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Dr. Alessandro Giardini
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When a child is referred for investigation of dizziness on standing, palpitations, or repeated near-fainting, one of the first investigations Dr Giardini will arrange is the active standing test. It is also called the orthostatic standing test, and in some clinical settings the NASA lean test, though the principles are the same.
Parents are often surprised by how straightforward it is. There is no injection, no needle, no sedation, and no scanner. The child simply lies down, and then stands up, while the heart rate and blood pressure are recorded at regular intervals. Yet the information it generates is some of the most diagnostically useful in the whole of paediatric cardiology.
The active standing test is primarily used to investigate symptoms of orthostatic intolerance: symptoms that are triggered or significantly worsened by being upright and that improve when the child lies down. Persistent dizziness on standing, a sensation of the heart racing when upright, near-fainting in queues or assemblies, and profound fatigue that is worse in the morning are all classic features of dysautonomia, in its various forms (postural tachycardia syndrome, or PoTS; Orthostatic intolerance: or vaso-vagal syncope)
PoTS is diagnosed when the heart rate rises persistently by 40 beats per minute or more within ten minutes of standing, in the absence of a significant drop in blood pressure (less than 20 mmHg systolic). In children an absolute heart rate above 120 beats per minute on standing can also meet the diagnostic threshold. The active standing test provides this data directly, quickly, and without any discomfort to the child.
It is also used to investigate vasovagal syncope, or simple fainting, particularly when the clinical history is unclear, and to assess children with unexplained fatigue, brain fog, or exercise intolerance where an autonomic component is suspected.
The child arrives having had a normal morning, though they should be well hydrated before attending. There is no fasting requirement for the active standing test, which is one of the things that distinguishes it from the tilt table test. Wearing comfortable clothing helps, as the test involves lying on a clinic couch.
The nurse or clinician fits a blood pressure cuff, typically on the arm, and in Dr Giardini's clinic an ECG recording is also attached to provide a continuous heart rate trace throughout. The child lies flat and still for few minutes. This lying down period is essential: the heart rate and blood pressure need to reach a genuine resting baseline before the standing phase begins. Some children find it hard to lie completely still, but it is worth the effort, because movement raises the heart rate artificially and makes the results harder to interpret.
At the end of the lying period, the resting measurements are recorded. The child is then asked to stand up and remain as still as possible, feet together, for up to ten minutes. They should avoid fidgeting, leaning, or moving their legs, as the muscle activity this produces pumps blood back to the heart and partially masks the cardiovascular response the test is trying to measure.
Heart rate and blood pressure are recorded frequently throughout the standing phase, typically every one to two minutes, though Dr Giardini uses continuous ECG monitoring which provides a second-by-second heart rate trace throughout. The child is asked to report any symptoms as they arise: dizziness, visual changes, nausea, feeling of the heart pounding, or any sense that they might faint.
The test is stopped early if the child develops significant symptoms, if the heart rate rises to a level that causes distress, or if the blood pressure drops substantially, indicating a vasovagal response.
A normal result is a modest rise in heart rate on standing, typically less than 30 beats per minute, with blood pressure maintained or minimally changed. This is the expected autonomic response to postural change and is entirely reassuring.
A rise in heart rate of 40 beats per minute or more, sustained throughout the standing phase without a significant drop in blood pressure, meets the diagnostic criteria for PoTS. This is a positive test. It is an objective, measurable finding that removes the diagnostic uncertainty that many families have lived with, sometimes for months or years.
A drop in blood pressure of more than 20 millimetres of mercury in the systolic reading, with or without a change in heart rate, indicates orthostatic hypotension, a different but related condition in which the blood pressure control mechanism fails on standing.
A late drop in both heart rate and blood pressure, occurring after several minutes of standing rather than immediately, is the pattern of vasovagal syncope. Children with this pattern sometimes actually faint during the test, which is uncomfortable but entirely safe in a clinical setting where the team is present and the child can be immediately laid back down.
The active standing test is the first-line investigation for suspected PoTS and orthostatic intolerance in almost all UK specialist centres. It is simple, reproducible, low-cost, and can be performed at the same appointment as the ECG and echocardiogram. It requires no special equipment beyond a blood pressure monitor and a couch.
