Q wave area for stratification of global left ventricular infarct size

Abstract

Left ventricular (LV) infarct size is a prognostic determinant after acute myocardial infarction (AMI). ECG data have been used to measure infarct size, but conventional approaches use multiparametric algorithms that have limited clinical applicability. This study tested a novel ECG approach - based solely on Q wave area - for calculation of LV infarct size. Serial 12-lead ECGs were performed in AMI patients. Computerized software was used to quantify Q wave area (summed across surface ECG leads) and Selvester QRS-score components. ECG analysis was compared to the reference of myocardial infarct size quantified by delayed enhancement cardiac magnetic resonance. Overall, 158 patients underwent ECG during early (4±0.4) and follow-up (29±5 days) post-AMI time points. Selvester QRS-score and Q wave area increased stepwise with LV infarct size (P<0.001). Whereas both methods manifested marked increases at a threshold of 10% LV infarction, magnitude was greater for Q wave area (>2.5-fold) than Selvester QRS-score (<two-fold). In receiver operating characteristic analysis, Q wave area (area under the curve=0.83-0.86) and Selvester QRS-score (0.82-0.87) manifested similar performance in relation to a 10% infarct cutoff. When Selvester QRS-score and Q wave area thresholds were selected to optimize sensitivity, both methods yielded similar negative predictive value (Q wave area: 89-91%, Selvester QRS-score: 92-94%) although specificity was higher for Q wave area (44-45 vs. 17-25%; P≤0.01). Q wave area provides an index for stratification of LV infarct size that performs similarly to conventional ECG assessment via the Selvester QRS-score for exclusion of large infarction.