Postural orthostatic tachycardia syndrome — branching viva

Opening

Examiner. A 15-year-old girl has had four months of daily dizziness, palpitations and fatigue that come on within minutes of standing and ease when she lies down. How do you approach her? [1]

Candidate (must-hit). I take an orthostatic history, do a cardiac red-flag screen, run a 10-minute active stand test, and obtain a 12-lead ECG on every child. I am looking to confirm a chronic orthostatic intolerance consistent with postural orthostatic tachycardia syndrome, and — first and foremost — to exclude cardiac syncope. [1] [3]

Branch 1 — The diagnosis and the threshold

Examiner. What defines POTS, and what numbers confirm it? [1]

Candidate (must-hit). POTS is a chronic orthostatic intolerance on most days for at least three months, in which standing produces a sustained heart-rate rise of ≥40 bpm in adolescents (≥30 bpm in adults, or an upright rate ≥120 bpm) within 10 minutes of standing or tilt, without an orthostatic blood-pressure fall of ≥20 mmHg systolic or ≥10 mmHg diastolic. The symptoms are provoked by standing and eased by lying down. [1] [2]

Examiner (probe). Why is the three-month rule there? [3]

Candidate. To exclude the transient tachycardia of fever, dehydration, anxiety or a single viral illness, which can all push a standing heart rate above 120 without being POTS. Premature labelling traps a child in a chronic diagnosis and a treatment ladder they do not need. [3] [9]

Branch 2 — The cardiac-exclusion step

Examiner. Before you settle on POTS, what must you exclude? [3]

Candidate (must-hit). Cardiac syncope. I screen for the red flags: exertional collapse, syncope while supine or swimming, syncope from a loud noise or fright, no prodrome, palpitations at the moment of collapse, chest pain, and a family history of sudden death before about 50. I obtain a 12-lead ECG on every child and read it myself for a long QTc, pre-excitation, a Brugada pattern, heart block and cardiomyopathic changes. [3] [1]

Examiner (probe). A registrar records only the heart rate during the stand test. What is the error? [1]

Candidate. Without the blood pressure, POTS cannot be distinguished from orthostatic hypotension — the blood-pressure fall of ≥20/10 mmHg is the discriminating feature. The stand test must measure both, at 2, 5 and 10 minutes. [1]

Branch 3 — Phenotypes and management

Examiner. Name the POTS phenotypes and how they guide treatment. [2]

Candidate (must-hit). Three overlapping phenotypes: neuropathic (venous pooling, acrocyanosis; compression and counter-pressure, midodrine if needed), hyperadrenergic (palpitations, tremor, sometimes a rising blood pressure; beta-blocker or ivabradine), and hypovolaemic (low volume, worse in heat and after illness; fluid, salt, fludrocortisone). One young person often has more than one. [2] [10]

Examiner (probe). Walk me up the management ladder. [5]

Candidate. Step 1 educate, validate and a school plan; step 2 hydration and salt (around 2–3 L fluid, titrated sodium chloride, avoiding hypertension or renal disease); step 3 counter-pressure and compression garments; step 4 structured recumbent or sub-threshold exercise to reverse the deconditioning spiral — the most evidence-based component; step 5 phenotype-guided pharmacotherapy. I treat sleep, mood and school return in parallel. [5] [10]

Examiner (probe). Why is reconditioning the centrepiece? [10]

Candidate. Deconditioning is both cause and consequence — less activity lowers blood volume and stroke volume, which worsens the tachycardia, which reduces activity further. Reconditioning runs that loop in reverse; resting makes it worse. [3] [10]

Branch 4 — The trap case

Examiner. A 14-year-old boy collapses sprinting the 400 metres, no prodrome; his father died suddenly at 34. Is this POTS? [3]

Candidate (must-hit). No. This is cardiac syncope until proven otherwise — exertional, warning-free collapse with a family history of sudden death points to hypertrophic cardiomyopathy, long-QT, CPVT or arrhythmogenic cardiomyopathy. I restrict sport, obtain an ECG, and refer urgently to cardiology for echo, monitoring, exercise testing and family screening. POTS is never the label for an exertional collapse. [3] [1]

Branch 5 — Post-COVID orthostatic intolerance

Examiner. An adolescent presents eight months after COVID-19 with the same daily orthostatic picture. How does this differ? [14]

Candidate. It does not differ in pathway — post-COVID orthostatic intolerance fits the same orthostatic-intolerance definition and is identified with the same 10-minute passive standing test. The management is the same: validate, hydrate and salt, recondition, and add medication only if needed. The trajectory may be more protracted. [14] [9]

Closing summary

POTS is a chronic orthostatic intolerance with an excessive heart-rate rise on standing without orthostatic hypotension; confirm it with a 10-minute active stand, exclude cardiac syncope with an ECG on every child, and treat with fluid, salt and recumbent exercise before reaching for phenotype-guided medication. [1] [3]