I51.3 Intracardiac thrombosis, not elsewhere classified

The ICD-10-CM code for Intracardiac thrombosis, not elsewhere classified is I51.3 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

9: Diseases of the circulatory system (I00-I99)

Section

I30-I5A: Other forms of heart disease (I30-I5A)

Category I51

12 codes (10 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to I51.3:

• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › intracardiac NEC (apical) (atrial) (auricular) (ventricular) (old)
• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › cardiac › not resulting in infarction
• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › atrium, auricular › not resulting in infarction
• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › atrium, auricular › old
• Embolism (multiple) (paradoxical) › cardiac › not resulting in infarction
• Embolism (multiple) (paradoxical) › heart (fatty) › not resulting in infarction
• Ischemia, ischemic › myocardium, myocardial (chronic or with a stated duration of over 4 weeks) › acute, without myocardial infarction
• Clot (blood) › heart › not resulting in infarction

Inclusion Terms

• Apical thrombosis (old)
• Atrial thrombosis (old)
• Auricular thrombosis (old)
• Mural thrombosis (old)
• Ventricular thrombosis (old)

U.S. Hospital Utilization

• An estimated 75,950 U.S. inpatient stays in 2023 included I51.3 among the documented diagnoses.
• 2,595 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Presumed relationship due to Index term “with”

The classification presumes a causal relationship between hypertension and heart involvement and between hypertension and kidney involvement, as the two conditions are linked by the term “with” in the Alphabetic Index. These conditions should be coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated.

Provider must link conditions not specifically indexed as related

For hypertension and conditions not specifically linked by relational terms such as “with,” “associated with” or “due to” in the classification, provider documentation must link the conditions in order to code them as related.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)