ICD-10 Code I42.1 – Obstructive hypertrophic cardiomyopathy (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I42.1 – Obstructive hypertrophic cardiomyopathy
What it is
Obstructive hypertrophic cardiomyopathy is a thickening of the heart muscle, usually the septum, that can block blood flow out of the left ventricle. The obstruction may be present at rest or only with provocation.
Clinical signs
Common findings include exertional dyspnea, chest pain, palpitations, syncope, or a systolic murmur that changes with maneuvers. Echocardiography may show asymmetric hypertrophy and left ventricular outflow tract obstruction; clinical features vary, refer to documentation.
When to use this code
Use I42.1 when the provider documents obstructive hypertrophic cardiomyopathy, hypertrophic obstructive cardiomyopathy, or HOCM. You should also use it when imaging or cardiology notes confirm dynamic outflow tract obstruction associated with hypertrophic cardiomyopathy. Check documentation if the record only says cardiomyopathy without obstruction.
Do not use for
Do not use this code for nonobstructive hypertrophic cardiomyopathy or other cardiomyopathies without left ventricular outflow obstruction. If the diagnosis is uncertain or the note only states “LVH,” check documentation.
Coding tip
Code I42.1 only when obstruction is clearly documented; “hypertrophic cardiomyopathy” alone is not enough.