Background: Immune checkpoint inhibitor (ICI)-induced cardiac side effects in cancer patients are increasingly being recognized and can be fatal. There is no standardized cardiac imaging test to examine the effects of ICIs in myocardial morphology and function. Objective: To study the utility of echocardiography and cardiac MRI in examining regional and global changes arising from ICI-induced myocarditis and cardiomyopathy in high-risk subjects suspected to have developed ICI cardiomyopathy. Methods: We studied eight consecutive patients referred for cardiac MRI (CMR) from a comprehensive cancer center for suspected ICI-induced myocarditis and compared the data with sixteen age-matched controls. Using newly developed strain analysis algorithms, we measured myocardial strain and strain rates using echocardiography and CMR. Then, we compared the mean longitudinal strain and strain rates derived from echocardiography and CMR in the same ICI-treated cohort of patients (n = 8). They underwent both of these imaging studies with images taken 24−48 h apart and followed up prospectively within the same hospital course. Results: All our cases had preserved ejection fraction (EF) > 50%. Echocardiogram showed reduced mean systolic longitudinal strain (LS, %) (ICI: −12.381 ± 4.161; control: −19.761 ± 1.925; p < 0.001), peak systolic strain rate (SRS, s−1) (ICI: −0.597 ± 0.218; control: −0.947 ± 0.135; p = 0.002) and early diastolic strain rate (SRE, s−1) (ICI: 0.562 ± 0.295; control: 1.073 ± 0.228; p = 0.002) in ICI-treated cases. Direct comparison between the echocardiogram vs. CMR obtained within the same hospital course demonstrated strong a correlation of LS scores (r = 0.83, p = 0.012) and SRS scores (r = 0.71, p = 0.048). The Bland−Altman plots showed that 95% of the data points fitted within the ±1.96 SD of the mean difference, suggesting an agreement among these two imaging modalities. Conclusion: In this feasibility cohort study, both echocardiography- and CMR-based strain indices illustrate changes in myocardial contractility and relaxation suggestive of ICI-induced cardiomyopathy. Our data, after validation in a larger cohort, can form the basis of myocardial imaging in cancer patients treated with ICIs.
Keywords: cardiac MRI; cardiotoxicity; checkpoint inhibitors; echocardiography; immunotherapy; strain imaging.