What are the diagnostic tests for orthostatic hypotension?

Diagnostic Tests for Orthostatic Hypotension

The definitive diagnostic test for orthostatic hypotension is measuring blood pressure and heart rate changes from supine to standing position, with a decrease in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing confirming the diagnosis. 1

Orthostatic Blood Pressure Testing Protocol

Standard Orthostatic Vital Sign Measurement

• Measure BP after 5 minutes of rest in supine or sitting position
• Measure BP at 1 minute and 3 minutes after standing
• Use a validated and calibrated blood pressure measurement device 1
• Test in a temperature-controlled environment (21-23°C)
• Patient should be fasted for 3 hours before testing
• Avoid nicotine, caffeine, alcohol, or smoking before the test 1

Diagnostic Criteria

• Classical orthostatic hypotension: Decrease in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing 2
• In patients with supine hypertension, a systolic BP drop ≥30 mmHg should be considered 1
• Initial orthostatic hypotension: BP decrease >40 mmHg systolic or >20 mmHg diastolic within 15 seconds of standing, with spontaneous recovery 2
• Delayed orthostatic hypotension: OH occurring beyond 3 minutes of standing 2

Pattern Recognition

• Classical OH shows a "concave" curve pattern of BP decrease 1
• In neurogenic OH, heart rate increase is blunted (usually <10 bpm) 2
• In non-neurogenic OH (e.g., hypovolemia), heart rate increase is preserved or enhanced 2

Additional Diagnostic Tests

Head-up Tilt Table Testing

• Indicated when:
  • Standard orthostatic vital signs are nondiagnostic but clinical suspicion is high
  • Patient is unable to stand safely 3
  • Need to assess treatment response in patients with autonomic disorders 4
• Performed at a 60-degree angle or greater 3
• Allows continuous monitoring of BP and HR changes

Basic Laboratory Tests

Based on ACC/AHA guidelines, the following tests should be performed to evaluate for secondary causes and assess cardiovascular risk 2:

• Fasting blood glucose
• Complete blood count
• Lipid profile
• Serum creatinine with eGFR
• Serum sodium, potassium, calcium
• Thyroid-stimulating hormone
• Urinalysis
• Electrocardiogram

Optional Testing Based on Clinical Suspicion

• Echocardiogram (to evaluate cardiac function)
• Urinary albumin to creatinine ratio
• Uric acid 2

Autonomic Function Testing

For suspected neurogenic orthostatic hypotension, additional autonomic testing may be required in a specialized laboratory to characterize cardiovascular sympathetic and parasympathetic function 2:

• Heart rate variability to deep breathing
• Valsalva maneuver response
• Sudomotor function testing
• Catecholamine levels (supine and standing)

Differential Diagnosis Testing

Postural Tachycardia Syndrome (POTS)

• Standing test showing increase in heart rate by >30 beats per minute without significant BP drop 2
• Typically occurs within 10 minutes of standing 2

Primary Orthostatic Tremor

• Electromyography showing 13-18 Hz tremor in weight-bearing muscles

Cervicogenic Headache

• Assessment of cervical range of motion
• Evaluation for myofascial tenderness 2

Clinical Pearls

• Always measure BP in both arms at initial assessment; if difference is >10 mmHg, use the arm with higher BP for subsequent measurements 1
• The rate of BP recovery after initial drop has important prognostic implications, particularly in elderly patients 1
• Both the magnitude of BP change and absolute BP values are important when assessing orthostatic responses 1
• Impaired BP recovery represents a negative prognostic factor in elderly patients 1
• Screening for orthostatic hypotension is particularly important in patients with hypertension, diabetes, and elderly patients 1, 3

Common Pitfalls to Avoid

1. Failing to wait the full 3 minutes during orthostatic testing, potentially missing delayed orthostatic hypotension
2. Not considering medication effects (especially antihypertensives, diuretics, vasodilators)
3. Overlooking neurogenic causes when heart rate response is blunted
4. Missing initial orthostatic hypotension by not measuring BP within the first 15 seconds
5. Failing to distinguish between orthostatic hypotension and vasovagal syncope

By following this systematic approach to diagnosing orthostatic hypotension, clinicians can accurately identify the condition, determine its subtype, and guide appropriate management strategies to reduce symptoms and prevent complications.