QUANTITATIVE-ANALYSIS OF CARDIAC-MUSCLE CELL DISORGANIZATION IN THE VENTRICULAR SEPTUM - COMPARISON OF FETUSES AND INFANTS WITH AND WITHOUT CONGENITAL HEART-DISEASE AND PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY

The presence of numerous abnormally arranged cardiac muscle cells in the ventricular septum has been considered a characteristic anatomic feature of hypertrophic cardiomyopathy. However, it has been suggested that the ventricular septum of infants with certain congenital cardiac diseases (such as aortic or pulmonic valve atresia) contains disorganized cardiac muscle cells similar to those in patients with hypertrophic cardiomyopathy. To test the validity of this concept and the true specificity and sensitivity of septal disorganization for hypertrophic cardiomyopathy, sections of ventricular septum were obtained at necropsy from 276 patients and the extent of ventricular septal disorganization was determined quantitatively. Disorganization was most marked in infants, children and adults with hypertrophic cardiomyopathy (i.e., present in 95% of 60 patients); the mean area of septum disorganized was 31 ± 3%. Although disorganized cells were present in 64% of 33 infants with aortic or pulmonic valve atresia, these cells occupied extremely small areas of ventricular septum (mean area of septum disorganized 2.8 ± 0.7%; p < 0.001). Furthermore, the minimal septal disorganization present in aortic or pulmonic valve atresia was similar to that found in 91 infants with other congenital heart malformations and in 92 normal fetuses or infants (mean area of septum disorganized was 1.4 ± 0.6 and 0.3 ± 0.1%, respectively). Hence, extensive ventricular septal disorganization is a highly sensitive and specific finding for hypertrophic cardiomyopathy, although small areas of disorganization may occur in infants with other heart diseases, including aortic or pulmonic valve atresia.