Bradbury and Eggleston1 first recognized orthostatic hypotension as a clinical entity in 1925. However, it continues to be relatively uncommon, since only about 100 cases have been published to date. The term "orthostatic" (or "postural") hypotension has been used in the broadest sense for any excessive fall in blood pressure on assuming the erect position. This syndrome falls into 2 major groups based on clinical and pathogenetic characteristics.
The first group comprises those cases in which there is an excessive fall of the systolic pressure and a rise, or no significant fall, of the diastolic pressure. The pulse rate generally rises. On maintaining the erect posture, syncope usually occurs with a sudden fall of both systolic and diastolic pressure, preceded by pallor and vagotonic effects such as sweating, nausea, and a sudden bradycardia. The defect in this group is inadequate cardiac venous return secondary to excessive peripheral venous pooling.