RESUMO
The effects of angiotensin II receptor blockers on cerebral hemodynamics in humans have not been well elucidated. The present study evaluated the effects of losartan on cerebral hemodynamics in hypertensive patients using positron emission tomography. Ten patients with essential hypertension (mean age, 60.8 years) were examined. In each patient, regional cerebral blood flow was measured by [O-15] labeled water positron emission tomography before and after the oral administration of losartan for 8 to 23 weeks. In 8 patients, the baseline regional cerebral blood flow measurement was followed by 1,000 mg of acetazolamide challenge to measure the cerebral perfusion reserve. Systemic blood pressures before and after treatment were 153.8 +/- 10.8/96.0 +/- 6.5 mmHg (systolic mean +/- SD/diastolic mean +/- SD) and 133.4 +/- 11.2/83.6 +/- 6.5 mmHg, respectively; this difference was significant. The baseline global cerebral blood flow values before and after treatment were 38.4 +/- 6.9 ml/min/100 g and 38.2 +/- 8.2 ml/min/100 g, respectively; this difference was not significant. The results of the global cerebral blood flow response to the acetazolamide challenges were not statistically different before and after treatment. A regional analysis showed no statistical difference in regional cerebral blood flow or cerebral perfusion reserve throughout the brain before and after treatment. Losartan's effect on reducing the blood pressure did not affect either the baseline regional cerebral blood flow or the cerebral perfusion reserve in patients with mild to moderate hypertension. The inclusion of losartan in anti-hypertensive regimens could be advantageous for cerebral circulation in patients with essential hypertension.