Postural Orthostatic Tachycardia Syndrome POTS

Postural Orthostatic Tachycardia Syndrome

Factsheet

  • POTS / Maladywise

Overview

  • Intermittent symptoms of orthostatic intolerance with excess tachycardia without arterial hypotension

  • Other entities include

    • Orthostatic hypotension = >20 mmHg drop in SBP or >10mmHg in DBP

    • Reflex Syncope = Vasovagal. Facial pallor, sweating, nausea, yawning, and transient LOC often with prolonged standing.

    • Chronic isolated orthostatic intolerance = Symptoms of orthostatic intolerance without excessive tachycardia. On the POTS spectrum.

Pathophysiology

Standing erect against gravity requires muscles, a skeletal frame, a sense of balance, consciousness, and coordination of cardiovascular autonomic function to compensate for the downward movement of up to 800mL of blood to the abdomen and legs.

The autonomic nervous system responds to the unloading of the carotid sinus and aortic arch baroceptors during standing by increasing cardiovascular sympathetic adrenergic outflow and decreasing cardiovagal parasympathetic outflow.

Mechanisms

  • Hypovolemia and deconditioning

    • Intravascular volume is reduced

    • Low blood volume, decreased left-ventricular mass, and reduced cardiac stroke volume, similar to people who are deconditioned or on prolonged bed rest

    • Many POTS patients avoid physical activity because of symptoms, exacerbating a deconditioned state, and worsening the symptoms.

    • Somatic hypervigilance is common including perceiving mild or routine sensory information as intense or distressing.

  • Neuroendocrine dysfunction

    • Some POTS patients have increased cardiovascular adrenergic function

    • Average patients have high levels of catecholamines than healthy controls

    • Some have increased norepinephrine on standing

    • Lower levels of renin and aldosterone

  • Neuropathy

    • Small fibre neuropathy in 50% of POTS with dysautonomia

    • 50% of POTS patients have sudomotor testing showing GIT symptoms including nausea, bloating, constipation and abdominal pain.

  • Autoimmunity

    • Linked due to observation of symptoms after a viral illness

    • Autoantibodies detected to ACH receptors, Alpha and Beta Adrenergic receptors

Epidemiology

  • Prevalence between 0.1 and 1 % of the population

  • Between the ages of 15 to 50 and a 5:1 ratio of female to male

  • Most first develop symptoms in adolescence

Clinical Features

Orthostatic intolerance

  • Brought on by standing and relieved by sitting down

  • Lightheadedness, palpitations, fading vision, presyncope, difficulty concentrating, headaches

  • Some patients get chest pain, nausea, dyspnoea, tremulousness, flushing, difficulty concentrating, blurred vision

  • Headache is dull occipital, cervical trapezius pain

  • Walking is generally better tolerated than standing still

  • Orthostatic symptoms and heart rates are more pronounced during conditions of increased orthostatic stress or vasodilation

  • Symptoms worse in early morning hours, hot weather, during menses, during febrile illness or stress.

  • POTS patients are almost always unable to tolerate standing while taking a warm shower and many sit down to bathe. After a shower, they may lie down and rest

  • Exaggerated symptoms from dehydration or BP-lowering medications

Symptoms unrelated to orthostasis

  • Anxiety - Common.

    • Usually different to GAD or panic disorder.

    • Characterised by somatic hypervigilance.

    • Heightened awareness of internal somatic sensors

    • Fear conditioning in anticipation of orthostatic stress rather than trait anxiety or neurosis

    • Measures of catastrophic thinking correlate with functional disability in POTS

  • Fatigue - Common

    • 20 to 90%

    • May be attributable to orthostatic intolerance and/or exercise intolerance

    • However, a sense of low energy does not always resolve upon sitting but persists at rest and may recur in cycles lasting for days or weeks at a time

  • Cognitive Dysfunction

    • Mild impairments in attention, processing speed, memory function and executive function, even when seated or supine.

    • Consistent evidence of mild to moderate depression in POTS. Doesn’t always correlate with heart rate changes but has been speculated to be due to high levels of circulating catecholamines or central norepinephrine dysregulation rather than decrease cerebral perfusion.

  • GIT disturbance - Common

    • Nausea, irregular bowel movements, bloating, diarrhoea, abdominal pain, cramping, constipation, heartburn, vomitting

    • IBS present in 30%

    • Gastroparesis in 15%

    • Nausea and vomiting leads to hypovolemia worsening symptoms

    • The mechanism not understood but may be excessive splanchnic pooling

  • Sleep Disturbance

    • Non-restorative sleep and daytime drowsiness are common

  • Headache

    • Primary headache syndromes including migraine and tension-type headaches are common

    • Prevalence of about 35%

    • Central sensitisation has been proposed as a contributing factor

  • Overactive Bladder

    • A study showed 13/19 patients with POTS met the criteria for OAB

    • Nocturia was the most bothersome symptom, then frequency and urgency

  • Skin

    • Acrocyanosis - a functional peripheral arterial disease, is a persistent, painless bluish discoloration of both hands and, less commonly, of both feet

    • Livedo reticularis - a netlike pattern of reddish-blue skin discoloration. The legs are often affected

    • Raynaud’s - discolouration of fingers and toes due to vasospasm - white, blue and red

Diagnosis

  • History of symptoms of orthostatic intolerance with or without systemic symptoms

  • Correlation of symptoms with a sustained increase in upright heart rate by at least 30 bpm within 10 minutes of standing or head-up tilt without orthostatic hypotension

  • Autonomic testing to correlate symptoms with heart rate changes confirms the diagnosis

Clinical Evaluation

  • The key finding is an excessive rise in resting heart rate within 10min of standing, without a decrease in blood pressure

  • Baseline heart rate and blood pressure should be measured after at least 5 minutes of rest supine and again after 1 minute of standing. If values are not diagnostic, repeating the measurement of vital signs at 3, 5, and 10 minutes of standing is often useful.

