POTS
Postural Orthostatic Tachycardia Syndrome
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 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 viral illness
Autoantibodies detected to ACH receptors, Alpha and Beta Adrenergic receptors
Epidemiology
Prevalence between 0.1 and 1 % of the population
Between 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, heart burn, vomitting
IBS present in 30%
Gastroparesis in 15%
Nausea and vomitting leads to hypovolemia worsening symptoms
Mechanism not understood but maybe excessive splanchnic pooling
Sleep Disturbance
Non restorative sleep and daytime drowsiness are common
Headache
Primary headache syndromes including mingraine and tension-type headache are common
Prevalence 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 symptoms, then frequency and urgency
Skin
Acrocyanosis
Livedo reticularis
Raynaud’s
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
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
Fludrocortisone 0.05 to 0.2mg daily
Pyridostigmine 30 to 60mg up to TDS
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
POTScast - Standing Up To POTS
