TIMI flow grade

Associate Editor-In-Chief:

Grade 0
No perfusion. No antegrade flow beyond the point of occlusion.

Grade 1
Penetration without perfusion. Contrast material passes beyond the area of obstruction but fails to opacify the entire coronary bed distal to the obstruction for the duration of the cineangiographic filming sequence.

This category is subdivided into:


 * 1.0: dye minimally leaks past the area of obstruction.


 * 1.5: dye leaks well past the area of obstruction but fails to opacify the entire coronary bed.


 * In the case of a TIMI Flow Grade 0, 1, or 1.5 there is no measurable TIMI Frame Count; therefore, DNA (Does Not Apply) is recorded on the case report form in the TIMI Frame Count field.

Grade 2
Partial perfusion. Contrast material passes across the obstruction and opacifies the coronary bed distal to the obstruction. However, the rate of entry of contrast material into the vessel distal to the obstruction or its rate of clearance from the distal bed (or both) are perceptibly slower than its flow into or clearance from comparable areas not perfused by the previously occluded vessel (i.e. opposite coronary artery or the coronary bed proximal to the obstruction).

This category is subdivided into:


 * 2.0: TIMI 2 slow flow, dye markedly delayed in opacifying distal vasculature.


 * 2.5: TIMI 2 fast flow, dye minimally delayed in opacifying distal vasculature.

Grade 3
Complete perfusion. Antegrade flow into the bed distal to the obstruction occurs as promptly as antegrade flow into the bed proximal to the obstruction, and clearance of contrast material from the involved bed is as rapid as clearance from an uninvolved bed in the same vessel or the opposite artery.

Clinical Importance and Evaluation
The Thrombolysis In Myocardial Infarction (TIMI) flow grade classification scheme has been widely used to assess coronary blood flow in acute coronary syndromes. TFG 0 means the artery is closed; TFG 1 means that dye penetrates the stenosis but does not reach the downstream bed; TFG 2 means that flow is slow down the artery and TFG 3 means that normal flow has been restored. The association of the TFGs with clinical outcomes (including mortality) has been well documented

The association of the TFGs with mortality must be interpreted with caution as there are several confounders:

1. The majority of TIMI grade 2 flow is observed in the left anterior descending artery (LAD) territory, whereas the majority of TIMI grade 3 flow is observed in the right coronary artery (RCA). Thus, the improved mortality observed among patients with TIMI grade 3 flow may be explained at least in part by the fact that inferior myocardial infarction (MI) location is associated with a lower mortality rate

2. The clinical improvement associated with TIMI grade 3 flow may have be nonlinear. For example, greater clinical benefits may be observed if a closed artery (TFG 0/1) is opened (TFG 2) compared with the improvement that might occur if an artery with TFG 2 is converted to TFG 3 flow.

3. As more arteries with TFG 2 flow are treated with adjunctive percutaneous coronary intervention (PCI), the prognosis associated with this flow grade may improve. The fact that patients who were treated with an inferior fibrinolytic monotherapy strategy faired so well in GUSTO V may be explained in part by the fact that these patients underwent PCI more often. Two-year follow-up in more recent studies indicates that the survival advantage of TFG 3 flow over TFG 2 flow at 2 years may not be as great as it once was in the era before aggressive utilization of rescue and adjunctive (PCI)

The TIMI Frame Count
The TIMI flow grade, while useful, has been largely supplanted by the more quantitative measure of the more quantitative TIMI frame count, which is the number of frames required for dye to traverse the length of the artery. The TIMI frame count provides prognostic information independent of the TIMI Flow Grade.