We investigated the presence of left ventricular hypertrophy (LVH) and features of diastolic dysfunction in genotype-confirmed children from families with hypertrophic cardiomyopathy (HCM) and healthy control children.

In subjects with HCM-causing mutations, LVH usually does not evolve until adolescence. Diastolic dysfunction has not been systematically evaluated in children carrying HCM-causing mutations.

All children (aged 1.5-16.7 years) from 14 HCM families with identified disease-causing mutations (the Arg719Trp mutation in the β-myosin heavy chain gene [MYH7], the Asp175Asn mutation in the α-tropomyosin gene [TPM1], the Gln1061X mutation in the myosin-binding protein C gene [MYBPC3], and the IVS5-2A→C mutation in the MYBPC3 gene) and 53 matched control children were examined with electrocardiography and 2- and 3-dimensional echocardiography (2DE and 3DE). Natriuretic peptides were measured in children from HCM families and 67 control children.

Of 53 children from HCM families, 27 (51%) had a disease-causing mutation (G+). G+ children had slightly thicker septum on 2DE compared with the control children (P = .004), but only 3 (11%) of 27 G+ children exceeded the 95th percentile values of the body surface area–adjusted maximal LV thickness of healthy children (the major echocardiographic criterion for HCM). However, prolonged isovolumetric relaxation time, increased left atrial volume on 3DE, or increased levels of NT-proANP, all features suggestive of diastolic dysfunction, were found in 14 (52%) of 27 G+ children.

In children with HCM-causing mutations, signs of diastolic dysfunction are found in about half of the cases, as LVH is present only in small percentage of these children.