Cardiomyopathy - dilated
Description
- LV (or biventricular) dilatation + systolic dysfunction, not explained by loading conditions or coronary disease
- "Not explained by" is the whole definition - DCM is a diagnosis of exclusion after ischaemia, valve disease and hypertension are excluded
- Fundamentally a disease of the cardiomyocyte cytoskeleton and sarcomere - force generation and force transmission both fail
Related phenotypes (ESC 2023 cardiomyopathy framework)
| DCM | Dilatation + systolic dysfunction |
| Hypokinetic non-dilated cardiomyopathy (HNDC) | Systolic dysfunction WITHOUT dilatation - same genetics and prognosis; the early or arrhythmogenic form |
| Arrhythmogenic DCM | DCM + frequent ventricular arrhythmia disproportionate to the degree of dysfunction (LMNA, FLNC, PLN, DSP, RBM20) |
| Peripartum cardiomyopathy | Last month of pregnancy to 5 months postpartum |
- The shift away from "idiopathic DCM": most cases are now assigned a genetic, toxic, inflammatory or arrhythmic cause
Epidemiology
- Prevalence ~1 in 250-400; incidence ~5-7/100,000/yr
- M>F (~2-3:1), men present earlier and more severely
- Peak presentation 20-50 yr
- Familial in 15-30%; a causative mutation is found in 20-35% on genetic testing
- Commonest indication for cardiac transplantation in adults
Aetiopathogenesis
Genetic - autosomal dominant in most, variable penetrance
| Gene | Protein | Clinical signature |
|---|---|---|
| TTN (truncating) | Titin | Commonest (~15-25% of familial); relatively better prognosis, may recover |
| LMNA | Lamin A/C | *Conduction disease FIRST, then DCM; very high SCD risk - ICD at a higher EF threshold* |
| FLNC (truncating) | Filamin C | Arrhythmogenic, high SCD, LGE-rich |
| PLN | Phospholamban | Arrhythmogenic, low voltage, Dutch founder mutation |
| RBM20 | Splicing factor | Early onset, aggressive, arrhythmic |
| DSP | Desmoplakin | Arrhythmogenic, "hot phases" mimicking myocarditis |
| MYH7, TNNT2, TPM1 | Sarcomere | Overlap with HCM |
| DMD (X-linked) | Dystrophin | Duchenne/Becker; female carriers develop DCM |
| TAZ | Tafazzin | Barth syndrome |
Acquired causes - all must be excluded
- Toxic - alcohol (dose-related, often reversible with abstinence), anthracyclines (cumulative dose-dependent), trastuzumab (usually reversible), checkpoint inhibitors, methamphetamine/cocaine, clozapine, chloroquine
- Inflammatory - viral myocarditis (parvovirus B19, HHV-6, coxsackie, SARS-CoV-2), giant cell myocarditis (fulminant, VT, needs urgent biopsy), Chagas, HIV, Lyme
- Autoimmune - SLE, systemic sclerosis, sarcoid, eosinophilic
- Endocrine/metabolic - thyrotoxicosis and hypothyroidism, phaeochromocytoma, acromegaly, Cushing, diabetes
- Nutritional - thiamine (wet beriberi), selenium (Keshan), carnitine, severe hypocalcaemia/hypophosphataemia
- Tachycardia-mediated - AF, atrial flutter, incessant SVT, frequent PVCs (>10-20% burden). Fully reversible - always look
- Peripartum
- Iron overload
- Stress (takotsubo) - apical ballooning; usually recovers
Mechanism
- Cytoskeletal/sarcomeric defect -> dec force transmission -> myocyte slippage and elongation
- -> chamber dilatation -> Laplace: inc wall stress -> inc O2 demand, subendocardial ischaemia
- -> neurohormonal activation (SNS, RAAS) -> fibrosis, further remodelling
- -> spherical LV -> papillary muscle displacement -> functional MR -> more volume load (self-reinforcing)
- Interstitial fibrosis -> re-entry substrate -> VT/VF
Diagnosis
Clinical
- Heart failure symptoms (breathlessness, orthopnoea, PND, fatigue, oedema)
- Arrhythmia or sudden death may be the first presentation - especially LMNA, FLNC, PLN
- Thromboembolism from mural thrombus
- Examination: displaced diffuse apex, S3, functional MR/TR murmurs, raised JVP, signs of congestion
First-line
- ECG - LBBB, conduction disease (LMNA), low voltage (PLN), AF, ventricular ectopy; a completely normal ECG makes DCM unlikely
- TTE - LVEDD, EF, sphericity, MR, RV function, thrombus
- NT-proBNP
- Bloods: UEC, LFT, TSH, iron studies, HbA1c, CK, FBE, HIV serology; ANA/ENA, ACE if suggestive
Exclude ischaemia in everyone
- CT coronary angiography or invasive angiography - DCM cannot be diagnosed without this
- The most common error is calling a globally hypokinetic ischaemic cardiomyopathy "DCM"
Cardiac MRI - now close to mandatory
- Distinguishes ischaemic (subendocardial/transmural LGE in a coronary territory) from non-ischaemic (mid-wall septal LGE)
- LGE presence and extent is an independent predictor of SCD and guides ICD decisions beyond EF
- Detects myocarditis (T2 oedema), amyloid, sarcoid, iron (T2*), Fabry (low T1)
