Q wave area for stratification of global left ventricular infarct size: comparison to conventional ECG assessment using Selvester QRS-score

Abstract

Objectives: 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.

Methods: 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.

Results: 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).

Conclusion: 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.

Trial registration: ClinicalTrials.gov NCT00539045.

Figure 1

Selvester QRS-score (left) and Q wave area (right) (mean ± standard deviation), as measured on follow-up ECG, in relation to DE-CMR evidenced infarct size. Note marked increase in both Selvester QRS-score and Q wave area among patients with infarct size ≥ 10% LV myocardium (grey bars).

Figure 2

Scatter plots relating DE-CMR quantified infarct size (y-axis) to ECG quantified Selvester QRS-score (2A-B) and Q wave area (2C-D) (x-axes). Correlation coefficients and corresponding linear regression lines for each respective scatter plot are shown for subgroups of patients with infarct size ≥ (grey) and < 10% (black) LV myocardium.

Figure 3

Diagnostic performance of Selvester QRS-score (red) and Q wave area (blue), as measured on early (left) and follow-up (right) ECG in relation to a cutoff of infarct size ≥ 10% LV myocardium.