Atrioventricular septal defect

Subvalvular aortic stenosis (SAS) has been reported to constitute 10 percent of all forms of left ventricular outflow tract obstruction,[1] and it is frequently associated with other congenital heart defects, including ventricular septal defect (VSD), patent ductus arteriosus, tetralogy of Fallot, and coarctation of the aorta.[2-5]

In the great majority of pediatric patients previously described, SAS was diagnosed with a measured left ventricular-aortic gradient and progressed to more severe obstruction.[1,6] In a few reported cases, SAS developed after early cardiac catheterization and echocardiographic examination had documented the absence of left ventricular outflow tract obstruction,[1,6-9] Therefore, the development of SAS, at least in a subgroup of patients, seems to be an "acquired" disease with progressive hemodynamic severity.[10,11] Although the development of SAS after surgical repair of several congenital heart defects has been described,[12-15] there are few data about the relative incidence of postsurgical SAS. The purpose of this report is to describe the development and the relative incidence of SAS after surgical correction of several congenital heart defects in patients who had no subaortic obstruction at echocardiography or cardiac catheterization before surgery.

Patients and Methods

Subvalvular aortic stenosis has been defined as a membrane or fibromuscular ring encircling the left ventricular outflow tract immediately below the aortic valve. The condition has been considered acquired when it has not been diagnosed or even suspected at the time of initial cardiac catheterization or echocadiographic evaluation or during the intraoperative inspection.

We reviewed the surgical, echocardiographic, and cardiac catheterization reports of 353 selected patients who underwent surgical repair between June 1982 and March 1990 in our institution. In all patients, the surgical procedures included the closure of a VSD; 153 children had an isolated VSD, 186 also had tetralogy of Fallot, and 14 also had a double-outlet right ventricle (DORV) (Table 1). We excluded from the study patients with unreliable echocardiographic or hemodynamic data.

Pre- and postoperative two-dimensional echocardiographic examinations were performed with Hewlett-Packard (Andover, Mass) equipment, with 2.5-, 3.5-, or 5.0-MHz transducers. The same standard subcostal, parasternal, apical, and suprasternal views were used (Fig 1) IN pre- and postoperative examinations. The studies were recorded on videotape and were independently reviewed by two of the authors (M.P.C., S.G.).

All patients included in this study underwent preoperative right and left cardiac catheterization. Left ventricular angiography was performed by using standard anteroposterior and lateral projections and left anterior oblique views of elongated axial projections (Fig 2). The diagnosis of acquired SAS was made in all patients by two dimensional and Doppler echocardiography[16] and in eight patients by hemodynamic evaluation as well, using the same angiographic projections.

Percutaneous balloon angioplasty was performed in one patient with DORV and postsurgical SAS. The choice of optimal balloon size was based on the criteria for valvular aortic stenosis (Fig 3).[17]

Results

We identified 12 patients (four with tetralogy of Fallot [2.1 percent of 186 patients], five with a VSD [3.2 percent of 153 patients], and three with DORV [21.4 percent of 14 patients]) with acquired postsurgical subaortic obstruction (Table 1) in whom an SAS was diagnosed one to six years (median, three years) after surgical repair (Table 2). In nine of these patients SAS was caused by a fibromuscular ridge and /or accessory mitral tissue; in three patients with DORV, it was caused by a left ventricular infundibular fold apposed to fibrous tissue around the patch.

[TABULAR DATA OMITTED]

Six patients had a left ventricular-aortic peak systolic gradient of less than 40 mm Hg without appearance of aortic regurgitation. Six patients had a left ventricular-aortic peak systolic gradient of 40 mm Hg or more with moderate aortic regurgitation (Fig. 4). Four of these sic patients underwent surgical resection of a subvalvular membrane, and one patient with DORV underwent resection of bilateral bulboventricular flanges. One patient with DORV underwent successful percutaneous balloon angioplasty, which more than halved the left ventricular-aortic (Table 2).

Discussion

The development and incidence of SAS after surgical repair of several congenital heart defects were documented in this series of patients. Although the small number of patients does not allow definitive conclusions, postsurgical SAS seems to be an uncommon complication in patients with VSD and tetralogy of Fallot (3.2 percent and 2.1 percent, respectively) but to be relatively more frequent in patients with DORV (21.4 percent). A possible cause of this difference can be found in the different morphologic features: in patients with DORV the left ventricular infundibular fold more frequently induces a subaortic narrowing apposed to fibrous tissue around the patch.

It is conceivable that, in the presence of a VSD, the hemodynamic diagnosis of a subaortic obstruction (peak-to-peak catheterization gradient or instantaneous echo-Doppler gradient) might be difficult.[2,18] The VSD may decompress the left ventricle and minimize any pressure gradient, and at angiocardiography the contrast material shunted through the VSD may mask the presence of a membrane in the left ventricular outflow tract. Thus, the obstruction may become hemodynamically relevant and unmasked only after closure of the VSD. Therefore, the diagnosis of subaortic obstruction is usually made on the basis of morphologic data obtained at two-dimensional echocardiography rather than on the basis of the hemodynamic gradient. However, in all of our cases, there was no evidence of obstruction at the angiographic, two-dimensional echocardiographic, and Doppler examinations obtained before surgical closure of the VSD.

