What is POTS?
POTS is defined as a chronic (more than 6 months) persistent heart rate
increase of more than 30 beats per minute within 10 minutes of active
standing, upright posture or head-up tilt without orthostatic
hypotension in the absence of other evident causes of orthostatic
tachycardia like prolonged bed rest. These medications dysregulate
autonomic function (e.g. diuretics, vasodilators, and antidepressants)
or chronic comorbidities which induce tachycardia (e.g. thyrotoxicosis
and anemia). Women of childbearing age (13–50 years) comprise most
patients with POTS[8].
Autonomic dysfunction is the underlying pathophysiologic mechanism for
this condition. The autonomic nervous system, responsible for regulating
respiration, digestion, heart rate and blood pressure, is
impaired[9]. This autonomic dysfunction might result from
autoimmunity, mast cell activation, partial sympathetic neuropathy,
hyperadrenergic state or hypovolemia. More than one mechanism can be the
underlying mechanism of POTS in a single patient. Epinephrine and
norepinephrine release causes substantial tachycardia, dyspnea and chest
discomfort, which is followed by paradoxical vasodilatation, sympathetic
activity withdrawal, and vagus nerve activation manifested as
hypotension, lightheadedness and fatigue[10].
This syndrome is manifested as palpitation, headache, nausea, abdominal
pain, fatigue, exercise intolerance, shortness of breath, chest or
abdominal discomfort, diplopia, mental clouding, memory loss, poor
sleep, orthostatic intolerance, dizziness, and presyncope. However,
fainting rarely occurs in the settings of POTS[11, 12]. This
syndrome is usually triggered by acute stressors like viral infections,
pregnancy, menstruation, major surgery, trauma, and psychological
stress[13, 14].
The diagnosis of POTS is usually delayed due to the nonspecific
presentations of this condition. The most sensitive method to detect
POTS is a detailed medical history, physical examination with vital
orthostatic signs or brief tilt table test, and a resting 12-lead
electrocardiogram. Additional diagnostic testing may be warranted in
selected patients based on clinical signs. Diagnosing orthostatic
tachycardia requires that orthostatic hypotension (a fall in blood
pressure of more than 20 mm Hg systolic or 10 mm Hg diastolic within
three minutes of standing) and other precipitants of tachycardia (e.g.,
anemia, dehydration, fever, sepsis, endocrinological conditions such as
hyperthyroidism or Addison’s disease, respiratory conditions such as
pulmonary embolism, and cardiac conditions) have been excluded. Hence,
thorough laboratory workup including measurement of blood glucose, serum
cortisol, complete blood count, renal and thyroid function tests,
inflammatory biomarkers like erythrocyte sedimentation rate (ESR) and C
reactive protein (CRP), ferritin, vitamin B12, folate and calcium, in
addition to chest x-ray imaging is required. However, it should be noted
that cardiac ischemia, myocarditis, and pulmonary embolism must be
considered in any patient presenting with possible acute cardiac
symptoms, as acute conditions need to be urgently detected and
managed[15-17].
Current management of POTS is predominantly dependent upon symptom
therapy and lifestyle modification. The management of POTS consists of
nonpharmacologic and pharmacologic therapies. Nonpharmacologic treatment
includes increasing fluid and salt intake, increasing isometric and
aerobic exercise, lower-limbs strengthening, the gradual elevation of
intensity and duration of physical activity, psychological support and
training to control pain and anxiety, rehabilitation, reassurance and
family education, wearing compression socks or using compression
garments extending up to the waist, and avoiding triggers like alcohol,
caffeine, heavy meals, prolonged standing or upright position, warm
places and hypotensive medications like diuretics, opiates, a-receptor
blockers, angiotensin-converting enzyme inhibitors, nitrates, tricyclic
antidepressants, monoamine oxidase inhibitors, phenothiazines, and
sildenafil citrate[18-20].
Pharmacologic treatment includes heart rate control, peripheral
vasoconstriction, and intravascular volume increase. Medical therapy is
usually individualized but is generally consisted of β-blockers
(Propranolol), channel blockers (Ivabradine), α-agonists (Clonidine),
antihistamines (Diphenhydramine), mineralocorticoids (Fludrocortisone),
vasopressin analogs (Desmopressin), anticholinesterase inhibitors
(Pyridostigmine), CNS stimulants (Modafinil), and selective serotonin
reuptake inhibitors (Sertraline). POTS may interfere with even the least
energy-requiring daily activities like bathing or doing housework,
significantly decreasing functional capacity. Nevertheless, it is not
associated with mortality; many patients improve over time after
diagnosis and proper treatment [21-24].