| name | cardiomyopathy-etiology-identifier |
| description | Identify the likely cause of a newly-diagnosed cardiomyopathy or unexplained heart failure by systematic red-flag pattern matching across history, examination, ECG, echo, and initial labs. Use when a clinician asks "what is causing this cardiomyopathy", "unexplained LV dysfunction workup", "which cardiomyopathy is this", "DCM etiology workup", "new HF with unclear cause", "cardiomyopathy red flags", or presents a case of new-onset HF or ventricular dysfunction and needs to narrow the differential. Applies to adults and to children — including those with congenital heart disease. Grounded in UpToDate (Colucci, Mar 2026) and the 2024 AHA Scientific Statement on chronic HF in pediatric CHD (Amdani et al). |
Cardiomyopathy Etiology Identifier
Turn a new HF or cardiomyopathy presentation into an etiology shortlist by systematic red-flag pattern matching. This skill identifies the likely cause — it does not treat. Use it before deciding on confirmatory testing, biopsy, or genetic panels.
Step 1 — Gate: is this actually a cardiomyopathy?
Proceed only if any of the following:
- Symptomatic HF (dyspnoea, fatigue, oedema) with structural or functional cardiac impairment
- Reduced systolic function on echo:
- Adults: LVEF ≤40% (HFrEF), 41–49% (HFmrEF), ≥50% + diastolic dysfunction (HFpEF)
- Paediatric CHD (systemic LV): mild 41–51%, moderate 30–40%, severe <30%
- Paediatric CHD (systemic or subpulmonary RV): RVEF <40% by CMR OR RVFAC <35% on echo
- Unexplained ventricular dilatation, hypertrophy, or wall motion abnormality on imaging
If none present, this is not a cardiomyopathy — stop.
Step 2 — Context stratify before pattern matching
Answer three questions first:
- Age band — adult (≥18) or paediatric (<18)
- Congenital heart disease present — yes / no. If yes, address the primary lesion first (residual shunt, valve regurgitation, coarctation, hypoxia) before attributing the dysfunction to a cardiomyopathy
- EF phenotype — reduced (HFrEF/HFmrEF) or preserved (HFpEF) — this shapes which etiologies to prioritise
Step 3 — Systematic red-flag scan
Walk through each row. Any trigger adds that etiology to the shortlist. Do NOT stop at the first hit — multiple etiologies can coexist.
3a. History red flags
| Trigger | Suspect |
|---|
| Classic exertional angina; prior MI; smoker; DM; dyslipidaemia; age >40 M / >50 F | Ischemic cardiomyopathy (the most common HFrEF etiology in adults — always test for CAD in new HFrEF unless another cause is very well established) |
| Antecedent flu-like illness (days to weeks) → new HF | Viral myocarditis |
| Long-standing untreated hypertension | Hypertensive cardiomyopathy |
| Chronic heavy alcohol intake | Alcohol-induced cardiomyopathy |
| Last month of pregnancy through 5 months post-partum | Peripartum cardiomyopathy |
| Known HIV | HIV cardiomyopathy |
| Prior anthracycline, trastuzumab, immune checkpoint inhibitor, TKI | Chemotherapy-induced cardiomyopathy (doxorubicin classic) |
| Family history: unexplained HF <60 yrs; SCD without ischaemia; prior HF transplant; ICD | Familial / inherited cardiomyopathy |
| Persistent tachyarrhythmia (AF with RVR, frequent PVCs, incessant SVT/VT) that preceded LV dysfunction | Tachycardia-mediated / arrhythmia-induced cardiomyopathy |
| Recent NSAID, verapamil, disopyramide, flecainide, β-blocker overuse | Drug-provoked HF exacerbation (not a primary CMP) |
| Acute pulmonary oedema during / shortly after transfusion | Volume overload — not CMP |
3b. Physical examination red flags
| Trigger | Suspect |
|---|
| Cardiac murmur | Primary valvular cause of HF |
| Cirrhosis + diabetes + skin pigmentation ("bronze diabetes") | Hereditary haemochromatosis — but iron studies even without the full triad, as cardiac disease can be the presenting feature |
| Periorbital purpura | Nearly pathognomonic for AL cardiac amyloidosis |
| Peripheral neuropathy | AL or hereditary ATTR amyloidosis |
| Skeletal myopathy | Duchenne/Becker muscular dystrophy; mitochondrial myopathy; laminopathy; sarcoglycanopathy |
