Disproportionate ventricular thickening may occur in patients with a variet
y of congenital heart malformations, but there are no studies indicating th
at hypertrophic cardiomyopathy (HC) is associated with an unusually high ra
te of ventricular septal defect (VSD).(1) Theoretically, an increased preva
lence of muscular VSD in HC would be conceivable because both diseases affe
ct the myocardium of the ventricular septum, In our study, we report a very
high prevalence of muscular VSD in a cohort of children with HC.