Cardiomyopathy — Clinical Documentation Guide (2026)

🔍 Definition

Cardiomyopathy is a heterogeneous group of diseases of the myocardium (heart muscle) associated with mechanical and/or electrical dysfunction that usually exhibits inappropriate ventricular hypertrophy or dilatation. Per the American Heart Association (AHA), cardiomyopathies are classified as either primary (predominantly affecting the heart) or secondary (resulting from a systemic or multiorgan disease process). These conditions are a leading cause of heart failure, sudden cardiac death, and cardiac transplantation in the United States.

From a coding and clinical documentation perspective, precision in identifying the type of cardiomyopathy—dilated, hypertrophic, restrictive, ischemic, infiltrative, or toxic—directly drives ICD-10-CM code selection, MS-DRG assignment, and risk-adjustment accuracy under CMS HCC v28.

🗂️ Alternative Terminology

Physicians, cardiologists, and hospitalists use varied terminology to describe cardiomyopathies. The table below lists common formal and lay terms to assist coders and CDI specialists in recognizing documentation that maps to cardiomyopathy codes.

🩺 Signs & Symptoms

Clinical presentation varies significantly by cardiomyopathy subtype. Coders and CDI specialists should recognize common signs and symptoms that frequently appear in documentation and may support or necessitate query for an underlying cardiomyopathy diagnosis.

🧭 Differential Diagnosis

Several conditions share clinical features with cardiomyopathy and must be distinguished through workup. Documentation of the final confirmed diagnosis (rather than symptoms or “rule-out” diagnoses) drives ICD-10-CM code selection per ICD-10-CM Official Guidelines FY2026, Section II (Hospital Inpatient).

📋 Clinical Indicators for Coders/CDI

CDI specialists and coders should recognize these documentation elements as indicators that a cardiomyopathy diagnosis may be present or should be queried. Per AHA Coding Clinic guidance, coders may query when clinical indicators are present but a confirmed diagnosis has not been documented by the treating physician.

🦴 Anatomy & Pathophysiology

The myocardium consists of cardiomyocytes—specialized muscle cells organized into a syncytium that enables coordinated contraction. Cardiomyopathies disrupt this architecture through distinct pathophysiologic mechanisms that determine both clinical presentation and coding category:

• Dilated Cardiomyopathy (DCM): Characterized by ventricular chamber enlargement and systolic dysfunction (reduced LVEF). The myocardium undergoes eccentric hypertrophy with sarcomere disarray, interstitial fibrosis, and myocyte loss. Causes include genetic mutations, viral myocarditis, alcohol toxicity, and chemotherapy-induced damage (e.g., anthracyclines). Per AHA/ACC 2023 HCM Guidelines, DCM is the most common form requiring cardiac transplantation.
• Hypertrophic Cardiomyopathy (HCM): Defined by unexplained left ventricular hypertrophy (LVH) without a secondary cause. Sarcomere gene mutations (MYH7, MYBPC3) disrupt cross-bridge cycling, producing myocyte disarray, microvascular dysfunction, and fibrosis. The obstructive subtype (HOCM) features dynamic left ventricular outflow tract (LVOT) obstruction due to systolic anterior motion (SAM) of the mitral valve leaflet.
• Restrictive Cardiomyopathy: The least common primary cardiomyopathy. Normal or near-normal wall thickness with severely impaired diastolic filling due to myocardial stiffness. Idiopathic or secondary to infiltrative disease (amyloidosis, sarcoidosis, hemochromatosis).
• Ischemic Cardiomyopathy: Results from significant coronary artery disease producing extensive myocardial scarring, hibernating myocardium, and remodeling, leading to global or regional systolic dysfunction. Classified under I25.5 in ICD-10-CM per ICD-10-CM FY2026 Official Guidelines.
• Takotsubo/Stress Cardiomyopathy: Transient, reversible LV dysfunction triggered by intense emotional or physical stress, leading to catecholamine surge and microvascular spasm. Classic apical ballooning pattern on ventriculography. Coded as I51.81 per FY2026 tabular.
• Amyloid Cardiomyopathy: Extracellular amyloid fibril deposition stiffens the myocardium, producing restrictive physiology. Transthyretin amyloidosis (ATTR) and light-chain amyloidosis (AL) are the two principal cardiac subtypes. Coded via I43 with additional amyloidosis code (E85.x).

💊 Medication Impact / Treatment

Pharmacologic therapy for cardiomyopathy is highly subtype-specific. Coders and CDI specialists must recognize medications listed in the record as indicators of underlying cardiomyopathy type and associated conditions (e.g., heart failure, atrial fibrillation).

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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📘 ICD-10-CM Guidelines (FY2026)

The following guidelines govern cardiomyopathy coding under the ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. These are mandatory for all inpatient and outpatient encounters.

