Lights and shadows of cardiac magnetic resonance imaging in acute myocarditis

Cardiac magnetic resonance (CMR) is considered a primary tool for the diagnosis of acute myocarditis, due to its unique potential for non-invasive identification of the various hallmarks of the inflammatory response, with relevant impact on patient management and prognosis. Nonetheless, a marked variation in sensitivity and negative predictive value has been reported in the literature, reflecting the intrinsic drawbacks of current diagnostic criteria, which are based mainly on the use of conventional CMR pulse sequences. As a consequence, a negative exam cannot reliably exclude the diagnosis, especially in patients who do not present an infarct-like onset of disease. The introduction of new-generation mapping techniques further widened CMR potentials, allowing quantification of tissue changes and opening new avenues for non-invasive workup of patients with inflammatory myocardial disease. Main messages: • CMR sensitivity varies in AM, reflecting its clinical polymorphism and the intrinsic drawbacks of LLc. • Semiquantitative approaches such as EGEr or T2 ratio have limited accuracy in diffuse disease forms. • T1 mapping allows objective quantification of inflammation, with no need to normalize measurements. • A revised protocol including T2-STIR, T1 mapping and LGE could be hypothesized to improve sensitivity.