ICD-10 Code I40.1 – Isolated Myocarditis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I40.1 – Isolated myocarditis
What it is
I40.1 identifies myocarditis limited to the heart muscle, without another specified associated condition. Use it when documentation states isolated myocarditis and does not describe a broader disease process.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings may include chest pain, shortness of breath, palpitations, or evidence of myocardial inflammation on cardiac evaluation.
When to use this code
Use I40.1 when the provider clearly documents isolated myocarditis as the diagnosis. It is appropriate when the record supports myocarditis affecting the myocardium alone and no more specific myocarditis type is stated.
If the note describes another cause, related systemic illness, or a different myocarditis category, code that more specific condition instead. Check documentation when the wording is unclear or incomplete.
Do not use for
Do not use this code for pericarditis, cardiomyopathy, or myocarditis with a different specified cause. Avoid it when the record does not explicitly support isolated myocarditis.
Coding tip
Confirm the exact provider wording; “isolated” matters, and unspecified myocarditis terminology may require a different code.