The TIMI flow grading system is as below: The TIMI (thrombolysis in myocardial infarction) flow grading system is a scoring classification from 0-3 referring to the levels of coronary blood flow assessed during coronary angiography. Furthermore, although TIMI flow grade has classically compared flow in the infarct-related vessel to flow in the "normal" nonculprit artery, flow in the non-infarct-related artery in patients with STEMI is not truly normal compared with flow in patients without STEMI.84 Difficulties in reproducibly assessing myocardial flow relative to other vessels (e.g., the right coronary artery, or in the setting of total occlusions of the contralateral vessel) led some investigators to modify the definition of "TIMI grade 3 flow" to include opacification of the distal coronary artery within three cardiac cycles.85 The "three cardiac cycle" definition of TIMI 3 flow results in an absolute rate increase of approximately 10% compared with the original definition.86 Accordingly, more quantitative measures of anterograde flow were developed.A coronary chronic total occlusion (CTO) is defined as 100% occlusion of a coronary artery for a duration of greater than or equal to 3 months based on angiographic evidence. Another limitation of the TIMI flow grade is that it provides ordinal values rather than continuous ones, limiting its statistical power in clinical trials. The lack of concordance for determining TIMI flow grade was also shown between experienced angiographic core laboratories. Substantial observer variability has been noted with the TIMI flow grade, with the best agreement between the angiographic core laboratory and clinical centers occurring when the artery is graded as either open or closed (TIMI 0 or 1 flow kappa value = 0.84).81 Observer agreement is only moderate when assessing TIMI grade 3 flow (kappa value = 0.55) and is poor in the assessment of TIMI grade 2 flow (kappa value = 0.38). In contrast, the mortality rate was lowest (4.4%) in patients with TIMI 3 flow.83ĭespite these important associations, there are a number of limitations of the TIMI classification system. Thrombolysis and clinical outcome.83 In the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) angiographic substudy, the mortality rate for patients with TIMI 2 flow (7.4%) was similar to the mortality rate for those with TIMI 0 or 1 flow (8.9%). Modified from Sheehan FH, Braunwald E, Canner P, et al: The effect of intravenous thrombolytic therapy on left ventricular function: A report on tissue-type plasminogen activator and streptokinase from the Thrombolysis in Myocardial Infarction (TIMI) Phase I Trial. Alternatively, contrast material clears from a segment distal to a stenosis noticeably more slowly than from a comparable segment not preceded by a significant stenosis.Ī small amount of contrast flows through the stenosis but fails to fully opacify the artery beyond. However, contrast enters the terminal segment perceptibly more slowly than more proximal segments. Contrast material clears as rapidly from the distal segment as from an uninvolved, more proximal segment.Ĭontrast material flows through the stenosis to opacify the terminal artery segment. TIMI Flow Grade Classificationģ (complete reperfusion) 2 (partial reperfusion)ġ (penetration with minimal perfusion) 0 (no perfusion)Īnterograde flow into the terminal coronary artery segment through a stenosis is as prompt as anterograde flow into a comparable segment proximal to the stenosis. Several throm-bolytic trials have identified an important relationship between 90-minute TIMI flow grade after The TIMI Flow Grade System is a valuable tool for assessing the efficacy of reperfusion strategies in patients with STEMI and for identifying patients at higher risk for an adverse outcome with acute coronary syndromes or undergoing PCI.
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