Simple ECG score helps estimate MI infarct size

A simple ECG score could help physicians estimate infarct size in patients with prior MI, according to work published Jan. 24 in the Journal of the American Heart Association.

Cardiac magnetic resonance (CMR) is the gold standard for visualizing and quantifying a myocardial infarction in 2020, Daniel C. Lee, MD, MS of Northwestern University Feinberg School of Medicine in Chicago, and colleagues wrote in JAHA, and the modality has proven useful in predicting a slew of risky future CV events, including recurrent MI, arrhythmias, heart failure, revascularization and death. But MR imaging is expensive, and electrocardiography—the industry’s first-line diagnostic test for patients with suspected ischemic heart disease—is more widely available in the U.S.

Lee et al. explained that several ECG abnormalities have been noted in heart attack survivors, including Q waves (QW), fragmented QRS (FQRS) and T wave inversions (TWI). Right now such abnormalities are considered dichotomous markers for the presence or absence of infarction, but their relationship to infarct size hasn’t been studied.

“The aim of this study was to evaluate whether abnormal ECG markers could be used to quantify infarct size measured by CMR in patients with prior MRI,” the authors wrote. “We hypothesized that the presence and extent of abnormal ECG markers would have independent and additive effects on estimation of infarct size.

“The ability to easily estimate infarct size from a 12-lead ECG would be extremely useful in the clinical evaluation of patients with prior MI.”

The team compared the accuracy of a simple ECG score for estimating infarct size, basing their evaluation on the presence and extent of abnormal ECG markers (measured with the DETERMINE Score), left ventricular ejection fraction (LVEF) and the Modified Sylvester Score, a 37-criteria, 29-point ECG scoring system. The DETERMINE (Defibrillators to Reduce Risk by Magnetic Resonance Imaging Evaluation) Score, used in the DETERMINE and PRE-DETERMINE clinical registries, is equal to the number of ECG leads with Q waves (multiplied by two), plus the number of leads with FQRS, plus the number of leads with TWI.

Five-hundred and fifty-one patients were included in the authors’ analysis, most of whom were men and on average in their early sixties. The researchers found that patients’ infarct size as a percentage of left ventricular mass (MI%) increased as the number of ECG markers increased, and the DETERMINE Score estimated MI% with an accuracy approaching that of LVEF but higher than the Modified Sylvester Score. 

By multivariate linear regression, addition of the DETERMINE Score improved MI% estimation over LVEF alone and over Modified Sylvester Score alone.

“To our knowledge, this is the first study to demonstrate that the presence and extent of Q waves, fragmented QRS and TWI on ECG are independently associated with an increase in infarct size, and that the DETERMINE Score calculated from the number of leads with these markers can be used to estimate infarct size measured by CMR in patients with a history of MI,” Lee and co-authors wrote. “As the ECG is the most basic diagnostic test in the clinician’s toolbox, these data provide an important new context for the clinician that may help guide further evaluation in the patient with a history of MI.”

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