Cardiomyopathy is a heterogeneous group of diseases of the myocardium in which the heart muscle is structurally and/or functionally abnormal — in the absence of coronary artery disease, hypertension, valvular disease, or congenital heart disease sufficient to explain the observed dysfunction. It is distinguished from heart failure (a syndrome of symptoms) and from ischemic heart disease (where myocardial dysfunction is secondary to coronary obstruction), though all three frequently coexist and overlap. The underlying pathological mechanisms vary by type: dilated cardiomyopathy (I42.0) involves ventricular dilation and systolic dysfunction due to myocyte loss and fibrosis; hypertrophiccardiomyopathy (I42.1, I42.2) involves asymmetric septal hypertrophy with diastolic dysfunction, often genetic in origin; and restrictive cardiomyopathy (I42.5) involves stiffening of the ventricular walls with impaired filling and preserved or reduced ejection fraction. Cardiomyopathy may be physiological (e.g., athlete’s heart — characterized by benign symmetric hypertrophy) or pathological (e.g., hypertrophic obstructive cardiomyopathy, peripartum cardiomyopathy O90.3). Clinically relevant subtypes most commonly encountered in coding include dilated (I42.0), obstructive hypertrophic (I42.1), non-obstructive hypertrophic (I42.2), endomyocardial (I42.3), endocardial fibroelastosis (I42.4), restrictive (I42.5), alcoholic (I42.6), and cardiomyopathy due to drug and external agents (I42.7). It is commonly confused with myocarditis — the key difference is that myocarditis is an acute inflammatory process (often viral) while cardiomyopathy refers to a chronic structural disease of the myocardium itself.
The word entered English in the 1950s as cardiomyopathy (noun), constructed from New Latin medical terminology drawing on Greek kardia (“heart”) + mys/myos (“muscle”) + pathos (“disease, suffering”) — literally “a disease condition of the heart muscle.” The root myo- (“muscle”) connects Cardiomyopathy to the entire -myo- ROOT FAMILY: myocarditis (inflammation of the heart muscle), myopathy (disease of skeletal muscle), and myositis (inflammation of muscle). The combining formcardio- is highly productive in medical terminology, appearing in cardiovascular, cardiology, cardiomegaly, cardiothoracic, and cardioplegia.
🔀 ALIASES / ALTERNATE TERMS
Cardiomyopathic(adjective form — clinical collocations include “cardiomyopathic changes,” “cardiomyopathic process,” “cardiomyopathic remodeling”)
Heart muscle disease(lay and clinical synonym; used in patient education and general cardiology contexts)
Myocardial disease(clinical synonym; used interchangeably in inpatient cardiology documentation)
Dilated cardiomyopathy (DCM)(most common subtype; characterized by ventricular dilation and systolic dysfunction; coded I42.0)
Hypertrophic obstructive cardiomyopathy (HOCM)(obstructive form with left ventricular outflow tract obstruction; ICD-10-CM I42.1; also called IHSS — idiopathic hypertrophic subaortic stenosis)
Hypertrophic non-obstructive cardiomyopathy(non-obstructive form without outflow tract gradient; I42.2)
Restrictive cardiomyopathy (RCM)(stiff, non-compliant ventricle with preserved or reduced EF; may be idiopathic or secondary to infiltrative disease such as amyloidosis or sarcoidosis; I42.5)
Alcoholic cardiomyopathy(cardiomyopathy directly caused by chronic, excessive alcohol consumption; I42.6)
Peripartum cardiomyopathy(cardiomyopathy arising in the last month of pregnancy or within 5 months postpartum; O90.3)
Ischemic cardiomyopathy(cardiomyopathy resulting from chronic myocardial ischemia and infarction; classified under ischemic heart disease categories rather than I42)
Takotsubo cardiomyopathy(stress-induced transient cardiomyopathy; also called apical ballooning syndrome or broken heart syndrome; I51.81)
Arrhythmogenic right ventricular cardiomyopathy (ARVC)(fibro-fatty replacement of right ventricular myocardium; associated with life-threatening arrhythmias; I42.8)
🔗 RELATED TERMS
Myocarditis — the acute inflammatory counterpart to cardiomyopathy; myocarditis is an active inflammatory process (often viral, autoimmune, or toxic) of the myocardium, while cardiomyopathy is a chronic structural disease — acute myocarditis can evolve into dilated cardiomyopathy (I42.0) over time
Heart failure — the downstream syndrome most commonly caused by cardiomyopathy; heart failure (I50.x) describes the clinical syndrome of reduced cardiac output, while cardiomyopathy describes the structural myocardial disease driving it — both codes are assigned when documented
Myocardium — the heart muscle tissue that is the primary anatomic site of cardiomyopathy; shares the myo- root
Cardiomegaly — enlargement of the heart as a whole; shares the cardio- root; often a radiographic finding in dilated cardiomyopathy (I51.7); not synonymous with cardiomyopathy
Ventricular remodeling — the structural and functional changes in ventricular geometry (dilation, hypertrophy, fibrosis) that characterize cardiomyopathy progression; the central pathophysiological mechanism
