Coronary Artery Disease (CAD) — Clinical Documentation Guide (2026)

This Clinical Documentation Guide (CDG) provides AAPC/AHIMA-credentialed coders and CDI specialists with comprehensive coding, clinical, and documentation guidance for coronary artery disease (CAD), classified under ICD-10-CM category I25 — Chronic Ischemic Heart Disease. Content reflects FY2026 ICD-10-CM guidelines effective October 1, 2025 through September 30, 2026, incorporates 2026 CPT procedure code updates, and addresses HCC v28 risk adjustment implications fully in effect for payment year 2026. Use this guide to ensure accurate diagnosis code assignment, appropriate CDI query triggers, and defensible documentation across all care settings. For acute myocardial infarction (AMI), see the separate MI Clinical Documentation Guide; I25.2 (Old myocardial infarction) is addressed briefly in Section 8 in the context of chronic CAD history.

🔍 1. Definition

Coronary artery disease (CAD) — also termed ischemic heart disease (IHD) or atherosclerotic heart disease (ASHD) — is a chronic condition characterized by the narrowing or obstruction of one or more coronary arteries due to atherosclerotic plaque accumulation within the arterial wall. The resulting reduction in coronary blood flow produces myocardial ischemia, manifesting clinically as stable angina, unstable angina, acute myocardial infarction, ischemic cardiomyopathy, or sudden cardiac death depending on the severity and acuity of the obstruction, as described by the American Heart Association.

Atherosclerosis — the underlying pathological process — begins with endothelial injury and lipid deposition forming fatty streaks, which progress to complex fibrous plaques. Plaque rupture or erosion triggers thrombosis and can cause acute coronary syndromes (ACS). Stable, obstructive plaques reduce luminal diameter, causing effort-induced angina when oxygen demand exceeds limited supply. Per the 2023 AHA/ACC Chest Pain Guideline, CAD remains the leading cause of morbidity and mortality in the United States, accounting for approximately 1 in 5 deaths annually.

CAD encompasses a spectrum including:

• Atherosclerotic heart disease of native coronary artery (I25.1x series) — the primary CAD category, with or without angina
• Ischemic cardiomyopathy (I25.5) — end-stage CAD with diffuse myocardial dysfunction
• CAD of bypass graft vessels (I25.7xx series) — atherosclerosis developing in surgical bypass conduits
• Chronic total occlusion (CTO) (I25.82) — complete coronary artery occlusion present ≥3 months
• Coronary atherosclerosis due to lipid-rich plaque (I25.83) or calcified coronary lesion (I25.84) — morphologic subtypes with distinct procedural implications

🗂️ 2. Alternative Terminology

Documentation in medical records, operative reports, and discharge summaries employs a wide range of terms that map to the I25 category. The following table summarizes key terminology coders and CDI specialists will encounter:

🩺 3. Signs & Symptoms

The clinical presentation of CAD varies substantially depending on lesion severity, acuity, and patient characteristics. Coders must document the specific manifestation, as it drives code selection:

• Stable angina: Predictable, reproducible chest pressure or tightness brought on by physical exertion or emotional stress; relieved by rest or nitroglycerin within minutes. Typically described as substernal pressure, squeezing, or heaviness, often radiating to the left arm, jaw, or back. Corresponds to I25.118 when CAD is concurrent.
• Unstable angina: New-onset angina, angina at rest, or accelerating angina (increased frequency, duration, or severity); not relieved by usual doses of nitroglycerin; requires urgent evaluation per ACC/AHA guidelines. Corresponds to I25.110 when concurrent CAD is documented.
• Variant/vasospastic angina (Prinzmetal’s): Angina occurring at rest, often in the early morning, caused by transient coronary artery spasm; may be associated with ST-segment elevation on ECG. Corresponds to I25.111.
• Dyspnea: Exertional or rest dyspnea may be the anginal equivalent, particularly in diabetic patients with autonomic neuropathy and women, per AHA Circulation (2023).
• Ischemic cardiomyopathy signs: Reduced ejection fraction, biventricular enlargement, symptoms of heart failure (dyspnea, orthopnea, edema, fatigue); I25.5 should be coded along with appropriate heart failure code (I50.xx).
• Chronic total occlusion: May be asymptomatic if collateral circulation has developed; discovered on angiography; I25.82 is an additional code to the primary CAD code.
• Silent ischemia: Objective evidence of ischemia (positive stress test, imaging) without chest pain; I25.6.

