Cardiomyopathy types
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Cardiomyopathy Types
Cardiomyopathy refers to intrinsic heart muscle diseases that cause mechanical and/or electrical dysfunction, independent of coronary artery disease, valvular disease, congenital heart disease, or hypertension. There are three classic pathophysiologic categories plus several important additional subtypes.
Classification Overview
| Type | Dominant Dysfunction | Prevalence |
|---|---|---|
| Dilated (DCM) | Systolic (contractile) | ~90% of cardiomyopathies |
| Hypertrophic (HCM) | Diastolic (relaxation) | 1 in 500 general population |
| Restrictive (RCM) | Diastolic (compliance) | Least common |
| Arrhythmogenic RV (ARVC) | Electrical + RV structural | Hereditary |
| Takotsubo (Stress) | Transient systolic | Acquired |
| Peripartum | Systolic | Pregnancy-related |
| Left Ventricular Non-Compaction (LVNC) | Mixed | Congenital/genetic |
1. Dilated Cardiomyopathy (DCM)
Pathophysiology: Systolic (contractile) dysfunction with a dilated, flabby, hypocontracting ventricle. EF is reduced.
Causes:
- Genetic: Autosomal dominant loss-of-function mutations (up to 50% of cases) affecting cytoskeletal, sarcolemmal, or nuclear envelope proteins. Titin-truncation mutations account for up to 20% of DCM cases.
- Myocarditis (viral - most common infectious cause in the US)
- Toxic: alcohol, anthracyclines, cocaine
- Pregnancy (peripartum cardiomyopathy)
- Idiopathic (remaining cases)
Clinical features: Bilateral heart failure symptoms, S3 gallop, mitral regurgitation from annular dilation, risk of ventricular arrhythmia, thromboembolic events.
Disease phases:
- Phase 1A: Genetic variant present, no structural disease yet
- Phase 1B: DCM present but asymptomatic (may last years)
- Phase 2: Symptomatic heart failure, arrhythmia, or embolus
(Braunwald's Heart Disease; Robbins & Cotran Pathologic Basis of Disease)
2. Hypertrophic Cardiomyopathy (HCM)
Pathophysiology: Diastolic dysfunction from a thick-walled, heavy, hypercontracting ventricle with poor compliance. Systolic function is usually preserved.
Genetics: Virtually all cases are autosomal dominant gain-of-function mutations in sarcomeric proteins. Over 400 mutations across 9 genes are known, most commonly:
- Myosin-binding protein C (MYBP-C)
- Beta-myosin heavy chain (MYH7)
- Cardiac troponins I, T, and alpha-tropomyosin Together these account for ~70% of cases.
Key features:
- Asymmetric septal hypertrophy (septum >> free wall)
- LV outflow tract obstruction in ~1/3 of cases via systolic anterior motion (SAM) of the mitral valve
- Obstruction is dynamic: worsens with reduced preload, reduced afterload, or increased contractility
Clinical significance: Most common cardiovascular cause of sudden cardiac death in young athletes, accounting for ~1/3 of such events. Risk of SCD increases at ~1% per year.
Distinguishing from: Amyloidosis, Fabry disease, hypertensive heart disease, valvular/subvalvular aortic stenosis.
(Robbins & Cotran; Braunwald's Heart Disease; Tintinalli's Emergency Medicine)
3. Restrictive Cardiomyopathy (RCM)
Pathophysiology: Stiff, noncompliant myocardium with impaired diastolic filling. Ventricular cavity size is normal or reduced, walls may be thickened, and systolic function is often preserved early on.
Causes:
| Mechanism | Examples |
|---|---|
| Infiltration | Amyloidosis (AL, ATTR), Sarcoidosis, Gaucher disease |
| Iron deposition | Hemochromatosis |
| Storage diseases | Fabry disease, glycogen storage disorders |
| Fibrosis | Radiation-induced interstitial fibrosis |
| Endomyocardial | Endomyocardial fibrosis, Löffler eosinophilic endocarditis |
| Endocrine | Carcinoid heart disease |
Key clinical distinction: Must be differentiated from constrictive pericarditis (both cause diastolic failure but management differs radically).
