What is ICD-10 code I77.71?

I77.71 is the ICD-10-CM diagnosis code for Dissection of carotid artery. A tear in the inner lining of the carotid artery in the neck, which can reduce blood flow to the brain and increase stroke risk. I77.71 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I77.71 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. I77.71 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. I77.71 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for I77.71?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. I77.71 was a payment HCC under V24 (Vascular Disease with Complications) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I77.71?

Specify laterality (right or left) when documented for more precise coding Often associated with neck trauma, sudden head turning, or can occur spontaneously Because I77.71 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM I77.71: Dissection of carotid

ICD-10-CM Code View

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Code lookupI77.71Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Diseases of arteries, arterioles and capillaries (I70-I79)

I77.71

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Dissection of carotid artery

A tear in the inner lining of the carotid artery in the neck, which can reduce blood flow to the brain and increase stroke risk.

Buddy Insight

Dissection of the carotid artery is a critical vascular condition that poses significant stroke risk due to the carotid artery's role in supplying blood to the brain.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 107

Vascular Disease with Complic...

RAF 0.383

ACA/HHS

Mapped

HCC 154

HHS-HCC 154

Varies by metal level

ESRD/PACE

Mapped

HCC 107

Vascular Disease with Complic...

RAF 0.144

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

I77Other disorders of arteries and arterioles

I77.7Other arterial dissection

I77.71Dissection of carotid artery

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for I77.71 in this effective period.

Excludes 2

Official

dissection of aorta (I71.0-)
dissection of coronary artery (I25.42)

Related Child Codes

Official

I77.70Dissection of unspecified artery

I77.72Dissection of iliac artery

I77.73Dissection of renal artery

I77.74Dissection of vertebral artery

I77.75Dissection of other precerebral arteries

Includes

Official

ICD-10-CM does not list Includes notes for I77.71 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I77.71 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I77.71 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I77.71 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I77.71 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Imaging confirmation of carotid artery dissection (CT angiography, magnetic resonance angiography, or ultrasound)

Laterality — right, left, or bilateral carotid involvement

Acuity — acute, subacute, or chronic/healed status

Neurological assessment including presence or absence of stroke symptoms

MEAT Support

HCC Buddy guidance

Imaging confirmation of carotid artery dissection (CT angiography, magnetic resonance angiography, or ultrasound)

Laterality — right, left, or bilateral carotid involvement

Acuity — acute, subacute, or chronic/healed status

Neurological assessment including presence or absence of stroke symptoms

Audit Caution

HCC Buddy guidance

Failing to capture laterality of the carotid dissection when documented

Confusing carotid dissection with carotid stenosis due to atherosclerosis

Not coding associated stroke or transient ischemic attack when documented alongside the dissection

Using I77.70 (unspecified) when the carotid artery is clearly identified in documentation

Common Mistakes

HCC Buddy guidance

I77.70 — Dissection of unspecified artery: less specific; use I77.71 when carotid is documented

I65.2x — Occlusion and stenosis of carotid artery: use for atherosclerotic narrowing, not dissection

I71.01 — Dissection of thoracic aorta: different vessel entirely

I67.0 — Dissection of cerebral arteries: for intracranial arteries, not extracranial carotid

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is I77.71 an HCC code?

Yes. I77.71 maps to Vascular Disease with Complications under the V24 model but is not retained in V28.

Code: I77.71
Description: Dissection of carotid artery
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 107, Vascular Disease with Complications

0.383

ESRDHCC 107, Vascular Disease with Complications

0.144

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work I77.71 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I77.71

For I77.71 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed I77.71 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I77.71 is the ICD-10-CM diagnosis code for dissection of carotid artery. A tear in the inner lining of the carotid artery in the neck, which can reduce blood flow to the brain and increase stroke risk. I77.71 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering diseases of arteries, arterioles and capillaries (i70-i79).

Under the older CMS-HCC V24 model, I77.71 maps to Vascular Disease with Complications (HCC 107) with a community, non-dual, aged base RAF weight of 0.383. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Specify laterality (right or left) when documented for more precise coding. Because I77.71 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for I77.71 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Specify laterality (right or left) when documented for more precise coding
•Often associated with neck trauma, sudden head turning, or can occur spontaneously

Clinical Significance

Dissection of the carotid artery is a critical vascular condition that poses significant stroke risk due to the carotid artery's role in supplying blood to the brain. This condition requires urgent evaluation and management to prevent cerebrovascular events. It reflects high clinical complexity and ongoing monitoring needs, mapping to the higher-weighted vascular disease with complications category.

Documentation Requirements

✓Imaging confirmation of carotid artery dissection (CT angiography, magnetic resonance angiography, or ultrasound)
✓Laterality — right, left, or bilateral carotid involvement
✓Acuity — acute, subacute, or chronic/healed status
✓Neurological assessment including presence or absence of stroke symptoms
✓Treatment plan including anticoagulation, antiplatelet therapy, or surgical intervention
✓Follow-up imaging schedule to monitor healing or progression

Commonly Confused Codes

•I77.70: Dissection of unspecified artery: less specific; use I77.71 when carotid is documented
•I65.2x: Occlusion and stenosis of carotid artery: use for atherosclerotic narrowing, not dissection
•I71.01: Dissection of thoracic aorta: different vessel entirely
•I67.0: Dissection of cerebral arteries: for intracranial arteries, not extracranial carotid