Clinical characteristics analysis of immune checkpoint inhibitors-related myocarditis

To investigate the clinical characteristics of immune checkpoint inhibitors (ICIs)-related myocarditis and the differences between mild and severe cases, aiming to provide evidence for early identification and stratified management.

A total of 74 patients diagnosed with ICIs-related myocarditis at our hospital from April 2020 to April 2024 were retrospectively enrolled. According to the *Chinese Expert Consensus on the Surveillance and Management of Immune Checkpoint Inhibitor-Related Myocarditis (2020 Edition)* and CTCAE 5.0 criteria, patients were divided into mild group (n=49) and severe group (n=25). The two groups were compared in terms of demographic characteristics, clinical manifestations, laboratory tests, auxiliary examinations, concomitant irAEs, treatment, and outcomes.

The time of onset in the severe group was significantly earlier than that in the mild group [23 days (18, 85) vs. 80 days (48, 132), P = 0.004]. Severe group more frequently presented with multisystem involvement: incidences of myasthenia (56.0% vs. 6.1%), dyspnea (24.0% vs. 0), and ptosis (16.0% vs. 0) were significantly higher (all P<0.05). Levels of cardiac biomarkers (cTnT/I, CK, NT-proBNP) and liver enzymes (ALT, AST) were markedly elevated (all P<0.01). Electrocardiographic ST-T segment changes (56.0% vs. 10.2%) and conduction blocks (32.0% vs. 4.1%) were more common in the severe group. Echocardiography showed higher rates of regional wall motion abnormality (28.0% vs. 6.1%) and pericardial effusion (28.0% vs. 6.1%) in the severe group. The severe group also had higher rates of concomitant myositis (68.0% vs. 40.8%), hepatitis (28.0% vs. 6.1%), and neurotoxicity (32.0% vs. 2.0%) (all P<0.05). Regarding treatment, 100% of the severe group received glucocorticoids (vs. 28.6%), 60.0% required intravenous immunoglobulin, and 28.0% needed respiratory support. Regarding outcomes, all patients in the mild group improved, while the mortality rate in the severe group was 32.0% (8/25).

Patients with severe ICIs-related myocarditis are characterized by early onset, multisystem involvement, marked elevation of cardiac enzymes, prominent electrocardiographic/echocardiographic abnormalities, frequent concomitant irAEs, and high mortality. Clinicians should be highly vigilant for patients presenting with early myasthenia, conduction blocks, or markedly elevated CK/cTn, and promptly initiate intensified immunosuppressive therapy to improve prognosis.