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Discrete subvalvular aortic stenosis
Discrete subvalvular aortic stenosis An evaluation of operative therapy Angiocardiographic and operative observations support the validity of classifying the spectrum of congenital subvalvular aortic stenosis into a membrane, fibromuscular collar, and tunnel. Our current operative method is to excise a thin membrane or thick fibrous ridge. and. if a fibromuscular collar or tunnel is identified. to effect a left ventricular myomectomy as described by Morrow for hypertrophic subaortic stenosis. Data from experience with 35 children indicate that this approach is effective and safe. Gradients are substantially reduced and residual obstruction acceptable. Successive clinical evaluations (100 percent of 33 survivors) over an interval of 1 to 13 years (mean of 6) affirm that amelioration of the obstruction endures.
Robert L. Hardesty, M.D. (by invitation), Bartley P. Griffith, M.D. (by invitation), Robert A. Mathews, M.D. (by invitation), Ralph D. Siewers, M.D. (by invitation), William H. Neches, M.D. (by invitation), Sang C. Park, M.D. (by invitation), and Henry T. Bahnson, M.D., Pittsburgh, Pa.
T
he morbid anatomy of congenital subvalvular aortic stenosis includes a spectrum of abnormalities which obstruct the outflow tract of the left ventricle. At one extreme is the thin membrane and at the other, the tubular tunnel. Midway in the spectrum an anatomic abnormality may be selected and labeled a fibromuscular collar. Angiocardiographic and operative observations support the validity of this classification, which is applicable to operative therapy and the evaluation of current operative methods.
Methods Data base. Thirty-five children have undergone operative treatment for congenital subvalvular aortic stenosis at the University Health Center of Pittsburgh, Pennsylvania, during the interval from Jan. 1, 1962, to Dec. 31, 1976. For this review, data have been extracted from the out-patient records and cardiac catheterizations of the Pediatric Cardiology Department at Children's Hospital of Pittsburgh as well as from the operative and hospital records. Cardiac catheterization. Resting peak systolic pressure gradients from the left ventricle to the aorta From the Departments of Surgery and Pediatric Cardiology. University Health Center of Pittsburgh, Pittsburgh. Pa. 15261. Read at the Fifty-seventh Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada. April 18, 19, and 20, 1977.
352
have been determined by sequential measurements for which access has been obtained by a retrograde arterial approach or an antegrade approach through a patent foramen ovale. Cineangiographic studies of the left ventricle and aorta have been performed; occasionally, a direct injection into the subaortic pouch! has been obtained. On the basis of angiocardiographic observations, the subvalvular aortic stenoses have been classified into three categories: the thin membrane; a longer, thicker ridge with a muscular base having the appearance of a collar; and the long, tunnel-like narrowing of the left ventricular outflow tract. 3. 5A spectrum has been evident, the transition from one category to another being indistinct, and the difference, one of degree. Operative procedure. High-flow cardiopulmonary bypass with moderate hypothermia (28 to 31 C.) has been used consistently. Topical hypothermia (lactated Ringer's solution at 170 C.) was added in 1973 for myocardial preservation during the average 25 minutes of ischemic arrest. The aortotomy has been transverse, close to the sinus ridge, and extending into the noncoronary sinus. The subvalvular area has been visualized by retracting the aortic leaflet. Membranous obstruction has been identified as a thin, crescent-shaped fibrous membrane extending across the anterior portion of the outflow tract beneath the aortic annulus and attaching at each 0
0
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Discrete subvalvular aortic stenosis
Number 3
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150 140 130 120 E 110 Iz 100 LLJ 90 0 <[ ll:: 80 <.::> 70 :><: <[ 60 LLJ c... 50 0 <[ 40 > 30 --l 20 10 0
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Fig. 1. Lack of correlation of electrocardiographic evidence of left ventricular hypertrophy (LVH) with magnitude of the left ventricular-aortic (LV-Ao) gradients and ages of patients preoperatively.
