A 13-year-old boy with fatigue and dizziness

A 13-year-old boy with a 3-month history of fatigue, nausea and lightheadedness on standing, was referred to our paediatric office for assessment. He did not have any abdominal pain, changes in bowel habits, chest pain, wheeze, headache, vomiting, blurry vision, fever or skin rashes. He denied any symptoms of depression. He was unable to attend school due to the severity of the presenting symptoms. He felt better sitting or in a recumbent position at home. In fact he was able to play around 6 hours of video games a day with no issues. His weight was 82.1 kg (above 95%), height was 179 cm (above 95%), with a BMI of 25.6 (above 95%). Prior investigations included: complete blood count, ferritin, liver function tests, renal function tests, thyroid stimulating hormone, mono spot test, celiac screen and abdominal ultrasound, which all returned normal. Upon focused questioning, it was revealed that his nausea was worsened with standing, and he also had symptoms of lightheadedness. There were no orthostatic blood pressure changes. Further investigations including an electrocardiogram and echocardiogram were negative. Utilizing a simple bedside test we were able to reach to a tentative diagnosis. Measuring the heart rate in three positions revealed significant postural changes. His blood pressure measurements were: 129/73, 125/78 and 129/80, however the pulse rates were 73, 80 and 121 bpm for supine, sitting and standing position, respectively. The heart rate increased more than 40 bpm without hypotension within 10 minutes of assuming an upright position, suggesting the diagnosis of postural orthostatic tachycardia syndrome (POTS). POTS is defined as a failure of the autonomic system to compensate for the upright posture (1). The prevalence is estimated to be 0.2% with a 5:1 female to male ratio and commonly affecting those aged 15 to 25 years. POTS has been associated with chronic fatigue, gastrointestinal problems, headaches, poor sleep, difficulty concentrating, tremor, palpitations, presyncopy and decreased exercise tolerance. Diagnosis is made based on (a) chronic symptoms (more than 6 months), (b) increase in pulse of ≥30 from supine to standing in adults, or ≥40 for patients aged 12 to 19 years within 10 minutes, in the absence of changes of systolic or diastolic blood pressure (a fall in BP>20/10 mmHg), (c) symptoms get worse with standing and better with recumbence and (d) absence of other overt cause of orthostatic symptoms or tachycardia (e.g., active bleeding, acute dehydration, medications). Failure of the regulatory mechanism to respond properly may lead to either orthostatic hypotension, as is seen in vasovagal syncope, or orthostatic tachycardia, as is seen in POTS. Orthostatic hypotension is defined as a fall in blood pressure on standing of more than 20/10 mmHg. However, it is common in patients with autonomic failure for the decline to be much greater than this, which may result in loss of consciousness soon after standing. On the other hand, in POTS, blood pressure is typically maintained on standing or may even increase. Heart rate rises more than 30 bpm and symptoms reminiscent of impaired cerebral perfusion may develop. Investigations should include orthostatic vitals and 12 lead electrocardiogram. Further workup with head-up tilt table testing, complete blood count, thyroid function test, 24-hour holter monitor, transthoracic echocardiogram and exercise stress testing can also be considered (1). The differential diagnosis includes: thyrotoxicosis, cardiac rhythm abnormalities, pheochromocytoma, hypoadrenalism, anxiety and iatrogenic causes such as diuretics and vasodilators (2). The prognosis for POTS is generally perceived to be benign. However, adolescents have been shown to experience moderate-to-severe disability related to their POTS (3). As patients get older, the increase in orthostatic heart rate generally decreases (1). The course of the condition varies between individuals, and as such the treatment regimens will need to be individualized (1). Treatments usually begin with nonpharmacological interventions and medications can be added on if there is no improvement (1). Patients should begin with supervised nonupright exercise such as recumbent cycling, rowing using machines and swimming. Grubb reported aerobic exercise three times a week for 20 minutes is also beneficial for patients who can tolerate it (4). Shibata had concluded in his study published in the Journal of Physiology in 2012, that exercise training improves physical fitness and cardiovascular responses during exercise in POTS (5). The study also highlighted the similarity between POTS and deconditioning (physical inactivity and lack of exercise) by showing lower physical performance due to a low stroke volume in both conditions. If patients are suspected to be hypovolemic, they should drink at least 2 to 3 L of water per day with a dietary salt intake of 10 to 12 g per day. The Food and Drug Administration has not approved any medications for the treatment of POTS. Therefore, all agents used for this disorder are ‘off label’. Propranolol (10 to 20 mg PO daily) is the only beta-blocker that has been studied to improve symptoms associated POTS. In patients in whom the presence of hypovolemia is either known or strongly suspected, fludrocortisone (aldosterone analogue) is often used. Through enhanced sodium retention, it should expand the plasma volume (6). There are several factors that make POTS difficult to manage. First, despite POTS being more common in the paediatric population, it can be misdiagnosed due to its nonspecific presentation (1). Second, even with management strategies in place, there is limited improvement in symptoms and function (3). Finally, there is currently very limited research exploring the efficacy of pharmacological agents for POTS (1). Therefore, it is prudent to increase awareness of this condition to promote its early diagnosis and management. Furthermore, there should be further research into the efficacy of management strategies for POTS. 1. Physicians should include POTS in their differential for nonspecific presentations such as symptoms of lightheadedness and generalized weakness, and specifically ask of it is worsened with standing. 2. Orthostatic HR increases of ≥30 in adults or ≥40 for patients aged 12 to 19 years, and lack of significant orthostatic systolic increase are sufficient for diagnosis of POTS. 3. Management with nonupright exercise programs and increasing water intake to 2 to 3 L/day with dietary salt intake of 10 to 12g/day should be considered before considering pharmacological agents such Propranolol.

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