Hypertrophic cardiomyopathy (HCM) is a genetically inherited disease that is characterized by unexplained left ventricular hypertrophy (LVH) often associated with diastolic dysfunction and myocardial ischemia. In patients with HCM, LVH may be present at birth or it may develop during childhood and adolescence, usually during periods of rapid body growth. Currently, it is not possible to identify, using clinical or laboratory methods, those children who will develop LVH from among those with a genetic predisposition for the disease. It would therefore be beneficial to find predictors of LVH development in normal children who have family history of HCM. Integrated backscatter analysis (IBS) is a recently developed ultrasound tool that has been studied in patients with various cardiac diseases. Integrated myocardial backscatter has been shown to vary throughout the cardiac cycle in normal subjects, both pediatric and adult, with peak values occurring during diastole and minimum values in end systole. Several studies in both children and adults with HCM have shown a blunting of this variation in backscatter analysis. We hypothesize that patients with a genetic predisposition for HCM, but no echocardiographic evidence of the disease, may have a greater prevalence of alterations in integrated myocardial backscatter when compared to children without a family history of HCM. We therefore propose to examine the cyclic variation of integrated myocardial backscatter in children with a normal echocardiogram and a first-degree relative with HCM, and compare it with the results obtained in a group of normal children, as well as in a group of children with unequivocal echocardiographic evidence of HCM.