SPECT Evaluation of Cerebral Perfusion in Uncomplicated Essential Hypertensives and Effects of Enalapril

Abstract

A semiquantitative evaluation of regional cerebral blood flow was performed by means of single photon emission computed tomography and ^99mTc-hexa-methylpropyleneamine oxime in 25 neurologically asymptomatic patients with essential hypertension and in 10 normotensive controls. Mean flow velocities and pulsatility indexes of intracranial arteries and the vasomotor reactivity of the middle cerebral artery after hyperventilation were assessed by means of transcranial Doppler sonography (TCD). The pattern of cerebral perfusion in hypertensive patients was similar to that of normotensive controls. However, the semiquantitative examination of the CBF flow maps revealed significantly different frontal, temporal and occipital asymmetry indexes in hypertensive patients, as an expression of disturbed perfusion. TCD did not reveal any significant difference in flow velocities between hypertensives and normotensive controls. In 10 randomly selected hypertensive patients the study was repeated after a 4-week oral treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril. Blood pressure fell significantly without any decrease in cerebral perfusion. The basal asymmetry index was also unaffected, confirming the absence of any steal effect. Thus, there are indications that focal hypoperfusion is a frequent finding among neurologically normal essential hypertensives and that the ACE inhibitor enalapril does not negatively affect cerebral blood flow in the asymptomatic essential hypertensive patients.

Abnormal cerebral electrogenesis is associated with impaired cognitive performance in hypertensive patients

“…7 Hypertensive patients are known to have reduced cortical perfusion, mainly in the parietal and temporal areas, even in the absence of cerebrovascular complications. 8 Low-amplitude EEGs may reflect this condition of relative cortical hypoperfusion, but this seems to be denied in our cohort by the lack of correlation between amplitude of EEG, MRI findings and duration of hypertension. Alternatively, low-voltage EEG reflect increased noradrenergic tone, often associated with hypertension.…”

Blood pressure control has distinct effects on executive function, attention, memory and markers of cerebrovascular damage

“…Well-managed, long-term antihypertensive treatment can decrease small vessel alterations and improve cerebrovascular reserve, as it has been shown with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. 30,31 Microcirculation improvement is not necessarily correlated to IMT and it may be accompanied by progression of macrovascular changes, as suggested by a previous study that showed improvement of focal brain hypoperfusion with long-term antihypertensive therapy, in spite of the progression of carotid artery atherosclerosis. 32 This can happen because macrovascular structural disease is less easily reversed than microvascular changes, which are, at least in part, functional.…”