The transmural extent of late gadolinium enhancement (LGE) CMR predicts functional recovery in acute myocardial infarction (AMI). Automated methods are recommended1 to define infarct extent on LGE imaging, such as ‘n-standard deviations’ (SD) and ‘full width at half maximum’ (FWHM). These define infarcted myocardium by signal intensity as compared to remote myocardium, which in turn depends on signal-to-noise and contrast. Individual variability in these parameters makes a single thresholding technique unlikely to be universally suitable. Extracellular volume (ECV) estimation by T1-mapping CMR is theoretically less affected by sequence and contrast variations. We compared infarct ECV with threshold-based measures of LGE transmural extent to predict contractile recovery in reperfused AMI.
Consecutive patients with reperfused first ST-elevation AMI underwent acute (day 2) and convalescent (3 months) CMR. Cine imaging, modified Look-Locker inversion T1 mapping natively and 15 min post gadolinium-contrast administration and LGE imaging were performed. Five LGE thresholding techniques were compared: 2, 5 and 6 SD, FWHM and a histogram-based technique (Otsu).2 The ability of acute infarct ECV to predict improvement in segmental wall motion was compared with these thresholding techniques.
n = 35 (28(80%) male, age 57 ± 11 years). Infarct characteristics are shown in Table 1. ECV showed modest correlation with all threshold measures of LGE (r2 = 0.16–0.31, p < 0.01). Reduced convalescent wall motion score correlated with acute ECV (p < 0.01), and acute LGE for 5 SD (p < 0.01), 6 SD (p < 0.01) and FWHM (p = 0.01), but not 2 SD (p = 0.2) or Otsu (p = 0.6). Acute infarct ECV demonstrated a significantly higher c-statistic for prediction of improved segmental convalescent wall motion score than all threshold measures of acute transmural LGE extent (p ≤ 0.02 for all, Figure 1).
Acute infarct ECV outperforms threshold-based LGE transmural extent to predict segmental LV functional recovery in reperfused AMI.
Schulz-Menger J, et al. J Card Magn Reson 2013;15:35
Otsu N. IEEE Trans Sys Man Cyber. 1979;9:62–6
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