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Fig. 2. Progression of left ventricular-aortic (LV-Ao) gradients preoperatively demonstrated by serial catheterizations (CATH). end to the anterior leaflet of the mitral valve. Continuing across this leaflet, it occasionally has formed a circumferential obstruction. Commonly, it has been contiguous with the base of the right and left leaflets of the aortic valve. Detaching the membrane from the ventricular septum and dissecting toward each end of the crescent has been useful in protecting the leaflets of the mitral and aortic valves. All abnormal fibrous suspensions between the mitral leaflet and the aortic annulus and ventricular septum have been excised as well. The resection of the membrane has been as exten-
sive as possible within the anatomic limitations of this region. A fibromuscular collar in the subvalvular area has been identified as a more diffuse narrowing of the left ventricular outflow tract characterized by a thick and irregular fibrous ridge instead of a thin membrane. When this thick ridge has been removed, the outflow tract has remained narrow owing to concentric thickening of that portion of the septum and free wall proximal to the aortic annulus. As described by Morrow and associates- for idiopathic hypertrophic subaortic
The Journal of Thoracic and Cardiovascular Surgery
354 Hardesty et al.
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Fig. 3. Absolute and median (f---l) left ventricular-aortic (LV-Ao) gradients preoperatively categorized according to type of subvalvular obstruction.
Table I. Symptoms, ages, types of subvalvular stenoses, and left ventricular-aortic (LV-Ao) gradients among six patients having symptoms preoperatively Symptom Dyspnea/fatique Syncope Fatique Dyspnea Dyspnea Chest pain
Age (yr.)
7 9
12 12 12
6
Type Membrane Membrane Valve + membrane Collar Collar Collar valve
LV-Ao gradient (torr)
60 60 60 70 70 80
stenosis, a left ventricular myomectomy has been accomplished. A knife blade has been used to make a myotomy just below the base of the right coronary leaflet and immediately to the right of the commissure between the left and right coronary leaflets. A second myotomy has been made parallel to and to the right of the first to remove a rectangular bar of septal muscle. The resulting channel has begun beneath the aortic annulus, extended over the "hump," and ended on the trabeculated portion of the septum. Its width has been approximately one half of the length of the right aortic leaflet at its attachment to the annulus, and its depth has been slightly less than the width. The distinction between a fibromuscular collar and tunnel stenosis has been the long, tubular narrowing characteristic of the latter. Thick fibrous scar has covered the ventricular free wall anteriorly, extended onto the anterior leaflet of the mitral valve at both ends, and
extended onto the papillary muscles toward the apex. The septum and free wall have been concentrically thickened to a greater degree than with the fibromuscular collar, and the narrowing of the left ventricular outflow tract has been longer and more severe. Idiopathic hypertrophic subaortic stenosis has been differentiated from the congenital stenoses by disproportionate thickening of the septum relative to the free wall. Late evaluation. Immediately following discharge, the patients have been evaluated by the surgical staff and subsequently by the staff of the pediatric cardiology department. Generally, each patient has been evaluated annually or at longer or shorter intervals chosen on the basis of the clinical assessment. Selection for a postoperative catheterization has been based on the presence of a systolic thrill, on a concern about having measured an unsatisfactory gradient operatively, or on persistent left ventricular hypertrophy. Recently, the trend has been to repeat the catheterization in every patient at an interval of 1 to 2 years following operation.
Results Preoperative considerations. The accurate clinical identification of isolated subvalvular aortic stenosis has been good, but on occasion a ventricular septal defect and subvalvular stenosis have been confused. Valvular aortic stenosis has been differentiated from the subvalvular type by the presence of a systolic click and a point of maximal intensity at the high right sternal border occurring with the valvular type. The presence of a
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Fig. 4. Left ventricular angiogram in right anterior oblique projection showing a thin, membranous subvalvularobstruction. systolic thrill at the mid-left sternal border has been the common indication for an initial catheterization. Fourty-nine percent of the patients (17/35) having a gradient from the left ventricle to the aorta of at least 50 torr had no evidence of left ventricular hypertrophy on the electrocardiogram. The age of the patient and the magnitude of the gradient have not correlated with the presence or absence of left ventricular hypertrophy (Fig. I). Symptoms, occurring in 17 percent (6/35), have included dyspnea, fatigue, syncope, and chest pain. Those children having symptoms have been the same age and have had the same gradient as the mean (Table I); those having the largest gradients have been asymptomatic. Progression of the gradient has been documented in seven instances over an interval of 2 to 6 years (Fig. 2) when a mild gradient has been identified initially or operative therapy has been delayed. The 35 children who were selected for operation had a resting peak systolic gradient (Fig. 3) ranging from 40 torr to 145 torr (mean 80 torr). Their ages ranged from 3 to 16 years (mean 7 years). Retrospectively, the obstructions could all be accurately recognized and classified into the categories of thin (Fig. 4) or thick membranes (Fig. 5), fibromuscular collars (Fig. 6), and tunnel (Fig. 7). Prospectively, nine of the thirteen fibromuscular collars had been accurately identified. Associated valvular stenosis has been accurately identified from the cineangiogram in each of the eight children with combined lesions.
