2026 ICD-10-CM Diagnosis Code T86.21Heart transplant rejection
ICD-10-CM Codes›S00–T88›T80-T88›T86
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 221
- Chronic Condition
T86.21 is a billable ICD-10-CM diagnosis code for heart transplant rejection. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 314 through 316. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 51 closely related codes. Coders also document this condition as accelerated rejection of cardiac transplant. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication of transplanted organs or tissue, initial encounter.
For Medicare Advantage risk adjustment, T86.21 maps to CMS-HCC Category 221 (Heart Transplant Status/Complications) under the V28 model, adding a risk factor of about 1.053 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
T86.21 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accelerated rejection of cardiac transplant
- Acute rejection of cardiac transplant
- Cardiac transplant failure
- Cardiac transplant rejection
- Chronic rejection of cardiac transplant
- Disorder of myocardium associated with rejection of cardiac transplant
- Heart transplant failure and rejection
- Hyperacute rejection of cardiac transplant
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Complications of transplanted organs and tissue (T86). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
heart T86.21
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Heart Transplantation
A heart transplant removes a damaged or diseased heart and replaces it with a healthy one. The healthy heart comes from a donor who has died. It is the last resort for people with heart failure when all other treatments have failed.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T86.21 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T86.21Overview
What is the ICD-10 code for heart transplant rejection?
The ICD-10-CM code for heart transplant rejection is T86.21 (sometimes written as T8621). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is T86.21 (Complications of heart transplant) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report heart transplant rejection on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does T86.21 group to?
When heart transplant rejection is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T86.21 a CC or MCC?
CMS lists T86.21 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 51 closely related codes in its exclusion list.
What is the ICD-9 equivalent of T86.21?
Under the General Equivalence Mappings, heart transplant rejection converts to ICD-9-CM 996.83 (compl heart transplant). The mapping is approximate, so confirm the match fits the documentation.
What HCC is T86.21?
T86.21 (heart transplant rejection) maps to CMS-HCC Category 221 (Heart Transplant Status/Complications), commonly written as HCC 221, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 186 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 396.
Does T86.21 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, T86.21 adds a risk adjustment factor of about 1.053 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.840 to 1.781 depending on the payment segment). HCC 221 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 221 category page.
