Paediatric Cardiomyopathy
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Direct answer
Dilated cardiomyopathy is the commonest phenotype in children, roughly half of all paediatric cardiomyopathy, and presents with heart failure in a child whose echo shows a dilated, poorly contracting left ventricle; the aetiological hunt must be deliberate, from myocarditis and anthracycline injury to neuromuscular disease and inborn errors of metabolism. Hypertrophic cardiomyopathy in an infant is more often metabolic or syndromic — Pompe disease, Noonan syndrome — than the sarcomeric disease of adolescents, while restrictive cardiomyopathy is the rarest and carries the worst prognosis, usually demanding early transplantation. Every child with a new cardiomyopathy deserves a systematic work-up, because a substantial fraction of paediatric dilated disease is secondary and some causes, like Pompe disease, are treatable.
What you must remember
- Dilated phenotype: echocardiographic shortening fraction well below the normal around 28 to 44 per cent, or ejection fraction below about 55 per cent, with a dilated left ventricle and functional mitral regurgitation; consider myocarditis (viral, including parvovirus and enterovirus), tachycardia-induced cardiomyopathy from uncontrolled arrhythmia, anthracycline exposure, thyroid disease, and Duchenne muscular dystrophy in boys.
- The Pompe pointer: an infant with massive cardiomegaly, hypotonia, macroglossia and a short PR interval on ECG has glycogen storage disease type II — the cardiomyopathy with a shortened PR interval, treatable with enzyme replacement.
- Hypertrophic phenotype: asymmetric septal hypertrophy with or without left ventricular outflow obstruction; sarcomeric genes MYH7 and MYBPC3 dominate in older children, while infancy points to Noonan and related RASopathies, Pompe, and mitochondrial disease; management is beta-blockers, volume repletion and avoidance of dehydration, with septal myectomy for refractory obstruction.
- Restrictive phenotype: bilateral dilated atria with normal ventricular size and systolic function, stiff filling; the highest transplantation-priority phenotype, and a reason to screen for Anderson-Fabry and desminopathies.
- Arrhythmogenic right ventricular cardiomyopathy: arrhythmia-dominated, epsilon waves and T-wave inversion in V1–V3, exercise restriction, and ICD decisions driven by risk stratification.
- Heart failure therapy mirrors adult practice — ACE inhibitors or ARNI where available, carvedilol and diuretics — with mechanical support as a bridge and transplantation as the destination.
- First-degree relatives of sarcomeric mutation carriers need longitudinal echo and ECG screening, since penetrance is age-dependent.
Worked example: the infant with a big heart
A seven-month-old presents with tachypnoea, poor feeding and sweating over three weeks; examination shows a gallop, hepatomegaly and a murmur of mitral regurgitation, and the chest radiograph shows cardiomegaly. The echo confirms a dilated left ventricle with an ejection fraction of 28 per cent. Now resist the label "idiopathic" and run the diagnostic ladder the examiner wants: ECG looking for the short PR of Pompe or the delta wave of pre-excitation; creatine kinase elevated, pointing to Duchenne or Becker dystrophy in a boy; troponin and viral serology for myocarditis; thyroid function; a Holter to exclude an incessant tachycardia causing a reversible tachycardiomyopathy; a metabolic screen including lactate, ammonia, acylcarnitine profile and urine organic acids; and a careful drug history, because anthracycline-exposed survivors of paediatric oncology are a growing cohort in Indian tertiary centres. Manage in parallel: diuretics and an ACE inhibitor, calorically dense feeds, anticoagulation, and influenza vaccination. If the CK comes back in the thousands with calf pseudohypertrophy, the diagnosis is Duchenne cardiomyopathy, and the conversation shifts to corticosteroids, early ACE inhibition and neuromuscular follow-up; if the ECG shows a short PR with macroglossia and hypotonia, start the Pompe pathway, where enzyme replacement can regress the cardiomegaly. The minority with no cause carry the idiopathic label, with transplant assessment in the same admission if dysfunction is severe.
The examiner's favourite trap
The infant HCM stem is the trap: candidates answer "sarcomeric mutation" for every hypertrophic ventricle, but hypertrophic cardiomyopathy presenting under one year is more likely metabolic or syndromic — Pompe with the short PR, Noonan with the characteristic facies and bleeding history. The second favourite inverts the phenotypes: a child with giant atria and normal systolic function is not "mild disease" but restrictive cardiomyopathy with the worst survival of all phenotypes and the clearest transplant indication. A third probe is the sports-medicine angle: a HCM adolescent asks about playing cricket — the answer is exclusion from competitive sport, which in an Indian family context needs explicit counselling, not a leaflet.
Frequently asked questions
Which cardiomyopathy shows a short PR interval in infants?
Pompe disease, glycogen storage disease type II, with massive cardiomegaly, hypotonia and macroglossia, treatable with enzyme replacement.
What is the commonest cardiomyopathy phenotype in children?
Dilated cardiomyopathy, accounting for roughly half of paediatric cases, presenting with heart failure and a poorly contracting dilated left ventricle.
Why must restrictive cardiomyopathy be referred for transplantation early?
It carries the worst prognosis of the phenotypes, with a stiff ventricle, giant atria and a high risk of sudden death or progressive failure.
Which neuromuscular disease causes dilated cardiomyopathy in boys?
Duchenne muscular dystrophy, through dystrophin deficiency — the reason every boy with new dilated cardiomyopathy gets a creatine kinase.
How is obstructive hypertrophic cardiomyopathy managed in children?
Beta-blockers with strict avoidance of dehydration and vasodilators, and surgical septal myectomy for refractory outflow obstruction.