Principal Diagnosis Selection (Inpatient)

Per ICD-10-CM Guidelines Section II, the principal diagnosis for an inpatient admission should reflect the condition established after study to be chiefly responsible for the admission. When a patient is admitted for cardiomyopathy with acute decompensated heart failure, query the attending physician to determine which condition drove the admission to ensure correct principal diagnosis selection.

Cardiomyopathy with Heart Failure

When cardiomyopathy and heart failure coexist, both conditions should be coded. Per AHA Coding Clinic guidance, cardiomyopathy is not the same as heart failure—they are distinct diagnoses. The HF code (I50.x) is assigned as an additional diagnosis unless it is the principal diagnosis for the encounter. The sequencing depends on the reason for the encounter.

Hypertensive Heart Disease + Cardiomyopathy

Per ICD-10-CM Guidelines Section I.C.9, hypertensive heart disease (I11.x) presumes a causal relationship between hypertension and heart failure when both conditions are documented. However, hypertensive cardiomyopathy is not equivalent to hypertrophic or dilated cardiomyopathy. If the physician documents a specific cardiomyopathy etiology separate from hypertension, both may be coded.

Cardiomyopathy in Diseases Classified Elsewhere (I43)

Category I43 is used for cardiomyopathy manifesting as part of a systemic disease. This is an etiology/manifestation code pair. The systemic disease (e.g., amyloidosis E85.x, sarcoidosis D86.85, hemochromatosis E83.110) is coded first, followed by I43 as the manifestation. Per the ICD-10-CM tabular, I43 has a “code first” instruction that must be followed.

Ischemic Cardiomyopathy (I25.5)

I25.5 (Ischemic cardiomyopathy) is indexed under coronary artery disease category I25. Per AHA Coding Clinic, when a patient has both ischemic cardiomyopathy (I25.5) and heart failure, assign I25.5 plus the appropriate I50.x code. Do not assign both I42.x (non-ischemic cardiomyopathy) and I25.5 for the same cardiomyopathy.

Peripartum Cardiomyopathy

Peripartum cardiomyopathy developing in the last month of pregnancy through 5 months postpartum is coded O90.3 (Peripartum cardiomyopathy) per the obstetric chapter guidelines. For subsequent encounters after the peripartum period, revert to I42.x if the condition persists.

Takotsubo Cardiomyopathy (I51.81)

Takotsubo (stress) cardiomyopathy was reclassified in FY2022 to I51.81. Do not use I42.9 (unspecified) for documented takotsubo. If heart failure occurs in the context of takotsubo, code both I51.81 and the appropriate I50.x.

🔢 ICD-10-CM Code Set (FY2026)

All codes below are valid under the ICD-10-CM FY2026 tabular list effective October 1, 2025.

Primary Cardiomyopathy Codes (I42.x)

Cardiomyopathy in Other Diseases (I43)

Ischemic and Hypertensive-Related Codes

Commonly Associated Additional Codes

🔎 Indexing

The following alphabetic index entries from the ICD-10-CM Alphabetic Index (FY2026) guide code lookup for cardiomyopathy:

• Cardiomyopathy — Main term; see subtypes below
• Cardiomyopathy, alcoholic → I42.6
• Cardiomyopathy, dilated → I42.0
• Cardiomyopathy, hypertrophic, obstructive → I42.1
• Cardiomyopathy, hypertrophic, nonobstructive → I42.2
• Cardiomyopathy, restrictive → I42.5
• Cardiomyopathy, in (due to) amyloidosis → See I43 “code first” amyloidosis (E85.x)
• Cardiomyopathy, ischemic → I25.5
• Cardiomyopathy, nutritional → I42.8 (index via “Beriberi, cardiac” or “deficiency, thiamine”)
• Cardiomyopathy, stress-induced / Takotsubo → I51.81 (index as “Takotsubo syndrome” or “Syndrome, takotsubo”)
• Cardiomyopathy, peripartum → O90.3 (index as “Cardiomyopathy, in pregnancy”)
• Cardiomyopathy, drug-induced → I42.7 (requires additional adverse effect code T36–T50 or code external cause if toxic)

🏥 CPT (2026)

The following AMA CPT 2026 codes are most relevant to cardiomyopathy diagnosis, monitoring, and interventional management.

Echocardiography

Cardiac MRI

Invasive / Interventional Procedures

🧾 HCPCS (2026)

HCPCS Level II codes apply to durable medical equipment, devices, and supplies related to cardiomyopathy management, particularly for LVAD systems and remote heart failure monitoring.

📚 AHA Coding Clinic (Recent Guidance)

The following AHA Coding Clinic advisories are particularly relevant to cardiomyopathy coding. Coders should apply these consistently and document the reference when questioned in an audit.

