title: Delayed orthostatic hypotension: a frequent cause of orthostatic intolerance.
abstract: OBJECTIVE
  To investigate the prevalence, symptoms, and neurophysiologic features of delayed orthostatic hypotension (OH).
  
  
  METHODS
  Blood pressures (BP) were measured at 1-minute intervals on 230 patients during 60 degrees head-up tilt for 45 minutes and standing for 5 minutes. OH was defined as a sustained fall in BP (>or=20 mm Hg systolic or >or=10 mm Hg diastolic) and delayed OH as a sustained BP fall occurring beyond 3 minutes of standing or upright tilt table testing. Beat-to-beat BP, tests of cardiovagal function, and sympathetic-adrenergic function were performed.
  
  
  RESULTS
  Of patients with OH, only 46% had OH within 3 minutes of head up tilt; 15% had OH between 3 and 10 minutes; and 39% had OH only after 10 minutes of tilt table testing. The magnitude and the temporal distribution of the BP fall did not differ between those with and without symptoms of orthostatic intolerance. Patients with OH beyond 10 minutes tended to be younger (p < 0.05), have smaller BP falls during phase II of the Valsalva maneuver (p < 0.01), and have greater phase IV overshoot (p < 0.01).
  
  
  CONCLUSIONS
  Delayed orthostatic hypotension occurred in 54% of our tested population and was associated with milder abnormalities of sympathetic adrenergic function, suggesting this disorder may be a mild or early form of sympathetic adrenergic failure.
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Gibbons
authors.forename: Roy
authors.initials: R
authors.lastname: Freeman
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000379:methods; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011187:Posture; D015995:Prevalence; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors; D014636:Valsalva Maneuver / Q000502:physiology