Postural Orthostatic Tachycardia Syndrome

Key Features

• Postural orthostatic tachycardia syndrome is more common in women than men and in patients between 20 and 50 years of age

• Its pathophysiology is uncertain but may involve cardiac deconditioning

• May be associated with joint hypermobility syndrome and mitral valve prolapse

• May follow pregnancy, surgery, trauma, chemotherapy, vaccinations, or viral infections

• Possible mechanisms

  • Neuropathic postural orthostatic tachycardia syndrome: Impaired peripheral vasoconstriction due to peripheral sympathetic denervation, leading to venous pooling in the legs upon standing and a compensatory tachycardia

  • Hyperadrenergic postural orthostatic tachycardia syndrome: An exaggerated sympathetic response to standing, with markedly elevated levels of plasma norepinephrine causing the tachycardia

  • Volume dysregulation postural orthostatic tachycardia syndrome: Hypovolemia, possibly from impaired function of the renin-angiotensin system and excessive mast cell activation leading to inappropriate release of histamine during physical activity

• The long-term prognosis is unclear but approximately 50% of patients recover within 3 years

Clinical Findings

• Orthostatic symptoms develop with a significant tachycardia within 10 minutes of standing

• The orthostatic symptoms include

  • Tremulousness

  • Lightheadedness

  • Palpitations

  • Visual disturbances

  • Weakness

  • Fatigue

  • Anxiety

  • Hyperventilation

  • Nausea

• Tachycardia is considered significant if there is

  • An increase of ≥ 30 beats/min or

  • A heart rate of ≥120 beats/min within 10 minutes of standing

Diagnosis

• Clinical

• Diagnosis requires absence of

  • Postural hypotension

  • An autonomic neuropathy

  • Other medical problems causing a tachycardia

Treatment

• For postural orthostatic tachycardia syndrome due to volume dysregulation or neuropathic mechanisms, management may involve

  • Volume repletion, including a high salt diet and copious fluids

  • Postural and psychophysiologic training

  • A graduated exercise program

• For patients with hyperadrenergic postural orthostatic tachycardia syndrome, pharmacotherapy may include

  • Propranolol, 10–40 mg three times daily

  • Phenobarbital, 15 mg in the morning, 60 mg at night

  • Clonidine, 0.2 mg twice daily

• For patients with hypotension, the clinician may consider therapy with

  • Midodrine (2.5–10 mg three times daily) or

  • Fludrocortisone (0.1– 0.2 mg daily)