Effect of angiotensin converting enzyme inhibitor on vascular reactivity in patients with chronic cerebral infarction
Background and Purpose: Based on the results from the laboratory settings, angiotensin converting enzyme (ACE) inhibitors are known to have an effect to improve cerebral blood flow in hypertensive animals, in addition to their antihypertensive effects. By using a positron emission tomography (PET), the present study endeavored to evaluate the effect of Cilazapril on vascular and metabolic reserve in patients with chronic cerebral infarction. Subjects and Methods: The present study included 9 hypertensive patients with chronic cerebral infarction. The subjects’ mean age was 67.4 years. By using PET, cerebral blood flow (CBF), cerebral oxygen metabolism (CMRO2), oxygen extraction fraction (OEF) and vascular transit time (VTT) were measured during resting state. To evaluate the vascular reactivity (VR), CBF was also measured during CO2 inhalation (hypercapnia) and hyperventilation (hypocapnia). Cilazapril (1mg/day) was administered for 35–93 (mean 64) days and the PET studies were repeated before and after the treatment with Cilazapril. Local values were obtained from 20 regions of interest located which were located in the thakamus, basal gangila and cerebral cortices. Using Student’s t-test, mean CBF, CMRO2, OEF, CBF/CBV and VR were compared before and after the treatment. Results: There was no significant change in the mean CBF, CMRO2, OEF or VTT before and after the treatment. The mean VR to hypercapnia was 4.68 ± 2.52 (%CBF/mmHg) at baseline, and 5.75 ± 4.35 (%CBF/mmHg) after the treatment. The VR to hypercapnia increased significantly after the treatment (p<0.01) The mean VR to hypocapnia was 2.59 ± 1.11 (%CBF/mmHg) at baseline and 2.99 ± 1.94 (%CBF/mmHg) after the treatment. There was a tendency toward the increase in VR to hypocapnia. Conclusion: The increase in VR to hypercapnia after the treatment may indicate an improvement in vascular reserve in patients with chronic cerebral infarction. As suggested by previous experimental studies, Cilazapril may have a beneficial effect on cerebral vascular reserve in those with chronic hypoperfusion by improving the compliance of the small vessels which dilate during hypercapnia.