🧭 4. Differential Diagnosis

Accurate documentation requires distinguishing CAD from other conditions that mimic its presentation. The following differential diagnoses are commonly encountered in inpatient and outpatient settings:

📋 5. Clinical Indicators for Coders/CDI

The following clinical indicators, when present in the medical record, support assignment of CAD diagnosis codes and should prompt review for specificity:

🦴 6. Anatomy & Pathophysiology

Coronary Anatomy: The coronary circulation consists of two primary arteries arising from the aortic sinuses: the left main coronary artery (LMCA), which divides into the left anterior descending (LAD) and left circumflex (LCx) arteries; and the right coronary artery (RCA). The LAD supplies the anterior wall and interventricular septum; the LCx supplies the lateral wall; the RCA supplies the right ventricle and, in right-dominant systems, the inferior wall and posterior septum, as described by StatPearls — Coronary Artery Anatomy (NCBI).

Atherosclerotic Progression:

1. Endothelial dysfunction: Triggered by risk factors (hypertension, dyslipidemia, smoking, diabetes); increased permeability allows LDL infiltration
2. Foam cell formation: Oxidized LDL is engulfed by macrophages forming foam cells; fatty streak develops
3. Fibrous plaque: Smooth muscle cell migration, extracellular matrix deposition; plaque enlarges, narrowing the lumen
4. Vulnerable plaque: Thin fibrous cap, large lipid core, inflammatory infiltrate; high risk of rupture — coded as I25.83 (lipid-rich plaque)
5. Plaque rupture/erosion: Triggers platelet aggregation and thrombosis → acute coronary syndrome (coded separately as I21.xx for MI)
6. Calcification: Calcium deposits within plaque over time; may paradoxically stabilize some lesions but creates procedural challenges (I25.84)

Coronary Flow Reserve and Ischemia: Clinically significant stenosis (≥70% luminal diameter reduction, or ≥50% with fractional flow reserve [FFR] ≤0.80) impairs the coronary flow reserve — the ability to increase blood flow with increased demand. This produces supply-demand mismatch manifesting as angina with exertion. Chronic total occlusion (I25.82) represents 100% obstruction present ≥3 months; collateral circulation may preserve viability but exercise tolerance remains limited.

Ischemic Cardiomyopathy (I25.5): Chronic ischemia leads to progressive cardiomyocyte loss through necrosis, apoptosis, and hibernating myocardium. The ventricle dilates and systolic function declines, producing a phenotype similar to dilated cardiomyopathy. Per AHA Circulation, ischemic etiology accounts for approximately 60–70% of dilated cardiomyopathy cases. I25.5 should be coded with the appropriate heart failure code (I50.xx) to capture the full clinical picture.

💊 7. Medication Impact / Treatment

Medications for CAD serve dual purposes: symptom relief and secondary prevention of MI and death. Understanding the pharmacologic regimen helps coders identify clinical indicators and CDI specialists recognize documentation opportunities.

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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📘 8. ICD-10-CM Guidelines (FY2026)

The following FY2026 ICD-10-CM Official Guidelines for Coding and Reporting (Section I.C.9 — Diseases of the Circulatory System) govern CAD coding:

Atherosclerotic Coronary Artery Disease and Angina: Combination Codes

ICD-10-CM uses a combination code to identify both atherosclerosis of the coronary artery and the angina pectoris. The combination codes in category I25 are used when both atherosclerotic CAD and angina pectoris are present. A causal relationship is assumed unless the documentation indicates the angina is due to something other than the atherosclerosis. When using combination codes for CAD with angina pectoris:

• Do not assign an additional code for angina pectoris (I20.xx). The combination code captures both diagnoses.
• If a patient with CAD undergoes CABG and still has angina postoperatively, the angina must be documented relative to the graft vessels (I25.7xx series) or native vessels (I25.1xx) — this is not automatically a complication of surgery unless documented as such.

