Reduction of QTD - A Novel Marker of Successful Reperfusion in NSTEMI. Pathophysiologic Insights by CMR

Background/Objectives: Non-ST segment elevation myocardial infarction (MI) poses similar detrimental long-term prognosis as ST-segment elevation MI. No marker on ECG is established to predict successful reperfusion in NSTEMI. QT dispersion is increased by myocardial ischemia and reduced by successful restoration of epicardial blood flow by PCI. Whether QT dispersion reduction translates to smaller infarcts and thus indicates successful reperfusion is unknown. We hypothesized that the relative reduction of QT dispersion (QTD-R(rel )) on a standard ECG in acutely reperfused NSTEMI is related to infarct size and infarct transmurality as assessed by delayed enhancement CMR (DE-CMR). Methods and Results: 69 patients with a first acute NSTEMI were included. QTD-R(rel )was stratified according to LV function and volumes, infarct transmurality and size as assessed by DE-CMR. Extensive myocardial infarction was defined as above median infarct size. LV function and end-systolic volume were only mildly related to QTD-R(rel ). QTD-R(rel )was inversely related to infarct size (r=-0.506,p=0.001) and infarct transmurality (r=-0.415, p=0.001). QTD-R(rel )was associated with extensive myocardial infarction in univariate analysis (odds ratio (OR) 0.958, CI 0.935-0.982; p=0.001). Compared to clinical and angiographic data QTD-R(rel )remained the only independent predictor of non-transmural infarcts (OR 1.110, CI 1.055-1.167; p=0.049). Conclusion: In patients with acute Non-ST-Segment Myocardial infarction QTd-R(rel )calculated on a surface ECG prior and post PCI for restoration of epicardial blood flow detects small, non-transmural infarcts as assessed by delayed enhancement CMR. Thus, QTd-R(rel )can indicate successful reperfusion therapy.