Myocardial Extracellular Volume Estimation by CMR Predicts Functional Recovery Following Acute MI

Abstract

ObjectivesIn the setting of reperfused acute myocardial infarction (AMI), the authors sought to compare prediction of contractile recovery by infarct extracellular volume (ECV), as measured by T1-mapping cardiac magnetic resonance (CMR), with late gadolinium enhancement (LGE) transmural extent.BackgroundThe transmural extent of myocardial infarction as assessed by LGE CMR is a strong predictor of functional recovery, but accuracy of the technique may be reduced in AMI. ECV mapping by CMR can provide a continuous measure associated with the severity of tissue damage within infarcted myocardium.MethodsThirty-nine patients underwent acute (day 2) and convalescent (3 months) CMR scans following AMI. Cine imaging, tissue tagging, T2-weighted imaging, modified Look-Locker inversion T1 mapping natively and 15 min post–gadolinium-contrast administration, and LGE imaging were performed. The ability of acute infarct ECV and acute transmural extent of LGE to predict convalescent wall motion, ejection fraction (EF), and strain were compared per-segment and per-patient.ResultsPer-segment, acute ECV and LGE transmural extent were associated with convalescent wall motion score (p < 0.01; p < 0.01, respectively). ECV had higher accuracy than LGE extent to predict improved wall motion (area under receiver-operating characteristics curve 0.77 vs. 0.66; p = 0.02). Infarct ECV ≤0.5 had sensitivity 81% and specificity 65% for prediction of improvement in segmental function; LGE transmural extent ≤0.5 had sensitivity 61% and specificity 71%. Per-patient, ECV and LGE correlated with convalescent wall motion score (r = 0.45; p < 0.01; r = 0.41; p = 0.02, respectively) and convalescent EF (p < 0.01; p = 0.04). ECV and LGE extent were not significantly correlated (r = 0.34; p = 0.07). In multivariable linear regression analysis, acute infarct ECV was independently associated with convalescent infarct strain and EF (p = 0.03; p = 0.04), whereas LGE was not (p = 0.29; p = 0.24).ConclusionsAcute infarct ECV in reperfused AMI can complement LGE assessment as an additional predictor of regional and global LV functional recovery that is independent of transmural extent of infarction.

Mapping Myocardial Salvage Index by Extracellular Volume Fraction

“…An overlap in acute ECV values between the salvaged and remote myocardium may also have affected the study by Garg et al, 3 with areas of acute ECV >33% observed in the remote myocardium ( Figure 3, case 1). Furthermore, a previous study by the same research group had reported an acute ECV of 29±6% in the remote myocardium, 18 confirming the potential for overlap in acute ECV values between salvaged and remote myocardium. Again, this may explain, in part, the wide limits of agreement (±10.4%) observed in this study, indicating a large variability in the observed values between acute ECV AAR and T2-STIR AAR.…”

Extra-cellular expansion in the normal, non-infarcted myocardium is associated with worsening of regional myocardial function after acute myocardial infarction

“…A recent study from our group demonstrated that acute 'infarct zone' ECV is predictive of regional and global LV functional recovery, and adds prognostic value over LGE [36]. Particularly for infarcts with higher transmural extent, acute infarct ECV was an additional predictor of functional recovery that can complement transmural infarct extent by LGE.…”

Cardiovascular Magnetic Resonance in Acute ST-Segment–Elevation Myocardial Infarction

“…47 However, as it stands, ECV-mapping may complement late gadolinium enhancement imaging to assess MI size and predict wall motion recovery at follow-up, as recently shown by 2 small studies. 16, 48 …”