Maladaptation of vascular response in frontal area of patients with orthostatic hypotension.
To clarify the relationship between abnormalities in cerebral blood flow (CBF) and in blood pressure regulation, we performed 99mTc-HMPAO brain SPECT in association with measurement of plasma norepinephrine and blood pressure in both the upright and supine positions.


METHODS
We studied six patients with orthostatic hypotension and six normal patients. No patient had any significant stenosis of the carotid arteries on echocardiography-Doppler ultrasound and no abnormalities on brain MRI or CT. Changes in systolic blood pressure were monitored during the upright test, and 8-ml blood samples were taken at baseline and at 1 and 5 min after the upright position.


RESULTS
Systolic blood pressure decreased by a mean of 38 +/- 10 and 9 +/- 3 mmHg in the orthostatic hypotension and normal groups, respectively. Compared with baseline values, plasma norepinephrine levels at 1 and 5 min after the upright test did not increase in the orthostatic hypotension group but did increase significantly in the normal group. In the orthostatic hypotension group, 99mTc-HMPAO brain SPECT showed postural cerebral hypoperfusion in the bilateral frontal areas, of which the mean count ratio of the frontal-to-cerebellar area between the upright and supine positions significantly changed from 0.871 +/- 0.029 to 0.942 +/- 0.067 and from 0.881 +/- 0.035 to 0.954 +/- 0.073 in the right and left areas, respectively. No postural change in CBF was evident in other areas in the orthostatic hypotension group. In the normal group, there were no such changes in CBF, blood pressure and plasma norepinephrine levels during the upright test.


CONCLUSIONS
Postural cerebral hypoperfusion in the frontal areas in the orthostatic hypotension group might relate to maladaptation of the vascular response during the upright test.
Department of Radiology, National Cardiovascular Center, Osaka, Japan.
K
K
Hayashida
Y
Y
Nishiooeda
Y
Y
Hirose
Y
Y
Ishida
T
T
Nishimura
D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D015609:Organotechnetium Compounds; D010091:Oximes; D011187:Posture / Q000502:physiology; D019690:Technetium Tc 99m Exametazime; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
D015609:Organotechnetium Compounds; D010091:Oximes; D019690:Technetium Tc 99m Exametazime; D009638:Norepinephrine