Orthostatic challenge tests: Active standing and head-up tilt

Syncope is a frequently occurring symptom and can originate from various causes. When syncope is related to the upright position or when there is a suspicion of a reflex mechanism, tests assessing the orthostatic cardiovascular adjustments are advised. The orthostatic response is classified into three stages: the initial response (first 30 s), which differs among active or passive changes in posture, the early phase of circulatory stabilization (1-2 min upright), and prolonged orthostatic stress (at least 5 min upright). Three tests of the orthostatic circulatory response are available, testing these different stages of the circulatory response. (1) The active lying-to-standing test using continuous blood pressure monitoring is used to study the quick cardiovascular responses directly after active standing and can detect initial orthostatic hypotension. (2) The active lying-to-standing test using the conventional cuff and stethoscope can be used to assess the orthostatic adjustments in the first 3-5 min after standing. It is used to detect classic orthostatic hypotension. (3) The head-up tilt test evaluates prolonged orthostatic stress and can be applied to detect reflex syncope, delayed orthostatic hypotension or postural tachycardia syndrome. Moreover, all tests may prevent recurrences by identification of symptoms and thus helping patients to recognize the premonitory symptoms for their syncope allowing them to take preventive measures and decrease their anxiety for episodes. Education of physical counterpressure manoeuvres during these tests can additionally increase patients' sense of control over their symptoms.