Dilated Cardiomyopathy in Children
When the heart muscle stretches and weakens — what causes it, what to expect, and how it is managed.
What Is It
Understanding Dilated Cardiomyopathy
Dilated cardiomyopathy (DCM) is a disease of the heart muscle where the left ventricle — and often both ventricles — becomes enlarged (dilated) and weakened, losing its ability to pump blood efficiently. It is the most common cardiomyopathy in children and the most common reason for heart transplantation in paediatric patients.
Unlike congenital heart disease (where the heart’s structure is abnormal from birth), DCM involves a previously normal heart that develops a muscle disease. The heart dilates, its walls thin, and its pumping function (ejection fraction) falls — sometimes dramatically.
What Causes DCM in Children?
| Cause | Frequency | Notes |
|---|---|---|
| Idiopathic (unknown) | ~50–65% | No cause identified despite full workup |
| Myocarditis (viral) | ~15–20% | Post-viral (Coxsackie B, adenovirus, parvovirus B19); may recover fully |
| Genetic / Familial | ~20–30% | Mutations in sarcomere, cytoskeletal, and nuclear envelope genes (TTN, MYH7, LMNA and others); screen family members |
| Neuromuscular disorders | Variable | Duchenne/Becker muscular dystrophy, Friedreich ataxia — cardiac involvement is common |
| Metabolic / Mitochondrial | Rare | Fatty acid oxidation defects, mitochondrial disease — always screen infants |
| Tachycardia-induced | Rare but important | Persistent, unrecognised tachyarrhythmia (e.g., incessant SVT) can cause reversible DCM |
Symptoms & Presentation
DCM in children can present across a wide spectrum — from a baby with fulminant (sudden, severe) heart failure at diagnosis to an older child found incidentally to have a dilated heart on an echocardiogram performed for another reason.
Common presenting symptoms: breathlessness, particularly during feeding in infants (the equivalent of exercise); poor weight gain; excessive sweating; persistent cough; abdominal distension (from liver congestion); easy fatigue; and — in older children — exercise intolerance, palpitations, or even sudden collapse.
Investigations
Echocardiography is the key diagnostic tool — it demonstrates the dilated, poorly contracting left ventricle and measures the ejection fraction (normal >55%; significantly impaired in DCM often <30–35%).
Cardiac MRI provides detailed tissue characterisation — late gadolinium enhancement can identify fibrosis (scarring) and may predict outcomes.
Genetic panel testing identifies a causative mutation in up to 30% of cases and should be offered to all affected children. Cascade screening of first-degree relatives is essential.
Viral serology and myocardial biopsy may be considered in selected cases, particularly to identify ongoing inflammation (myocarditis) that may respond to immunosuppression.
Treatment
Heart failure medications form the backbone of treatment: ACE inhibitors or ARBs (reduce afterload), beta-blockers (reduce adrenergic drive and allow reverse remodelling), diuretics (reduce fluid overload), and aldosterone antagonists. These medications are often life-changing and can allow significant recovery of cardiac function.
Device therapy: Some children require implantable defibrillators (ICD) for prevention of sudden cardiac death. Biventricular pacing (cardiac resynchronisation therapy, CRT) can improve pump function in selected cases with conduction abnormalities.
Mechanical circulatory support (MCS): For children in acute severe heart failure, ventricular assist devices (VADs) can bridge the child to recovery or to transplantation.
Heart transplantation is the definitive treatment for children who do not respond to medical therapy. Outcomes after paediatric heart transplantation have improved significantly, with median survival exceeding 15 years post-transplant in experienced centres.
Not necessarily — and certainly not immediately. Approximately 40% of children with DCM, particularly those whose DCM follows viral myocarditis, recover normal or near-normal heart function with medical therapy. Another 30–40% stabilise with ongoing treatment. Only those who fail to respond and continue to deteriorate ultimately require transplantation. The trajectory varies enormously by cause, age at diagnosis, and degree of initial impairment. Give the medical therapy time — improvement can occur over months.
Yes. Genetic or familial DCM accounts for 20–30% of all cases. All first-degree relatives — parents, siblings, and children — of a child with DCM should have a baseline echocardiogram and ideally genetic testing if a mutation is identified. Many relatives with familial DCM are asymptomatic at the time of screening, and early detection allows protective therapy to be started before symptoms or significant heart dysfunction develop.
Children with DCM and reduced ventricular function are generally advised to avoid competitive sport and strenuous exercise until their cardiac function has recovered. Gentle activity and normal daily living are usually encouraged. The exact restrictions depend on the degree of impairment, the presence of arrhythmias, and whether an ICD is in situ. Your cardiologist will review activity guidance at each appointment as function improves.
The ejection fraction (EF) measures the percentage of blood pumped out of the left ventricle with each heartbeat. A normal EF is 55–70%. In DCM, the EF is reduced — often to 20–40% at diagnosis. The EF is the single most important measure of how well the heart is working and is tracked closely on serial echocardiograms to monitor treatment response.
Key Takeaways
- Dilated cardiomyopathy is the most common cardiomyopathy in children and the leading cause of paediatric heart transplantation.
- The cause is unknown in ~50% of cases; viral myocarditis and genetic mutations are the next most common causes.
- Always check for tachycardia-induced cardiomyopathy — it is fully reversible with arrhythmia control.
- About 40% of children recover normal heart function with medical therapy.
- First-degree relatives should be screened with echocardiography and genetic testing.
- Heart transplantation is available for refractory cases, with excellent outcomes in specialist centres.
Sources
Towbin JA et al. Incidence, Causes, and Outcomes of Dilated Cardiomyopathy in Children. JAMA 2006;296(15):1867–1876.
Allen HD et al. Moss and Adams’ Heart Disease in Infants, Children, and Adolescents, 10th Ed. Wolters Kluwer, 2021.
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