Dr Nicholas Gall looks at existing guidelines on postural (orthostatic) tachycardia syndrome, and discusses the need for national guidance to manage the increasing number of people presenting with this condition, often associated with long COVID
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Definition and Diagnosis of PoTSPostural (orthostatic) tachycardia syndrome (PoTS) appears to be an abnormality in the neural control of the cardiorespiratory system and is therefore neither a heart problem nor a lung problem, but an abnormality in the regulation of those systems.1,2,3 It is defined on the basis of an abnormal increase in heart rate on standing, associated with symptoms.1,2 PoTS was first defined as a condition in 1993 on the basis of a small study.4 It is formally diagnosed when the heart rate increases by more than 30 bpm in a sustained fashion without a fall in blood pressure of more than 20 mmHg systolic over a 10-minute period, and associated with symptoms;2 for patients aged less than 20 years, the heart rate increase required is 40 bpm.2 It must be recognised that heart rate increase is variable, and can often be more pronounced in the mornings,5 in female patients when menstruating,6 after a meal, after exercise, and when unwell, for example. Therefore, the latest Canadian Cardiovascular Consensus2 suggests the inclusion of an additional group of patients who may be defined as having orthostatic intolerance or postural symptoms without tachycardia (PSWT) when the increase in the clinical heart rate is less prominent but is abnormal. The diagnosis, therefore, may be better defined as cardiovascular symptoms occurring on standing associated with an abnormal increase in heart rate, in an individual in whom there are no alternative causes and who is responding to therapy.
How PoTS Usually Presents
The typical patient2,7 presenting with postural tachycardia is young, more often female, and often describes the development of a set of cardiovascular symptoms after a precipitating illness (particularly commonly COVID-19)8 although any illness can precipitate it—including glandular fever,6 an operation, pregnancy, a road traffic accident, or a stressful event. Most patients describe some degree of cardiovascular symptomatology, although this can be variable. Chest pain is often described;7 this may be musculoskeletal in nature but can also relate to a central chest pressure, frequently associated with breathlessness that has features of dysfunctional breathing.9 Patients describe a sense of insufficient air and a perception that they cannot fill their lungs adequately. Patients rarely document significant respiratory symptoms. They may note ectopic beats, but these are infrequent, and patients often describe palpitation with a sense that their heart is beating faster or harder, particularly on exertion or when standing. Most patients describe faintness on standing and a smaller proportion, perhaps one-third, will lose consciousness, with vasovagal syncope.7
About one-quarter of PoTS patients are hypermobile,2,10 and may describe joint symptoms with other connective tissue symptoms.
Aetiology of PoTS
A clear understanding of the underlying causes is lacking, and there may be many. It may relate to abnormalities in heart rate control, and/or blood volume control, and/or blood vessel vasoconstriction, and/or the ability of the body to direct blood in the right quantity to the right organ systems at the right time. One family has been described with a norepinephrine transporter gene abnormality (A457P) in which excess norepinephrine persists in the synapses,11 but whether this is present in other individuals remains uncertain. It is increasingly recognised that a small fibre neuropathy may be an underlying cause in some.1
Impact of COVID-19
Although data are only just beginning to accrue, there is no doubt that clinics specialising in PoTS in the UK and around the world are recognising an increased prevalence as a direct result of a COVID-19 infection.12 Estimates vary, but it may be that up to 10% of long COVID could relate to POTS.8 (Data also sourced from personal communication.) The recognition of PoTS has been mentioned in NICE guidance on the management of long COVID,13 and the American Autonomic Society highlights PoTS as a growing problem.12
Burden of Disease
The true incidence of PoTS in the population is unknown—it has been suggested that perhaps 170 per 100,000 patients in the UK may have PoTS, based on estimates of the number of patients with chronic fatigue syndrome who may also have PoTS.14 Because of the very large number of long COVID sufferers, with hundreds of thousands detailing persistent symptoms even 2 years post-infection, it seems likely that the number of PoTS patients will increase significantly.
