ICD-10 I23.6
Billable / Specific HCC v28: 87 CCThrombosis of atrium, auricular appendage, and ventricle as current complications following acute myocardial infarction
About ICD-10-CM I23.6
ICD-10-CM code I23.6 represents Thrombosis of atrium, auricular appendage, and ventricle as current complications following acute myocardial infarction. This is a billable/specific code in the Circulatory System chapter (block I23). The 2026 edition of ICD-10-CM I23.6 became effective on October 1, 2025.
Coding Tips for I23.6
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
I23.6 is a CMS-HCC v28 risk-adjustment code (category 87). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
I23.6 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Type 1 Excludes
Pure excludes, these codes can never be coded together with I23.6. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- thrombosis of atrium, auricular appendage, and ventricle not specified as current complication following acute myocardial infarction (I51.3)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, CC
codes Thrombosis of atrium, auricular appendage, and ventricle as current complications following acute myocardial infarction. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for I23.6
Local Coverage Determinations (LCDs) from CMS MACs that list I23.6 as a covered diagnosis.
Showing top 10 of 429 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing I23.6.
5 Medicare
1 Aetna
Convert I23.6 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| I23.6 | 42979 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To I23.6
Other codes in section I20-I25 (Ischemic heart diseases).
ICD-10 I23.6, Billing FAQ
Is ICD-10 code I23.6 billable? +
Yes, I23.6 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What codes are Type 1 Excludes for I23.6? +
Type 1 Excludes (never code together with I23.6): thrombosis of atrium, auricular appendage, and ventricle not specified as current complication following acute myocardial infarction (I51.3)
Does I23.6 affect Medicare Advantage HCC risk adjustment? +
Yes. I23.6 maps to CMS-HCC v28 category 87. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is I23.6 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with I23.6? +
Procedures frequently paired with I23.6 include: A9520, C9176.
What ICD-9 codes does I23.6 map to? +
Per CMS GEMs, I23.6 maps to ICD-9 codes: 42979. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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