Differentiation of acute non-ST elevation myocardial infarction and acute infarct-like myocarditis by visual pattern analysis: a head-to-head comparison of different cardiac MR techniques
Authors: Jahnke Charlotte , Sinn Martin , Hot Amra , Cavus Ersin , Erley Jennifer , Schneider Jan , Chevalier Celeste , Bohnen Sebastian , Radunski Ulf , Meyer Mathias , Lund Gunnar , Adam Gerhard , Kirchhof Paulus , Blankenberg Stefan , Muellerleile Kai , Tahir Enver 
Published: July 2023

Abstract
Objectives

Parametric cardiac magnetic resonance (CMR) techniques have improved the diagnosis of pathologies. However, the primary tool for differentiating non-ST elevation myocardial infarction (NSTEMI) from myocarditis is still a visual assessment of conventional signal-intensity-based images. This study aimed at analyzing the ability of parametric compared to conventional techniques to visually differentiate ischemic from non-ischemic myocardial injury patterns.

Methods
Twenty NSTEMI patients, twenty infarct-like myocarditis patients, and twenty controls were examined using cine, T2-weighted CMR (T2w) and late gadolinium enhancement (LGE) imaging and T1/T2 mapping on a 1.5 T scanner. CMR images were presented in random order to two experienced fully blinded observers, who had to assign them to three categories by a visual analysis: NSTEMI, myocarditis, or healthy.

Results
The conventional approach (cine, T2w and LGE combined) had the best diagnostic accuracy with 92% (95%CI: 81–97) for NSTEMI and 86% (95%CI: 71–94) for myocarditis. The diagnostic accuracies using T1 maps were 88% (95%CI: 74–95) and 80% (95%CI: 62–91), 84% (95%CI: 67–93) and 74% (95%CI: 54–87) for LGE, and 83% (95%CI: 66–92) and 73% (95%CI: 53–87) for T2w. The accuracies for cine (72% (95%CI: 52–86) and 60% (95%CI: 38–78)) and T2 maps (62% (95%CI: 40–79) and 47% (95%CI: 28–68)) were significantly lower compared to the conventional approach (p < 0.001 and p < 0.0001).

Conclusions
The conventional approach provided a reliable visual discrimination between NSTEMI, myocarditis, and controls. The diagnostic accuracy of a visual pattern analysis of T1 maps was not significantly inferior, whereas the diagnostic accuracy of T2 maps was not sufficient in this context.

Clinical relevance statement
The ability of parametric compared to conventional CMR techniques to visually differentiate ischemic from non-ischemic myocardial injury patterns can avoid potentially unnecessary invasive coronary angiography and help to shorten CMR protocols and to reduce the need of gadolinium contrast agents.

Key Points
•A visual differentiation of ischemic from non-ischemic patterns of myocardial injury is reliably achieved by a combination of conventional CMR techniques (cine, T2-weighted and LGE imaging).
•There is no significant difference in accuracies between visual pattern analysis on native T1 maps without providing quantitative values and a conventional combined approach for differentiating non-ST elevation myocardial infarction, infarct-like myocarditis, and controls.
•T2 maps do not provide a sufficient diagnostic accuracy for visual pattern analysis for differentiating non-ST elevation myocardial infarction, infarct-like myocarditis, and controls.