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Fig. 5. Left ventricular angiogram in the posteroanterior projection demonstrating a thick, membranous subvalvular obstruction.
Fig. 6. Left ventricular angiogram in the lateral viewshowing a fibromuscular collar.
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Surgery
Fig. 8. Distribution of types of subvalvular aortic stenosis and incidence of valvular aortic stenosis encountered among 35 children treated operatively.
Fig. 7. Left ventricular angiogram in a lateral projection demonstrating a tunnel subvalvular stenosis.
Table II. Information regarding three reoperations for subvalvular aortic stenosis _ _ _ _ _1
Case 1
Preop. gradient Operation
85
Postop. gradient Reoperation
70
torr Membrane
torr Valve + membrane 100 torr Myomectomy
Postop. gradient
No thrill
45
torr Valve
Case 3
1--c-a-s-e-2-100
torr
torr Valve + membrane 80 torr Valve + myomectomy 35 torr 145
Associated anomalies have included an atrial septal defect (one), ventricular septal defects (three), patent ductus arteriosus (three), coarctation (two), valvular pulmonic stenosis (one), and infundibular pulmonic stenosis (two). Operative considerations. The types of subvalvular obstruction have been categorized according to the anatomy described intraoperatively (Fig. 8). These have consisted of fifteen thin membranes (43 percent), six thin membranes having valvular stenosis (17 percent), eleven fibromuscular collars (31 percent), two fibromuscular collars with associated valvular stenosis
(6 percent), and one tunnel-like obstruction (3 percent). Excision of the membrane alone has been accomplished in 15 instances and combined with an aortic valvulotomy in six. In one boy who had a residual intraoperative gradient of 60 torr, asystole developed very early in the postoperative period. Excision of an unrecognized membrane was necessary once as a second procedure one year following an aortic commissurotomy (Table II). Two injuries of the anterior leaflet of the mitral valve were repaired; in no case has the aortic leaflet been damaged. Removal of the thick fibrous ridge and scarring combined with a left ventricular myomectomy has been executed as a primary procedure II times. Ventricular myomectomy has been performed as a second procedure twice and has resulted in a satisfactory reduction of the residual gradient. Both patients had a concomitant valvulotomy with the first procedure; although a repeat commissurotomy was done on one occasion at the time of myomectomy, the subvalvular component was believed to be dominant (Table II). One girl died, but the cause of her low cardiac output remained obscure. The mitral and aortic leaflets have not been injured, and in no case has an iatrogenic ventricular septal defect been created. Complete heart block necessitating insertion of a permanent pacemaker developed in one girl. The single child having a tunnel-like subvalvular obstruction has had the fibrous component excised but has not undergone myomectomy. Left ventricular pressures have been measured trans-
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Fig. 9. Reduction of the left ventricular-aortic (LV-Ao) gradients from measurements made at the conclusion of the procedures (Op).
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Fig. 10. Reduction in the intensity of aortic stenosis murmurs postoperatively except in instances where the residual gradients have been unacceptable.
septally and simultaneously with that in the brachial artery during 60 percent of the procedures (21/35). Two children had significant residual gradients (Fig. 9).
