Table 5.

Syndromes of orthostatic intolerance

Syndrome	Test	Time to abnormal BP response	Pathophysiology	Symptoms	Associated Conditions
Initial OH	Beat-to-beat BP on active standing test	0–15 s	Transient mismatch between cardiac output and total peripheral resistance	Light-headedness, dizziness, visual disturbances few seconds after standing.	Old age, drug-induced (alpha-blockers)
Classical OH	Active standing test; TT	<3 min	Impaired total peripheral resistance and HR increase in autonomic failure; severe volume depletion	Dizziness, light-headedness, weakness, visual and hearing disturbances	Frailty, drug-induced (vasoactive drugs, diuretics), autonomic failure, hypovolaemia
Delayed OH	TT	>3 min	Likely progressive fall in venous return and low cardiac output	Prolonged prodromes: dizziness, light-headedness, visual and hearing disturbances, low back pain, neck or precordial pain	Frailty, incipient autonomic failure, drug-induced (vasoactive drugs and diuretics), comorbidity

BP, blood pressure; ESC, European Society of Cardiology; OH, orthostatic hypotension; TT, tilt testing.

Adapted from 2018 ESC Guidelines for the diagnosis and management of syncope.³²