Prevalence and characteristics of disproportionate ventricular septal thickening in patients with coronary artery disease.

Echocardiographic or necropsy studies were performed in 151 patients with coronary artery disease. Prevalence of disproportionate septal thickening (septal to free wall ratio greater than or equal to 1.3) was 11%. An abnormally increased septal-free wall ratio in these patients had two principal etiologies. First, it was a manifestation of genetically transmitted hypertrophic cardiomyopathy, as evidenced by disproportionate septal thickening in first degree relatives. Second, it was due to disproportionate septal thickening which did not appear to be a manifestation of genetically transmitted hypertrophic cardiomyopathy. This latter conclusion was suggested by negative echocardiographic studies in some families of patients with both coronary artery disease and disproportionate septal thickening. In addition, numerous disorganized cardiac muscle cells, characteristically present in patients with genetically transmitted hypertrophic cardiomyopathy, were absent from the septum of all patients with disproportionate septal thickening studied at necropsy. Although the mechanism responsible for this secondary type of disproportionate septal thickening is unknown, our results indicate that the presence of disproportionate septal thickening in a patient with coronary artery disease does not, per se, indicate the coexistence of genetically transmitted hypertrophic cardiomyopathy.