The operative mortality rate was 6 percent (2/35). Late evaluations. Thirty-three survivors (100 percent) have been evaluated during an interval of 1 to 13 years following their operations (mean, 6 years). Although one patient changed residence after 7 years of evaluation and no subsequent information has been obtained, her postoperative result has been a good one with no suggestion of any potential problem. Seven children have had a residual thrill leading to
suspicion of a significant residual gradient. Two had had a fibromuscular collar for which they were treated by resection of the fibrous ridge and a myomectomy; one of these had had a valvulotomy as well. Reduction of the gradients from 100 to 46 torr 1 year later and from 70 to 47 torr 9 years postoperatively has been considered to be acceptable. A boy in whom the operative description was that of a thin membrane and valvular stenosis had a residual gradient of 80 torr 1 year later, for which another procedure has been suggested. The single child whose obstruction of 110 torr was due to a tunnel deformity had a persistent gradient of 100 torr when studied 4
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Fig. 11. Reduction of the left ventricular-aortic (LV-Ao) gradients ascertained by postoperative catheterizations. years following operation; his parents had refused a myomectomy 7 years following the initial procedure. In two children, a myomectomy performed as a second procedure has reduced the gradients from 100 to 46 torr and 80 to 35 torr, respectively, 1 year later. The child whose gradient was 46 torr continued to have a thrill. A thin membrane that was not recognized at the time of valvulotomy resulted in a persistent gradient of 70 torr 1 year thereafter; 8 years following resection of that membrane, the boy had no thrill. Twenty-six patients have had persistent systolic murmurs without a thrill from 1 to 6 years postoperatively. Twelve patients have had no thrill 6 to 13 years after operation (Fig. 10). Seven of these without a thrill' have been restudied, and each has a residual gradient of less than 35 torr (Fig. II). Catheterization values have exceeded intraoperative figures by 5 to 25 torr. Three children who had no aortic insufficiency prior to the operation have acquired a faint diastolic murmur (Grade 1/6). All murmurs had been evident immediately after operation, and none had progressed over a 1 to 6 year period. A faint murmur present in four instances preoperatively, and confirmed as a trace of aortic insufficiency by cineaortograms, progressed (Grade 2/6) in the 1 to 6 years of evaluation. One had progressed to a murmur of moderate intensity (Grade 3/6) 10 years postoperatively, but the patient had not shown radiographic evidence of left ventricular enlargement, and she was not symptomatic. All seven patients with new or progressive aortic regurgitation had an aortic commissurotomy in addition to treatment of the subvalvular obstruction (Fig. 12).
Six patients with isolated subvalvular obstruction had a faint diastolic murmur (Grade 1/6) prior to operation which did not progress; 22 continue to have none (Fig. 12). Symptoms have abated immediately (6/6), and no one has been symptomatic subsequently. Left ventricular hypertrophy has resolved in 64 percent (11/ 17). The remaining six have unacceptable residual gradients (2 patients) or an acceptable gradient of 40 to 47 torr. One injury of the mitral valve has not progressed, but another led to a late death. Acute bacterial endocarditis, not related to the operative procedure, resulted in one late death, and malfunction of a pacemaker resulted in the third (Table III). Discussion
The pathological anatomy of congenital valvular stenosis includes a broad spectrum of abnormalities which narrow and obstruct the outflow tract of the left ventricle. At one end of this spectrum is' the thin (discrete) subvalvular membranous stenosis, which is characterized by a relatively thin (1 to 2 em.) crescent-shaped or circumferential fibrous diaphragm extending across the anterior portion of the outflow tract beneath the aortic annulus and attaching to the anterior leaflet of the mitral valve. At the opposite end of the spectrum is the diffuse tubular narrowing of tunnel subvalvular stenosis, which is characterized by a thick and irregular ridge of fibrous tissue covering the ventricular septum and the left ventricular free wall anteriorly and extending onto the aortic leaflet of the mitral valve. Toward the apex it involves the papillary
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Discrete subvalvular aortic stenosis
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• SUBVALVULAR + VALVULAR
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Fig. 12. Intensity of aortic insufficiency (AI) murmur during postoperative evaluations.
