ICD-10 Code I42.4 – Endocardial fibroelastosis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I42.4 – Endocardial fibroelastosis
What it is
Endocardial fibroelastosis is a rare heart muscle disorder marked by thickening of the endocardium, the inner lining of the heart. It is usually associated with impaired ventricular function and enlarged heart chambers.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include heart failure in infancy or childhood, cardiomegaly, and reduced ventricular performance on imaging or echocardiography.
When to use this code
Use I42.4 when the provider documents endocardial fibroelastosis as the diagnosis or confirms it by imaging, pathology, or specialist assessment. Code it for congenital or acquired cases when the record specifically identifies this condition. If the chart only notes nonspecific cardiomyopathy, check documentation.
Do not use for
Do not use this code for general cardiomyopathy, endocarditis, or unspecified heart enlargement without documentation of fibroelastosis. If the condition is only suspected, confirm the diagnosis before coding.
Coding tip
Match the code only to explicit provider wording; if fibroelastosis is mentioned in historical imaging or pathology, verify it is still relevant to the current encounter.