Hemodynamics and oxygen extraction in chronic large artery steno-occlusive disease: Clinical applications for predicting stroke risk

Abstract

Depending on the adequacy of collateral sources of blood flow, arterial stenosis or occlusion may lead to reduced perfusion pressure and ultimately reduced blood flow in the distal territory supplied by that vessel. There are two well-defined compensatory mechanisms to reduced pressure or flow - autoregulatory vasodilation and increased oxygen extraction fraction. Other changes, such as metabolic downregulation, are likely. The positive identification of autoregulatory vasodilation and increased oxygen extraction fraction in humans is an established risk factor for future ischemic stroke in some disease states such as atherosclerotic carotid stenosis and occlusion. The mechanisms by which ischemic stroke may occur are not clear, and may include an increased vulnerability to embolic events. The use of hemodynamic assessment to identify patients with occlusive vasculopathy at an increased risk for stroke is very appealing for several different patient populations, such as those with symptomatic intracranial atherosclerotic disease, moyamoya phenomenon, complete internal carotid artery occlusion, and asymptomatic cervical carotid artery stenosis. While there is very good data for stroke risk prediction in some of these groups, no intervention based on these tools has been proven effective yet. In this manuscript, we will review these topics above and identify areas for future research.

A Prospective, Longitudinal Magnetic Resonance Imaging Evaluation of Cerebrovascular Reactivity and Infarct Development in Patients With Intracranial Stenosis

“…While atherosclerotic and non-atherosclerotic moyamoya intracranial vasculopathies exhibit different etiologies, both result in intracranial steno-occlusion, and, in many cases, reduced cerebral perfusion pressure (CPP) and tissuelevel hemo-metabolic impairment. [6][7][8][9] More specifically, as CPP reduces, compensatory increases in microvascular cerebral blood volume (CBV) will ensue to maintain cerebral blood flow (CBF; mL blood/100 g tissue/minute). As CBV increases, the cerebrovascular reserve capacity, or ability of arterioles to increase CBV in response to a further reduction in CPP, will reduce.…”

Remote ischemic conditioning for the treatment of ischemic moyamoya disease

“…In addition, collateral compensation may contribute to the perfusion improvement, despite with poor evidences of the mechanisms in this study . Further demonstration based on hemodynamic tests (cerebral vascular response to hypocapnia) may be assist and to confirm the effect of RIC on hemodynamic improvement …”

MRI Assessment of Oxygen Metabolism and Hemodynamic Status in Symptomatic Intracranial Atherosclerotic Stenosis: A Pilot Study

“…The assessment of the hemodynamic impact of different steno‐occlusive diseases may be limited due to the heterogeneity of imaging methods . Furthermore, extra and intracranial occlusion or stenoses are often associated, and ischemic damages are poorly documented.…”