Dilated cardiomyopathy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

DCM is a phenotype with inherited, inflammatory, toxic, metabolic, tachycardia-mediated and peripartum causes. Establishing a cause informs family screening, exposure removal and arrhythmic risk.

Management runs in parallel: stabilise congestion or shock, establish guideline-directed HFrEF therapy, quantify rhythm risk and investigate the phenotype with imaging and targeted laboratory/genomic testing.

The diagnostic label should be revisited when new conduction disease, ventricular arrhythmia, extracardiac features or a family event emerges.

Key points

DCM is LV or biventricular dilatation with systolic dysfunction not explained solely by abnormal loading or coronary disease.
A normal coronary angiogram identifies non-ischaemic dysfunction; it does not establish an idiopathic diagnosis.
Ask specifically about family sudden death, alcohol, pregnancy, myocarditis, chemotherapy, toxins and neuromuscular features.
CMR defines ventricular phenotype and scar; mid-wall or ring-like fibrosis can materially alter arrhythmic risk.
Treat the HFrEF phenotype promptly while investigating its cause; do not wait for genetic results.
Genotype, fibrosis, syncope and ventricular arrhythmia can justify ICD discussion even when LVEF is above a simple threshold.
A pathogenic result should trigger genetic counselling and cascade testing; a negative panel does not erase familial risk.
Recovery of LVEF is remission, not proof of cure: continue disease-modifying therapy unless a specialist gives a compelling reason to stop.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Inherited myocardial disease

Pathogenic variants affecting myocardial structure or electrical stability may produce familial DCM, sometimes with early conduction disease or ventricular arrhythmia. Reduced penetrance means an apparently negative family history does not exclude inheritance.

Toxic and treatment-related injury

Heavy alcohol exposure, stimulants and cardiotoxic cancer therapy can injure myocytes and impair contraction. Susceptibility and cumulative exposure vary, so careful chronology helps judge whether an exposure is causal or contributory.

Inflammatory and peripartum disease

Myocarditis may leave persistent systolic dysfunction and fibrosis after the acute illness. Peripartum cardiomyopathy develops around late pregnancy or after delivery through interacting vascular, inflammatory and individual susceptibility mechanisms.

Systemic and potentially reversible drivers

Persistent tachyarrhythmia, endocrine or nutritional disease and some neuromuscular disorders can create a dilated, weak ventricle. Identifying the driver matters because rhythm control or cause-specific treatment may permit remodelling.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Myocyte dysfunction
Genetic, inflammatory, toxic or metabolic injury reduces effective force generation and may cause myocyte loss. As systolic performance falls, chamber enlargement and higher filling pressure may help maintain output initially but add mechanical stress.
2
Eccentric remodelling
The left ventricle, or both ventricles, dilates as wall stress rises. This may initially help maintain stroke volume but progressively worsens mechanical efficiency and systolic function.
3
Neurohormonal compensation
Falling cardiac output activates sympathetic and renin–angiotensin–aldosterone pathways. Vasoconstriction and sodium retention temporarily support perfusion but increase afterload, congestion and further adverse remodelling.
4
Congestion and valve leakage
Raised ventricular filling pressures transmit to the lungs and systemic veins. Chamber and annular dilatation may cause functional mitral or tricuspid regurgitation, adding volume overload and worsening heart failure.
5
Electrical instability
Myocardial stretch, fibrosis and genetic electrical vulnerability disrupt conduction and create arrhythmic substrate. Atrial fibrillation, ventricular tachycardia or progressive block may emerge before or after overt congestion.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Heart-failure phenotype

Exertional breathlessness, orthopnoea, fatigue, oedema, displaced apex, functional MR/TR and a third heart sound are typical but may be absent early.

Electrical presentation

AF, frequent ventricular ectopy, non-sustained VT, AV block or bundle-branch disease may precede overt congestion.

Familial clues

Cardiomyopathy, transplant, pacemaker at a young age, sudden unexplained death or skeletal myopathy/deafness warrants a three-generation pedigree and inherited-cardiac referral.

Acquired triggers

Heavy alcohol use, stimulants, cardiotoxic cancer therapy, pregnancy, persistent tachyarrhythmia, endocrine or nutritional disease and recent inflammatory illness may be causal or contributory.

High-risk courseRed flag

Unexplained syncope, sustained VT, extensive scar, severe biventricular failure or progressive conduction block signals risk beyond symptoms or LVEF alone.