Etiology/Manifestation Convention: Old MI (I25.2)

Code I25.2 (Old myocardial infarction) — formerly the primary code for healed/resolved MI — represents a completely healed infarction with no current symptoms. Per FY2026 guidelines, I25.2 is used when the old MI is documented and relevant to the current encounter but there is no ongoing ischemic heart disease. If CAD is also present (which is almost always the case), code both I25.10 (or appropriate I25.1xx) AND I25.2 as applicable. Note: the acute MI CDG addresses I21.xx codes in detail — this guide focuses on the chronic IHD spectrum.

Post-CABG Status and Graft CAD

When a patient with a history of CABG develops atherosclerosis in the bypass graft conduits, assign codes from the I25.7xx series (not I25.1xx native artery codes), per ICD-10-CM tabular instruction. The graft type must be specified:

• I25.71x = autologous vein graft (e.g., saphenous vein)
• I25.72x = autologous artery graft (e.g., internal mammary, radial artery)
• I25.73x = nonautologous biological graft
• I25.79x = other bypass graft

Additionally assign Z95.1 (Presence of aortocoronary bypass graft) as a secondary code to indicate the surgical history. If native vessels also have CAD post-CABG, code both the graft CAD (I25.7xx) and native vessel CAD (I25.1xx).

Chronic Total Occlusion (I25.82) — Additional Code Instruction

Per the FY2026 tabular “Use Additional Code” instruction at I25, code I25.82 must be assigned as an additional code alongside the primary chronic ischemic heart disease code (e.g., I25.10). It is NOT a standalone principal diagnosis. CTO has significant procedural and clinical implications: CTO PCI is one of the most complex interventional procedures and is associated with longer fluoroscopy times, higher contrast volumes, and increased complication risk.

Cardiac Transplant CAD (I25.810–I25.811)

Cardiac allograft vasculopathy (CAV) — CAD developing in transplanted hearts — is classified as follows:

• I25.810 — Atherosclerosis of bypass graft of transplanted heart without angina
• I25.811 — Atherosclerosis of native coronary artery of transplanted heart without angina

Assign the appropriate transplant complication code (T86.298 Other complications of heart transplant) if applicable. Z94.1 (Heart transplant status) should also be coded per tabular instruction.

Coding Sequence and Principal Diagnosis

For inpatient encounters: sequence the condition that, after study, is determined to be chiefly responsible for admission. If a patient is admitted for unstable angina with known CAD, I25.110 is the appropriate principal diagnosis — not I25.10. For outpatient encounters, code the condition confirmed or established to the highest degree of certainty, consistent with ICD-10-CM Guideline Section IV.

🔢 9. ICD-10-CM Code Set (FY2026)

All codes listed below are valid for FY2026 per CMS/NCHS ICD-10-CM FY2026 tabular. Effective October 1, 2025.

Commonly Assigned Companion Codes

🔎 10. Indexing

Use the FY2026 ICD-10-CM Alphabetic Index to locate CAD codes. Key index entries include:

🏥 11. CPT (2026)

The following CPT codes apply to diagnostic and interventional procedures for CAD. The 2026 CPT code set includes important changes to the PCI series per the ACC 2026 CPT Update and CMS PCI Billing/Coding Article.

