ABSTRACT
Background: While immune checkpoint inhibitors (ICI) -induced myocarditis and coronavirus disease 2019 (COVID-19) vaccine-induced myocarditis are considered to be rare;they are both significant side effects, suggested being caused by activation of the immune system against the myocardium. We aimed to assess whether both phenomena share similar presenting characteristics. Method(s): We included patients diagnosed with either ICI or COVID-19 vaccine-induced myocarditis at our medical center. We performed a retrospective assessment of clinical presentation, blood tests, and advanced echocardiography, including speckle strain. Result(s):We included 18 patients diagnosed with ICI (ICI group) or COVID- 19 vaccine (COVID-19 group)-induced myocarditis, and 20 patients with viral myocarditis (Viral group) as a control group. The median age was significantly older in the ICI group (74 years) compared to the COVID-19 and Viral groups (20 and 24 years), p<0.001. The clinical presentation in the COVID-19 group was more similar to the Viral group, presenting mainly with chest pain and fever, while the ICI group presented mainly with dyspnea. ST-elevation was frequent in the COVID-19 and Viral groups and absent in the ICI group, p=0.004. Median peak high sensitivity troponin I values were markedly lower in the ICI group compared to the COVID-19 and Viral groups (619 ng/L vs. 15527 ng/L vs. 7388 ng/L, p=0.004). While the median left ventricular ejection fraction was 60% among all groups, patients in the ICI group presented with mean lower LV global longitudinal strain (-13%) and left atrial conduit strain (17%), compared to the COVID-19 (-17% and 30%) and Viral groups (-18% and 37%), p=0.016 and p=0.001. Conclusion(s): While the suspected mechanism is an activation of the immune system in both ICI and the COVID-19 vaccine-induced myocarditis, we found that the clinical presentation, cardiac biomarkers, and advanced echocardiography of the COVID-19 vaccine, are more similar to viral myocarditis than to ICI-induced myocarditis.