Dear Editor,

Raj et al. are to be commended for their study on psychiatric profile in patients with postural tachycardia syndrome (POTS) (1). Despite small sample size, the study addresses an important aspect in POTS research, which is its relationship to anxiety disorder. The results of the study demonstrate that patients with POTS do not have an increased prevalence of anxiety disorders compared to general population, thereby challenging a common misconception that patients with POTS are more likely to have anxiety disorders. The study by Raj et al. is in agreement with two other studies that differentiated POTS from anxiety disorders. One study showed that excessive heart rate response during a tilt table test was not due to anxiety (2), and another one demonstrated that symptoms of POTS were phenomenologically different and clinically distinguishable from panic disorder symptoms (3). Taken together, the three studies provide evidence against a hypothesis that POTS and anxiety disorders are linked either by association or causation.

As a symptom, anxiety can occur in a number of common medical conditions. Furthermore, anxiety can be directly caused by various physiologic factors, such as hypoglycemia, hypoxia, hypercapnia, hypovolemia and hypoperfusion. Therefore, it should come as no surprise that patients with POTS, a disorder that is characterized by hypovolemia, orthostatic cerebral hypoperfusion and excessive rise in standing plasma norepinephrine, may experience anxiety among many other symptoms. As the authors point out astutely, the anxiety observed in POTS is caused by physiologic mechanisms rather than psychological factors that exist in patients with anxiety and panic disorders.

In addition to pathophysiologic implications, the study underscores key clinical points: recognizing POTS in patients presenting with symptoms compatible with this syndrome and differentiating it from POTS mimics, which include generalized anxiety disorder, panic disorder and others. Despite existence of the objective diagnostic criteria for POTS, i.e. greater than 30 bpm increase in heart rate within the first 5 minutes of standing or upright tilt with the associated symptoms of orthostatic intolerance (4), many patients with POTS continue to be misdiagnosed with anxiety disorders by their health care providers. Emphasizing to clinicians that POTS is a medical disorder, with its distinct clinical features, diagnostic criteria and therapeutic options, is instrumental in providing appropriate care to patients affected by this disorder.

References

1. Raj V, Haman KL, Raj SR, Byrne D, Blakely RD, Bioggioni I, Robertson D, Shelton RC.
Psychiatric profile and attention deficits in postural tachycardia syndrome.
Journal of Neurology, Neurosurgery and Psychiatry 2009; 80: 339-44.

2. Masuki S, Eisenach JH, Johnson C et al.
Excessive heart rate response to orthostatic stress in postural tachycardia syndrome is not caused by anxiety.
Journal of Applied Physiology 2006; 102: 1134-42.

3. Khurana RK.
Experimental induction of panic-like symptoms in patients with postural tachycardia syndrome.
Clinical Autonomic Research 2006; 16: 371-7.

4. Low PA, Opfer-Gehrking TL, Textor SC et al.
Postural tachycardia syndrome (POTS).
Neurology 1995; 45: S19-S25.