Note: Amyloidosis causes restriction only in late stages when extensive infiltration of the myocardial interstitium has occurred. 4% of African Americans carry a specific transthyretin (ATTR) mutation that raises cardiac amyloidosis risk more than fourfold.
(Braunwald's Heart Disease; Goldman-Cecil Medicine)
4. Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
Pathophysiology: Progressive fibro-fatty replacement of the right ventricular myocardium, causing right-sided heart failure and ventricular arrhythmias. Left-sided involvement can also occur.
Genetics: Autosomal dominant, variable penetrance. Mutations predominantly in desmosomal junction proteins at the intercalated disk:
- Plakoglobin (JUP) - also causes Naxos syndrome (ARVC + palmoplantar keratoderma + woolly hair)
- Desmoplakin (DSP), Desmoglein-2 (DSG2), Desmocollin-2 (DSC2)
- PKP2 (plakophilin-2) is the most common mutation
ECG hallmarks: T-wave inversion in V1-V3; epsilon waves (delayed ventricular activation); VT with left bundle branch block morphology (right ventricular origin).
Diagnosis: Uses Task Force Criteria (major + minor) based on structural imaging (echo/MRI), tissue characterization, ECG repolarization/depolarization, arrhythmia pattern, and family history.
(Robbins & Cotran; Tintinalli's; Braunwald's Heart Disease)
5. Takotsubo (Stress) Cardiomyopathy
Also called "apical ballooning syndrome" or "broken heart syndrome."
- Trigger: Intense emotional or physical stress causes catecholamine surge
- Pattern: Transient apical and mid-ventricular ballooning with preserved or hyperkinetic basal function; mimics anterior STEMI
- Population: Predominantly postmenopausal women
- Course: Usually reversible within days to weeks
- Mechanism: Catecholamine-mediated myocardial stunning; coronary arteries are typically normal
(Braunwald's Heart Disease - chapter listing: Takotsubo Cardiomyopathy, p.1042)
6. Peripartum Cardiomyopathy
- Develops in the last month of pregnancy or within 5 months postpartum
- Presents as end-stage low-output heart failure
- No pre-existing cardiac disease
- Etiology: Likely multifactorial - anti-angiogenic factors (sFlt-1), prolactin cleavage products, myocarditis, immune mechanisms
- Prognosis variable; partial or full recovery possible in many patients
(Goldman-Cecil Medicine; Creasy & Resnik Maternal-Fetal Medicine)
7. Left Ventricular Non-Compaction (LVNC)
- Failure of the normal compaction of the ventricular myocardium during embryogenesis
- Prominent trabeculations with deep intertrabecular recesses in the LV
- Can overlap with DCM, HCM, or RCM phenotypes
- Risk of heart failure, arrhythmia, and thromboembolic events
- Genetic associations: TTN, MYH7, MYBPC3, and others
(Braunwald's Heart Disease)
Quick Comparison at a Glance
| Feature | DCM | HCM | RCM | ARVC |
|---|---|---|---|---|
| LV size | Dilated | Normal/small | Normal | Normal |
| Wall thickness | Thin/normal | Thick | Thick (infiltration) | RV thinned |
| Systolic function | Reduced | Normal/hyperdynamic | Normal (early) | RV reduced |
| Diastolic function | Impaired | Markedly impaired | Severely impaired | Impaired |
| Main risk | Heart failure, SCD | SCD (young athletes) | Heart failure | SCD, VT |
| Genetics | AD loss-of-function | AD gain-of-function | Variable | AD desmosomes |
Sources:
- Robbins, Cotran & Kumar Pathologic Basis of Disease (Cardiomyopathy, p.535-536)
- Braunwald's Heart Disease (Chapter 52 - Classification of Cardiomyopathies, p.1032-1049)
- Tintinalli's Emergency Medicine (Sudden Cardiac Death section, p.95)
- Goldman-Cecil Medicine (Cardiomyopathy chapter)
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