This case-insensitive code system https://kip.rkkp.dk/fhir/CodeSystem/MTICIClassification defines the following codes in an undefined hierarchy:
Lvl
Code
Display
Definition
1
grade0
Grade 0
Grade 0: No perfusion
1
grade1
Grade 1
Grade 1: Antegrade reperfusion past the initial occlusion, but limited distal branch filling with little or slow distal reperfusion
1
grade2
Grade 2
Grade 2
2
grade2a
Grade 2a
Grade 2a: Antegrade reperfusion of less than half of the occluded target artery previously ischemic territory (e.g. in one major division of the middle cerebral artery (MCA) and its territory)
2
grade2b
Grade 2b
Grade 2b: Antegrade reperfusion of more than half of the previously occluded target artery ischemic territory (e.g. in two major divisions of the MCA and their territories)
2
grade2c
Grade 2c
Grade 2c: Near complete perfusion except for slow flow or distal emboli in a few distal cortical vessels
1
grade3
Grade 3
Grade 3: Complete antegrade reperfusion of the previously occluded target artery ischemic territory, with absence of visualized occlusion in all distal branches