Shock or pulmonary oedemaRed flag

Cold peripheries, confusion, oliguria, hypotension, hypoxia or severe respiratory distress needs immediate acute-heart-failure care.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
12-lead ECG and ambulatory rhythm monitoringFirst step
Why
Detect AF, conduction disease and ventricular arrhythmia.
Interpretation and limitations
Arrhythmia burden, AV block or characteristic conduction disease may refine aetiology and ICD/pacing decisions.
02
TTE
Why
Measure LV/RV size and function, valves, filling and pulmonary pressure.
Interpretation and limitations
Confirm the phenotype and look for alternative loading lesions; repeat after treatment to document remodelling.
03
FBC, U&E/eGFR, LFT, TSH, glucose/HbA1c, ferritin and transferrin saturation, NT-proBNP
Why
Assess severity, treatment safety and reversible/systemic causes.
Interpretation and limitations
Abnormalities guide treatment but NT-proBNP does not identify the aetiology.
04
Coronary imaging
Why
Exclude coronary disease sufficient to explain dysfunction.
Interpretation and limitations
Choose CT coronary angiography or invasive angiography according to probability, acuity and revascularisation implications.
05
CMR with tissue characterisation
Why
Define anatomy, oedema, infiltration and fibrosis.
Interpretation and limitations
Scar pattern distinguishes likely ischaemic from non-ischaemic injury and contributes to prognosis; active inflammation may prompt targeted testing.
06
Genomic testing with counselling
Why
Find a monogenic cause when phenotype, family history or red flags support testing.
Interpretation and limitations
Act on pathogenic/likely pathogenic variants; do not use a variant of uncertain significance for predictive testing.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Ischaemic cardiomyopathy

Coronary disease can produce a similarly dilated, weak ventricle. Regional wall-motion abnormalities, infarct-pattern scar on CMR or coronary disease sufficient to explain dysfunction favour an ischaemic cause.

Pressure or volume overload

Longstanding hypertension, primary severe valve disease or a congenital shunt can cause ventricular enlargement and failure. Evidence that the loading lesion predates and is sufficient to explain remodelling favours a secondary cardiomyopathy; functional regurgitation can instead be a consequence of DCM.

Acute myocarditis

Recent inflammatory illness, chest pain, troponin elevation and CMR oedema favour active myocarditis rather than established DCM, although unresolved myocarditis can evolve into the chronic dilated phenotype.

Physiological athletic remodelling

Endurance training can enlarge cardiac chambers, but systolic reserve, exercise capacity and tissue characterisation are usually reassuring. Disproportionate dysfunction, scar, symptoms or ventricular arrhythmia argues against adaptation.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01AcuteDecompensation or shockFirst stepPulmonary oedema, hypoperfusion or serious arrhythmia.

1Assess ABCDE, continuous ECG, oxygen only if hypoxaemic, IV access, renal/electrolytes, troponin/NT-proBNP and urgent bedside echo.
2EscalationTreat congestion with IV loop diuretic; if shock persists, escalate immediately to critical care and an advanced-heart-failure centre for inotrope or mechanical-support assessment.
3Correct a precipitant such as ACS, infection, AF/VT, medication interruption or toxicity; cardiovert an unstable tachyarrhythmia without delaying for aetiological work-up.
4Once perfusion and renal function permit, introduce or re-establish disease-modifying HFrEF therapy before discharge with early review.

02CausePhenotype-to-aetiology work-upNew unexplained LV systolic dilatation/dysfunction.

1Confirm DCM on echo and exclude sufficient coronary, valvular, hypertensive or congenital loading disease.
2Take a three-generation pedigree and exposure history; examine for neuromuscular, syndromic, endocrine and inflammatory clues.
3Obtain CMR and targeted blood tests; reserve endomyocardial biopsy for a result likely to change urgent treatment, such as selected inflammatory or infiltrative disease.
4Refer for genomic counselling/testing when indicated and arrange clinical screening of first-degree relatives independent of a pending test.

03ChronicHFrEF and arrhythmic protectionStable DCM after congestion is controlled.

1Offer the NICE HFrEF disease-modifying combination at tolerated doses: ACE inhibitor or ARNI/ARB as appropriate, evidence-based beta-blocker, MRA and SGLT2 inhibitor; titrate with BP, renal function and potassium surveillance.
2Use loop diuretic for residual congestion, counsel on salt/fluid only when clinically indicated, vaccination, alcohol avoidance and graded rehabilitation.
3After optimisation, reassess LVEF, symptoms, scar, genotype, syncope and ventricular arrhythmia; discuss ICD/CRT where criteria or phenotype-specific risk support it.
4If deterioration continues despite therapy, refer early for advanced therapies rather than waiting for irreversible end-organ failure.

