Impaired Clearance of Emboli (Washout) Is an Important Link Between Hypoperfusion, Embolism, and Ischemic Stroke

Abstract

Hypoperfusion and embolism often coexist and their pathophysiological features are interactive. Arterial lumenal narrowing and endothelial abnormalities stimulate clot formation and subsequent embolization. Reduced perfusion limits the ability of the bloodstream to clear or wash out emboli and microemboli and reduces available blood flow to regions rendered ischemic by emboli that block supply arteries. The brain border zones are a favored destination for microemboli that are not cleared. We posit that impaired washout is an important but neglected concept that intertwines hypoperfusion, embolization, and brain infarction.

Risks for Impaired Cerebral Autoregulation During Cardiopulmonary Bypass and Postoperative Stroke

“…Conditions of cerebral hypoperfusion, though, often coexist in patients with embolic stroke, particularly for blood flow to the vulnerable ischaemic penumbra. 27 Regardless, acute stroke is known to result in impaired CBF autoregulation. 23 Thus, our monitoring methods may have identified patients with stroke during surgery.…”

Worsening in Ischemic Stroke Patients: Is it Time for a New Strategy?

“…When perfusion is adequate, microemboli are often cleared efficiently. 13 Chronic hypertension, and also likely diabetes and hyperviscosity, impair microvascular function and blood flow. This likely reduces the potential of the microvasculature to provide collateral circulation to ischemic areas.…”

Hemodynamic Instability Increases New Ischemic Brain Lesions on Diffusion-Weighted Imaging After Carotid Artery Stenting

“…15) Almost all microembolisms produced during CAS are thought to be washed out, as previously proposed. 6) In patients with carotid artery stenosis of more than 50%, a decrease in blood pressure would not produce an active vascular response, but would reduce cerebral blood volume and velocity due to impairment of dynamic cerebral autoregulation. 20) Therefore, in patients with carotid artery stenosis, HI may impair clearance of microembolisms and cause an increase in the number of new ischemic brain lesions detected on DWI.…”