# Immune-related myocarditis from checkpoint inhibitors

Source: https://onco.cc/protocols/irae-myocarditis/  
OnCo record `irae-myocarditis` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Rarely, immunotherapy inflames the heart muscle. It usually starts in the first three months and can be fatal, so new chest pain, breathlessness, palpitations, fainting, or new muscle weakness, drooping eyelids or double vision need urgent assessment. It is treated in hospital with very high-dose steroids straight away.

## Summary

Uncommon (about 1% in an eight-centre registry) but with high mortality: 50% of patients with myocarditis died in one retrospective series, and it clusters with myositis and myasthenia gravis, so suspicion of one should prompt a search for all three (SITC 2021). Median onset 34 days after starting. Troponin is raised in 94% and the ECG abnormal in 89%, while ejection fraction is normal in about half.

SITC 2021: consider myocarditis in anyone with new cardiac symptoms, arrhythmia, heart block or a raised troponin who has had a checkpoint inhibitor in the past 12 weeks; admit, involve cardiology, and obtain ECG, troponin and cardiac MRI (with or without endomyocardial biopsy), plus the shared myositis and myasthenia panel. Give methylprednisolone 1000 mg IV daily for 3 to 5 days as soon as the diagnosis is likely, until troponin normalises, then a 4 to 6 week prednisone taper; seriously consider permanent discontinuation. If there is no response within 24 hours add antithymocyte globulin, mycophenolate mofetil, abatacept or alemtuzumab (LE: 4); avoid infliximab (LE: 4). Manage in a coronary care unit with temporary pacing available. A retrospective study found steroids within 24 hours of admission were followed by fewer major cardiac events than later steroids.

ASCO 2021 makes cardiac toxicity one of the exceptions to continuing treatment for grade 1 toxicity. The ESC 2022 and ESC 2025 guidelines could not be read here.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: checkpoint inhibitor myocarditis; ICI myocarditis; immune checkpoint inhibitor-associated myocarditis; immunotherapy heart inflammation; myocarditis-myositis-myasthenia overlap
- Tags: protocol; irae; acute-oncology; cardio-oncology

## Connected records

- protocols: [Baseline tests and monitoring before and during checkpoint inhibitor treatment](https://onco.cc/protocols/checkpoint-inhibitor-baseline-and-monitoring/), [Joint, muscle and other rheumatic side effects of checkpoint inhibitors](https://onco.cc/protocols/irae-rheumatological/), [Neurological side effects of checkpoint inhibitors: myasthenia gravis, Guillain-Barré syndrome, meningitis and encephalitis](https://onco.cc/protocols/irae-neurological/), [Restarting a checkpoint inhibitor after an immune-related side effect](https://onco.cc/protocols/irae-rechallenge/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/), [Troponin and natriuretic peptide monitoring during cancer treatment](https://onco.cc/technologies/cardiac-biomarker-monitoring/)
- drugs: [Alemtuzumab](https://onco.cc/drugs/alemtuzumab/), [Atezolizumab](https://onco.cc/drugs/atezolizumab/), [Avelumab](https://onco.cc/drugs/avelumab/), [Cemiplimab](https://onco.cc/drugs/cemiplimab/), [Dostarlimab](https://onco.cc/drugs/dostarlimab/), [Durvalumab](https://onco.cc/drugs/durvalumab/), [Ipilimumab](https://onco.cc/drugs/ipilimumab/), [Methylprednisolone](https://onco.cc/drugs/methylprednisolone/), [Nivolumab](https://onco.cc/drugs/nivolumab/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Tremelimumab](https://onco.cc/drugs/tremelimumab/)
- institutions: [American Society of Clinical Oncology (ASCO)](https://onco.cc/institutions/asco/), [European Society for Medical Oncology (ESMO)](https://onco.cc/institutions/esmo/), [Society for Immunotherapy of Cancer](https://onco.cc/institutions/sitc/)
- terms: [Immune-related adverse events (irAEs)](https://onco.cc/terms/irae/), [Immune-related myocarditis](https://onco.cc/terms/myocarditis/)
- key papers: [2022 ESC Guidelines on cardio-oncology developed in collaboration with the European Hematology Association (EHA), the European Society for Therapeutic Radiology and Oncology (ESTRO) and the International Cardio-Oncology Society (IC-OS)](https://onco.cc/key-papers/paper-lyon-eur-heart-j/), [ASCO 2021 guideline: how to recognise and manage the immune-related side effects of checkpoint inhibitors](https://onco.cc/key-papers/paper-asco-irae-guideline-jco-2021/)

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