04FamilyRelatives and longitudinal reviewFamilial disease, pathogenic variant or unexplained DCM.

1Offer first-degree relatives ECG and cardiac imaging through an inherited-cardiac service; frequency is age-, genotype- and family-specific.
2Cascade-test a known pathogenic family variant; discharge genotype-negative relatives only after specialist confirmation that the variant explains the disease.
3Advise prompt review for syncope, palpitations, breathlessness or pregnancy planning; re-evaluate apparently unaffected relatives because penetrance is age-related.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

One component of disease-modifying HFrEF therapy, with or without diabetes.

Dapagliflozin

10 mg orally once daily for chronic HFrEF.

Check renal function and volume status; pause during major surgery or acute serious illness and assess suspected ketoacidosis even if glucose is not markedly raised.

Mineralocorticoid-receptor antagonist for HFrEF.

Spironolactone

Usually 25 mg orally once daily; reduce or titrate according to renal function, potassium and response.

Hyperkalaemia and renal deterioration; check U&E before and shortly after starting or dose change. Avoid potassium supplements unless specifically directed.

Relieves fluid overload but does not replace disease-modifying therapy.

Furosemide

Common oral starting dose 20-40 mg once daily, adjusted to congestion; acute IV dosing is individualised to prior exposure and severity.

Hypovolaemia, hypotension, renal dysfunction, hypokalaemia and gout; review the dose when euvolaemic.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Progressive heart failure

Continued remodelling can cause recurrent congestion, low output and eventually biventricular failure. Repeated admissions or worsening renal and hepatic function may signal need for advanced-heart-failure assessment.

Ventricular arrhythmia and sudden death

Fibrosis, ventricular stretch and some genotypes create a substrate for sustained ventricular tachycardia or fibrillation. Risk may remain important even when ejection fraction alone appears only moderately impaired.

Atrial fibrillation and thromboembolism

Atrial enlargement and raised filling pressure promote atrial fibrillation, which may worsen output and permit atrial thrombus formation. Severe ventricular stasis can also produce intracardiac thrombus and systemic embolism.

Functional mitral or tricuspid regurgitation

Ventricular and annular enlargement prevents normal leaflet coaptation. The resulting regurgitation increases chamber volume load, pulmonary pressure and right-sided congestion, reinforcing the heart-failure cycle.

Conduction disease

Progressive myocardial or specialised conduction-system disease may cause bundle-branch block or atrioventricular block. This can reduce synchrony, cause bradycardia and influence pacing or resynchronisation decisions.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Record weight, NYHA symptoms, BP, pulse, congestion and adherence at each titration review.
Check renal function and electrolytes before and after RAAS/ARNI, MRA or diuretic changes and during intercurrent illness.
Repeat TTE after treatment optimisation and sooner if symptoms or rhythm change.
Use ambulatory ECG/device interrogation when palpitations, syncope, genotype or prior ectopy warrants surveillance.
Review alcohol/toxin exposure, pregnancy intentions and family-screening completion.
Escalate falling BP, rising creatinine with congestion, recurrent admissions, ventricular arrhythmia or progressive RV failure to an advanced-HF team.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

DCM is a phenotype

Do not stop at 'non-ischaemic': tachycardia, toxins, pregnancy, inflammation and monogenic disease carry different actions.

Family history can be falsely reassuring

Reduced penetrance, small families and unrecognised deaths mean a negative pedigree does not exclude inherited DCM.

Scar matters

CMR fibrosis and genotype can identify arrhythmic risk not captured by LVEF alone.

Recovered EF is not cured

Withdrawal can precipitate relapse; maintain disease-modifying therapy unless a specialist-led exception applies.

VUS is not a diagnosis

A variant of uncertain significance must not be used to label or predictive-test relatives.

11Common pitfallsFrequent interpretation and management errors.

01
Calling DCM idiopathic after coronary imaging without a pedigree, exposure review or CMR.
02
Withholding HFrEF treatment while waiting for aetiology or genetic results.
03
Using LVEF alone to dismiss arrhythmic risk in a scarred or high-risk genetic phenotype.
04
Stopping disease-modifying therapy after LVEF normalises.
05
Treating a VUS as causal in the patient or relatives.