Table 4. Summary of observational studies.

ICI = Immune checkpoint inhibitor, MACE = Major adverse cardiac events, irAEs = Immune-related adverse effects.

Study	Type of study	Period of study	Result	Conclusion
Asuka Furukawa et al. 2023 [16]	Prospective study	From April 2017 to May 2020	One hundred twenty-six patients with cancer enrolled to study for ICI treatment; 18 (14.3%) had elevated troponin I levels; 13 (10.3%) had symptoms; and 4 (3.2%) needed to stop receiving ICIs.	The study revealed a higher-than-anticipated incidence of myocarditis, but most cases lacked symptoms or were mild enough to continue treatment.
Syed S. Mahmood et al. 2018 [27]	A retrospective and prospective study	From November 2013 to July 2017	Thirty-five patients with ICI-associated myocarditis compared with a control group of 105 patients who were treated with ICIs without myocarditis; the prevalence of myocarditis was 1.14%; 54% didn't have any other irAEs. Most myocarditis was seen in combined ICIs therapy (34% vs. 2%) and diabetes patients (34% vs. 13%). The steroid was administered to 89% of patients.	Myocarditis isn't a common side effect of ICIs, but it's concerning as it can cause major adverse cardiac events (MACE). Due to this fact, the workup and management of myocarditis induced by ICIs are important.
Samantha N. Champion et al. 2020 [25]	Retrospective study	From January 2016 to February 2019	Ten cases of ICI-induced myocarditis were identified (nine based on endometrial biopsy and one based on autopsy). Eight of them had clear signs of myocarditis, and two of them had borderline characteristics of myocarditis. Low-grade ICI myocarditis compared with high-grade ICIs, and there was no significant difference in troponin levels, number of cycles, or even time from the first cycle, although all high-grade ICI myocarditis died even despite therapy.	ICI myocarditis can be high-grade or low-grade. A high-grade ICI has more clinical symptoms and is more aggressive, but a low-grade ICI has mild clinical symptoms. ICIs myocarditis, compared to acute cellular rejection, has more lymphohistiocytic inflammation.