| Noonan syndrome features (short stature, pectus, hypertelorism, webbed neck) + CHD | Consider HCM on Noonan background (higher HF-presenting rate than other HCM) |
| Hypertension present | HTN as cause or contributor — never assume it's only a bystander |
3c. ECG red flags
| Pattern | Suspect |
|---|
| Coronary-distribution Q waves; prior infarct pattern | Ischemic cardiomyopathy |
| LV hypertrophy voltage + pseudoinfarct pattern | Hypertensive CMP or HCM |
| Low limb-lead voltage + pseudoinfarct (loss of R progression V1–V6) | Infiltrative — cardiac amyloidosis |
| Low limb voltage + precordial LVH criteria + widened QRS or LBBB | Idiopathic dilated cardiomyopathy |
| Complete heart block or unusual intraventricular conduction defect | Cardiac sarcoidosis |
| Persistent AF with rapid ventricular response | Tachycardia-mediated CMP |
| Epsilon wave; TWI V1–V3; ventricular ectopy of LBBB morphology | Arrhythmogenic RV cardiomyopathy (ARVC) |
| 1° AV block + LBBB + non-specific IVCD | Consistent with DCM (non-specific) |
3d. Echo red flags
| Finding | Suspect |
|---|
| Four-chamber dilation with reduced LV systolic function | Idiopathic dilated cardiomyopathy |
| Regional wall motion abnormality in a coronary distribution | Ischemic CMP — but note 50–60% of idiopathic DCM also have RWMA; not specific |
| Dobutamine echo showing ≥6 akinetic segments | 80% sensitive / 96% specific for ischemic dilated cardiomyopathy |
| Concentric LVH without hypertension; "sparkling" myocardium; biatrial dilation; thickened valves; small LV cavity; grade-3 diastolic dysfunction | Cardiac amyloidosis |
| Severe LVH + LVOT obstruction ± SAM | HCM |
| Enlarged RV with RV dysfunction | ARVC — or PH / RV volume overload |
| Spongy myocardium with deep intertrabecular recesses | LV noncompaction |
| Pericardial thickening + preserved EF + diastolic dysfunction | Constrictive pericarditis (not CMP) |
| Intracardiac shunt or valve abnormality | Structural / congenital heart disease — return to Step 2 |
| Elevated E/e' >15 | Elevated PCWP consistent with HFpEF |
3e. Initial labs
| Finding | Suspect |
|---|
| Elevated ferritin + high transferrin saturation | Hereditary haemochromatosis |
| Abnormal SPEP / UPEP / serum free light chains | AL cardiac amyloidosis |
| Positive HIV serology | HIV CMP |
| Positive ANA / connective tissue serology | Connective tissue / lupus CMP |
| TSH abnormal | Thyroid-precipitated HF |
| Peripheral eosinophilia | Löffler / eosinophilic cardiomyopathy |
| Low thiamine, carnitine, or selenium | Nutritional / metabolic CMP |
| Elevated troponin persistently (no ACS) | Myocarditis; sarcoidosis; ATTR |
Step 4 — Etiology shortlist → confirmatory test map
For each shortlisted etiology, order the specific next test — do NOT do all of them.
| Suspected etiology | Confirmatory test |
|---|
| Ischemic CMP | Coronary angiography (high probability); CCTA or stress imaging (low–moderate probability) |
| AL amyloidosis | SPEP + UPEP + serum free light chains → fat pad or endomyocardial biopsy for Congo red |
| ATTR amyloidosis | ⁹⁹ᵐTc-PYP (or DPD/HMDP) scan; TTR genetic testing if positive |
| Cardiac sarcoidosis | CMR with late gadolinium AND/OR FDG-PET; extracardiac biopsy where possible; consider EMB |
| Haemochromatosis | Ferritin + transferrin saturation → HFE genotyping if positive |
| Fulminant myocarditis (new HF <2 weeks + haemodynamic compromise, OR unexplained new HF + early AV block / arrhythmia / refractory course) | Endomyocardial biopsy — one of the few clear EMB indications |
| Peripartum CMP | Clinical timing + rule out other causes; consider genetic testing |
| HCM / DCM / ARVC / LVNC / RCM (familial) | See Step 5 for genetic panel threshold |
| Chemotherapy-induced | Timeline correlation + serial echo (GLS) + CMR for microstructure |
| Tachycardia-mediated CMP | Rhythm control trial — reassess EF at 3–6 months; near-normalisation is diagnostic |
Interpretation trap: nonobstructive CAD on angiography ≠ ischemic cardiomyopathy. Attribute to ischaemia only if there is prior infarct, viable but hibernating myocardium, or no other explanation.
