PREVALENCE AND CHARACTERISTICS OF DISPROPORTIONATE VENTRICULAR SEPTAL THICKENING IN INFANTS WITH CONGENITAL HEART-DISEASE

Necropsy studies were performed in 125 infants, .ltoreq. 2 yr, with a variety of congenital heart malformations. Disproportionate ventricular septal thickening (septal-to-left ventricular free wall thickness ratio .gtoreq. 1.3) was present in 31 (25%) of the 125 patients. In the majority of patients, an abnormal septal-to-free wall ratio did not appear to be a manifestation of genetically transmitted hypertrophic cardiomyopathy, since marked disorganization of septal myocardium (involving .gtoreq. 5% of the tissue section) was present in only 5 of the 31 patients with disproportionate septal thickening; and echocardiographic studies in 1st degree relatives of 4 other patients with disproportionate septal thickening and normal septal architecture did not show asymmetric septal hypertrophy. The relatively high prevalence of septal-to-free wall ratios of 1.3 or greater appeared to be due in part to minor differences in ventricular wall thicknesses (in patients with relatively thin absolute wall thicknesses) which may produce particularly large deviations from unity in septal-to-free wall ratio. Non-genetically transmitted disproportionate septal thickening is relatively common in infants with congenital heart diseases studied at necropsy; and a septal-to-free wall ratio of .gtoreq. 1.3 cannot be used as the sole criterion for identifying associated hypertrophic cardiomyopathy in infants with other congenital heart diseases, particularly if marked absolute septal thickening is absent.