💰 HCC / Risk Adjustment (v28)

Under the CMS-HCC Risk Adjustment Model version 28 (effective January 1, 2024 for MA plans), cardiomyopathy maps to specific HCC categories that drive risk-adjustment factor (RAF) scores for Medicare Advantage and Part C plans.

MS-DRG Impact: For inpatient encounters, cardiomyopathy with heart failure typically maps to MS-DRG 291–293 (Heart Failure and Shock) when HF is the principal diagnosis. Cardiomyopathy as a secondary diagnosis adds to CC/MCC severity when appropriately documented. ICD/LVAD insertion encounters map to MS-DRG 515–517 and 001–002 respectively, with significant reimbursement implications.

✍️ CDI Query Templates

All query templates below are constructed per ACDIS and AHIMA compliant query standards: non-leading, multiple-choice format with clinical indicators cited, and a “clinically undetermined” option. Queries must be signed/responded to by the treating, attending, or consulting physician.

🧑‍⚕️ Treatments (Clinical)

Clinical management of cardiomyopathy is individualized by subtype, disease severity, and comorbidities. The following overview assists CDI specialists in understanding the treatment context that surrounds documentation queries.

Dilated Cardiomyopathy (DCM)

Guideline-directed medical therapy (GDMT) per 2022 AHA/ACC/HFSA Heart Failure Guidelines includes: ACE inhibitors or ARBs (or ARNI for HFrEF), beta-blockers (carvedilol, metoprolol succinate, or bisoprolol), mineralocorticoid receptor antagonists (spironolactone, eplerenone), and SGLT2 inhibitors (dapagliflozin, empagliflozin). Device therapy includes ICD (LVEF ≤35%) and CRT-D (LVEF ≤35% with LBBB QRS ≥150 ms). Advanced refractory DCM may require LVAD (CPT 33979) as bridge-to-transplant or destination therapy.

Hypertrophic Cardiomyopathy (HCM)

For obstructive HCM (I42.1), first-line therapy includes non-vasodilating beta-blockers (metoprolol, propranolol) or non-dihydropyridine calcium channel blockers (verapamil, diltiazem). Disopyramide can be added for refractory obstruction. Mavacamten (Camzyos), a cardiac myosin inhibitor, is FDA-approved (2022) for symptomatic obstructive HCM. For drug-refractory obstruction, surgical septal myectomy (CPT 33416) or alcohol septal ablation (CPT 93583) may be performed. SCD prevention with ICD implantation (CPT 33249) uses risk calculators incorporating LVH severity, syncope, family history of SCD, and NSVT.

Restrictive Cardiomyopathy

Treatment is largely supportive. For amyloid cardiomyopathy, tafamidis (Vyndaqel/Vyndamax) is FDA-approved for ATTR and reduces cardiovascular mortality. AL amyloidosis requires hematologic treatment (daratumumab-based regimens). Cardiac transplantation may be considered in end-stage disease.

Advanced Heart Failure / End-Stage Cardiomyopathy

LVAD implantation (HeartMate 3, HVAD) as destination therapy (DT) or bridge-to-transplant (BTT) is indicated for INTERMACS profiles 1–4 per ISHLT guidelines. Documentation should specify LVAD indication (DT vs. BTT), device model, and operative details for accurate DRG assignment (MS-DRG 001–002).

🎓 Patient Education / Summary

Patient and family education for cardiomyopathy supports adherence, reduces hospital readmissions, and is a component of CMS quality measures for heart failure. The following key points summarize what patients and caregivers should understand:

• What is cardiomyopathy? It is a disease of the heart muscle that makes it harder for the heart to pump blood effectively. There are several types, and the treatment depends on the specific type.
• Signs to report immediately: Sudden shortness of breath, rapid weight gain (more than 2–3 pounds in a day), worsening swelling in legs, chest pain, or fainting. These may signal decompensated heart failure.
• Medications: Take all prescribed medications even when feeling well. Do not stop beta-blockers or diuretics without physician guidance. Report any new medications (including OTC and supplements) to your care team.
• Activity and lifestyle: Regular moderate exercise is encouraged for most cardiomyopathy patients under physician guidance. High-intensity competitive sports are generally restricted in hypertrophic cardiomyopathy. Alcohol abstinence is mandatory for alcoholic cardiomyopathy.
• Device awareness (ICD/LVAD): Patients with an ICD should understand what to do if the device fires. LVAD patients require daily device checks and driveline site care to prevent infection.
• Follow-up and monitoring: Regular echocardiograms and cardiology visits are essential. Many patients will require genetic counseling, particularly those with hypertrophic or dilated familial cardiomyopathies, as first-degree relatives may need screening.
• Sources for patients: American Heart Association — Cardiomyopathy, Hypertrophic Cardiomyopathy Association (HCMA), Amyloidosis Research Consortium.

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)