muscles. The septum and free wall are concentrically thickened, the aortic annulus may be small, the mitral orifice is of normal size, and the mitral valve is positioned normally in the left ventricular cavity. 4 Arbitrarily, an anatomic abnormality may be selected midway in the spectrum and labeled a fibromuscular collar. 3 Such a subdivision is justified to compare the effectiveness of current operative methods. This spectrum of abnormalities can be differentiated by angiocardiography. 5. 6 The significance of distinguishing between a thin, membranous diaphragm and a thick, annular fibrous band located at a greater distance below the valve (Types I and II of Deutsch and associates") is dubious. Delineating a fibromuscular collar (Type III of Deutsch and associates") is of great import in assessing the efficacy of the operative method. A thin membrane and the tubular narrowing of tunnel stenosis are readily apparent to the surgeon at operation. The distinction between a thick membrane and a fibromuscular collar necessarily invokes judgement as to whether or not the outflow tract remains narrow because of concentric thickening of the septum and free wall after the thick fibrous ridge is excised. Our current operative method is to excise a thin membrane or thick fibrous ridge, and, if a fibromuscular collar is identified by angiocardiogram or operative inspection, to effect a left ventricular myomectomy as described by Morrow and colleagues" for hypertrophic subaortic stenosis. Our data show that this approach is effective and safe. Operative and postoperative measurements of gradients indicate a substantial reduction and acceptable residual obstruction when the appropriate operative method is selected, and the successive
Table III. Causes of operative and late deaths _ _ _ _ _ _ _ _ _ _ _ _ _ _I_ _y_e_ar
Operative deaths Asystole Low cardiac output Late deaths Mitral insufficiency Bacterial endocarditis Pacer malfunction
_
1966 1967 1963-1967 1962-1964 1971-1974
clinical evaluation affirm that amelioration of the obstruction endures. Tunnel stenosis is a severe malformation, and the operative treatment is not as uniformly effective. Substantial reduction of the outflow gradient can be achieved, but a significant residual may rernain.s- 4. 6-8 The adequacy of treatment of the fibromuscular collar depends on the severity of the malformation and the operative method. Our results with a left ventricular myomectomy and excision of the thick fibrous ridge establish that the gradient can be reduced significantly and abolished frequently. An effective operation during childhood must convert the fixed stenotic orifice to an unobstructed one which can continue to increase as growth occurs. Hemodynamic studies of fixed subvalvular aortic stenosis indicate that the outflow gradient progresses because of increasing flow across a fixed obstruction and that, in rare instances, a decreasing orifice area is an additional factor in the progression. 9 Recurrence after satisfactory alleviation of the obstruction has not been evident in our experience. An unacceptable residual obstruction is
The Journal of Thoracic and Cardiovascular Surgery
3 60 Hardesty et al.
a consequence of an inadequate operative methodincomplete excision of a membrane, nonrecognition of a fibromuscular collar, or confinement to a meager excision and myomectomy by the anatomic boundaries. Scant evidence is available to support the thought that proliferation and regrowth of fibromuscular tissue occurs. An associated valvular stenosis does not alter the effectiveness of the operation in reducing the left ventricular-aortic gradient and obtaining a satisfactory residual. In the short and long term, its presence is associated with iatrogenically acquired and augmented aortic regurgitation which is slowly progressive. In the absence of a commissurotomy, aortic insufficiency is neither worsened by treatment of the subaortic stenosis nor made progressive. Fixed subvalvular aortic stenosis is progressive ,9 and current operative methods are effective and safe. It is reasonable to accept a 40 to 50 torr gradient": 6. 10. 11 as a criterion for operative treatment even when valvular stenosis occurs concomitantly. A membrane can be removed readily, the fibrous ridge of a fibromuscular collar or tunnel excised, and a left ventricular myomectomy executed. The outflow gradient can be reduced and a satisfactory residual attained. The best result will occur on the thin membrane end of the spectrum and substantial improvement will ensue toward the tunnellike side. Hypoplasia of the aortic annulus occurring concomitantly justifies application of a peak systolic gradient of more than 75 torr" as the criterion for operative intervention. In a young child having a gradient of more than 75 torr, associated with the severe form of tunnel deformity and severe hypoplasia of the aortic annulus, palliation can be achieved by using resection of the fibrous ridge and myomectomy as a means of preserving left ventricular function. When growth permits, a left ventricular-aortic prosthesis coupled to a Dacron conduit containing a porcine xenograft can be interposed between the left ventricular apex and the descending thoracic'! or abdominal aorta.P: 14 Symptoms, progressive left ventricular hypertrophy, or left ventricular strain indicate a need for operative treatment.
