I21.B Myocardial infarction with coronary microvascular dysfunction
The ICD-10-CM code for Myocardial infarction with coronary microvascular dysfunction is I21.B (FY2026). It is a billable, claim-ready diagnosis code.
Classification
- Section
- I20-I25: Ischemic heart diseases (I20-I25)
- Category I21
- 18 codes (13 billable)
- FY2026 Status
- Stable since FY2024
Also Known As
ICD-10-CM Alphabetic Index entries that lead to I21.B:
- Dysfunction › coronary microvascular › with › myocardial infarction
- Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › with › coronary microvascular dysfunction
- Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › with › coronary microvascular disease
- Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › with › nonobstructive coronary arteries [MINOCA] with microvascular disease
- Disease, diseased › coronary (artery) › microvascular › with › myocardial infarction
Inclusion Terms
- Myocardial infarction with coronary microvascular disease
- Myocardial infarction with nonobstructive coronary arteries [MINOCA] with microvascular disease
U.S. Hospital Utilization
- An estimated 570 U.S. inpatient stays in 2023 included I21.B among the documented diagnoses.
- 415 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
Assign I21.B for MI with coronary microvascular dysfunction (CMD)6) Myocardial Infarction with Coronary Microvascular Dysfunction Coronary microvascular dysfunction (CMD) is a condition that impacts the microvasculature by restricting microvascular flow and increasing microvascular resistance. Code I21.B, Myocardial infarction with coronary microvascular dysfunction, is assigned for myocardial infarction with coronary microvascular disease, myocardial infarction with coronary microvascular dysfunction, and myocardial infarction with
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.
Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026