Orthostatic hypotension: framework of the syndrome.

According to the 1996 consensus definition, orthostatic hypotension (OH) is diagnosed when a fall in systolic blood pressure of at least 20 mm Hg and/or diastolic blood pressure of at least 10 mm Hg within 3 min of standing is recorded. The elements of orthostatic blood pressure drop that are relevant to the definition of OH include magnitude of the drop, time to reach the blood pressure difference defined as OH, and reproducibility of the orthostatic blood pressure drop. In each of these elements, there exist issues that argue for modification of the presently accepted criteria of OH. Additional questions need to be addressed. Should one standard orthostatic test be applied to different patient populations or should tests be tailored to the patients' clinical circumstances? Are different OH thresholds relevant to various clinical settings, aetiologies of OH and comorbidity? Which test has the best predictive power of morbidity and mortality?