Abstract 18372: Differences in Quantitative Assessment of Myocardial Scar and Gray Zone by Delayed Enhanced Cardiac Magnetic Resonance Imaging Using Established Gray Zone Protocols

Abstract

Background: Delayed enhanced cardiac magnetic resonance imaging (DE-CMRI) is the gold standard for scar evaluation. Heterogeneous areas in the scar, known as ‘gray zone’ (GZ), may serve as arrhythmogenic substrate. Various signal intensity (SI) thresholds have been described and validated for GZ and infarct core definition. Little is known about the effect of these protocols on the presence and amount of GZ and infarct core. We aimed to compare 3 previously described methods.

Methods: Postprocessing analysis of good quality DE-CMRI images was performed in 14 patients with ischemic (12) or non-ischemic (2) cardiomyopathy and no implanted cardiac devices. Myocardial scar was defined as core and GZ using the following SI thresholds. The core was defined as >50% of maximal SI (MSI) in the hyperenhanced area for the full width at half-maximum (FWHM) and ‘modified-FWHM’ (or ‘Roes’) methods and >3SD of mean SI of remote myocardium for the n-standard deviation (NSD) method. GZ was defined as > peak SI of remote myocardium to 50% of MSI (FWHM), between ≥ 35% -50% of MSI (Roes) and 2-3SD of mean SI of remote myocardium (NSD).

Results: All patients had evidence of scar on DE-CMRI. The GZ mass was significantly different for the 3 methods with 46±38 g vs. 15±6 g vs. 17±7 g for FWHM, NSD and Roes respectively (p = 0.01). There was no difference in GZ mass between the NSD and Roes (p = 0.12). Infarct core mass was similar for FWHM and Roes (22±13 g) but significantly higher with NSD (63±36 g, p < 0.01). There was a difference in total myocardial scar (core + GZ) with 68±40 g vs. 78±40 g vs. 39±19 g for FWHM, NSD and Roes respectively (p < 0.01). The GZ extent (% of scar that was GZ) also varied significantly for the 3 methods, 62±22% vs. 22±10% vs. 45±11% for FWHM, NSD and Roes respectively (p < 0.01). A strong correlation was shown between GZ mass and total myocardial scar (r = 0.94, p < 0.01 for FWHM, r = 0.74, p < 0.01 for NSD and r = 0.84, p < 0.01 for Roes).

Conclusion: Considerable variability exists among the current methods for MRI scar quantification of GZ and scar core. There is a 3-fold increase in GZ mass quantified by the FWHM method compared to the NSD and Roes methods. Infarct core and total myocardial scar mass also differ using these methods. Further evaluation of the most accurate quantification method is needed.