Kim Mi O, Li Yan, Wei Fangfei, Wang Jiguang, O'Rourke Michael F, Adji Audrey, Avolio Alberto P
aDepartment of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia bCenter for Epidemiological Studies and Clinical Trials, Shanghai Key Laboratory of Hypertension, The Shanghai Institute of Hypertension, Department of Hypertension, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China cSt. Vincent's Clinic dUniversity of New South Wales/VCCRI eAustralian Institute of Health Innovation, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia.
J Hypertens. 2017 Nov;35(11):2245-2256. doi: 10.1097/HJH.0000000000001459.
Cerebral syndromes in older humans, secondary stroke in younger persons following trauma, and sickle cell anaemia in children, are linked by unexplained microvascular damage and high cerebral pressure or flow pulsations. The aim of this study was to characterize age-related pressure and flow waveforms patterns entering the brain, to explain these in terms of disturbed physiological function, and to consider clinical implications.
Blood flow velocity waves were measured in four cerebral vascular territories by transcranial Doppler of 1020 apparently normal patients (497 men, 21-78 years). Central pressure waveforms were generated from radial artery applanation tonometry with SphygmoCor. Relationships were described in time and frequency domains.
Flow waveforms entering the brain showed similar pattern to central aortic pressure waveforms, and similar changes with age. Augmentation index of flow and of pressure had high correlation at different ages, and in men and women (r = 0.58, P < 0.01). Calculated cerebral vascular impedance was similar in both sexes, and at different ages, with low modulus and phase, indicating a dilated, passive cerebral vascular bed. This vascular bed is subject to pressure and flow fluctuations generated directly by the heart and boosted by strong wave reflections from the lower body.
Cerebral microvascular damage in older patients is attributable to high pulsatile pressure tearing the delicate media, causing haemorrhage, and high pulsatile flow dislodging endothelial cells, causing thrombosis and microinfarcts. High pulsations in older patients are caused by early wave reflection from the lower body. Reduction of or delay in wave reflection is a logical strategy for aortic stiffening in older humans.
老年人的脑综合征、年轻人创伤后继发性中风以及儿童镰状细胞贫血，都与不明原因的微血管损伤和高脑压或血流搏动有关。本研究的目的是表征进入大脑的与年龄相关的压力和血流波形模式，从生理功能紊乱的角度解释这些模式，并探讨其临床意义。
通过经颅多普勒对1020名表面正常的患者（497名男性，年龄21 - 78岁）的四个脑血管区域的血流速度波进行测量。使用SphygmoCor通过桡动脉压平式眼压测量法生成中心压力波形。在时域和频域中描述两者的关系。
进入大脑的血流波形与中心主动脉压力波形显示出相似的模式，并且随年龄有相似的变化。不同年龄以及男性和女性的血流和压力增强指数具有高度相关性（r = 0.58，P < 0.01）。计算得出的脑血管阻抗在两性和不同年龄中相似，模量和相位较低，表明脑血管床扩张且呈被动状态。该血管床受到心脏直接产生的压力和血流波动影响，并因来自下半身的强烈波反射而增强。
老年患者的脑微血管损伤归因于高搏动压力撕裂脆弱的中膜导致出血，以及高搏动血流使内皮细胞移位导致血栓形成和微梗死。老年患者的高搏动是由下半身的早期波反射引起的。减少或延迟波反射是老年人类主动脉硬化的合理策略。
