From trivial to severe arrhythmias: the diagnostic role of multimodality imaging in inflammatory cardiomyopathy through a case series.

The diagnosis of inflammatory cardiomyopathy remains challenging in cases presenting with arrhythmia as sole manifestation. An early diagnosis is critical as it may prevent life-threatening complications such as sudden cardiac death and atrioventricular block (AVB). The diagnostic workup of suspected cases includes multimodality imaging that requires an adequate interpretation in order to limit the risk of overdiagnosis. Herein, we report three cases presenting with various new-onset arrhythmias. The first patient was admitted for a third-degree AVB. The second patient suffered from a supraventricular tachycardia which degenerated into ventricular fibrillation. The third case was investigated for symptomatic premature ventricular complexes. No apparent heart disease was observed on standard exams (clinical, biological examinations, and echocardiography). However, cardiac magnetic resonance imaging (MRI) and nuclear imaging ( <sup>68</sup> Ga-DOTATOC and/or <sup>18</sup> F-FDG PET/CT) suggested an inflammatory substrate that seemed to correlate with the arrhythmic phenotype. Cardiac inflammation disappeared on immunotherapy for the first case and spontaneously for the third case. These cases emphasize the incremental diagnostic yield of multimodality imaging to highlight myocardial inflammation. Nuclear imaging modalities may complement MRI by enabling the detection of active inflammation. The <sup>18</sup> F-FDG PET/CT is well established for the diagnosis of cardiac sarcoidosis but its role remains to be clarified for the diagnosis of myocarditis. An alternative radiotracer, <sup>68</sup> Ga-DOTATOC, appears promising by overcoming the main limitation of <sup>18</sup> F-FDG but its specificity is not yet well established. The role of functional investigations is discussed as well as the benefit of immunosuppressive treatments