What is the likely cause of dizziness that begins a few minutes after standing, with tachycardia and tunnel‑vision, and how should it be evaluated and managed?

Postural Orthostatic Tachycardia Syndrome (POTS) or Delayed Orthostatic Hypotension

The combination of dizziness beginning a few minutes after standing, tachycardia, and tunnel vision most strongly suggests either Postural Orthostatic Tachycardia Syndrome (POTS) or delayed orthostatic hypotension, both of which require formal orthostatic vital sign testing over a full 10-minute standing period to differentiate. 1

Why This Presentation Points to Orthostatic Intolerance

The timing is critical here—symptoms that begin after a couple of minutes of standing (rather than immediately) distinguish this from classical orthostatic hypotension, which typically causes symptoms within 30 seconds to 3 minutes. 1, 2

• Tunnel vision is explicitly recognized as a cardinal visual disturbance of cerebral hypoperfusion in orthostatic syndromes by the European Society of Cardiology. 1, 2
• Tachycardia developing with upright posture strongly suggests POTS, where the heart rate increases excessively (>30 bpm in adults, >40 bpm in adolescents aged 12-19) within 10 minutes of standing. 1, 3
• The delayed onset (a couple of minutes rather than immediate) fits the pattern of either POTS or delayed orthostatic hypotension, which can take 3-30 minutes to fully manifest. 1, 4

Diagnostic Evaluation: The 10-Minute Standing Test

You must perform orthostatic vital signs with measurements extending to 10 minutes—not just the standard 1-3 minute protocol—because both POTS and delayed orthostatic hypotension can be missed with abbreviated testing. 1

Specific Protocol:

• Measure blood pressure and heart rate after 5 minutes of supine rest. 1
• Record both parameters at 1,3,5, and 10 minutes of continuous standing. 1
• Document any symptoms (dizziness, tunnel vision, palpitations) at each time point. 1

Diagnostic Thresholds:

• POTS: Heart rate increase >30 bpm (or absolute rate >120 bpm) within 10 minutes, without meeting blood pressure criteria for orthostatic hypotension. 1, 3
• Classical orthostatic hypotension: Systolic BP drop ≥20 mmHg or diastolic drop ≥10 mmHg within 3 minutes. 1, 5
• Delayed orthostatic hypotension: Blood pressure remains stable for 3-10 minutes but then falls severely after 10-30 minutes of standing. 1, 4

Common Pitfall:

Limiting measurements to only 1-2 minutes will miss delayed presentations entirely—the heart rate rise in POTS may not peak until 10 minutes, and delayed orthostatic hypotension by definition occurs after the standard 3-minute window. 1, 4

Associated Features to Assess

• Physical deconditioning is frequently linked to POTS and should be explored in the history. 1
• Joint hypermobility is commonly associated with POTS and should be examined. 1
• Ask about exacerbating factors: hot showers, large meals, morning hours, prolonged standing, and heat exposure all worsen orthostatic intolerance syndromes. 1, 2
• Screen for autonomic symptoms: palpitations, fatigue, brain fog, nausea, and "coat-hanger" neck/shoulder pain (the latter suggests autonomic failure). 1, 2

Initial Management Strategy

Immediate Measures:

• Position supine immediately during symptomatic episodes to restore cerebral perfusion. 1
• Teach physical counter-pressure maneuvers (leg-crossing, squatting, muscle tensing) to abort symptoms when they begin. 1

Non-Pharmacologic First-Line Therapy (Offer to All Patients):

• Increase fluid intake to 2-3 liters daily and salt consumption to 5-10 grams daily. 1, 3
• Avoid triggers: prolonged standing, hot showers, large meals, rapid postural changes. 1
• Gradual exercise reconditioning starting with recumbent activities (rowing, swimming) because deconditioning perpetuates POTS. 1, 3
• Consider waist-high compression stockings to reduce venous pooling. 1

Medication Review:

• Withdraw or reduce hypotensive medications where safe: diuretics, vasodilators, negative chronotropes, sedatives. 1

Pharmacologic Options (If Non-Pharmacologic Measures Fail):

• Fludrocortisone is first-line for volume expansion in hypovolemic orthostatic hypotension. 1
• Midodrine enhances vascular tone but requires monitoring for supine hypertension and urinary retention (especially in older males). 1
• Low-dose beta-blockers may control tachycardia in severe POTS cases. 3

When to Consider Alternative Diagnoses

• Vestibular disorders (BPPV, vestibular neuritis) are provoked by head position changes relative to gravity, not by standing or heat exposure, and typically cause true vertigo rather than lightheadedness. 1
• Cardiac arrhythmias cause abrupt syncope but are not characteristically precipitated by posture or heat. 1
• Posterior circulation insufficiency usually presents with additional neurologic deficits beyond isolated dizziness. 1

Nuance: Mixed Presentations

Some patients exhibit features of both POTS and orthostatic hypotension (e.g., tachycardia with a near-threshold BP drop of 18 mmHg systolic), suggesting inadequate compensatory mechanisms or volume depletion. 3 This mixed picture still responds to the same initial non-pharmacologic interventions. 3