Intracoronary ECG during primary percutaneous coronary intervention for ST-segment elevation myocardial infarction predicts microvascular obstruction and infarct size

Introduction Microvascular obstruction (MVO) following ST-segment elevation myocardial infarction (STEMI) is associated with larger infarct size and an increased mortality. Although angiographic predictors of MVO in primary percutaneous coronary intervention (primary-PCI) setting have been identified, an earlier and objective “in-lab” predictor may be beneficial, in order to potentially influence therapies administered during primary-PCI. We hypothesised that intracoronary-electrocardiogram (IC-ECG) is a simple, objective and accurate predictor of MVO evaluated by cardiac magnetic resonance (CMR) and is comparable to myocardial blush grade (MBG) and TIMI myocardial perfusion grade (TMPG). Method Intracoronary ECG was performed during primary-PCI. Intracoronary ST-segment measurement was performed before and immediately after opening of infarct-related-artery. Intracoronary ST-segment resolution (IC-STR) was defined as ≥1mm improvement compared to baseline. Contrast enhanced CMR was performed at 4 and 90days post primary-PCI. Primary endpoint was MVO on late gadolinium hyperenhancement assessed by CMR at day 4. Results Sixty-four consecutive patients (age 59±11years; 55 males) were recruited. Intracoronary ST-segment resolution correlated with MVO (p=0.005). Furthermore, IC-STR correlated with infarct-mass, non-viable-mass, peak creatinine kinase and end-systolic-volume at day 4. Intracoronary ST-segment resolution also correlated with favourable left ventricular end-diastolic-volume at day 90 (p=0.022). On multivariate analysis, IC-STR was an independent predictor of MVO. Conclusion Intracoronary ST-segment resolution is a strong in-lab predictor of MVO assessed 4days after STEMI on CMR. Furthermore, IC-STR correlates with infarct size and left ventricular remodelling at 3months. Further studies are required to understand potential clinical utility of this tool.