The Effects of Bilateral Narrowing the Internal Carotid Artery on the Cerebrovascular Reserve Capacity of the Posterior Cerebrovascular System
Abstract
The bilateral narrowing of the internal carotid artery has significant effects on the cerebral hemodynamics and cerebrovascular reserve capacity (CVR). Our study aimed at determining the degree of influencing the hemodynamics of the posterior cerebrovascular system in patients with these affection by means of measuring cerebrovascular reserve capacity using transcranial dopplerometry and CO2.
The study involved 20 patients with bilateral stenosis of the internal carotid artery 80 %, one of which was symptomatic. Transcranial dopplerometry was used for monitoring the changed velocity of blood flow in the middle cerebral arteries (ACM) and in the basillary artery (BA) in response to the inhalation of exogenous CO2.
Eighteen patients (90 %) demonstrated decreased CVR in BA (-10.5 up to 23.2 %/ kPa CO2, the normal value of CVR in BA is 31.0 +- 5.9 %/kPa CO2). Out of these subjects, three patients showed negative value of CVR in BA (-10.5, -9.8, -5.0 %/kPa CO2).
These patients had also depleted CVR in ACM (1.4, 2.4, 0.9 %/kPa CO2). However, quite normal value of CVR in BA (26.4, 26.9 %/kPa CO2) was found out in two patients.
CVR in BA in patients with the bilaterally narrowed internal carotid artery may be various, ranging from quite normal up to negative values. In the future the investigations of CVR in BA could serve for the better evaluation of the degree of hemodynamic affection to the posterior circulation at stenoses of internal carotid arteries.