Orthostatic syncope refers to syncope resulting from a postural decrease in blood pressure, termed orthostatic hypotension. Orthostatic hypotension occurs when there is a persistent reduction in blood pressure of at least 20mmHg systolic or 10mmHg diastolic within 3 minutes of standing or being upright to 60 degrees on the head-up tilt table. In people with initial orthostatic hypotension, the decrease in blood pressure occurs within 15 seconds, while in those with delayed orthostatic hypotension it occurs after over 3 minutes of assuming an upright position.