In Dr Giardini's practice, the active standing test, ECG, and echocardiogram are performed together at a single appointment. For the majority of children presenting with PoTS symptoms, this means a diagnosis and management plan can be established on the day, without the need for further investigations or waiting for a tilt table test appointment.
The tilt table test is reserved for children in whom the active standing test is inconclusive or in whom a more controlled and prolonged orthostatic challenge is needed to characterise the autonomic response in detail. The tilt table test is explained in its own post here.
The most important preparation is hydration. A child who arrives at the test significantly dehydrated will have a higher resting heart rate and an exaggerated response to standing, which can make a borderline result appear more abnormal than it is on a typical day. Conversely, a child who has drunk exceptionally well on the morning of the test may show a better response than usual. Dr Giardini asks families to ensure the child has a normal fluid intake in the 24 hours before the test, without any special loading or restriction.
Salt intake on the day before the test should also be normal, not increased. Some families, having read about the role of salt in PoTS management, give their child extra salt before the appointment in the hope of improving how they feel. This will affect the test result and should be avoided until after the assessment is complete.
Caffeine and stimulant drinks should be avoided on the morning of the test. They raise the resting heart rate and can make the cardiovascular response harder to interpret.
Some medications affect the autonomic cardiovascular response and should be discussed with Dr Giardini before the appointment. Beta-blockers in particular slow the heart rate response and may suppress a PoTS pattern that would otherwise be clearly positive. The decision whether to withhold or continue medication before the test depends on the clinical situation and is made on an individual basis.
No. Fasting is not required for the active standing test. The child can have a normal breakfast and lunch if the appointment is in the afternoon. Being well hydrated is more important than being fasted. Avoiding caffeine and energy drinks on the morning of the test is advised.
Possibly, but not commonly. A child who faints during the active standing test does so because the test has triggered the cardiovascular response it is designed to investigate. The test takes place in a clinical setting with a nurse or clinician present throughout, and if a faint occurs the child is immediately laid back down on the couch and recovers quickly. Being aware that this might happen, and not being frightened by it, is the most helpful preparation.
Not always. If the clinical history is strongly consistent with PoTS, Dr Giardini will consider repeating the test under different conditions or proceeding to a tilt table test, which provides a more controlled orthostatic challenge. A single normal active standing test does not definitively rule out the diagnosis.
The standing test itself lasts up to ten minutes on top of the few minute lying rest period, making the test component approximately twenty minutes. The full appointment at Dr Giardini's clinic includes an ECG and echocardiogram as well as the standing test, and the consultation before and after the investigations, so families should allow approximately 45-60 minutes for the complete assessment.
Yes. There are no restrictions on activity after the active standing test. Some children feel tired or slightly unwell if symptoms were triggered during the standing phase, and it is sensible to have a drink and sit quietly for a few minutes before leaving the clinic. Most children are entirely well to attend school or return to normal activities the same day.
The diagnostic threshold for PoTS in adolescents is 40 beats per minute. A rise of 35 beats per minute is below the formal threshold but it needs to be interpreted in the specific clinical context. In a child who where symptoms are very reproducible and characteristics, a borderline result might still carry some clinic weight. In this setting response to a treatment trial or a repeat test under different conditions often clarifies the picture.
Anxiety and fear of the test can raise the heart rate during both the lying and standing phases, which can potentially mimic a PoTS response. However, anxiety alone does not typically produce the sustained, progressive heart rate rise of PoTS: anxiety-related tachycardia tends to settle as the child relaxes, while the PoTS response persists or worsens throughout the standing period. Dr Giardini is experienced in distinguishing these patterns on the continuous ECG trace.
This depends on the clinical situation and should be discussed with Dr Giardini before the appointment. Beta-blockers slow the heart rate response and can suppress the PoTS pattern, leading to a falsely normal result. In some cases it is appropriate to hold the medication for a defined period before testing; in others, the clinical risk of stopping the medication outweighs the diagnostic benefit. Dr Giardini will advise on this specifically based on the individual child's condition and medication regimen.
Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist
Written: 02/07/2026
Last reviewed: 02/07/2026