Postural Orthostatic Tachycardia Syndrome (POTS)

• Postural Orthostatic Tachycardia Syndrome, and Overlapping Syndrome (POTS) was first defined in the adult population as an increase in heart rate by more than 30 bpm or an increase to heart rate greater than 120 bpm within 10 minutes when moving from supine to the upright position (1)
  • patients with similar clinical and physiologic profiles were later identified in the teenager population
    • patients with POTS are predominantly young women ranging in age groups from menarche to menopause
      • females predominate over males by 5:1
      • mean age of onset in adults is about 30 years and most patients are between the ages of 20-40 years (2)
      • estimated prevalence is at least 170/100,000 (2)
    • more recently, shorter times (eg 5 minutes) for heart rate change have been suggested. In the young, blood pressure may decrease
      • whereas in older subjects blood pressure does not decrease and may even increase during orthostatic challenge
  • Clinical features
    • development of tachycardia and other symptoms during upright position, and relieved by recumbence, are central features of this syndrome complex (3,4)
    • symptoms always include dizziness and light-headedness
    • frank syncope can occur at times, although not a predominant feature
    • other possible associated symptoms include:
      • headache, tunnel vision, fatigue, neurocognitive impairment, exercise intolerance, weakness, dyspnea, tremulousness, nausea, chest or abdominal pain, sweating, anxiety, and palpitations
    • intensity and frequency of symptoms is often variable and in some instances may occur and persist even when the patient is supine
  • Pathophysiology:
    • many of the symptoms in the upright position appear to be related to a reduced cerebral blood flow
      • during upright posture, some patients increase depth of respiration, causing hypopnea and cerebral vasoconstriction, resulting in symptoms of light-headedness, visual blurring, and weakness
      • underlying cause of orthostatic hyperpnoea remains elusive, but is likely multifactorial
        • patients with POTS do not have significant orthostatic hypotension or overt systemic autonomic neuropathy
        • several mechanisms of POTS have been suggested, including length-dependent autonomic neuropathy, beta-receptor supersensitivity, alpha-receptor hypersensitivity or hyposensitivity, altered sympatho-parasympathetic balance, brain stem dysregulation, idiopathic hypovolemia, and excessive venous pooling
  • Diagnosis (7):
    • need a complete medical history to evaluate the triggers, time of onset, severity of orthostatic intolerance, possible associated nonorthostatic symptoms, and precipitating or aggravating factors;
    • require comprehensive cardiac and neurologic examinations
    • head-up tilt test with noninvasive beat-to-beat hemodynamic monitoring
  • Treatment:
    • requires specialist advice
    • there is, at present, no "gold standard" treatment regime for POTS. Various treatment options available include (2,3,4,5):
      • sleeping with head of the bed elevated (15 degrees) and expanding of plasma volume through generous salt and fluid intake can be helpful with minimal risk in most patients
        • salt intake and blood pressure are closely related. Some patients are sensitive to salt intake alone, requiring close surveillance especially in patients with known labile blood pressure
        • fluid intake should be targeted at 2-2.5 L/day
        • if evidence of hypovolaemia persists liberal salt and fluid intake, fludrocortisone with a dose of 0.1 mg/day can be initiated and adjusted upward up to 1 mg/day in young patients
      • compression stockings may provide additional benefit in patients with evidence of venous pooling, although inconvenience frequently prohibits long-term use
      • some patients seem to obtain favorable outcome with a 3-month program of graduated training
      • patients with peripheral adrenergic dysfunction, manifested as a loss or attenuated late phase II response during Valsalva maneuver or evidence of mild orthostatic hypotension, are best treated with fludrocortisone and an alpha-agonist
      • evidence of beta-receptor methyl supersensitivity is usually associated with multisystem complaint
        • patients often respond to but are sometimes highly sensitive to beta-antagonists
          • a nonselective beta-blocker such as propranolol can be started at low dose, titrated upward according to heart rate response and tolerance over 2-4 weeks
          • a small study (6) revealed that treatment with either midodrine and beta-blockers was associated with overall improvement in adolescents with POTS general health
      • logical to consider assessment of psychiatric status in patients with overt psychosomatic complaints
        • such approach should lead to a more rational integrated management of these complex patients although the clinical dilemma is confounded by the frequent rejection of any psychiatric aetiology by many patients

Patient Support organisations and further information about POTS:

• www.stars.org.uk
  
  
• www.potsuk.org

Reference:

• 1. Schondorf R, Low P. Idiopathic postural orthostatic tachycardia syndrome: An attenuated form of acute pan dysautonomia. Neurology 1993; 43: 132-137.
• 2. Low PA et al. Postural Tachycardia Syndrome (POTS). J Cardiovasc Electrophysiol. 2009
• 3. Stewart JM, Gewitz MH, Weldon A, Munoz J. Patterns of orthostatic intolerance: The orthostatic tachycardia syndrome and adolescent chronic fatigue. J Pediatr 1999; 135: 218-225.
• 4. Tanaka H et al. Instantaneous orthostatic hypotension in children and adolescents: a new entity of orthostatic intolerance. Pediatr Res 1999; 46: 691-696
• 5. Brady PA et al. Inappropriate Sinus Tachycardia, Postural Orthostatic Tachycardia Syndrome, and Overlapping Syndromes Pacing and Clinical Electrophysiology 2005; 28(10): 1112-1121.
• 6. Lai CC et al. Outcomes in Adolescents with Postural Orthostatic Tachycardia Syndrome Treated with Midodrine and beta-Blockers. Pacing and Clinical Electrophysiology 2009; 32 (2): 234-238.
• 7. Safavi-Naeini P, Razavi M. Postural Orthostatic Tachycardia Syndrome. Tex Heart Inst J. 2020 Feb 1;47(1):57-59. doi: 10.14503/THIJ-19-7060. PMID: 32148459; PMCID: PMC7046364.