Comprehensive Cardiac Magnetic Resonance Imaging in Patients with Suspected Myocarditis the MyoRacer-Trial

Background Data suggest that T₁ and T₂ mapping have excellent diagnostic accuracy in patients with suspected myocarditis. However, the true diagnostic performance of comprehensive cardiac magnetic resonance (CMR) mapping versus endomyocardial biopsy (EMB) has not been determined. Objectives This study assessed the performance of CMR imaging, including T₁ and T₂ mapping, compared with EMB in an unselected, consecutive patient cohort with suspected myocarditis. It also examined the potential role of CMR field strength by comparing 1.5-T versus 3.0-T imaging. Methods Patients underwent biventricular EMB, cardiac catheterization (for exclusion of coronary artery disease), and CMR imaging on 1.5- and 3-T scanners. The CMR protocol included current standard Lake Louise criteria (LLC) for myocarditis as well as native T₁, calculation of extracellular volume fraction (ECV), and T₂ mapping (only on 1.5-T). Patients were divided into 2 groups according to symptom duration (acute: ≤14 days vs. chronic: >14 days). Results A total of 129 patients underwent 1.5-T imaging. In patients with acute symptoms, native T₁ yielded the best diagnostic performance as defined by the area under the curve (AUC) of receiver-operating curves (0.82) followed by T₂ (0.81), ECV (0.75), and LLC (0.56). In patients with chronic symptoms, only T₂ mapping yielded an acceptable AUC (0.77). On 3.0-T, AUCs of native T₁, ECV, and LLC were comparable to 1.5-T with no significant differences. Conclusions In patients with acute symptoms, mapping techniques provide a useful tool for confirming or rejecting the diagnosis of myocarditis and are superior to the LLC. However, only T₂ mapping has acceptable diagnostic performance in patients with chronic symptoms. (Magnetic Resonance Imaging in Myocarditis [MyoRacer]; NCT02177630)