Step 5 — Genetic testing threshold
Test when either of the following:
- Clinical findings clearly point to an inherited CMP phenotype (HCM, ARVC, LVNC, familial DCM, RCM), OR
- Family history contains ≥1 of:
- Unexplained HF before age 60
- SCD without ischaemia or ICD therapy
- Prior heart transplant or mechanical circulatory support in a relative
"Unexplained" DCM without family history — score for genetic likelihood.
Each of the following raises gene-positive probability (each OR ~2–4; ~20% per factor):
Refer for genetic testing / counsellor when ≥2 factors are present. Test a broad panel unless a specific disease is clearly suspected.
Paediatric CHD population — additional genetic-test triggers:
- Phenotypic features of cardiomyopathy in a CHD patient
- Ventricular dysfunction that is disproportionate to the anatomical lesion
- Syndromic features / suggestive lesions: Noonan, Ebstein, HLHS, LVNC → target α-dystrobrevin, β-myosin heavy chain (MYH7), NKX2.5, sarcomeric panel
Step 6 — Family screening once inherited CMP is confirmed or strongly suspected
Screen first-degree relatives regardless of genotype result (progressive disease can appear in asymptomatic mutation carriers).
Baseline screen: history + exam + ECG + echo + CK-MM (once).
Rescreen intervals by CMP type:
| CMP | Rescreen |
|---|
| HCM | Every 3 yrs; yearly during puberty; until age 30 |
| DCM | Every 3–5 yrs from childhood |
| ARVC | Every 3–5 yrs after age 10 |
| LV noncompaction | Every 3 yrs from childhood |
| Restrictive CMP | Every 3–5 yrs from adulthood |
Add Holter to HCM and ARVC screening. Add exercise treadmill in HCM. Add CMR in ARVC screening.
Guardrails
- In adult new HFrEF, always test for CAD unless another etiology is very well established — coronary disease is the modal cause and revascularisation is treatable.
- Regional wall motion abnormalities do NOT prove ischaemia — 50–60% of idiopathic DCM have them. Confirm with angiography or dobutamine echo (≥6 akinetic segments).
- Nonobstructive CAD ≠ ischemic CMP. Attribute cautiously.
- Do not skip family history. It changes management (genetic testing yield, cascade screening).
- EMB has narrow indications — fulminant HF <2 weeks with haemodynamic compromise; new HF <2–3 months with early AV block, arrhythmia, or refractory course. Do not order routinely.
- HFpEF differential is broader than diastolic dysfunction — obesity, lung disease, occult ischaemia can produce identical symptoms. Confirm elevated filling pressures (invasive with provocation if needed) before labelling.
- Pre-transplant diagnoses are wrong 17–30% of the time on explant pathology. Sarcoidosis, myocarditis, ARVC, HCM, LVNC are the most commonly missed. Keep them on the differential even when idiopathic DCM seems obvious.
- Paediatric CHD: standard adult EF cutoffs do not apply. Use CHD-specific cutoffs (Step 1). Also, patch material, ventriculotomy, and intraventricular dyssynchrony reduce echo EF accuracy — prefer CMR when volumes matter.
- β-blocker caution in single-ventricle / systemic RV physiology (peds CHD) — trial data suggest worse outcomes; not a cardiomyopathy diagnostic issue but a management one worth flagging when the etiology work-up ends with this substrate.
Sources
-
Colucci WS. Determining the etiology and severity of heart failure or cardiomyopathy. UpToDate (Wolters Kluwer). Section editor: Gottlieb SS. Literature review through Jun 2026; topic last updated Mar 09 2026.
-
Amdani S, Conway J, George K, Martinez HR, Asante-Korang A, Goldberg CS, Davies RR, Miyamoto SD, Hsu DT, on behalf of the American Heart Association Council on Lifelong Congenital Heart Disease and Heart Health in the Young; Council on Arteriosclerosis, Thrombosis and Vascular Biology; Council on Cardiovascular Surgery and Anesthesia; and Council on Cardiovascular and Stroke Nursing. Evaluation and Management of Chronic Heart Failure in Children and Adolescents With Congenital Heart Disease: A Scientific Statement From the American Heart Association. Circulation. 2024;150:e33–e50. DOI: 10.1161/CIR.0000000000001245