  • Pulsox devices are useful for measuring heart rates faster

  • A transient increase in heart rate in the first 20 seconds of standing is normal. In POTS, the heart rate increases from 30 to 60 seconds.

  • Some patients may demonstrate subtle behaviours such as shifting their weight back and forth whilst standing, or entwining their legs whilst seated.

  • Red or purple acrocyanosis of distal lower extremities on standing, resolves on lying.

  • Neuro exam is normal

Autonomic Testing

  • Tilt table testing

    • Increases diagnosis yield of assessing tachycardia in patients with POTS and helps exclude orthostatic hypotension.

  • Sudomotor testing

Laboratory Testing

  • UEC, FBC, TFT

  • ECG

  • Consider morning cortisol

  • Consider Echo

  • Consider supine and standing plasma catecholamines

  • Consider 24-hour urinary sodium

  • Consider GIT motility testing

Differential Diagnosis

  • Dehydration

  • Pharmacologic syndrome

  • Orthostatic hypotension

  • Reflex Syncope

  • Chronic Isolated Orthostatic TAchycardia

  • Inappropriate Sinus Tachycardia

  • Panic and Anxiety Disorder

    • 77% of POTS patients initially had a psychiatric diagnosis, only 37% continued after diagnosis

  • hEDS

  • MCAS

  • Spontaneous intracranial hypotension

  • Chiari malformation

Types

Neuropathic POTS

Some have preferential denervation of sympathetic nerves innervating the lower legs

These patients are hypersensitive to infusions of norepinephrine and phenylephrine into veins of the foot

Hypovolemia

Many POTS patients have low plasma volumes but not all

RAAS plays a key role in neurohormonal regulation of plasma volume

Patients with orthostatic tachycardia who were hypovolemic have low levels of standing plasma renin activity and aldosterone compared to normovolemic patients

Maybe RAAS has a role in pathophysiology of POTS

Maybe a neuropathic process involving the kidney

Central Hyperadrenergic POTS

Some cases in which the primary underlying problem seems to be excessive sympathetic discharge

These patients have extremely high levels of upright norepinephrine

Comprises 10% of patients

Norepinephrine Transporter Deficiency

Genetic abnormality has been identified that mimics hyperadrenergic POTS

Blocking the NE transporter e.g. atomoxetine or reboxetine

MCAS

Some patients with POTS have co-existent Mast Cell activation

Episodic flushing, dyspnoea, headache, light headedness, peeing, GIT symptoms

Management

Involves symptom management through intravascular volume expansion, physical exercise, and lifestyle changes as well as compressive garments. Drugs may be needed.

  • Increase fluid and salt intake

    • 3L of water per day

    • 8 to 12g of salt

  • Advise an exercise regimen

    • Incremental aerobic exercise

    • Recumbent options include a recumbent bike, rowing machine, swimming

    • Leg resistance strength training helps

    • Start with 30 to 40 minutes per session for 3 to 4 sessions per week

    • Aim for 75% maximum predicted heart rate

  • Targetted lifestyle management

    • Upright as much as possible during the day and to avoid prolonged bed rest

    • Manage catastrophising, anxiety and functional disability with counselling and CBT

    • Learn physical habits to reduce symptoms

      • Leg muscle tension, leg crossing, weight shifting

    • Improve sleep quality with a constant bedtime and wake time, don’t spend time in bed during the day

  • Add compressive garments

    • Waist high stockings at 30 to 40 mmHg or abdominal binders at 10mmHg

  • Medications

    • Beta-blockers to reduce orthostatic tachycardia

      • Propranolol is effective at 20mg daily

      • Metoprolol at 0.35 to 0.5mg/kg in kids and adolescents

    • Vasopressor therapy can be effective for patients with neuropathic symptoms

      • Midodrine up to 10mg TDS (Alpha-1 agonist)

      • Fludrocortisone 0.05 to 0.2mg daily (blood volume expansion)

      • Pyridostigmine 30 to 60mg up to TDS (ACH inhibitor)

      • Methylphenidate 10mg BD

    • Avoid medications that inhibit NA uptake

Prognosis

  • Most patients with POTS improve with treatment or spontaneously

  • In one study, orthostatic symptoms improved at 1-year follow-up in most patients, and more than a third no longer met tilt-table criteria

  • Chronic condition and many patients may be subject to occasional flares or recurrences

  • 500 patients at 5 years since diagnosis, 20% had complete resolution, 50 percent had persistent but improved symptoms, 15% had intermittent continued symptoms

  • POTS does not affect mortality

Podcasts

Tools

References