Coronary Angiography / Diagnostic Catheterization

Percutaneous Coronary Intervention (PCI) — 2026 Updated Series

CABG (Coronary Artery Bypass Graft Surgery)

🧾 12. HCPCS (2026)

📚 13. AHA Coding Clinic (Recent Guidance)

The AHA Coding Clinic is the official ICD-10-CM/PCS coding guidance publication. Relevant guidance applicable to CAD includes:

💰 14. HCC / Risk Adjustment (v28)

The CMS-HCC Model V28 is fully operative for payment year 2026 (100% v28, per CMS transition completion). Key v28 changes for CAD are significant: I25.10 (CAD without angina) is now a non-payment HCC under v28, meaning it no longer generates a risk adjustment factor score. Per AAFP Family Practice Management (2023): “Coronary atherosclerosis remains non-payment in V28, but the more severe manifestations of unstable angina (HCC 229) and acute myocardial infarction (HCC 228) are payment HCCs.”

Critical v28 Takeaways for CDI and Coding

• I25.10 generates no RAF under v28. Documenting CAD without specifying angina type misses all risk adjustment capture. Coders and CDI specialists should focus on accurate anginal classification.
• Only unstable angina (I25.110, I25.710, I25.720, etc.) triggers HCC 229 (RAF ~0.240). Stable, vasospastic, and unspecified angina with CAD (I25.111, I25.118, I25.119) are non-payment under v28 per McLaren HCC Cardiology Guide.
• I25.5 (ischemic cardiomyopathy) maps to HCC 227 (Cardiomyopathy/Myocarditis) with RAF ~0.217. When combined with heart failure codes (I50.xx → HCC 224–226), significant additive RAF impact is possible.
• MS-DRG implications: For inpatient CAD admissions, CAD with unstable angina typically groups to MDC 5 (Diseases and Disorders of the Circulatory System), MS-DRGs 282–285 (Cardiac Arrhythmias — not applicable) or more specifically MS-DRGs 313–316 (Chest Pain) or MS-DRGs related to angina. CABG procedures group to MS-DRGs 231–236 (Coronary Bypass with/without PTCA). PCI procedures group to MS-DRGs 246–251 (Percutaneous Cardiovascular Procedures with/without DES).

✍️ 15. CDI Query Templates

All query templates below follow AHIMA/ACDIS compliant query standards: non-leading, multiple-choice with clinically reasonable options, and include an “other” or “clinically undetermined” option.

🧑‍⚕️ 16. Treatments (Clinical)

Understanding treatment modalities helps coders and CDI specialists identify additional diagnoses, assess clinical complexity, and assign appropriate procedural codes.

Medical Management (Optimal Medical Therapy — OMT)

• Antiplatelet therapy: Aspirin 75–100 mg daily indefinitely; DAPT (aspirin + P2Y12 inhibitor) for ≥12 months post-ACS/PCI per ACC/AHA Guideline on the Management of Patients with Chronic Coronary Disease (2023)
• High-intensity statin therapy: Atorvastatin 40–80 mg or rosuvastatin 20–40 mg as first-line secondary prevention; LDL-C targets now refined in the 2026 AHA/ACC Dyslipidemia Guideline
• Beta-blocker therapy: Indicated post-MI and in CAD with systolic dysfunction; reduces angina frequency and MI recurrence risk
• RAAS inhibition: ACE inhibitor or ARB for all CAD patients with diabetes, hypertension, or LVEF ≤40%
• Lifestyle modification: Cardiac rehabilitation (CPT 93797–93798), diet, exercise, smoking cessation

Revascularization — PCI (Percutaneous Coronary Intervention)

PCI with drug-eluting stent (DES) is preferred over bare metal stent (BMS) for most lesion types due to lower restenosis rates. Indications include:

• Stable CAD with symptoms refractory to OMT and ischemia-guided revascularization criteria (FFR ≤0.80 or iFR ≤0.89)
• Acute coronary syndromes (STEMI: primary PCI; NSTEMI: early invasive strategy)
• Complex lesions: bifurcation lesions (CPT 92930 new for 2026), CTO (92943, 92945)
• Rotational atherectomy (92924) for severely calcified lesions (I25.84)

Revascularization — CABG (Coronary Artery Bypass Graft)

CABG is preferred over PCI for:

• Left main coronary artery disease (≥50% stenosis)
• 3-vessel CAD with reduced LVEF (EF <35%) — ischemic cardiomyopathy (I25.5)
• Multivessel CAD with diabetes (SYNTAX score-based selection)
• Complex lesions unsuitable for PCI

Standard surgical approach uses cardiopulmonary bypass (on-pump); off-pump CABG (OPCAB) is an alternative in high-risk patients. Internal mammary artery (IMA) is gold standard conduit for LAD revascularization due to superior long-term patency.