Genetics - Class I where there is a family history or a red-flag phenotype
- Test the proband, then cascade-screen first-degree relatives (clinical + genetic)
- Relatives without the variant: discharge. With the variant or no variant identified: serial ECG + echo every 1-3 years
- Genetic result changes management in LMNA, FLNC, PLN, RBM20, DMD - not merely academic
Endomyocardial biopsy - selective
- Fulminant presentation, rapidly deteriorating HF, high-grade AV block or VT with a new cardiomyopathy, eosinophilia
- Looking for giant cell myocarditis, eosinophilic myocarditis, sarcoid, amyloid
Management
A. Remove the cause - first and highest-yield step
- Alcohol abstinence (can normalise EF), stop stimulants, treat thyroid disease, venesect iron, thiamine replacement
- Treat the arrhythmia: rhythm control or ablation for AF, ablation for >10% PVC burden, rate control for incessant SVT
- Tachycardia-mediated cardiomyopathy recovers fully - always exclude it before calling the disease irreversible
- Withhold cardiotoxic chemotherapy; involve cardio-oncology
B. Guideline-directed medical therapy - as for HFrEF
Start together and up-titrate rapidly (STRONG-HF), rather than sequentially
- ARNI (or ACEi/ARB), beta blocker (bisoprolol, carvedilol, metoprolol succinate, nebivolol), MRA, SGLT2 inhibitor
- Loop diuretic for congestion (symptomatic only)
- IV iron if deficient; consider ivabradine, hydralazine/nitrate, digoxin as add-ons
C. Device therapy and sudden death prevention
- Standard: ICD if EF <=35% after >=3 months of optimal therapy, NYHA II-III, survival >1 yr
- DANISH: primary-prevention ICD did not reduce all-cause mortality in non-ischaemic cardiomyopathy - individualise, weight toward younger patients and those with extensive LGE
- CRT if QRS >=130 ms with LBBB (greatest benefit >=150 ms)
- *Genotype overrides the EF threshold*
- LMNA: ICD at EF <45% with >=2 of: non-sustained VT, male sex, non-missense variant, EF <45% - do not wait for EF 35%
- FLNC, PLN, RBM20, DSP: lower threshold for ICD, weight LGE burden heavily
- Anticoagulate if AF, LV thrombus, or prior embolism (routine anticoagulation for low EF alone is not indicated)
D. Advanced heart failure
- Refer early - before irreversible end-organ damage
- Transplantation, durable LVAD as bridge or destination
- Withdrawal of GDMT after recovery causes relapse (TRED-HF) - "recovered" DCM stays on therapy indefinitely
E. Peripartum cardiomyopathy
- Standard HF therapy adapted for pregnancy/lactation (ACEi/ARB/ARNI/MRA contraindicated antenatally; hydralazine + nitrate instead)
- Bromocriptine with anticoagulation - adjunct, reduces prolactin fragment-mediated injury
- Counsel against subsequent pregnancy if EF has not normalised
F. Everyone
- Vaccination, cardiac rehabilitation, HF nurse/MDT, self-monitoring plan
- Family screening and genetic counselling
- Exercise advice - aerobic exercise encouraged; competitive sport restricted in arrhythmogenic genotypes
Associations
- Skeletal myopathy - Duchenne/Becker (and female DMD carriers), myotonic dystrophy, Emery-Dreifuss, limb-girdle; check CK in every new DCM
- Conduction disease and family history of pacemakers - LMNA
- Sensorineural deafness, cataracts - mitochondrial cardiomyopathy
- Family history of sudden death, "epilepsy", drowning or unexplained motor vehicle accidents
- Haemochromatosis, thalassaemia with transfusional iron overload
- Alcohol use disorder, methamphetamine use
- Prior breast cancer or lymphoma treatment (anthracycline, trastuzumab, chest radiotherapy)
- HIV, Chagas (South American birth)
Natural history & complications
- Highly variable: ~40% improve or normalise, ~40% remain stable, ~20% progressively deteriorate
- Modern GDMT has transformed outcomes - 5-year survival now >80% in treated non-ischaemic DCM
- Reverse remodelling usually occurs within 6-12 months of starting therapy - do not commit to ICD or transplant before then unless arrhythmic risk demands it
- Recovery is not cure (HFimpEF) - relapse on treatment withdrawal (TRED-HF)
Poor prognostic markers
- Lower EF, larger LVEDD, RV dysfunction
- Extensive mid-wall LGE on CMR
- LMNA, FLNC, PLN genotype
- Persistent NYHA III-IV, high NT-proBNP, hyponatraemia, renal impairment
- Failure to reverse remodel at 6-12 months
Complications
- Progressive pump failure
- Ventricular arrhythmia and SCD (may precede symptomatic HF entirely in arrhythmogenic genotypes)
- AF - both a cause and consequence
- Functional MR - drives further volume loading
- LV mural thrombus and systemic embolism
- Cardiorenal and cardiohepatic syndrome
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