2 Morrow, A. G., Reitz, B. A., Epstein, S. E., Henry, W. L., Konkle, D. M., Itscoitz, S. B., and Redwood, D. R.: Operative Treatment in Hypertrophic Subaortic Stenosis, Circulation 52: 88, 1974. 3 Newfeld, E. A., Muster, A. J., Paul, M. H., Idriss, F. S., and Riker, W. L.: Discrete Subvalvular Aortic Stenosis in Childhood, Am. J. Cardio!. 38: 53, 1976. 4 Maron, B. 1., Redwood, D. R., Roberts, W. c., Henry, W. L. Morrow, A. G., and Epstein, S. E.: Tunnel Subaortic Stenosis, Circulation 54: 404, 1976. 5 Deutsch, V., Shem-Lov, A., Yahini, J. H., and Newfeld, H. N.: Subaortic Stenosis (Discrete Form): Classification and Angiocardiographic Features, Radiology 101: 275, 1971. 6 Heoffel, J. c., Gengler, L., Henry, M., and Pernat, c.: Angiocardiography in Congenital Subvalvular Aortic Stenosis: Prognosis and Operative Indications, Ann. Thorac. Surg. 23: 122, 1977. 7 Reis, R. L., Peterson, L. M., Mason, D. L., Simon, A. L., and Morrow, A. G.: Congenital Fixed Subvalvular Aortic Stenosis, Circulation 43: II, 1971 (Suppl. I). 8 Kelly, D. L., Wulfsberg, G. A., and Raive, R. D.: Discrete Subaortic Stenosis, Circulation 46: 309, 1972. 9 EI-Said, G., Galioto, F. M., Mullins, C. E., and McNamara, D. G.: Natural Hemodynamic History of Congenital Aortic Stenosis in Childhood, Am. J. Cardio!. 30: 6, 1972. 10 McGoon, D. C., Geha, A. S., Scofield, E. L., and DuShane, J. W.: Surgical Treatment of Congenital Aortic Stenosis, Chest 55: 388, 1969. II Cohen, L. S., Friedman, W. F., and Braunwald, E.: Natural History of Mild Congenital Aortic Stenosis Elucidated by Serial Hemodynamic Studies, Am. J. Cardio!' 30: I, 1972. 12 Bernhard, W. F., Poirer, V., and LaFarge, C. G.: Relief of Congenital Obstruction to Left Ventricular-Aortic Prosthesis, 1. THORAc. CARDIOVASC. SURG. 69: 223, 1975. 13 Cooley, D. A., Norman, J. C., Mullins, C. E., and Grace, R. R.: Left Ventricle to Abdominal Aorta Conduit for Relief of Aortic Stenosis, Cardiovasc. Dis. 2: 376, 1975. 14 Dembitsky, W. P., and Weldon, C. S.: Clinical Experience With the Use of a Valve-Bearing Conduit to Construct a Second Left Ventricular Outflow Tract in Cases of Unresectable Intra-ventricular Obstruction, Ann. Surg. 184: 317, 1976.
We express appreciation to Robert G. Pontius, M.D., for inclusion of his patients in this review.
Discussion DR. CLARENCES. WELDON St. Louis, Mo.
REFERENCES Schaffer, A. J., Kania, H., Cucci, C. E., and DePasquale, N. P.: New Technique for Angiographic Visualization of Membranous Subaortic Stenosis, Br. Heart J. 34: 743, 1972.