Breathlessness in PoTS may have many causes, but dysfunctional breathing appears to be a major factor.9 The exact reasons are unclear, but it was recently postulated that reduced blood supply to the oxygen sensing system in the carotid body may be relevant.9,15 This may be an important cause of breathlessness in PoTS post COVID, and it is therefore important to recognise that it may be contributory. Respiratory physiotherapy can be a particularly helpful treatment.9
There is no international consensus on which investigations should be undertaken in individual patients. For the vast majority, clinical examination, oxygen saturations, a clinic stand or a home stand test (where heart rate and blood pressure are monitored on standing after a 5–10 minute period lying flat, assessing heart rate and blood pressure every minute over a 10-minute period to look for a pattern) is appropriate.2 Other investigations such as echocardiography,2 Holter monitoring,1 cardiopulmonary exercise test,2 and a more formal active stand/tilt with beat-to-beat blood pressure may be needed in selected cases, but due to the intensity of investigations it is unlikely to be appropriate for many.
Management of PoTS1,2
Cardiovascular symptoms relate to a combination of an inappropriately fast heart rate, reduced blood volume, and reduced peripheral vasoconstriction. Simple non-pharmacological therapies therefore revolve around increased fluid and salt intake,16 which can be guided by a 24-hour urine collection for sodium and volume, aiming for more than 2.5 litres and more than 170 mmol of sodium.16 Compression clothing17—such as sports compression leggings or compression tights—can be prescribed to improve venous return, and a slow and gradual increase in exercise,18,19 where appropriate, can be undertaken and has been proven to assist in many cases. Usually, it is important to undertake very small degrees of exercise, often performed horizontally—for example, rowing, recumbent cycling, or swimming.19 It is important to recognise situations in which symptoms can worsen, such as during hot conditions,20 when unwell, or following a big meal, so as to control the environment.
Pharmacological therapies have been used, and revolve around medications to slow the heart rate, such as low-dose beta-blockers (propranolol),21 pyridostigmine,22 or ivabradine.23 Increased fluid retention with fludrocortisone and salt tablets can be considered, and midodrine can also be used as a peripheral vasoconstrictor.24 All of these medications can be prescribed together if necessary, and there are other, more rarely used medications,25 including EPO and octroetide, that are often used in specialist units.
PoTS is not purely a heart rate problem, but is a dysregulatory process and, therefore, collaboration is important,14 including with respiratory physiotherapy. In many cases, there is dysregulation in other organ systems, including the bowels, bladder, joints, migraines, sleep, and allergy systems.7 Depending on the burden of symptoms, referral to expert colleagues who understand these areas is important. The national charity POTS-UK has information on its website that provides further insight and advice.26
Development of Secondary and Tertiary Care Services
Very few services in the UK, and indeed globally, specialise in PoTS. The condition appears to be an abnormality in the neural control of the cardiovascular system—a neurological issue presenting with cardiovascular symptoms—and is therefore a problem spanning both neurology and cardiology that is often rarely focussed upon. Because of the large number of patients in the UK, increasing due to COVID-19, funding to increase the number of centres, and to support existing centres, is required in order to reduce waiting times. Management techniques can be highly effective. Although patients do not die due to their symptoms, the impact can be significant, and many are unable to study or work, creating a significant societal financial burden. Improved management is vital, and likely to be cost-effective in the long term.
No national guidelines currently exist for the management of PoTS, although the Heart Rhythm Society produced guidance in 2015,1 PoTS is mentioned in the European Society of Cardiology’s syncope guidance published in 2018,27 and the Canadian Cardiovascular Society released a consensus statement in 2020.2 Given the recent increase in evidence from randomised controlled trials in this area,22 a UK-specific guideline is now needed—not only to summarise the data, but also to underline the importance of the management of this condition, and to mandate a focus on it in both secondary and primary care. At present, the health service does not provide services in every locality for PoTS, nor does it encourage national provision, leaving it to local health systems to develop services themselves if they see fit. This has led to a relatively small number of UK services; often, these have been developed due to a particular clinician’s interest and subsequently close up on their retirement. National guidance would emphasise the importance of a more formal development of these services for this increasingly frequent condition.
Dr Nicholas Gall
Consultant Cardiologist (Arrhythmias and Neuro-cardiology), and an Honorary Senior Lecturer at King’s College London, London. He is also a Patron of POTS UK, and a Medical adviser for STARS and HMSA