The finding of significant SAS some years after surgery in all of these patients suggests that trivial or mild obstruction tend to progress. The etiology and pathogenesis of SAS are still incompletely understood. A possible mechanism can be found in the hemodynamic changes due to surgical repair. However, there are still some unresolved questions: Is the development of the subaortic obstruction in congenital heart defects an acquired, progressive, independent process? Is the surgical closure of VSD a determinant or just an accelerating factor?

In conclusion, we believe that discrete SAS is an uncommon late complication of surgical repair of several congenital heart defects, including VSD closure, and that it is an acquired condition with progressive hemodynamic severity. Recent studies and our experience suggest that this malformation requires surgical treatment or percutaneous balloon angioplasty.[18-22]

References

[1] Newfeld EA, Muster AJ, Paul MH, Idrin FS, Riker WL. Discrete subaortic stenosis in childhood. Am J Cardiol 1977; 38:53-61 [2] Vogel M, Freedom RM, Brand A, Trusler GA, Williams WG, Rowe DR. Ventricular septal defect and subaortic stenosis: an analysis of 41 patients. Am J Cardiol 1983; 52:1258-63 [3] Radhakrishnan S, Shrivastava S. Tetralogy of Fallot with discrete subaortic shelf: cross-sectional echocardiographic and Doppler diagnosis of a rare association. Int J Cardiol 1989; 23:413-14 [4] Sanders JH Jr, Van Praagh R, Sade RM. Tetralogy of Fallot with discrete fibrous subaortic stenosis. Chest 1976; 69:543-44 [5] Moene RJ, Gihenberger-de Groot AC, Oppenheimer-Dekker A, Bartelings MM. Anatomic characteristics of ventricular septal defect associated with coarctation of the aorta. Am J Cardiol 1987; 59:952-55 [6] Mathewson JW, Riemenschneider TA, McGough EC, Condon VR. Left ventricular outflow tract obstruction produced by redundant mitral valve tissues in a neonate: clinical, angiographic and operative findings. Circulation 1976; 53:196-99 [7] Edwards JE. Pathology of left ventricular outflow tract obstruction. Circulation 1965; 32:586-99 [8] Moulaert AJ, Oppenheimer-Dekker A. Anterolateral muscle bundle of the left ventricle bulboventricular flange and subaortic stenosis. Am J Cardiol 1963; 11:714-25 [9] Wright GB, Keane JF, Nadas AS, Bernhard WF, Castaneda AR. Fixed subaortic stenosis in the young: medical and surgical course in 83 patients. Am J Cardiol 1983; 52:830-35 [10] Freedom RM, Fowler RS, Duncan WJ. Rapid evolution from "normal" left ventricular outflow tract to fatal subaortic stenosis in infancy. Br Heart J 1981; 45:605-09 [11] Leichter DA, Sullivan I, Gersony WH. "Acquired" discrete subvalvular aortic stenosis: natural history and hemodynamics. J Am Coll Cardiol 1989; 14:1539-44 [12] Ben-Shachar G, Moller JH, Castaneda-Zuniga W, Edwards JE. Signs of membranous subaortic stenosis appearing after correction of persistent common atrioventricular canal. Am J cardiol 1981; 48:340-44 [13] Christy C, Noonan JA, O'Connor WN. Discrete subvalvular aortic stenosis after tetralogy of Fallot. Br Heart J 1983; 49:510 12 [14] Misra M, Thakur R, Bhandari K. Development of subaortic stenosis and regurgitation several years after successful operation on a common atrium. Br Heart J 1987; 531-33 [15] Hegesh JT, Marx GR, Allen HD. Development of subaortic membrane after surgical closure of a membranous ventricular septal defect in an infant. Am Heart J 1987; 114:899-901 [16] Pierli C, Marino B, Picardo S, Corno A, Pasquini L, Marcelletti C. Discrete subaortic stenosis. Chest 1989; 96:325-28 [17] Rocchini AP, Beekman RH, Ben-Shachar G, Benson L, Schwartz D, Kan JS. Balloon aortic valvuloplasty: results of the valvuloplasty and angioplasty of congenital anomalies registry. Am J Cardiol 1990; 65:784-89 [18] Freedom RM, Culham J, Rowe RD. Angiocardiography of subaortic obstruction in infancy. AJR 1977; 129:813 [19] Swarez De Lezo J, Pan M, Sancho M, Herrera N, Arizon J, Franco M, et al. Percutaneous transluminal balloon dilatation for discrete subaortic stenosis. Am J Cardiol 1986; 58:619-21 [20] Lababidi Z, Weinhaus L, Stoeckle, Walls JT. Transluminal balloon dilatation for discrete subaortic stenosis. Am J Cardiol 1987; 59:423-25 [21] Bahl VK, Radhakrishnan S, Shrivastava S. Balloon dilatation of subaortic stenosis due to a thick fibrous shelf. Int J Cardiol 1988; 18:259-60 [22] Arora R, Goel PK, Lochan R, Mohan JC, Khalilullah M. Percutaneous transluminal balloon dilatation in discrete subaortic stenosis. Am Heart J 1988; 116:1091-92

COPYRIGHT 1992 American College of Chest Physicians
COPYRIGHT 2004 Gale Group