Map to the future of cardiac magnetic resonance in myocarditis

Cardiac magnetic resonance (CMR) imaging is an excellent tool for the diagnosis of acute myocarditis and to differentiate acute myocarditis from ischemic events in acute coronary syndromes. CMR has therefore been included in recent guidelines for the management of patients with acute myocarditis. Monitoring of healing or persistence of myocardial inflammation in patients with acute myocarditis is important, since persistent myocardial inflammation is perceived as a key factor for the development of dilative cardiomyopathy. Accurate monitoring of the healing process of myocardial inflammation by non-ivasive means is therefore highly desirable since endomyocardial biopsy (EMB), the gold standard technique to demonstrate myocardial inflammation, is limited by its invasiveness, availability of experienced centres, cost and rather low sensitivity. ‘Lake-Louise’ CMR criteria have been widely used to diagnose myocarditis: the diagnosis is likely if two of the three criteria are present: (i) myocardial oedema (T2-weighted imaging); (ii) late Gadolinium enhancement (LGE) in a mid-wall noncoronary pattern; and (iii) hyperaemia/capillary leak (increased early Gadolinium enhancement). Radunski et al. have shown that LGE together with extracellular volume (ECV) quantification significantly improved the diagnostic accuracy to 90% [95% confidence interval (CI): 84–95%] compared with 79% (95% CI: 71–85%; P = 0.0043) for the ‘LakeLouise’ CMR criteria. Bohnen et al. report on their study of 48 patients with infarct-like or cardiomyopathy-like acute myocarditis who underwent a CMR study during the acute stage, 3 and 12 months later. The CMR protocol included standard ‘Lake-Louise’ sequences as well as T1, T2, and ECV mapping. It could be shown that (i) native T1 and T2 values normalized during healing; (ii) a combination of native T1 and T2 values could differentiate acute from healed stages of myocarditis with high accuracy; and (iii) combined analysis of LGE images and ECV values had the best diagnostic accuracy to identify diseased patients independent from the disease stage. The authors conclude that healing of myocarditis can be monitored by native myocardial T1 and T2 and that both native myocardial T1 and T2 provide an excellent performance for assessing the stage of myocarditis by CMR. Native T1, post-contrast T1, and ECV in fibrosis detection