What criteria define orthostatic hypotension?

Defining Orthostatic Hypotension

Orthostatic hypotension is defined as a sustained decrease in systolic blood pressure ≥20 mmHg or diastolic blood pressure ≥10 mmHg (or systolic BP falling to <90 mmHg absolute) within 3 minutes of standing or head-up tilt to at least 60 degrees. 1

Standard Diagnostic Criteria

The diagnostic thresholds are:

• Systolic BP drop ≥20 mmHg, OR
• Diastolic BP drop ≥10 mmHg, OR
• Systolic BP falling to absolute value <90 mmHg
• Must occur within 3 minutes of postural change 1

Special Consideration for Supine Hypertension

In patients with baseline supine hypertension, a systolic BP drop ≥30 mmHg should be considered diagnostic rather than the standard 20 mmHg threshold. 1 This is particularly relevant in neurogenic orthostatic hypotension where supine hypertension commonly coexists. 1

Measurement Methodology

Preferred Testing Approach

• Active standing test with continuous BP monitoring is preferable to tilt-table testing, particularly for detecting initial orthostatic hypotension 1
• Baseline measurement requires 5 minutes of supine rest before standing 2
• Measurements should be taken at 1 and 3 minutes after standing 1, 3
• Head-up tilt testing at ≥60 degrees is an alternative when active standing is not feasible 1

Clinical Testing Protocol (Simplified Schellong Test)

1. Measure BP and heart rate after 5 minutes supine 3
2. Have patient stand and measure BP at 1 minute and 3 minutes 3
3. If unable to stand safely or high clinical suspicion with normal bedside findings, proceed to head-up tilt table testing 3

Subtypes of Orthostatic Hypotension

The European Society of Cardiology guidelines recognize distinct temporal patterns 1:

Initial Orthostatic Hypotension

• BP decrease >40 mmHg systolic and/or >20 mmHg diastolic within 15 seconds of standing 1
• BP spontaneously and rapidly returns to normal within <40 seconds 1
• May still cause syncope despite brief duration 1

Classical Orthostatic Hypotension

• Occurs within 3 minutes of postural change 1
• Characterized by a "concave" BP curve on continuous monitoring 1
• Heart rate response distinguishes neurogenic (blunted, usually <10 bpm increase) from non-neurogenic (preserved or enhanced HR increase) 1

Delayed Orthostatic Hypotension

• BP drop meeting criteria occurs beyond 3 minutes of standing or tilt 1
• Shows slow progressive decrease in BP 1
• Absence of bradycardia helps differentiate from reflex syncope 1

Clinical Significance and Prognosis

Classical orthostatic hypotension is associated with increased mortality and cardiovascular disease prevalence, even when asymptomatic. 1 The condition independently increases risk of myocardial infarction, stroke, heart failure, and atrial fibrillation, with up to 50% increase in relative risk of all-cause mortality. 4, 3

Symptom Correlation

Symptoms depend more on the absolute BP level reached than the magnitude of the fall. 1 Cerebral autoregulation plays a key role in symptom occurrence, explaining wide variability in symptom severity among patients with similar BP drops. 1

Important Caveats

• Reproducibility of OH testing is poor - repeated measurements may be necessary 2
• OH may be symptomatic or asymptomatic - absence of symptoms does not exclude the diagnosis or its prognostic significance 1
• The rate of BP recovery after initial drop has important prognostic consequences in elderly patients - impaired recovery represents a negative prognostic factor 1
• Prevalence is age-dependent: 5% in patients <50 years versus 30% in those >70 years 4