• revascularization is a broader term and includes:
    • recanalization (clot removal from the target vessel)
    • anterograde reperfusion of the peripheral circulation
  • recanalization does not automatically mean reperfusion (if peripheral embolizations persist, recanalization will have mild or no effect)
  • reperfusion is a better marker of revascularisation as it takes into account the state of the tissue and is thus more closely related to the clinical outcome
  • on the other hand, the quantification of recanalization is an important parameter of the direct effect of the intervention
  • at the end of each endovascular intervention, both recanalization (AOL scale) and reperfusion (mTICI scale) should be assessed and reported
    • criteria of a successful intervention: mTICI 2b-3 and AOL 2-3
  • other scales have been proposed, but these are not used on a regular basis:
    • The Qureshi scale
    • The Recanalization in Brain Ischemia (RBI) scale
    • the Mori scale
Revascularization
Recanalization
flow restoration in the occluded artery segment (primary arterial occlusive lesion)
AOL
Reperfusion
flow restoration in the territory of an occluded vessel (distal vascular bed)
mTICI

Reperfusion assessment

Modified Treatment In Cerebral Infarction (mTICI)

  • modified Treatment In Cerebral Infarction (mTICI) score specifies the extent of tissue perfusion; it was derived from the original TICI classification (Thrombolysis In Cerebral Infarction)
    • the original name was changed to reflect current endovascular practice
    • TICI 2 was divided – reperfusion in < 1/2 of the target vascular territory (mTICI 2a) and > 1/2 of it (mTICI 2b)   [Zaidat, 2013]
    • it has good inter-rater reliability and strongly predicts clinical outcome
    • the mTICI has better reproducibility and predictive value than the original TICI   [Yoo, 2013]
Modified Treatment In Cerebral Infarction (mTICI)
Grade Definitions
0 no perfusion
1 antegrade reperfusion past the initial occlusion, but limited distal branch filling with little or slow distal reperfusion
2a antegrade reperfusion of less than half of the occluded target artery previously ischemic territory (e.g., in 1 major division of the MCA and its territory)
2b antegrade reperfusion of more than half of the previously occluded target artery ischemic territory (e.g., in 2 major divisions of the MCA and their territories)
3 complete antegrade reperfusion of the previously occluded target artery ischemic territory, with the absence of visualized occlusion in all distal branches Recanalization of M1 occlusion with the TREVO retriever, mTICI 3
Some authors proposed a further modification: grade 2c – near-complete perfusion except for slow flow or distal emboli in a few distal cortical vessels

Recanalization assessment

  • recanalization scales evaluate the direct effect of therapeutic intervention on Target Arterial Lesion (TAL)
  • they do not directly assess downstream perfusion but may still provide additional prognostic information (residual stenosis increases the risk of reocclusion or distal embolization)

Arterial Occlusive Lesion (AOL) scale

  • the Arterial Occlusive Lesion (AOL) scale is the grading scale intended to measure the degree of recanalization at the TAL
    • it is preferred because of its ease of use and precise assessment of device efficacy at the occlusion
    • AOL describes arterial patency at the site of occlusion based on the degree of luminal opening (none, partial, or complete) with further qualification based simply on the presence (grades 2 or 3) or absence (grades 0 or 1) of  downstream flow
  • there is good agreement between AOL and mTICI and an excellent ability to predict the outcome
  • problem with the target lesion (TAL) assessment may arise (see below)
    • e.g., tandem lesions ACI+M1 – recanalization of the siphon with ongoing M1 occlusion may give a different assessment – AOL 3 / mTICI 0
    • it is rather necessary to evaluate the whole thrombus (⇒ problem with determining its distal end)
  • differentiation of partial recanalization with residual intraluminal thrombus from underlying intracranial atherosclerotic stenosis is another challenge
The Arterial Occlusive Lesion (AOL) scale
0 Complete occlusion of the target artery
1 Incomplete occlusion or partial local recanalization at the target artery with no distal flow
2 Incomplete occlusion or partial local recanalization at the target artery with any distal flow
3 Complete recanalization and restoration of the target artery with any distal flow
  • TAL = the most proximal part of the intracranial occlusion
    • except for isolated extracranial artery occlusion (e.g., ICA occlusion with distal hypoperfusion)
  • in combined occlusion of the cervical segment of ICA+ M1, the target artery is the MCA
ICA MCA
  • T-occlusion (terminal ICA+M1+A1)
  • L-occlusion (terminální ICA+M1)
  • isolated terminal ICA occlusion
  • M1
    • proximal lesion with occlusion of the lenticulostriate arteries
    • distal lesion without occlusion of the lenticulostriate arteries
  • M2
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