FIBROUS OBSTRUCTION WITHIN THE LEFT-VENTRICULAR OUTFLOW TRACT ASSOCIATED WITH VENTRICULAR SEPTAL-DEFECT - A PATHOLOGICAL-STUDY

Objectives. We examined the nature of ridges within the left ventricul ar outflow tract associated with ventricular septal defects that might be found by echocardiography. Background. Echocardiography displays e ven small ridges well. Surgical removal of such ridges at the time of defect closure is recommended. Methods. We examined 37 heart specimens with ventricular septal defects with a ridge, noting its nature and r elation to the defect and adjacent valves. We excluded left ventricula r outflow tract obstruction associated with complex lesions. Results. Defects were perimembranous in 25 specimens, muscular in 8 and part of an atrioventricular septal defect in 5. Some hearts had multiple defe cts. Many of the original reports had not mentioned ridges. Three dist inct ridge patterns were found. The first (n = 18) was a fold of endoc ardial tissue related to the membranous septum. The second (n = 12) wa s a defect of a fibrous nature; in 8 this,vas a discrete, protuberant fibrous ridge, and in 4 the obstruction was diffuse, which we termed k eloidal. The third pattern (n = 7) lay circumferentially around the ve ntricular septal defect, seemingly associated with the defect's attemp ted spontaneous diminution in size. Endocardial folds were not found i n specimens from patients >5 years old. Fibrous and keloidal lesions, which may represent a continuum of progression, generally were found i n specimens from older patients. Histologic studies of 17 specimens co nfirmed the morphologic findings. The endocardial folds were endotheli al tissue, whereas the fibrous and keloidal ridges were of fibrous tis sue, as were circumferential lesions. All specimens had mitral-semilun ar valvular continuity. Conclusions. Endocardial fold and circumferent ial lesions appear to be benign. The endocardial folds arose from the membranous ventricular septum, were not protuberant and usually were f ound in younger patients. The fibrous ridges, in contrast, were protub erant and were always associated with the underlying muscle of the out let septum. These pathologic distinctions may facilitate echocardiogra phic diagnosis and prognosis.