Cardiovascular Toxicities Associated With Immune Checkpoint Inhibitors: Clinical Phenotypes, Mechanisms, Diagnosis, and Management—A Narrative Review

OBJECTIVE: Immune checkpoint inhibitors (ICIs) have improved cancer outcomes, yet cardiovascular toxicities remain difficult to recognize and manage. We review their clinical spectrum, mechanistic evidence, diagnostic work-up, surveillance, and treatment, with particular attention to where evidence is established and where it remains preliminary. METHODS: We conducted a narrative review of PubMed through September 2026 and hand-searched reference lists of relevant guidelines, reviews, and primary studies. We prioritized international guidance, systematic reviews, multicenter registries, prospective cohorts, and clinically informative mechanistic studies. Case reports and experimental studies were retained when they addressed questions not covered by higher-level evidence. The review was not protocol driven and did not include duplicate screening, formal risk-of-bias assessment, or a PRISMA flow diagram. RESULTS: ICI-related cardiovascular toxicity extends beyond myocarditis to temporally associated atherosclerotic events, pericardial disease, and heart failure without demonstrable myocardial inflammation, although causal attribution is less secure for these non-myocarditis phenotypes. Current guidance supports baseline cardiovascular assessment and risk-adapted surveillance, but neither a universal troponin threshold nor an outcome-proven monitoring schedule has been established. Corticosteroids remain first-line treatment for clinically significant ICI myocarditis. Abatacept, ruxolitinib, alemtuzumab, and other intensified regimens are off-label and rest largely on nonrandomized or case-level evidence. CONCLUSION: Management should combine early recognition, careful exclusion of competing diagnoses, and coordinated oncology-cardiology decision-making. Current evidence does not justify uniform screening thresholds or a standard rescue regimen, and investigational biomarkers, imaging probes, and targeted immunomodulators require prospective validation.