U-curve relationship between orthostatic blood pressure change and silent cerebrovascular disease in elderly hypertensives: orthostatic hypertension as a new cardiovascular risk factor.

The study investigated the clinical significance and mechanism of orthostatic blood pressure (BP) dysregulation in elderly hypertensive patients. Although orthostatic hypotension (OHYPO), often found in elderly hypertensive patients, has been recognized as a risk factor for syncope and cardiovascular disease, both the clinical significance and the mechanism of orthostatic hypertension (OHT) remain unclear. We performed a head-up tilting test and brain magnetic resonance imaging (MRI) in 241 elderly subjects with sustained hypertension as indicated by ambulatory BP monitoring. We classified the patients into an OHT group with orthostatic increase of systolic blood pressure (SBP) of >or=20 mm Hg (n = 26), an OHYPO group with orthostatic SBP decrease of >or=20 mm Hg (n = 23), and a normal group with neither of these two patterns (n = 192). Silent cerebral infarcts were more common in the OHT (3.4/person, p < 0.0001) and OHYPO groups (2.7/person, p = 0.04) than in the normal group (1.4/person). Morning SBP was higher in the OHT group than in the normal group (159 vs. 149 mm Hg, p = 0.007), while there were no significant differences of these ambulatory BPs between the two groups during other periods. The OHT (21 mm Hg, p < 0.0001) and OHYPO (20 mm Hg, p = 0.01) groups had higher BP variability (standard deviation of awake SBP) than the normal group (17 mm Hg). The associations between orthostatic BP change and silent cerebrovascular disease remained significant after controlling for confounders, including ambulatory BP. The orthostatic BP increase was selectively abolished by alpha-adrenergic blocking, indicating that alpha-adrenergic activity is the predominant pathophysiologic mechanism of OHT. Silent cerebrovascular disease is advanced in elderly hypertensives having OHT. Elderly hypertensives with OHT or OHYPO may have an elevated risk of developing hypertensive cerebrovascular disease.