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].