TIMI thrombus grade

Brief Note on TIMI Thrombus Grade

An angiographically evident thrombus can be classified as follows for the purpose of quantitative evaluation in clinical trials and day to day practice if needed [1]:

  • TIMI grade 0: no angiographic evidence of thrombus
  • TIMI grade 1 (possible thrombus present): reduced contrast density, haziness, irregular lesion contour, or a smooth convex meniscus at the site of total occlusion suggestive but not diagnostic of thrombus
  • TIMI grade 2 (small thrombus): definite thrombus, with greatest dimensions ?1/2 the vessel diameter
  • TIMI grade 3 (moderate thrombus): definite thrombus but with greatest linear dimension >1/2 but <2 vessel diameters
  • TIMI grade 4 (large-sized thrombus): definite thrombus, with the largest linear dimension >2 vessel diameters
  • TIMI thrombus grade 5: total occlusion

Angiographic evidence of thrombus for study purpose is taken as the presence of thrombus grades 2 to 5.
Abbreviation: TIMI: Thrombolysis In Myocardial Infarction (From the landmark TIMI trial [2])

  1. Gibson CM, de Lemos JA et al. Combination therapy with abciximab reduces angiographically evident thrombus in acute myocardial infarction: a TIMI 14 substudy. Circulation. 2001;103:2550-4.
  2. TIMI Study Group. The Thrombolysis in Myocardial Infarction (TIMI) trial. N Engl J Med. 1985;31:932–936.

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