Subvalvular aortic stenosis is not an uncommon problem. Of all patients in a pediatric age group who require surgery for aortic stenosis in its various forms, about 20 percent will have subvalvular aortic stenosis. I wish to mention a very simple but, I think, a very useful
Volume74 Number 3 September, 1977
technique in doing this operation. Once the aortic valve has been opened and then retracted, a suture placed in the subvalvular membrane permits the surgeon or an assistant to apply traction at a distance. This maneuver puts the junctions of the membrane with the normal structures of the heart into very prominent relief. It also leaves the operative field totally unobstructed so that it is possible to do a very precise resection of the membrane. The maneuver even permits removal of the endocardium from the septum of the heart. As the incision is carried around in a circle, additional traction sutures can be placed to provide a precise definition of the junction of the membrane with the anterior leaflet of the mitral valve. Thus injury to the mitral valve can be avoided. With these maneuvers, it should always be possible to open the outflow tract of the left ventricle. DR. ANTHONYR. C. DOBELL Montreal, Quebec, Canada
I was struck by the statement in the abstract that aortic insufficiency remains after operation in a number of these patients. It seemed to me that the murmur of aortic insufficiency usually is gone after operation. In fact, I had decided that the murmur of aortic insufficiency was due to the slowing of aortic valve closure by eddy currents above the vascular ring. I would like Dr. Hardesty to expand on the postoperative murmur of aortic insufficiency. Can he explain why this murmur is present so often in those children with discrete subvalvular aortic stenosis?
Discrete subvalvular aortic stenosis
36 1
DR. JOHN C. NORMAN Houston, Texas
In regard to the creation of double-outlet left ventricles, in 14 patients we have used a rigid Pyrolite prosthesis which is inserted into the left ventricular apex and anastomosed to a valved conduit leading to the supraceliac abdominal aorta. All of the gradients have been markedly reduced. We have made similar conduits for about fifty groups in the country and the reported results are essentially the same. DR. ROB E R T L. H A R DES T Y (Closing) I would like to thank the discussers for their comments. Among the four patients who had aortic insufficiency murmurs preoperatively, there was no progression over a relatively short interval prior to the operation. Subsequent to the operation, among those who had isolated subvalvular aortic stenosis without concomitant valvular stenosis, there was no progression of the aortic insufficiency immediately following the operation or later. The only patients in whom aortic insufficiency progressed, based on the murmur alone (which are relatively soft data), were those who had concomitant valvulotomies. One of the explanations for the presence of the aortic insufficiency prior to operation is the fibrous scar which is frequently attached to the base of the leaflets. Whether this is acquired or not remains speculative.
Robert L. Hardesty, M.D. (by invitation), Bartley P. Griffith, M.D. (by invitation), Robert A. Mathews, M.D. (by invitation), Ralph D. Siewers, M.D. (by invitation), William H. Neches, M.D. (by invitation), Sang C. Park, M.D. (by invitation), and Henry T. Bahnson, M.D., Pittsburgh, Pa.
T
he morbid anatomy of congenital subvalvular aortic stenosis includes a spectrum of abnormalities which obstruct the outflow tract of the left ventricle. At one extreme is the thin membrane and at the other, the tubular tunnel. Midway in the spectrum an anatomic abnormality may be selected and labeled a fibromuscular collar. Angiocardiographic and operative observations support the validity of this classification, which is applicable to operative therapy and the evaluation of current operative methods.
Methods Data base. Thirty-five children have undergone operative treatment for congenital subvalvular aortic stenosis at the University Health Center of Pittsburgh, Pennsylvania, during the interval from Jan. 1, 1962, to Dec. 31, 1976. For this review, data have been extracted from the out-patient records and cardiac catheterizations of the Pediatric Cardiology Department at Children's Hospital of Pittsburgh as well as from the operative and hospital records. Cardiac catheterization. Resting peak systolic pressure gradients from the left ventricle to the aorta From the Departments of Surgery and Pediatric Cardiology. University Health Center of Pittsburgh, Pittsburgh. Pa. 15261. Read at the Fifty-seventh Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada. April 18, 19, and 20, 1977.
