https://orcid.org/0000-0001-8165-5268
A 76-year-old male with advanced hepatocellular carcinoma presented with fatigue and minor myalgias after his first immunotherapy with atezolizumab and bevacizumab. Laboratory tests were as follows: creatine kinase (CK), 1926 U/L; CK-MB, 69 U/L; and troponin I, 79.7 pg/mL. Electrocardiogram revealed slight T-wave abnormalities in the precordial leads, while echocardiography showed normal left ventricular (LV) systolic function. Global longitudinal strain was −19% without ≥ 12% relative reduction from the baseline value. Cine cardiovascular magnetic resonance (CMR) also demonstrated normal LV cavity size, ejection fraction, mass index, and no pericardial effusion. There was no increased global myocardial native T1, T2, and extracellular volume fraction on multiparametric mapping (1248 ms, 46 ms, and 31.5%, respectively) or high signal intensity on T2-weighted short-TI inversion recovery without late gadolinium enhancement (LGE) on LGE-CMR (Panels A–E). Coronary angiography revealed no abnormal findings, and biopsy samples were taken from the mid interventricular septum. Histological samples revealed a focal but intense lymphocytic infiltrate and myocyte necrosis, resulting in a diagnosis of immune checkpoint inhibitor (ICI) myocarditis (Panel F). A previous pathological study reported that more than half of ICI myocarditis cases showed a low degree of inflammatory cell infiltration. LGE or elevated T2-weighted short-TI inversion recovery was present in fewer than 30% of ICI myocarditis. Furthermore, the sensitivity of quantitative CMR using clinical parametric mapping is limited by its inability to cover the whole myocardium. These data suggest caution when relying on a CMR-based approach for the exclusion of ICI myocarditis. The identification of concomitant myositis being considered as a ‘red flag’ for myocarditis should help alert the clinician to pursue endomyocardial biopsy even after negative CMR.
Acknowledgement
We thank Masaki Ishida, MD and Kyoko Imanaka-Yoshida, MD at Mie University Hospital for providing helpful suggestions.
Funding: None declared.
Author notes
Conflict of interest: None declared.
