dilated cardiomyopathy
Contents
LV (or biventricular) dilatation with systolic dysfunction not explained by abnormal loading conditions (HTN, valve disease) or coronary artery disease. Aetiologies range from genetic (30–50% of “idiopathic” DCM) to toxic, inflammatory, and metabolic. Management follows standard HFrEF GDMT. Key distinguishing features: the role of cardiac MRI in aetiology, genetic testing and family screening, the ICD debate (DANISH), and the possibility of myocardial recovery.
aetiology
| Category | Examples |
|---|---|
| genetic | TTN (titin — most common, ~25%), LMNA (lamin A/C — high arrhythmia risk), MYH7, DSP, FLNC, RBM20, PLN |
| toxic | alcohol (>80 g/day for >5 years), cocaine, methamphetamine, chemotherapy (anthracyclines, trastuzumab) |
| inflammatory | post-viral myocarditis (enterovirus, parvovirus B19, SARS-CoV-2), autoimmune (SLE, sarcoidosis), giant cell myocarditis |
| metabolic / endocrine | thyroid disease, phaeochromocytoma, acromegaly, nutritional (thiamine, selenium, carnitine deficiency) |
| peripartum | onset in last month of pregnancy to 5 months postpartum; may recover; recurrence risk with subsequent pregnancies |
| tachycardia-mediated | sustained tachycardia (AF, incessant SVT/VT) → reversible LV dysfunction; often underdiagnosed |
| infiltrative | amyloidosis, haemochromatosis (iron overload — ferritin, TSAT; consider in young males) |
| idiopathic | diagnosis of exclusion — but ~30–50% have identifiable genetic variants on panel testing |
Tachycardia-mediated CM, alcohol, thyroid disease, and peripartum CM can fully recover with cause removal + GDMT. These are the “don’t miss” diagnoses.
investigation
cardiac MRI — central role in non-ischaemic CM
| Feature | Interpretation |
|---|---|
| mid-wall LGE (septal stripe) | typical of idiopathic/genetic DCM; predicts arrhythmia risk and mortality independently of LVEF |
| subendocardial LGE (coronary territory) | suggests ischaemic aetiology — pursue coronary assessment |
| epicardial / patchy LGE | myocarditis pattern |
| diffuse subendocardial LGE | amyloidosis |
| elevated native T1 / T2 | active inflammation (myocarditis, sarcoidosis) |
| no LGE | better prognosis; higher likelihood of myocardial recovery |
Mid-wall LGE on CMR predicts SCD risk independently of LVEF. In NICM patients with borderline LVEF (e.g. 36–40%), mid-wall fibrosis may tip the balance toward ICD implantation. This is relevant to the DANISH debate.
genetic testing
- recommended for all patients with DCM — ESC Cardiomyopathy Guidelines 2023
- clinical gene panel (typically 50–100 genes); whole exome/genome for research or unresolved cases
- high-risk genotypes requiring closer surveillance and lower ICD threshold:
- LMNA — high risk of malignant arrhythmias even with mild LV dysfunction; ICD indicated with ≥2 risk factors (male sex, NSVT, LVEF <45%, non-missense variant)
- FLNC (filamin C) — arrhythmogenic, associated with LGE and SCD
- DSP (desmoplakin) — overlap with ARVC; episodic myocardial injury (troponin flares)
- PLN (phospholamban) — Dutch founder variant; progressive, arrhythmogenic
- RBM20 — arrhythmogenic, aggressive course
family screening
- first-degree relatives: clinical screening (ECG + echo) at diagnosis and every 2–3 years
- cascade genetic testing if pathogenic variant identified
- early detection allows GDMT initiation before advanced remodelling
standard workup
- coronary assessment (CT angiography or invasive) to exclude ischaemic aetiology
- iron studies (ferritin + TSAT) — haemochromatosis
- TSH — thyroid disease
- autoimmune screen if clinical suspicion (ANA, complement, CRP)
- viral serology rarely changes management — not routinely recommended
- endomyocardial biopsy: reserved for suspected giant cell myocarditis, eosinophilic myocarditis, sarcoidosis, or unexplained rapidly deteriorating CM
management
GDMT — same as HFrEF
Quadruple therapy backbone: ARNI + BB + MRA + SGLT2i — see HFrEF management for details.
- alcohol-related: complete abstinence is mandatory — LVEF recovery occurs in ~50% with abstinence + GDMT
- tachycardia-mediated: rate/rhythm control of the underlying arrhythmia; LVEF often normalises within weeks to months
- chemotherapy-related: cardio-oncology co-management; dexrazoxane for anthracycline cardioprotection; trastuzumab-related CM is often reversible (stop agent + GDMT)
- peripartum: standard GDMT (avoid ACEi/ARB if breastfeeding — use hydralazine/ISDN); bromocriptine (experimental, some evidence); contraception counselling critical; high recurrence risk
- LMNA mutation carriers: low threshold for ICD — arrhythmia risk exceeds what LVEF alone predicts
- sarcoidosis: immunosuppression (corticosteroids ± steroid-sparing agents); ICD threshold is lower due to granulomatous arrhythmia substrate
anticoagulation
- no routine anticoagulation for DCM in sinus rhythm — trials have not shown net benefit
- anticoagulate if: AF (standard indications), LV thrombus, prior embolic event
- consider if LVEF severely reduced (<20%) with large akinetic segments (individualised)
ICD in non-ischaemic DCM — the DANISH debate
| Trial | Year | Key finding |
|---|---|---|
| DEFINITE (2004) | 2004 | ICD reduced arrhythmic death but not overall mortality (trend only) |
| SCD-HeFT (2005) | 2005 | ICD reduced all-cause mortality in NYHA II–III HF (mixed ischaemic/non-ischaemic) |
| DANISH (2016) | 2016 | ICD did not reduce all-cause mortality in NICM; reduced SCD but offset by non-SCD deaths. Subgroup: benefit in age <68 |
DANISH was conducted in the era of modern GDMT (including CRT in 58% of patients). SCD rate was low (~4% over 5 years) — GDMT and CRT may reduce the arrhythmia substrate enough that prophylactic ICD adds less incremental benefit than in older trials.
Current practice:
- guidelines still recommend ICD for NICM with LVEF ≤35% and NYHA II–III (class I in CCS/AHA) — DANISH has not changed this
- shared decision-making is emphasised, particularly in older patients
- CMR with mid-wall LGE may identify higher-risk subgroups who benefit more
- age <59 had clear benefit in DANISH subgroup analysis
- LMNA and other high-risk genotypes warrant ICD at higher LVEF thresholds
myocardial recovery
DCM has a real chance of LV recovery — unlike ischaemic CM where scar is permanent.
- ~40% of “new” DCM patients improve LVEF to ≥50% with GDMT
- absence of LGE on CMR predicts recovery
- shorter symptom duration predicts recovery
- tachycardia-mediated, alcohol, peripartum CM have highest recovery rates
TRED-HF (2019) — withdrew GDMT in recovered DCM (LVEF normalised): 40% relapsed within 6 months. GDMT must be continued lifelong even after LVEF normalisation. The substrate remains — the drugs are compensating, not curing.