Ventricular septal defects can occur in isolation or as part of complex lesion and are often classified according to their location as a) peri-membranous, b) inlet, c) muscular, or d) sub-pulmonic or supra-cristal defects (Figure 1). The importance of anatomically differentiating the lesions relates to the probability for spontaneous closure, surgical approach, involvement of the conducting system as well as associated valvular dysfunction. Perimembranous defects, account for 70% of VSD. They are located in the membranous septum just inferior to the level of the aortic valve. Perimembranous defects can close spontaneously and/or undergo aneurysmal transformation where the tricsupd valve closes the defect. When tissue forms on the right ventricular septal surface (often thought to be atrioventricular valvular in origin), it is termed an aneurysm of the membranous septum. Such tissue serves as a mechanism of spontaneous closure. The defect may be partially or completely occluded by the septal leaflet of the tricuspid valve.
A subset of patients with a ventricular septal defect (VSD) will develop aortic insufficiency (AI). This complicates sub-pulmonic VSD’s about five times more often than perimembranous VSD’s. The aortic cusp adjacent to the VSD has a characteristic deformity in which the nadir of the cusp is elongated and there is associated cusp prolapse with resultant insufficiency. Proposed mechanisms leading to AI in patients with a VSD include a lack of structural support for leaflets adjacent to the VSD, abnormal commissural suspension, lack of appositional forces, loss of continuity between the aortic media and aortic annulus, and last but not least prolapse of leaflets adjacent to the defect because of the Venturi effect from the high velocity jet of blood traversing it. (ref.)
For patients with a subarterial VSD (below the pulmonic valve) and aortic valve prolapse, VSD closure is indicated because of the high likelihood of progression of AVP and development of AI and the fact that spontaneous closure is unlikely. For the patient with a hemodynamically insignificant perimembranous VSD with AVP but without AI, indications for surgery are less clear. Progression of AI is variable and spontaneous closure of the VSD can occur. Patients with a restrictive perimembranous VSD and AVP should therefore be followed closely with serial echocardiography; surgery is indicated only if AI develops.
In our patient the closure of the VSD with aneurysm formation probably led to delay in the progression of the aortic regurgitation since the Venturieffect hat would lead to aortic leaflet prolapse is no longer operative.
1. LEE B. BEERMAN, MD, FACC, SANG C. PARK, MD, FACC, DONALD R. FISCHER, MD, FACC, FREDERICK J. FRICKER, MD, FACC, ROBERT A. MATHEWS, MD, FACC,
WILLIAM H. NECHES , MD, FACC, CORA C. LENOX , MD, FACC,
JAMES R. ZUBERBUHLER, MD, FACC Ventricular Septal Defect Associated With Aneurysm of the Membranous Septum JACC Vol. 5, No. I January 1985:118-23
2. James S. Tweddell,*,‡ Andrew N. Pelech,†,‡ and Peter C. Frommelt†,‡ Ventricular Septal Defect
and Aortic Valve Regurgitation: Pathophysiology and Indications for Surgery Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 9:147-152 © 2006