Hypotension unawareness in profound orthostatic hypotension

Clinicians depend on history given by the patients when considering the diagnosis of orthostatic hypotension.

Patients with a decrease in systolic blood pressure more than 60 mm Hg from baseline during a head-up tilt table test were included. They were classified according to their symptoms during the head-up tilt table test. Localization of the cause of orthostatic hypotension was sought in each of these groups.

Eighty-eight (43%) patients had typical symptoms, 49 (24%) had atypical symptoms, and 68 (33%) were asymptomatic. The average decrease in systolic blood pressure was 88 mm Hg, 87.5 mm Hg, and 89.8 mm Hg in the typical, atypical, and asymptomatic groups, respectively (P=.81). Patients reported severe dizziness with a similar frequency as lower extremity discomfort. Backache and headache also were common atypical complaints. Patients with peripheral cause of dysautonomia were able to sustain the longest upright position during the head-up tilt table test (21 minutes, compared with central dysautonomia [15 minutes]) (P=.005). There was no correlation between the cause of dysautonomia and the occurrence of symptoms during the head-up tilt table test (P=.58).

A third of the patients with severe orthostatic hypotension are completely asymptomatic during the head-up tilt table test, and another quarter have atypical complaints that would not lead physicians toward the diagnosis of orthostatic hypotension. These findings suggest that they might not provide adequate information in diagnosing profound orthostatic hypotension in a subset of patients with this disorder.