Cerebral blood supply with aging: Normal, stenotic and recanalized

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Abstract

The prosperity of brain parenchyma during aging depends on the preservation of cerebral blood flow (CBF) parameters. We have analysed ultrasonographic measurements of peak systolic (PSV) and end diastolic velocities (EDV) along with pulsatility (PI) and resistance indexes (RI) in common (CCA), internal (ICA) and external carotid artery (ECA) (N = 199) and in vertebral arteries (VA) (N = 200) in patients without any signs of stenosis. In two other cohorts patients with internal carotid artery stenosis (N = 231) and patients prior to and after therapeutic recanalization (N = 81) were evaluated in the same parameters.

Results: in the range of 21–92 years PSV in CCA decreases by 7 mm/s/year, while in ICA only by 2.31 mm/s/year. The decrease of EDV in carotid arteries occurs between 1.72 and 2.28 mm/s/year. PSV in VA drops down by 0.91 mm/s/year, EDV by 0.86 mm/s/year. PI and RI increase with age in all vessels, but not significantly. Stenotic ICAs are associated with increased PSV in the range of 0.7–2.9 m/s, but also with an increasing PSV variability along the growing stenosis in individual patients. In all degrees of stenoses some patients preserve normal velocities. In average the increment for each 10% of the stenosis below 50% makes 8 cm/s, while above 50% it makes already 50 cm/s. In persons with bilateral stenoses the increment with growing stenosis is steeper. The restoration of normal ICA lumen by means of carotid endarterectomy or by angioplasty with stenting results in an average drop by 1.23 m/s in PSV and by 0.4 m/s in EDV. We have investigated the ophthalmic artery and other substitution supplies and deduce, that the remarkable differences in blood flow velocity reactions to a compromised carotid lumen depend on the formation of collaterals in mutual interplay with peripheral resistance.

Introduction

It is well known, that cerebral circulation during aging is endangered by the development of atherosclerosis and by a decreasing driving force due to disturbances of cardiac output. To compensate for this lifelong gradual degradation of cerebral supply the resistance vessels in the brain gradually diminish their vasomotor tonus and thus preserve a relatively constant perfusion. Nevertheless the vasomotor reserve capacity is being gradually exhausted and the brain is less effectively protected against acute fluctuations in cardiovascular parameters.

One of the most important parameters of cerebral blood supply is the easy to access blood flow velocity in cervical arteries. To deepen our knowledge of its behavior in simple aging, in stenotic carotid processes and after recanalization by means of endarterectomy or stenting we have carried out Doppler ultrasonographic measurements in 3 groups of patients.

Section snippets

Subjects and methods

  • a)

    To study blood flow velocities in healthy aging we have collected data of 199 patients for analysis of carotid arteries (mean age 58.15 years, range 21–92, 83 males) and data of 200 persons for analysis of vertebral arteries (mean age 62.32, range 20–85 years, 101 males). Excluded were patients with any stenotic changes, malformations or conspicuous alterations in the vascular wall. Diffuse discrete atherosclerotic signs like slightly increased intimomedial thickness or minute calcified plaques

CCA velocities

The average PSV 0.62 m/s comes from a broad spectrum of individual values, ranging between 0.17 and 1.39 m/s. The mean EDV 0.13 m/s ranges in individual persons between 0 and 0.38 m/s. Zero end diastolic velocities have been found on each side in less than 3% of the patients.

ICA velocities

The PSV is in average 0.73 m/s ranging between 0.23 and 1.49 m/s. EDV of 0.24 m/s in average ranges between 0 and 0.55 m/s. The zero EDV values were encountered only in 2% of all instances.

ECA velocities

The average PSV 0.79 m/s ranges

Discussion

Our bilateral blood flow velocity measurements in several segments of the carotid system on the neck have brought quite consistent results in 3 different cohorts of patients. The 3 studies disregard observations in individual persons, which would be of course much different in particular haemodynamic arrangements. Our averaged data in the cohorts allow to describe rather general tendencies in driving forces of the blood flow.

We were attracted by the proportion of blood flow velocities in the

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This paper has been supported by a research project grant no. 0021620816 of the Czech Ministry of Education.

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