Journal Article

Modelling the impact of clot fragmentation on the microcirculation after thrombectomy

El-Bouri, Wahbi K., Gounis, Matthew J., Józsa, Tamás I., Payne, Stephen J., MacGowan, Andrew

2021

Overview

Many ischaemic stroke patients who have a mechanical removal of their clot (thrombectomy) do not get reperfusion of tissue despite the thrombus being removed. One hypothesis for this ‘no-reperfusion’ phenomenon is micro-emboli fragmenting off the large clot during thrombectomy and occluding smaller blood vessels downstream of the clot location. This is impossible to observe in-vivo and so we here develop an in-silico model based on in-vitro experiments to model the effect of micro-emboli on brain tissue. Through in-vitro experiments we obtain, under a variety of clot consistencies and thrombectomy techniques, micro-emboli distributions post-thrombectomy. Blood flow through the microcirculation is modelled for statistically accurate voxels of brain microvasculature including penetrating arterioles and capillary beds. A novel micro-emboli algorithm, informed by the experimental data, is used to simulate the impact of micro-emboli successively entering the penetrating arterioles and the capillary bed. Scaled-up blood flow parameters–permeability and coupling coefficients–are calculated under various conditions. We find that capillary beds are more susceptible to occlusions than the penetrating arterioles with a 4x greater drop in permeability per volume of vessel occluded. Individual microvascular geometries determine robustness to micro-emboli. Hard clot fragmentation leads to larger micro-emboli and larger drops in blood flow for a given number of micro-emboli. Thrombectomy technique has a large impact on clot fragmentation and hence occlusions in the microvasculature. As such, in-silico modelling of mechanical thrombectomy predicts that clot specific factors, interventional technique, and microvascular geometry strongly influence reperfusion of the brain. Micro-emboli are likely contributory to the phenomenon of no-reperfusion following successful removal of a major clot.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Aging / Analysis / Biology and Life Sciences / Blood clotting / Blood coagulation / Blood flow / Blood vessels / Blood-brain barrier / Brain Ischemia - pathology / Brain Ischemia - therapy / Brain research / Care and treatment / Catheters / Cerebral blood flow / Cerebral embolism and thrombosis / Clinical outcomes / Clotting / Data collection / Diagnosis / Experiments / Humans / Hypotheses / Inflammation / Ischemia / Leukocytes / Medical instruments / Medicine and Health Sciences / Microcirculation / Microvasculature / Occlusion / Oxidative stress / Patients / Permeability / Physical Sciences / Research and Analysis Methods / Stalling / Stroke / Surgery / Thrombectomy / Thrombosis - pathology / Treatment Outcome / Ultrastructure / Vasoconstriction / Veins & arteries