Association between activated clotting time and TIMI flow in STEMI patients pre-treated with unfractionated heparin

Early patency in the infarct-related artery (IRA) in patients with STEMI is associated with reduced mortality. Pretreatment with unfractionated heparin (UFH) is standard in many STEMI networks. Whether a specific Activated Clotting Time (ACT) value predicts the IRA's flow restoration remains unclear. Our main aims were to assess the relationship between initial ACT and Thrombolysis in Myocardial Infarction (TIMI) flow 2-3 in STEMI patients pretreated with UFH and to develop a predictive model for early IRA reperfusion based on ACT.

We conducted a retrospective, single-centre study of 898 consecutive STEMI patients from the Codi-IAM network (Catalonia, Spain) between 2015 and 2023. All subjects received 5000 units of UFH within 120 min of symptom onset. ACT was measured at arterial catheterisation, and IRA-TIMI flow was assessed during diagnostic angiography. Median ACT values were compared, and a logistic regression model with bootstrap variable selection identified independent predictors of TIMI 2-3 flow. Model performance was evaluated using ROC curves and the Brier score.

Median ACT was 180 s (163-200) in patients with TIMI 0-1 and 185 s (168-203) in those with flow TIMI 2-3. Higher ACT, diabetes, shorter time to heparin administration, and absence of hypertension were independently associated with TIMI 2-3 flow. However, ACT showed modest discrimination (area under the curve = 0.612), limiting its predictive value.

ACT measured on arrival did not reliably predict IRA patency in STEMI patients pretreated with 5000 units of UFH.