Lily, a 15-year-old student, comes to see you with her father following a recent trip to the Emergency Department.
She tells you that for the last nine months, she has struggled with the feeling of her heart racing. When this happens, she feels sick, gets a headache and feels light-headed as if she might pass out. These episodes used to occur only when she first stood up in the morning. Now they happen whenever she gets up from sitting or if she needs to stand, such as on the bus.
She had a bad day yesterday and panicked that there was something seriously wrong with her heart. Her parents took her to the Emergency Department, but the doctors didn’t find anything abnormal.
She’s found something on Google called Postural Orthostatic Tachycardia Syndrome (PoTS) – could this be what she has?
PoTS is a disorder of the autonomic nervous system characterised by tachycardia on standing. It predominantly affects women aged 15-40 years, with a prevalence of 0.2-1.0% in developed countries, which has increased since the COVID-19 pandemic. The pathophysiology of PoTS remains unclear, but symptoms arise due to an inability to peripherally vasoconstrict even in the presence of elevated adrenaline and noradrenaline levels. This can be in combination with a reduced circulating blood volume.
The ED discharge letter states that Lily’s ECG showed sinus rhythm.
Her Full Blood Count, Urea and Electrolytes, Liver Function, Thyroid Function, Troponin and Glucose blood tests were all normal.
Her blood pressure (BP) readings were 110/72 mmHg while sitting, with a heart rate of 68 beats per minute (bpm), and 112/70 mmHg while standing, with a heart rate of 120 bpm.
Cardiac examination was unremarkable. She was discharged with a diagnosis of anxiety and advised to see her GP for treatment. Lily herself doesn’t feel that her symptoms are due to anxiety, and her father would like further investigations.
PoTS is commonly undiagnosed or misdiagnosed. According to PoTS UK, the mean time from symptom onset to diagnosis in the UK is 7 years. Up to 85% of PoTS patients will be given a misdiagnosis of anxiety, with physical symptoms labelled as psychosomatic. This is partly due to the overlap of symptoms with other differential diagnoses, but mainly due to a general lack of understanding and education among healthcare professionals.
The history should detail the extent of the symptoms and their effect on function. It should also outline other systems that are involved, as patients frequently experience gastrointestinal and neurological symptoms. It should also focus on ruling out other conditions that present with similar symptoms. A physical examination should include postural vital signs, a cardiovascular examination, and clinical features of hypermobility.
Many alternative causes for symptoms can be excluded, and a presumptive diagnosis can be made using the Active Stand Test. Paediatric patients in whom a diagnosis is suspected should be referred to Secondary Care such as paediatric or adolescent services, paediatricians with expertise in cardiology, or paediatric cardiologists. In the United Kingdom, PoTS UK has a helpful list of NHS clinicians and clinics with a special interest in PoTS.
Lily tells you that she was previously fit and well.
She was diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) when she started Secondary School, but she doesn’t take any medication for this.
She had COVID for the second time about 12 months ago and was quite unwell, but didn’t need to go to the hospital.
There is no family history of any illnesses. She doesn’t smoke, and although some of her friends have started drinking alcohol at parties, she doesn’t as she finds it makes her symptoms worse.
PoTS may be classified as Primary or Secondary.
In Primary (Idiopathic) PoTS, there is no known trigger or associated medical condition. Primary PoTS can be further subclassified into neuropathic, hyperadrenergic or hypovolaemic according to characteristics of presentation. These subclassifications may overlap.
Secondary PoTS can be triggered by infectious illnesses such as COVID-19 and Epstein-Barr Virus. It can also be associated with other medical conditions such as autoimmune diseases, malignancy and chemotherapy, diabetes, alcohol excess, and heavy metal poisoning. Joint hypermobility and hypermobility syndromes such as Ehlers-Danlos are common in patients with PoTS. There is also an association between PoTS and neurodivergent conditions such as Autism and ADHD.
Lily explains that her symptoms are now interfering with all aspects of her life.
She finds standing on public transport too difficult. She is often unable to get to school and is concerned that she may fail her upcoming exams. She doesn’t go out to socialise with friends anymore, and she’s stopped playing netball.
PoTS impacts all aspects of everyday living, including physical, emotional, social and financial life. Although there is no increased mortality associated with PoTS, patients report similar levels of functional disability to those living with conditions such as Chronic Obstructive Pulmonary Disease (COPD) and congestive cardiac failure.
Up to 25% of adult patients with PoTS will be unable to work. The prognosis for adolescents is generally good, and most will recover to lead a normal life in adulthood.
