What constitutes positive orthostatic vitals?

Defining Positive Orthostatic Vitals

Positive orthostatic vitals are defined as a sustained decrease in systolic blood pressure ≥20 mmHg, diastolic blood pressure ≥10 mmHg, or a sustained decrease in systolic BP to an absolute value <90 mmHg within 3 minutes of active standing or head-up tilt of at least 60 degrees. 1, 2

Types of Orthostatic Hypotension

Classical Orthostatic Hypotension

• Defined as a sustained decrease in systolic BP ≥20 mmHg, diastolic BP ≥10 mmHg, or a sustained decrease in systolic BP to an absolute value <90 mmHg within 3 minutes of active standing or head-up tilt 1
• In patients with supine hypertension, a systolic BP drop ≥30 mmHg should be considered positive 1
• Orthostatic HR increase is blunted in neurogenic OH (usually <10 beats per minute) due to impaired autonomic HR control 1
• HR increase is preserved or enhanced in OH due to hypovolemia 1
• Associated with increased mortality and cardiovascular disease prevalence 1

Initial Orthostatic Hypotension

• Characterized by a BP decrease on standing of >40 mmHg for systolic BP and/or >20 mmHg for diastolic BP within 15 seconds of standing 1
• BP spontaneously and rapidly returns to normal, with hypotension and symptoms lasting <40 seconds 1
• The rate of BP recovery after initial fall has prognostic significance; impaired recovery represents a negative prognostic factor in the elderly 1

Delayed Orthostatic Hypotension

• Defined as OH occurring beyond 3 minutes of head-up tilt or active standing 1
• Characterized by a slow progressive decrease in BP 1
• The absence of bradycardia helps differentiate delayed OH from reflex syncope 1

Postural Orthostatic Tachycardia Syndrome (POTS)

• Characterized by an inappropriate HR increase (>30 b.p.m. or >120 b.p.m. within 10 minutes of standing) without concomitant BP fall 1
• In patients aged 12-19 years, HR increase should be >40 b.p.m. 1
• Associated with orthostatic intolerance symptoms but rarely syncope 1

Testing Methodology

• For diagnosis, blood pressure should be measured after 5 minutes of lying supine, then continued after 1 or 3 minutes of standing 2
• Active standing test or head-up tilt test of at least 60 degrees can be used 1
• Beat-to-beat BP monitoring is particularly useful for detecting initial OH 1

Clinical Significance

• Symptoms depend more on the absolute BP level than the magnitude of the fall 1
• Cerebral autoregulation plays a key role in symptom occurrence 1
• OH is associated with increased mortality, cardiovascular disease prevalence, and falls 1, 3
• OH increases relative risk of all-cause mortality by up to 50% 3

Common Pitfalls in Diagnosis

• Failing to consider a higher threshold (≥30 mmHg systolic drop) in patients with supine hypertension 1
• Not measuring BP beyond 3 minutes, potentially missing delayed OH 1
• Overlooking asymptomatic OH, which still carries prognostic significance 1
• Not considering POTS in young patients with orthostatic symptoms but without BP drop 1