Advanced / Emerging Therapies

• Intravascular lithotripsy (IVL): For severely calcified coronary lesions (I25.84); uses Shockwave Medical device; coded under 92924 (atherectomy CPT family) pending specific CPT assignment
• Enhanced external counterpulsation (EECP): CPT 92971; for refractory angina (I25.112) not amenable to revascularization
• Transcatheter aortic valve replacement (TAVR): May be concurrent in CAD patients with aortic stenosis — separate coding required
• Cardiac rehabilitation: CPT 93797 (outpatient, no ECG monitoring); 93798 (with ECG monitoring); 12 weeks post-MI/CABG/PCI per CMS coverage

🎓 17. Patient Education / Summary

The following summary provides patient-facing language for discharge instructions and patient education materials. CDI specialists may also use these concepts to guide query wording when patients describe symptoms in lay terms.

What Is Coronary Artery Disease?

Coronary artery disease (CAD) means the arteries that supply blood to your heart muscle have become narrowed or blocked by a buildup of fatty deposits called plaque. This reduces the flow of oxygen-rich blood to the heart. When your heart doesn’t get enough blood — especially during physical activity — it can cause chest pain or pressure (called angina), shortness of breath, or other symptoms. Over time, CAD can weaken the heart muscle and lead to heart failure. In some cases, a piece of plaque can rupture and cause a heart attack.

Key Patient Education Points

• Take your medications every day. Aspirin, statins, beta-blockers, and other prescribed medications are essential even when you feel well — they protect your heart and prevent future heart attacks.
• Know your angina symptoms. Chest pressure, tightness, or heaviness with exertion that goes away with rest may be stable angina. Chest pain at rest or that is worsening needs immediate medical attention (call 9-1-1 or go to the ER).
• Report new or changing symptoms. If angina becomes more frequent, occurs at rest, or is not relieved by nitroglycerin within 15 minutes (3 doses, 5 minutes apart), call 9-1-1 immediately.
• Heart-healthy lifestyle: Eat a Mediterranean-style or heart-healthy diet low in saturated fats and sodium. Exercise regularly as recommended by your cardiologist. Quit smoking — smoking greatly accelerates coronary artery disease. Control blood pressure, blood sugar, and cholesterol.
• Cardiac rehabilitation: If recommended by your doctor, cardiac rehab is a supervised exercise and education program proven to reduce heart attack risk and improve quality of life after PCI or CABG.
• Know your numbers: LDL cholesterol, blood pressure, blood sugar (HbA1c if diabetic), and weight — all affect CAD progression.

For Post-CABG Patients

CABG (bypass surgery) creates new pathways for blood to reach your heart by using vessels from other parts of your body. The bypass grafts can also develop blockages over time — especially saphenous vein grafts. Maintaining your medications, lifestyle modifications, and follow-up care is essential to protect both the new grafts and your original heart arteries.

Resources for Patients

• American Heart Association — Coronary Artery Disease
• National Heart, Lung, and Blood Institute (NHLBI) — Coronary Heart Disease
• American College of Cardiology — CardioSmart Patient Resources

About this Guide

This Clinical Documentation Guide is published by CCO Academy and is intended for credentialed coding, CDI, and clinical documentation professionals. Content is updated for FY2026 ICD-10-CM (effective October 1, 2025). All code assignments should be verified against the official ICD-10-CM Tabular List, AHA Coding Clinic, and applicable payer-specific policies. This guide does not constitute legal, medical, or compliance advice.

Last reviewed: April 2026 · Next scheduled review: October 2026 (FY2027 update)