Cardiac magnetic resonance imaging in patients with suspected myocarditis from immune checkpoint inhibitor therapy - A real-world observational study.

Background and aims: Cardiotoxicity from immune checkpoint inhibitor (ICI) therapy is a challenge in clinical practice, and the assessment of ICI-related myocarditis (ICI-M) is often complicated by a variable phenotype. Cardiac magnetic resonance imaging (CMR) is used frequently, but evidence is poor. Here, we aim to assess the role of CMR in the assessment of suspected ICI-M in a real-world clinical setting. Methods: All patients receiving CMR at our centre for suspected ICI-M between September 2019 and January 2024 were included and retrospectively analysed. CMR parameters were correlated with clinical, laboratory and echocardiographic parameters and stratified for presence of myocarditis as per final diagnosis. Results: A total of 55 patients who received CMR for suspected ICI-M were analysed, including 25 patients with ICI-M and 30 patients with non-myocarditis cardiotoxicity (non-M). The mean age (ICI-M versus (vs.) non-M) was 65.7 ± 13.6 vs. 67.3 ± 9.9 (p = 0.61) years, 32.0 % vs. 26.7 % (p = 0.67) were female, and 40.0 % vs. 26.7 % (p = 0.29) had pre-existing coronary heart disease. Cardiac biomarkers and echocardiographic data did not differ between the groups. In CMR analysis, presence of LGE was associated with ICI-M (56.0 % in ICI-M vs. 26.7 % in non-M, p = 0.03). Myocardial oedema was generally rare and not associated with ICI-M. Conclusion: In this real-life assessment of routine clinical practice, the diagnostic assessment of ICI-M is challenged by low sensitivity of common diagnostic measures, often requiring a multimodal approach. Presence of LGE in CMR is associated with ICI-M, but sensitivity and specificity are low. Prospective data to improve diagnostic criteria is needed.