You explain to Lily that her symptoms are suggestive of PoTs, but that she will need further investigations to confirm the diagnosis, and that you will refer her to a specialist.
You explain that there are some lifestyle measures she can implement whilst awaiting a diagnosis.
You reassure her that the prognosis for recovery is likely to be good, although this may take some time. Lily thanks you for listening to her and appreciating that her symptoms may not be ‘all in her head’.
A few months later, Lily is seen in a paediatric cardiology clinic. The clinic letter details the results of a repeat Active Stand Test, again demonstrating a persistent rise in heart rate of >40 bpm at 10 minutes with no change in blood pressure, a list of blood tests, which were all normal, and the result of a 24-hour Holter Monitor, which showed runs of sinus tachycardia associated with periods of standing.
PoTS can be identified using an active stand test through the measurement of heart rate and blood pressure initially when supine and then while standing for 10 minutes. If a more detailed recording of heart rate and blood pressure is needed or if the patient is unable to perform a standing test, then tilt-table testing may be performed. Access to tilt-table testing is limited for young people, although it is more readily available for those 16 and over. If the patient has a positive active stand test with symptoms, there is limited additional benefit to tilt table testing.
Routine laboratory investigations, as listed above, are typically sufficient. Urinary catecholamines should be reserved for patients in whom there is a high index of suspicion for phaeochromocytoma, as the diagnostic yield is low in routine cases. More advanced testing, including measurement of resting and standing catecholamines, is not routinely available outside of specialised autonomic units.
A 24-hour Holter will demonstrate heart rate trends, mean and maximum heart rates. Accompanied by a symptom diary, it can provide helpful insights. It may also guide decision-making in commencing pharmacological therapy if there is evidence of marked tachycardia. It can also help rule out arrhythmia if suspected.
The clinic letter went on to outline the recommended management, stating that Lily had been referred to a physiotherapist and advised to start an exercise programme, concluding that Lily had been reassured that her symptoms would most likely settle and that medications were not recommended at this time.
Non-pharmacological management is the primary treatment approach for the majority of patients. Exercise programmes of mild to moderate intensity, beginning in a semi-recumbent position and progressing to an upright position, are highly effective when performed 3-5 times per week. A small randomised controlled trial demonstrated that this program was more effective than beta-blockade (with propranolol) in improving haemodynamics and quality of life scores. Patient reassurance is important as the majority of teenagers will recover into adulthood.
A recent systematic review highlighted that the body of scientific literature on the pharmacological treatment of PoTS is limited. This is even more true in paediatric settings. Currently, there are no medications specifically licensed for the treatment of PoTS in the UK or the USA.
Pharmacological treatment is directed towards improving orthostatic tolerance. It should be reserved for severe or refractory cases in which concerted non-pharmacological efforts have failed. It is not commonly utilised in the paediatric setting. There are limited comparative studies between differing pharmacological approaches. There are several sub-types of PoTS: hyperadrenergic, neuropathic and hypovolaemic, with some authors suggesting therapies be targeted to sub-type. However, crossover exists between subtypes.
Ivabradine is a selective blocker of the If(funny) channel in the sinoatrial node. It is used in the treatment of heart failure and reduces heart rate with minimal effect on blood pressure. A small randomised, double-blinded, crossover trial of ivabradine vs placebo in adult patients with the hyper-adrenergic subtype of PoTS showed a statistically significant reduction in heart rate while standing and improvements in quality of life scores, with a favourable side effect profile.
Midodrine, a selective α1-adrenoceptor agonist, causes venoconstriction and vasoconstriction and is one of the best-assessed pharmacological therapies in the treatment of PoTS, with some limited evidence for its efficacy in the paediatric population. Midodrine may be most effective in the neuropathic subtype, where there is pooling of blood in the lower extremities or splanchnic vasculature.
Beta-blockers, such as propranolol or bisoprolol, are used to reduce standing heart rate. Doses of propranolol on the low end of the dosing schedule are considered as effective as high doses in lowering heart rate when standing, with better symptom control (20mg vs 80mg). Bisoprolol and propranolol are equally effective in improving symptoms compared to controls.
Fludrocortisone, a mineralocorticoid, is used in combination with sodium supplementation in the treatment of PoTS to increase blood volume and decrease symptoms. It has a limited evidence base, but was effective in a small study when used in combination with bisoprolol.
The next time you see Lily she reports she’s been compliant with her exercise regime.
Although she is still experiencing symptoms of PoTS, she has seen some improvement over the last month. She is now able to attend school, and feels more confident she’ll be able to sit her state exams.
References
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