Epidemiology of cardiomyopathies in children and adolescents: a retrospective study over the last 10 years.

We conducted a retrospective study at the Department of Paediatric Cardiology of the University Hospital Centre Rebro, Zagreb, over the period from 1988 to 1998, so as to assess the epidemiology of childhood cardiomyopathies. The patients were categorized according to the guidelines of the Task Force on Cardiomyopathies of the World Health Organization and the International Society and Federation of Cardiology. We identified 121 infants, children and adolescents as having cardiomyopathy, giving an average occurrence for all cardiomyopathies of 38.81 for each 10,000 patients examined in our outpatient clinics for paediatric cardiology. Of the patients, 50 were female (41.3%) and 71 were male (58.7%). The cardiomyopathy was of the dilated variant in 52 patients (42.9%), with 43 patients (35.5%) having hypertrophic cardiomyopathy, and 6 patients (4.8%) identified with restrictive cardiomyopathy. We encountered no patients with arrhythmogenic right ventricular cardiomyopathy. In nine patients (7.4%), it proved impossible to classify the cardiomyopathy. We placed 11 patients (9.0%) in the group of specific cardiomyopathies. Most of those with dilated cardiomyopathy had been diagnosed prior to the age of 3 years (RR 1.9, 95% CI 1.4-2.47). There were no statistically significant differences in the incidences of dilated as compared to hypertrophic cardiomyopathy (Z 0.923, p = 0.1779), but we encountered a significantly lower occurrence of restrictive cardiomyopathy (Z 6.044, p < 0.001). Of those with hypertrophic cardiomyopathy, 15 patients (34.8%) had the asymmetric variant, while 28 patients (65.2%) exhibited the concentric form. During the period of follow-up, 10 patients died, 4 with dilated cardiomyopathy, 4 with hypertrophic cardiomyopathy, 1 with restrictive cardiomyopathy, and 1 with a specific cardiomyopathy. We encountered 12 (9.9%) patients who, besides cardiomyopathies, also suffered from neuromuscular disorders. Most of these had dilated cardiomyopathy. Mitochondrial disorders, in contrast, were more frequently found in patients with hypertrophic cardiomyopathy.