The correct TIMI frame count. The new gold standard?

Over the last decade Thrombolysis in Myocardial Infarction (TIMI) flow grades have been the gold standard for the assessment of efficacy of infarct-artery reperfusion. However, with the introduction of core angiographic laboratories, the reproducibility of TIMI flow grades has been questioned. The corrected TIMI frame count (CTFC) has been developed as a more reproducible method of quantifying infarct artery blood flow after myocardial infarction (MI). We have utilised the CTFC in two studies to examine infarct-artery bloodflow. In the Hirulog in Early Reperfusion and Occlusion (HERO 1) study, the CTFC was measured at 90-120 minutes after administration of aspirin, streptokinase and either Hirulog or heparin. Only 27% of patients had a normal CTFC (less than or equal to 27) in the infarct-related artery. Patients with a prolonged CTFC (>27) had more abnormal left ventricular function (LVF) as measured by the mean chord score in the 'area at risk' (-2.51 vs -2.06 p=0.02), on left ventriculography. In a second study, infarct-artery flow was examined four weeks and one year after MI. At four weeks, only 43% of patients with patent infarct-related arteries had a 'normal' CTFC of less than or equal to 27. A prolonged CTFC at four weeks was a univariate predictor of increased reocclusion at one year (p=0.001). CTFCs are frequently abnormal in parent infarct-related arteries, and predict reocclusion. Whether frame counting is a better predictor of late clinical outcomes than the TIMI flow grade needs to be prospectively examined in large clinical trials.