Complications and ill-defined descriptions of heart disease (I51) ICD-10-CM
The I51 code range covers complications and ill-defined descriptions of heart disease with 12 ICD-10-CM diagnosis codes. 10 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Codes in the I51 Range 12 codes · 10 billable
- I51 Complications and ill-defined descriptions of heart diseaseNon-billable
- I51.0 Cardiac septal defect, acquired
- I51.1 Rupture of chordae tendineae, not elsewhere classified
- I51.2 Rupture of papillary muscle, not elsewhere classified
- I51.3 Intracardiac thrombosis, not elsewhere classified
- I51.4 Myocarditis, unspecified
- I51.5 Myocardial degeneration
- I51.7 Cardiomegaly
- I51.8 Other ill-defined heart diseasesNon-billable
- I51.81 Takotsubo syndrome
- I51.89 Other ill-defined heart diseases
- I51.9 Heart disease, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the I51 range.
Cachexia
General ill health, malnutrition, and weight loss, usually associated with chronic disease.
Cardiomegaly
Enlargement of the HEART, usually indicated by a cardiothoracic ratio above 0.50. Heart enlargement may involve the right, the left, or both HEART VENTRICLES or HEART ATRIA. Cardiomegaly is a nonspecific symptom seen in patients with chronic systolic heart failure (HEART FAILURE) or several forms of CARDIOMYOPATHIES.
Cardiomegaly, Exercise-Induced
Non-pathological heart enlargement and other remodeling in cardiac morphology and electrical circuitry found in individuals who participate in intense repeated exercises.
Cardiotoxicity
Damage to the HEART or its function secondary to exposure to toxic substances such as drugs used in CHEMOTHERAPY; IMMUNOTHERAPY; or RADIATION.
Chagas Cardiomyopathy
A disease of the CARDIAC MUSCLE developed subsequent to the initial protozoan infection by TRYPANOSOMA CRUZI. After infection, less than 10% develop acute illness such as MYOCARDITIS (mostly in children). The disease then enters a latent phase without clinical symptoms until about 20 years later. Myocardial symptoms of advanced CHAGAS DISEASE include conduction defects (HEART BLOCK) and CARDIOMEGALY.
Myocarditis
Inflammatory processes of the muscular walls of the heart (MYOCARDIUM) which result in injury to the cardiac muscle cells (MYOCYTES, CARDIAC). Manifestations range from subclinical to sudden death (DEATH, SUDDEN). Myocarditis in association with cardiac dysfunction is classified as inflammatory CARDIOMYOPATHY usually caused by INFECTION, autoimmune diseases, or responses to toxic substances. Myocarditis is also a common cause of DILATED CARDIOMYOPATHY and other cardiomyopathies.
Takotsubo Cardiomyopathy
A transient left ventricular apical dysfunction or ballooning accompanied by electrocardiographic (ECG) T wave inversions. This abnormality is associated with high levels of CATECHOLAMINES, either administered or endogenously secreted from a tumor or during extreme stress.
About the I51 Code Range
The ICD-10 code I51 covers complications and ill-defined descriptions of heart disease, capturing various abnormal conditions that affect the heart but may not fall into more specific categories. These codes are essential for identifying heart issues such as acquired septal defects, ruptures in cardiac structures, myocarditis, cardiomegaly, and other less clearly defined heart diseases.
This group includes detailed conditions like I51.0 for acquired cardiac septal defects, commonly known as traumatic or acquired atrioventricular septal defects, and I51.1 and I51.2 for ruptures of the chordae tendineae and papillary muscles, respectively—key components that maintain heart valve function. I51.3 refers to intracardiac thrombosis, which includes clots within the heart chambers such as atrial or ventricular thrombi. I51.4 codes for unspecified myocarditis, an inflammation of the heart muscle that can involve infectious or immune causes. Cardiomegaly (I51.7) describes enlargement of the heart often associated with hypertrophy or dilatation of cardiac chambers. The section also contains codes for conditions like Takotsubo syndrome (I51.81) and other ill-defined or unspecified heart diseases (I51.8, I51.89, I51.9), facilitating documentation when precise diagnoses are challenging. This coverage helps coders accurately represent complex or uncertain cardiac complications using the ICD-10 code for heart disease complications and ill-defined heart disease.
Questions About This Page
How many billable codes are in the I51 range?
Of the 12 codes in this range, 10 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the I51 range classify?
The range classifies complications and ill-defined descriptions of heart disease. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
