Asymmetric septal hypertrophy and hypertrophic cardiomyopathy.

Open Access
Publisher Website
Google Scholar
Abstract
Families (19) were selected for study in which hypertrophic cardiomyopathy and/or isolated asymmetric septal hypertrophy occurred in successive generations. All 19 propositi had hypertrophic cardiomyopathy proven by cardiac catheterization and angiocardiography (8), operation (4) or necropsy (7). These 19 families consisted of the 19 propositi and their 39 siblings, 38 parents and 23 children. Of these 119, 114 were examined, or, if dead before the study, there was sufficient evidence from necropsy or operation reports to establish the diagnosis. In 5 (4 parents and 1 sibling) who had died before the study there was insufficient evidence to establish the presence or absence of heart disease. These 19 families were selected from > 100 cases of familial cardiomyopathy with a miniumum follow-up of 5 yr. The main points leading to selection were the presence of the disease in 2 successive generations and the availability of the 1st-degree relatives for examination. The families were divided into 2 subsets. One consisted of 12 families where not only the propositus had all the clinical manifestations of hypertrophic cardiomyopathy but so did 1 of the parents. In the 2nd subset of 7 families, the propositus had proven hypertrophic cardiomyopathy, but 1 of the parents had isolated asymmetric septal hypertrophy, with no other manifestation of cardiovascular disease. For the purpose of this study differentiation was made between relatives with clinical, radiological, ECG and echocardiographic signs of hypertrophic cardiomyopathy, and those in whom the only abnormality was in the interventricular septum and detected solely by echocardiography. The term isolated asymmetric septal hypertrophy was applied to the latter if the interventricular septal:posterior left ventricular wall (IVS/PLVW) ratio was 1.3 or more, when allowance had been made for the thickening of the interventricular septum which occurs with age. In the 12 families (subset I) where both the propositi and 1 parent had hypertrophic cardiomyopathy, there were the 12 propositi with 22 siblings. Of these 34, 19 had hypertrophic cardiomyopathy and 1 had isolated asymmetric septal hypertrophy; thus there were 20 affected. In the 7 families (subset II) in which the popositi had proven hypertrophic cardiomyopathy and 1 of the parents had isolated asymmetric septal hypertrophy, there were the 7 propositi with 17 siblings. Of these 24, 11 had hypertrophic cardiomyopathy and 1 had isolated asymmetric septal hypertrophy; thus 12 were affected. Applying Smith''s method of analysis, the expected number affected if the condition was inherited as a dominant characteristic was 20.1 in subset I and 13.4 in subset II. These figures did not differ significantly from those actually found, i.e., 24 and 12, respectively. Apparently, in familial hypertrophic cardiomyopathy isolated asymmetric septal hypertrophy is part of the clinical spectrum and has the same genetic implications as hypertrophic cardiomyopathy. Thus, parents with clinical hypertrophic cardiomyopathy can produce offspring with either isolated asymmetric septal hypertrophy or clinical hypertrophic cardiomyopathy. Conversely, parents with isolated asymmetric septal hypertrophy can produce children with either anomaly. In all circumstances other than hypertrophic cardiomyopathy, asymmetric septal hypertrophy does not appear to be an inherited characteristic.