Fürst H, Hartl W H, Janssen I
Department of Surgery, Klinikum Grosshadern, Ludwig-Maximilian University Munich, FRG.
Stroke. 1994 Jun;25(6):1193-200. doi: 10.1161/01.str.25.6.1193.
Intracranial hemodynamic status varies in patients with unilateral significant carotid artery stenosis. It ranges from normal, because of sufficient collaterals, to poor, because of a severely reduced blood supply that puts the patient at an increased risk of stroke or cerebral ischemia. The present study examined patterns of abnormal cerebrovascular hemodynamics in patients with asymptomatic carotid artery stenosis.
The CO2 reactivity of the cerebral resistance index (CRi) and of mean blood flow velocity (vmean) was determined via transcranial Doppler sonography in 91 patients with unilateral high-grade to threadlike carotid artery stenosis and in 37 control subjects. The interhemispheric asymmetry of CRi reactivity of the control group was used to differentiate between normal and abnormal findings.
We found that 64.8% of the patients demonstrated normal CRi asymmetry with comparable CRi reactivity (ipsilateral, 4.42 +/- 0.44 %CRi/vol%CO2; contralateral, 4.51 +/- 0.39 %CRi/vol%CO2) and vmean reactivity (ipsilateral, 0.080 +/- 0.004 m/s per vol%CO2; contralateral, 0.079 +/- 0.005 m/s per vol%CO2) at both hemispheres. In 16.5% of the patients, CRi reactivity was supranormal at the affected hemisphere. This phenomenon was due to an exaggerated dilatory response of the ipsilateral hemisphere and was combined with an absent CRi reactivity of the contralateral hemisphere (ipsilateral, 6.63 +/- 1.03 %CRi/vol%CO2; contralateral, -1.16 +/- 1.78 %CRi/vol%CO2). In contrast, hemispheric vmean reactivities were comparable (ipsilateral, 0.078 +/- 0.008 m/s per vol%CO2; contralateral, 0.077 +/- 0.008 m/s per vol%CO2). The remaining 18.7% showed severely diminished ipsilateral CRi reactivity (ipsilateral, 1.91 +/- 0.83 %CRi/vol%CO2; contralateral, 8.48 +/- 1.00 %CRi/vol%CO2) and vmean reactivity (ipsilateral, 0.073 +/- 0.007 m/s per vol%CO2; contralateral, 0.108 +/- 0.012 m/s per vol%CO2; P < .01), compatible with a significantly reduced perfusion pressure at the poststenotic hemisphere.
Most asymptomatic patients do not suffer from severely abnormal hemodynamics at the poststenotic hemisphere. One small subgroup of patients presented with severely disturbed ipsilateral hemodynamics; another small subgroup demonstrated a steal phenomenon with secondary dilation of large cerebral vessels at the contralateral hemisphere. These subgroups require specific evaluation of proper treatment.
单侧严重颈动脉狭窄患者的颅内血流动力学状态各异。其范围从因侧支循环充足而正常，到因血供严重减少致使患者中风或脑缺血风险增加而变差。本研究检测了无症状性颈动脉狭窄患者异常脑血管血流动力学的模式。
通过经颅多普勒超声测定91例单侧高度至线状颈动脉狭窄患者及37例对照者的脑阻力指数（CRi）和平均血流速度（vmean）的二氧化碳反应性。利用对照组CRi反应性的半球间不对称性来区分正常与异常结果。
我们发现64.8%的患者双侧半球的CRi不对称性正常，CRi反应性（同侧，4.42±0.44%CRi/vol%CO₂；对侧，4.51±0.39%CRi/vol%CO₂）及vmean反应性（同侧，0.080±0.004 m/s per vol%CO₂；对侧，0.079±0.005 m/s per vol%CO₂）相当。16.5%的患者患侧半球的CRi反应性超常。此现象是由于同侧半球扩张反应过度，且对侧半球CRi反应性缺失（同侧，6.63±1.03%CRi/vol%CO₂；对侧，-1.16±1.78%CRi/vol%CO₂）。相比之下，半球vmean反应性相当（同侧，0.078±0.008 m/s per vol%CO₂；对侧，0.077±0.008 m/s per vol%CO₂）。其余18.7%的患者患侧CRi反应性严重减弱（同侧，1.91±0.83%CRi/vol%CO₂；对侧，8.48±1.00%CRi/vol%CO₂）及vmean反应性（同侧，0.073±0.007 m/s per vol%CO₂；对侧，0.108±0.012 m/s per vol%CO₂；P <.01），这与狭窄后半球灌注压显著降低相符。
多数无症状患者狭窄后半球的血流动力学无严重异常。一小部分患者患侧血流动力学严重紊乱；另一小部分患者出现盗血现象，伴有对侧半球大脑大血管继发性扩张。这些亚组需要进行适当治疗的具体评估。
