Purpose: Variations in the reported prevalence of orthostatic hypotension (4% to 33%) are attributed to population selection and varied criteria used to define orthostatic hypotension. Variation in the reproducibility of hemodynamic responses to orthostasis could be a further confounding variable. The purpose of this study was to evaluate reproducibility of orthostatic blood pressure changes in patients with documented symptomatic orthostatic hypotension.
Patients and methods: Forty outpatients (mean age 77+/- 8 years; 24 women) were recruited after initial presentation to a morning outpatient clinic with postural symptoms of dizziness (92%), falls (67.5%), or syncope (30%). Patients had a symptomatic drop in orthostatic systolic blood pressure of >20 mm Hg documented in clinic. Subsequent cardiovascular assessment included autonomic function tests, carotid sinus massage (supine and erect), and prolonged head-up tilt tests. Blood pressure and heart rate measurements were repeated during standing and head-up tilt on two further attendances in the morning.
Results: A total of 67.5% patients had a drop in systolic blood pressure of >20 mm Hg on both visits during orthostatic stimuli; in the remainder, the response was not reproducible, and 5% had no significant orthostatic drop at either attendance. In 19 patients autonomic function tests were abnormal; orthostatic hypotension was reproducible in 79% of this group. In patients with normal autonomic function tests, 57% had reproducible orthostatic hypotension, of which only 60% were reproducible in those patients when further assessed in the afternoon.
Conclusions: Orthostatic blood pressure responses may not be reproducible in patients with documented symptomatic orthostatic hypotension, particularly if autonomic function is normal and measurements are taken in the afternoon. Repeated systolic blood pressure measurements in the morning may be necessary to make a diagnosis in older patients with suspected orthostatic hypotension.