Fibrosis — replacement of functional myocytes with fibrous scar tissue; a key histological feature of dilated and end-stage cardiomyopathy
Apoptosis — programmed cell death of cardiomyocytes; a cellular mechanism underlying the myocyte loss seen in dilated cardiomyopathy
Amyloidosis — infiltrative systemic disease that deposits amyloid protein in the myocardium, causing restrictive cardiomyopathy (E85.82 — cardiac amyloidosis); commonly coded as secondary cardiomyopathy
Sarcoidosis — granulomatous systemic disease that can involve the myocardium, causing restrictive or dilated cardiomyopathy and arrhythmias (D86.85 — sarcoid cardiomyopathy)
Hemochromatosis — iron overload disorder that deposits iron in myocardial tissue, causing restrictive cardiomyopathy (E83.110 — hereditary hemochromatosis)
Ejection fraction (EF) — the percentage of blood ejected from the left ventricle per beat; the primary echocardiographic measure used to classify and monitor cardiomyopathy (normal ≥55%; reduced in DCM; often preserved in HCM and RCM)
Echocardiography — the primary diagnostic imaging tool for evaluating cardiomyopathy type, severity, and hemodynamic impact
CODING CORNER
🏥 ICD-10-CM CODES
Cardiomyopathy — Primary/Intrinsic Forms (I42.x — Type Specificity Required)
Code
Description
I42.0
Dilated cardiomyopathy
I42.1
Obstructive hypertrophic cardiomyopathy (HOCM)
I42.2
Other hypertrophic cardiomyopathy (non-obstructive)
🔧 COMMON CPT CODES (Cardiomyopathy-Related Diagnosis & Treatment)
CPT Code
Description
93306
Echocardiography, transthoracic, real-time with image documentation (2D), includes M-mode recording, complete study with spectral Doppler and color flow Doppler — primary diagnostic tool for cardiomyopathy evaluation
93307
Echocardiography, transthoracic, real-time with image documentation (2D), complete study without spectral or color Doppler
93308
Echocardiography, transthoracic, real-time (2D), follow-up or limited study
93303
Transthoracic echocardiography for congenital cardiac anomalies — complete study
93304
Transthoracic echocardiography for congenital cardiac anomalies — follow-up or limited
93351
Echocardiography, transthoracic, real-time with image documentation — complete study performed during rest and cardiovascular stress testing (treadmill/pharmacological)
93015
Cardiovascular stress test using maximal or submaximal treadmill or bicycle exercise — complete procedure with physician supervision, interpretation and report
93016
Cardiovascular stress test — physician supervision only, without interpretation and report
93018
Cardiovascular stress test — interpretation and report only
93000
Electrocardiogram, routine ECG with at least 12 leads; with interpretation and report
93010
Electrocardiogram, routine ECG with at least 12 leads; interpretation and report only
93280
Programming device evaluation (in person) with iterative adjustment of the implantable device to test the function of the device and select optimal permanent programmed values — single chamber ICD (commonly placed for cardiomyopathy with reduced EF ≤35%)
93282
Programming device evaluation — dual chamber ICD
93285
Programming device evaluation — subcutaneous ICD
33249
Insertion or replacement of permanent implantable defibrillator (ICD) system with transvenous lead(s); single or dual chamber — primary prevention in cardiomyopathy with EF ≤35%
33270
Insertion or replacement of subcutaneous implantable defibrillator system (S-ICD)
⚠️ Coding Note: The I42.x category requires type specificity — never assign I42.9 (unspecified) when documentation supports a more specific subtype such as dilated (I42.0), obstructive hypertrophic (I42.1), or alcoholic (I42.6); a physician query is warranted when documentation says only “cardiomyopathy” without type designation. For secondary cardiomyopathy (e.g., due to amyloidosis, sarcoidosis, hemochromatosis, or drug toxicity), use I43 and sequence the underlying etiology first per the etiology/manifestation convention — the I43 code never stands alone. A common undercoding alert on inpatient profee claims: when a provider documents “dilated heart,” “ventricular dilation,” or “reduced EF” without explicitly naming cardiomyopathy, query the attending — this clinical picture typically supports I42.0 and significantly impacts DRG assignment and CC/MCC capture. For I42.7 (cardiomyopathy due to drug/external agent), an additional code for adverse effect (T36-T65 with 5th/6th character for intent) is required, and payers such as Medicare and BCBS may require documentation of the specific causative agent in the claim record. When cardiomyopathy coexists with heart failure, code both — the cardiomyopathy as the underlying structural disease and the specific heart failure type (I50.x) as a secondary diagnosis, selecting the most specific heart failure code based on systolic vs. diastolic and acute vs. chronic status.
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