment should take a graded approach, beginning with increasing salt and water intake, exercise, and compression stockings.
  • If needed, consider medications to expand blood volume, slow heart rate, or reduce central sympathetic tone.
  • Certain medications, including venodilators, diuretics, and serotonin-norepinephrine reuptake inhibitors, can exacerbate symptoms and should be avoided.


 

References

Some people, most of them relatively young women, experience lightheadedness, a racing heart, and other symptoms (but not hypotension) when they stand up, in a condition known as postural tachycardia syndrome (POTS).1 Although not known to shorten life,1 it can be physically and mentally debilitating.2,3 Therapy rarely cures it, but a multifaceted approach can substantially improve quality of life.

This review outlines the evaluation and diagnosis of POTS and provides guidance for a therapy regimen.

HOW IS POTS DEFINED?

POTS is a multifactorial syndrome rather than a specific disease. It is characterized by all of the following1,4–6:

  • An increase in heart rate of ≥ 30 bpm, or ≥ 40 bpm for those under age 19, within 10 minutes of standing from a supine position
  • Sustained tachycardia (> 30 seconds)
  • Absence of orthostatic hypotension (a fall in blood pressure of ≥ 20/10 mm Hg)
  • Frequent and chronic duration (≥ 6 months).

These features are critical to diagnosis. Hemodynamic criteria in isolation may describe postural tachycardia but are not sufficient to diagnose POTS.

The prevalence of POTS is estimated to be between 0.2% and 1.0%,7 affecting up to 3 million people in the United States. Most cases arise between ages 13 and 50, with a female-to-male ratio of 5:1.8

MANY NAMES, SAME CONDITION

In 1871, Da Costa9 described a condition he called “irritable heart syndrome” that had characteristics similar to those of POTS, including extreme fatigue and exercise intolerance. Decades later, Lewis10 and Wood11 provided more detailed descriptions of the disorder, renaming it “soldier’s heart” or “Da Costa syndrome.” As other cases were documented, more terms arose, including “effort syndrome” and “mitral valve prolapse syndrome.”

In 1982, Rosen and Cryer12 were the first to use the term “postural tachycardia syndrome” for patients with disabling tachycardia upon standing without orthostatic hypotension. In 1986, Fouad et al13 described patients with postural tachycardia, orthostatic intolerance, and a small degree of hypotension as having “idiopathic hypovolemia.”

In 1993, Schondorf and Low14 established the current definition of POTS, leading to increased awareness and research efforts to understand its pathophysiology.

MULTIFACTORIAL PATHOPHYSIOLOGY

During the last 2 decades, several often-overlapping forms of POTS have been recognized, all of which share a final common pathway of sustained orthostatic tachycardia.15–19 In addition, a number of common comorbidities were identified through review of large clinic populations of POTS.20,21

Hypovolemic POTS

Up to 70% of patients with POTS have hypovolemia. The average plasma volume deficit is about 13%, which typically causes only insignificant changes in heart rate and norepinephrine levels while a patient is supine. However, blood pooling associated with upright posture further compromises cardiac output and consequently increases sympathetic nerve activity. Abnormalities in the renin-angiotensin-aldosterone volume regulation system are also suspected to impair sodium retention, contributing to hypovolemia.1,22

Neuropathic POTS

About half of patients with POTS have partial sympathetic denervation (particularly in the lower limbs) and inadequate vasoconstriction upon standing, leading to reduced venous return and stroke volume.17,23 A compensatory increase in sympathetic tone results in tachycardia to maintain cardiac output and blood pressure.

Hyperadrenergic POTS

Up to 50% of patients with POTS have high norepinephrine levels (≥ 600 pg/mL) when upright. This subtype, hyperadrenergic POTS, is characterized by an increase in systolic blood pressure of at least 10 mm Hg within 10 minutes of standing, with concomitant tachycardia that can be similar to or greater than that seen in nonhyperadrenergic POTS. Patients with hyperadrenergic POTS tend to report more prominent symptoms of sympathetic activation, such as palpitations, anxiety, and tremulousness.24,25

Norepinephrine transporter deficiency

The norepinephrine transporter (NET) is on the presynaptic cleft of sympathetic neurons and serves to clear synaptic norepinephrine. NET deficiency leads to a hyperadrenergic state and elevated sympathetic nerve activation.18 NET deficiency may be induced by common antidepressants (eg, tricyclic antidepressants and serotonin-norepinephrine reuptake inhibitors) and attention-deficit disorder medications.4

Mast cell activation syndrome

The relationship between mast cell activation syndrome and POTS is poorly understood.4,26 Mast cell activation syndrome has been described in a subset of patients with POTS who have sinus tachycardia accompanied by severe episodic flushing. Patients with this subtype have a hyperadrenergic response to postural change and elevated urine methylhistamine during flushing episodes.

Patients with mast cell activation syndrome tend to have strong allergic symptoms and may also have severe gastrointestinal problems, food sensitivities, dermatographism, and neuropathy. Diagnosis can be difficult, as the condition is associated with numerous markers with varying sensitivity and specificity.

Autoimmune origin

A significant minority of patients report a viral-like illness before the onset of POTS symptoms, suggesting a possible autoimmune-mediated or inflammatory cause. Also, some autoimmune disorders (eg, Sjögren syndrome) can present with a POTS-like manifestation.

Research into the role of autoantibodies in the pathophysiology of POTS offers the potential to develop novel therapeutic targets. Auto­antibodies that have been reported in POTS include those against M1 to M3 muscarinic receptors (present in over 87% of patients with POTS),27 cardiac lipid raft-associated proteins,28 adrenergic G-protein coupled receptors, alpha-1-adrenergic receptors, and beta-1- and beta-2-adrenergic receptors.29 Although commercial enzyme-linked immunosorbent assays can assess for these antibody fragments, it is not known whether targeting the antibodies improves outcomes. At this time, antibody testing for POTS should be confined to the research setting.

LINKS TO OTHER SYNDROMES

POTS is often associated with other conditions whose symptoms cannot be explained by postural intolerance or tachycardia.

Ehlers-Danlos syndromes are a group of inherited heterogeneous disorders involving joint hypermobility, skin hyperextensibility, and tissue fragility.30 The hypermobile subtype is most commonly associated with POTS, with patients often having symptoms of autonomic dysregulation and autonomic test abnormalities.31–33 Patients with POTS may have a history of joint subluxations, joint pain, cervical instability, and spontaneous epidural leaks. The reason for the overlap between the two syndromes is not clear.

Chronic fatigue syndrome is characterized by persistent fatigue that does not resolve with rest and is not necessarily associated with orthostatic changes. More than 75% of patients with POTS report general fatigue as a major complaint, and up to 23% meet the full criteria for chronic fatigue syndrome.34

Pages

Next Article:

Dabigatran-induced esophagitis

Related Articles