ICD-10 Code I51.4 – Myocarditis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I51.4 – Myocarditis, unspecified
What it is
I51.4 identifies myocarditis when the record does not specify the cause or type. It means inflammation of the heart muscle, documented without enough detail for a more specific code.
Clinical signs
Clinical features vary; refer to documentation. Commonly noted findings include chest pain, shortness of breath, palpitations, fatigue, or evidence of myocardial inflammation on testing.
When to use this code
Use I51.4 when the provider documents myocarditis but does not name an infectious, autoimmune, or other specific cause. It also fits when the note states “myocarditis” without further detail. If the record later specifies a cause, code the more specific diagnosis instead.
Do not use for
Do not use this code for pericarditis, cardiomyopathy, or ischemic heart disease. If documentation identifies a specific myocarditis type or cause, check documentation and code that condition instead.
Coding tip
Query the provider when myocarditis is mentioned but the cause or acuity is unclear, since specificity may change code selection.