Features of Vascular Autoregulation in Patients With Initial Manifestations of the Chronic Cerebral Ischemia

Summary: - Studied were the cerebral hemodynamics and various brain blood flow autoregulation circuits in patients with initial manifestations of the chronic cerebral ischemia (IMCCI) using Doppler sonography. Forty-eight patients (29 women and 19 men) in the age of 28 to 55 years with IMCCI caused by arterial hypertension (AH) in 30 patients, and by cerebral atherosclerosis (CA) in 18 patients were investigated. The controls were 25 healthy adults matching as to gender and age. The cerebral hemodynamics was studied by measuring the linear blood flow velocity (BFV) in extra- and intracranial vesssels on a Doppler sonography. The state of various autoregulation circuits was carried out by functionally loading the patients with: hypercapnia, calculating the reactivity coefficient CrCO2, nitroglycerine, calculating the reactivity coefficient CrFNT, and orthostatic loading, determining the orthostatic instability. The investigation of cerebral hemodynamics has revealed isolated hemodynamically insignificant lesions of the carotids (63.7 %) or vertebral (36.3 %) arteries in 28.4 % patients with IMCCI accompanied by the BFV interhemispheric asymmetries (20-30 %) in the Willis’ arteries in 68 % of the patients. The investigation of CVR has shown that the patients with IMCCI have disorders of the autoregulative response as to metabolic and myogenic circuits with the tendency to hyperreactivity in the patients with AH and hyporeactivity in those with CA. The patients also have the inverted reactions to nitroglycerine and orthostatic loads, this inversion being more pronounced in the patients with CA with the tendency to increase in the groups of older patients. The analysis of obtained data makes it possible to suppose that the CVR changes at various levels of autoregulation characterising the dysfunctioning of homeostatic range support mechanisms are the triggering mechanism of cerebral hemodynamic disorders in the patients with IMCCI. Unifying various values of the CVR as to the Doppler sonography data makes it possible to optimise diagnosing and treatment tactics for the patients with IMCCI.