Other syndromes of orthostatic intolerance: Delayed orthostatic hypotension, postprandial hypotension, postural orthostatic tachycardia syndrome, and reflex syncope

Apart from classical orthostatic hypotension, the gravitational force may strongly contribute to other forms of orthostatic intolerance, delayed and postprandial OH, postural orthostatic tachycardia syndrome (POTS), and reflex syncope. In delayed OH, the significant blood pressure drop occurs first after 3-min period of orthostasis, whereas in postprandial OH, the symptoms appear first approximately 15-30 min after the meal. POTS is rarely seen in older adults and presents as abnormal sinus tachycardia on standing with symptoms of orthostatic intolerance, dizziness, fatigue, and cognitive impairment. Reflex syncope may manifest as orthostatic vasovagal reflex, situational syncope, or carotid sinus hypersensitivity, which becomes a clinical syndrome when associated with history of unexplained syncope and positive provocation test, carotid sinus massage. Older patients with a history of orthostatic intolerance, unexplained syncope and fall trauma, and negative result of active standing test should be further evaluated using cardiovascular autonomic tests such as head-up tilt testing, Valsalva maneuver, and carotid sinus massage.