Estimating Myocardial Infarction Size With a Simple Electrocardiographic Marker Score

Abstract

Background Myocardial infarction (MI) size is a key predictor of prognosis in post-MI patients. Cardiovascular magnetic resonance (CMR) is the gold standard test for MI quantification, but the ECG is less expensive and more widely available. We sought to quantify the relationship between ECG markers and cardiovascular magnetic resonance infarct size. Methods and Results Patients with prior MI enrolled in the DETERMINE (Defibrillators to Reduce Risk by Magnetic Resonance Imaging Evaluation) and PRE-DETERMINE Trial and Registry were included. ECG leads were analyzed for markers of MI: Q waves, fragmented QRS, and T wave inversion. DETERMINE Score=number of leads with [Q waves×2]+[fragmented QRS]+[T wave inversion]. Left ventricular ejection fraction (LVEF) and infarct size as a percentage of left ventricular mass (MI%) were quantified by cardiovascular magnetic resonance. The Modified Selvester Score estimates MI size from 37 ECG criteria. In 551 patients (aged 62.1±10.9 years, 79% men, and LVEF=40.3±11.0%), MI% increased as the number of ECG markers increased (P<0.001). By univariable linear regression, the DETERMINE Score (range 0-26) estimated MI% (R²=0.18, P<0.001) with an accuracy approaching that of LVEF (R²=0.22, P<0.001) and higher than the Modified Selvester Score (R²=0.09, P<0.001). By multivariable linear regression, addition of the DETERMINE Score improved estimation of MI% over LVEF alone (P<0.001) and over Modified Selvester Score alone (P<0.001). Conclusions In patients with prior MI, a simple ECG score estimates infarct size and improves infarct size estimation over LVEF alone. Because infarct size is a powerful prognostic indicator, the DETERMINE Score holds promise as a simple and inexpensive risk assessment tool.

Keywords: electrocardiography; magnetic resonance imaging; myocardial infarction; prognosis; sudden death.

Figure 1

Patient examples. ECG and CMR in patients with (A) no abnormal ECG markers, DETERMINE Score 0, infarct size 4.3% in the left circumflex coronary artery territory, (B) pathological Q waves in leads III and aVF, one contiguous ECG marker (cQWMI), DETERMINE score 4, infarct size 13.8% in the right coronary artery territory, (C) pathological Q waves in leads V_1‐3, fragmented QRS complexes in leads V_1‐4, T wave inversion in leads V_2‐4, 3 contiguous ECG markers (cQWMI, cFQRS, cTWI), DETERMINE Score 13, infarct size 24.8% in the left anterior descending coronary artery territory. Yellow arrows denote the location of myocardial infarction visualized by late gadolinium enhanced cardiovascular magnetic resonance imaging. CMR indicates cardiovascular magnetic resonance imaging; cFQRS, contiguous fragmented QRS; cQWMI, contiguous Q wave myocardial infarction; cTWI, contiguous T wave inversion; DETERMINE Score, simple ECG score for estimating infarct size based on the presence and extent of abnormal ECG markers.

Figure 2

Distribution of contiguous ECG markers of myocardial infarction in 551 patients. Most patients (66%) had at least 1 ECG marker, and many (26%) had multiple ECG markers.. cFQRS indicates contiguous fragmented QRS; cQWMI, contiguous Q wave myocardial infarction; cTWI, contiguous T wave inversion. F indicates cFQRS; Q, cQWMI; T, cTWI. For example: Q only=patients with cQWMI, but without cFQRS or cTWI. Q&F=patients with cQWMI and cFQRS, but without cTWI.

Figure 3

Number of contiguous ECG markers and myocardial infarction size by cardiovascular magnetic resonance. Myocardial infarction size increased as the number of ECG markers increased (P<0.001). Bar graphs denote mean and error bars denote standard deviation. cFQRS indicates contiguous fragmented QRS; cQWMI, contiguous Q wave myocardial infarction; cTWI, contiguous T wave inversion; LV, left ventricle.

Figure 4

Myocardial infarction size according to DETERMINE Score. Myocardial infarction size increased as the DETERMINE Score increased (P<0.001). The DETERMINE Score is calculated by summing the number of leads with Q waves (× 2), fragmented QRS, and T wave inversion. Bar graphs denote mean, and error bars denote standard deviation. DETERMINE Score indicates simple ECG score for estimating infarct size based on the presence and extent of abnormal ECG markers; LV, left ventricle.

Figure 5

Relationship to infarct size of (A) Modified Selvester Score, (B) DETERMINE Score, (C) left ventricular ejection fraction, and (D) infarct size predicted by Model 2 from Table 3 (left ventricular ejection fraction plus DETERMINE Score). DETERMINE score indicates simple ECG score for estimating infarct size based on the presence and extent of abnormal ECG markers; LV, left ventricle; LVEF, left ventricular ejection fraction.