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The World Health Organization classification of cardiomyopathies has four categories: dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and arrhythmogenic right ventricular dysplasia–cardiomyopathy. Although there may be some overlap, most patients are classifiable as having one of these types. Dilated cardiomyopathy (DCM), with a dilated left ventricle and systolic dysfunction, is the most common form and the most common reason for heart transplantation in children and adults. Incidences of 0.34 and 1.13 cases per 100000 children per year have been reported from Finland and the USA. Now, a large epidemiological study has been reported from the US (Jeffrey A Twobin and colleagues. JAMA 2006;296:1867–76).
The study included two prospective cohorts in New England and the central Southwestern USA and a retrospective cohort based on 39 tertiary centres in the USA and Canada. In all, there were 1426 children with DCM. The annual incidence of DCM in children <18 years of age was 0.57 cases per 100000 children per year. The incidence was higher in boys than in girls (0.66 vs 0.47 cases per 100000 per year), in black children than in white (0.98 vs 0.46), and in infants than in older children (4.4 vs 0.34). Two thirds of children (66%) had idiopathic DCM, 16% had myocarditis, 9% neuromuscular disorders (usually Duchenne or Becker muscular dystrophy), 5% familial DCM, 4% inborn errors of metabolism and 1% malformation syndromes. Of the 66 cases of familial DCM, 45 had autosomal dominant inheritance, 16 autosomal recessive, 1 X linked and 4 the complex phenotype of left ventricular non‐compaction with gene mapping. The main types of inborn errors of metabolism (54 cases) were mitochondrial disorders (n=20), Barth syndrome (n=13), and primary or systemic carnitine deficiency (n=7). Of the 15 patients with malformation syndromes, there were 7 with a chromosomal defect and 5 with Alström syndrome.
The 1‐year and 5‐year survival rates after the diagnosis were 87% and 77%, respectively. The corresponding rates of survival without transplantation were 69% and 54%. The median age at diagnosis was 1.5 years, at decision to transplant 4 years, at transplantation 4.8 years and at death (among those who died during the study) 3 years. A quarter of the survivors had been followed up for >4 years. Risk factors for death or transplantation present at diagnosis were older age, congestive heart failure, lower left ventricular fractional shortening z score and cause of DCM (risk doubled with idiopathic DCM compared with myocarditis).
The incidence of DCM varies with age, sex and race, and prognosis depends on the cause, the age of the child at diagnosis, and the presence or absence of congestive heart failure.