TIMI thrombus grade

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Thrombus Grade

Thrombus assessed visually using the following grading system:

Grade 0

No cineangiographic characteristics of thrombus present.

Grade 1

Hazy, possible thrombus present. Angiography demonstrates characteristics such as reduced contrast density, haziness, irregular lesion contour, or a smooth convex "meniscus" at the site of total occlusion suggestive but not diagnostic of thrombus.

Grade 2

Thrombus present – small size: Definite thrombus with greatest dimensions less than or equal to 1/2 vessel diameter.

Grade 3

Thrombus present – moderate size: Definite thrombus but with greatest linear dimension greater than 1/2 but less than 2 vessel diameters.

Grade 4

Thrombus present – large size: As in Grade 3 but with the largest dimension greater than or equal to 2 vessel diameters.

Grade 5

Recent total occlusion, can involve some collateralization but usually does not involve extensive collateralization, tends to have a “beak” shape and a hazy edge or appearance of distince thrombus.

Grade 6

Chronic total occlusion, usually involving extensive collateralization, tends to have distinct, blunt cut-off/edge and will generally clot up to the nearest proximal side branch.

Natural History, Complications, Prognosis

Angiographically evident thrombus is associated with embolization and impaired myocardial perfusion.