What defines orthostatic hypotension?

Definition of Orthostatic Hypotension

Orthostatic hypotension is defined as a reduction of systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg within 3 minutes of quiet standing or during head-up tilt at 60 degrees. 1

Diagnostic Criteria

The definition of orthostatic hypotension includes specific parameters:

• Systolic blood pressure decrease: ≥20 mmHg
• Diastolic blood pressure decrease: ≥10 mmHg
• Timing: Within 3 minutes of standing
• Alternative method: Similar fall during head-up tilt at 60 degrees

Special Considerations

• In patients with supine hypertension: A systolic BP drop ≥30 mmHg should be considered diagnostic 1
• Measurement technique: Ideally performed using a validated and calibrated device with proper measurement technique 1

Types of Orthostatic Hypotension

Several distinct types of orthostatic hypotension have been identified:

1. Classical OH: Sustained decrease in BP within 3 minutes of standing 1

   • Characterized by immediate BP drop after standing
   • Rate of BP drop decreases over time
   • Low BP may be sustained for many minutes

2. Initial OH:

   • Characterized by BP decrease >40 mmHg systolic or >20 mmHg diastolic within 15 seconds of standing 1
   • BP spontaneously and rapidly returns to normal
   • Period of hypotension and symptoms is short (<40 seconds)

3. Delayed OH:

   • Occurs beyond 3 minutes of standing 1
   • Characterized by slow progressive decrease in BP
   • Absence of bradycardia helps differentiate it from reflex syncope
   • Common in elderly persons

Clinical Manifestations

Orthostatic hypotension may present with various symptoms due to cerebral hypoperfusion:

• Lightheadedness
• Dizziness
• Visual disturbances (blurring, enhanced brightness, tunnel vision)
• Weakness
• Fatigue
• Neck and shoulder pain ("coat hanger" pain)
• Hearing disturbances
• Syncope (fainting)

Diagnostic Assessment

The diagnosis of orthostatic hypotension is made through:

1. Office-based assessment:

   • Measure BP after 5 minutes in supine position
   • Measure BP immediately upon standing and at 1-3 minutes afterward
   • Record heart rate response

2. Active standing test:

   • Measure BP and heart rate after 5 minutes of lying supine
   • Measure immediately upon standing
   • Continue measurements at 2,5, and 10 minutes thereafter 1

3. Head-up tilt test:

   • Alternative when patient cannot stand safely
   • Tilt at 60 degrees or more
   • Monitor BP continuously or at intervals

Clinical Significance

Orthostatic hypotension has important clinical implications:

• Associated with increased mortality and cardiovascular disease prevalence 1
• Significant risk factor for falls, especially in the elderly
• May indicate underlying autonomic dysfunction
• Can be a side effect of medications, particularly antihypertensives

Pathophysiology

The pathophysiology varies depending on the type:

• Neurogenic OH: Impaired increase in peripheral resistance and heart rate due to autonomic failure 1
• Non-neurogenic OH: Often related to hypovolemia, medications, or deconditioning

Understanding the definition and proper assessment of orthostatic hypotension is crucial for appropriate management of affected patients and prevention of adverse outcomes such as falls and cardiovascular events.