The Natural History of the So-Called Aneurysm of the Membranous Ventricular Septum in Childhood

Fifty-six children with isolated membranous ventricular septal defect (VSD) included in the National Natural History Cooperative Study for Congenital Heart Disease were studied at the Johns Hopkins Hospital Center to determine the occurrence and natural history of an associated “aneurysm of the membranous septum’ (AMS). These patients represented a wide range of ages and VSD size. Each child was evaluated by two cardiac catheterizations four years apart, with regular clinical examinations in the interval. The diagnosis of AMS was based on angiographic criteria, and as such may encompass several distinct anatomic lesions.Twenty children had AMS at the first catheterization; all were over age two, and all but one had a pulmonic-to-systemic flow ratio (Qp/Qs) of less than 2.0, with normal intracardiac pressures. Four years later, repeat catheterization revealed only minor changes in Qp/Qs and angiographic appearance of the aneurysms in this group. Twelve new cases of AMS were also demonstrated at the second study; seven of these children underwent a significant diminution in Qp/Qs during the period in which the aneurysm was formed. No cases of spontaneous anatomic closure were observed in the course of our study, nor were there any serious complications which could be attributed to the presence of an aneurysm. Overall, AMS was found in 32 of 56 patients (57%), and in 31 of 44 (70%) of those with a Qp/Qs less than 2.0.These findings suggest that AMS is common among children with small membranous VSD, and that its course in childhood is usually stable and asymptomatic. Although anatomic closure of the VSD was not observed during this four year study, our data support suggestions that aneurysm formation may play an important role in some cases of spontaneous diminution in the functional size of an associated membranous VSD.