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Dynamic cerebral autoregulation in CVR testing strategy not reported by Immink. Since statins are known to improve CVR 32 possibly by improving endothelial function, it is conceivable that statins also may improve or even normalize worsened dCA. Cerebrovascular reactivity The median CVR found in our study group is 67 %. Molinaet al 19 found values of 65% in control subjects and 50% in lacunar infarct patients, which are signifi- cantly lower. Other investigators have reported lower CVR normal values rang- ing from 36-52 % 20, 31. As such, this shows that our CVR results are, except for three patients (CVR=20, 28 and 29 %), in the normal range. Molinaet al evaluated their infarct patients at least one month post-infarct. This leaves statin treatment the most plausible cause of normal CVR in 88% of our lacunar infarct patients one to two month post infarct. However, further study is needed to determine the contribution of the effect of statin treatment on CVR results. Dumvilleet al 7 showed that in CO2 reactivity testing blood pressure monitor- ing is needed because the CO2 challenge also increased mean arterial blood pressure. CO2 and ACZ both have a potent systemic vasodilatory effect. In our study blood pressure was also monitored, but no effect of ACZ infusion on mean ABP was observed, ruling out systemic blood pressure increase as the cause of post-ACZ increased CBFV. Dynamic cerebral autoregulation and cerebrovascular reactivity testing This study firstly evaluates dCA parameters based on transfer function analysis in the course of CVR-testing with acetazolamide. The, as compared to baseline, decrease of the phase in the low frequency range from median 1.05 to 0.77 rad after administration of 15 mg/kg ACZ indicates less efficient cerebral autoregula- tion. However, post ACZ infusion LF values are still mostly (in 83 %) within normal range 13, 28. So, cerebral autoregulation is far from full exhaustion at least ten minutes after the end of infusion of ACZ. Reinhardet al 29 showed that in patients with ipsilateral ICA occlusion the phase angle in the MCA can even get below zero. It is therefore likely that phase angle values lower than those we obtained after ACZ administration indeed indicate a more disturbed cerebral autoregulation. It can be assumed that the evaluation of CVR only informs us about a fraction of the reserve capacity of the cerebral autoregulation system. 51


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