Asymmetric septal hypertrophy in childhood. Unreliability of histologic criteria for differentiation of obstructive and nonobstructive forms.

Two cases of obstructive asymmetric septal hypertrophy with biventricular outflow obstruction in childhood are presented. Both patients were treated first with propranolol and later by ventriculoseptal myotomy-myectomy. The first patient died two and one-half years following surgery, and the second patient died in the immediate postoperative period. In the first patient the 690 gm. heart had an interventricular septum to posterior left ventricular wall ratio of 1.9, and in the second patient the ratio in the 460 gm. heart was 1.8. In both cases the posterobasal left ventricular free wall was rounded and hypertrophied, as has been reported grossly in obstructive asymmetric septal hypertrophy. However, in both cases, the bizarre disoriented cardiocytes typical of asymmetric septal hypertrophy were present in both ventricular free walls as well as in the interventricular septum, as has been reported in the nonobstructive variety. In these two cases, previously reported morphologic criteria for the differentiation of obstructive and nonobstructive disease are not considered reliable.