352
have been determined by sequential measurements for which access has been obtained by a retrograde arterial approach or an antegrade approach through a patent foramen ovale. Cineangiographic studies of the left ventricle and aorta have been performed; occasionally, a direct injection into the subaortic pouch! has been obtained. On the basis of angiocardiographic observations, the subvalvular aortic stenoses have been classified into three categories: the thin membrane; a longer, thicker ridge with a muscular base having the appearance of a collar; and the long, tunnel-like narrowing of the left ventricular outflow tract. 3. 5A spectrum has been evident, the transition from one category to another being indistinct, and the difference, one of degree. Operative procedure. High-flow cardiopulmonary bypass with moderate hypothermia (28 to 31 C.) has been used consistently. Topical hypothermia (lactated Ringer's solution at 170 C.) was added in 1973 for myocardial preservation during the average 25 minutes of ischemic arrest. The aortotomy has been transverse, close to the sinus ridge, and extending into the noncoronary sinus. The subvalvular area has been visualized by retracting the aortic leaflet. Membranous obstruction has been identified as a thin, crescent-shaped fibrous membrane extending across the anterior portion of the outflow tract beneath the aortic annulus and attaching at each 0
0
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Discrete subvalvular aortic stenosis
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September, 1977
150 140 130 120 E 110 Iz 100 LLJ 90 0 <[ ll:: 80 <.::> 70 :><: <[ 60 LLJ c... 50 0 <[ 40 > 30 --l 20 10 0
•
o NO LVH • LVH
0
~
0
• 0
•
0
• • • •
0
0 0
• 0
• •
• 0
tl
•
•
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o
•
• 0
o
0
•
•
0
I
0
2
3
4 5 6 7 8 9 10 II 12 13 14 15 16 AGE AT OPERATION (YEARS)
Fig. 1. Lack of correlation of electrocardiographic evidence of left ventricular hypertrophy (LVH) with magnitude of the left ventricular-aortic (LV-Ao) gradients and ages of patients preoperatively.
130 120 I - 110 z LLJ a<[ 100 90 ll:: <.::> 80 :><: 70 <[ LLJ c... 60 0 50 <[ I 40 > --l 30 20 10 0
o MEMBRANE o MEMBRANE
+ VALVE • COLLAR o COLLAR + VALVE
t
2
3
4
CATH I
5 6 7 8 YEARS POST -CATH
9
10
II
Fig. 2. Progression of left ventricular-aortic (LV-Ao) gradients preoperatively demonstrated by serial catheterizations (CATH). end to the anterior leaflet of the mitral valve. Continuing across this leaflet, it occasionally has formed a circumferential obstruction. Commonly, it has been contiguous with the base of the right and left leaflets of the aortic valve. Detaching the membrane from the ventricular septum and dissecting toward each end of the crescent has been useful in protecting the leaflets of the mitral and aortic valves. All abnormal fibrous suspensions between the mitral leaflet and the aortic annulus and ventricular septum have been excised as well. The resection of the membrane has been as exten-
sive as possible within the anatomic limitations of this region. A fibromuscular collar in the subvalvular area has been identified as a more diffuse narrowing of the left ventricular outflow tract characterized by a thick and irregular fibrous ridge instead of a thin membrane. When this thick ridge has been removed, the outflow tract has remained narrow owing to concentric thickening of that portion of the septum and free wall proximal to the aortic annulus. As described by Morrow and associates- for idiopathic hypertrophic subaortic
The Journal of Thoracic and Cardiovascular Surgery
354 Hardesty et al.
140
~ 120 l-
z 100
lJ.J
Cl
c:: <.::>
:.::
80
60
0
40
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• • • A •
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•
-
~
•
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20 0
MEMBRANE MEMBRANE + VALVE
COL LAR
COLLAR
+ VALVE
TUNNEL
Fig. 3. Absolute and median (f---l) left ventricular-aortic (LV-Ao) gradients preoperatively categorized according to type of subvalvular obstruction.
Table I. Symptoms, ages, types of subvalvular stenoses, and left ventricular-aortic (LV-Ao) gradients among six patients having symptoms preoperatively Symptom Dyspnea/fatique Syncope Fatique Dyspnea Dyspnea Chest pain
Age (yr.)
7 9
12 12 12
6
Type Membrane Membrane Valve + membrane Collar Collar Collar valve
LV-Ao gradient (torr)
60 60 60 70 70 80
stenosis, a left ventricular myomectomy has been accomplished. A knife blade has been used to make a myotomy just below the base of the right coronary leaflet and immediately to the right of the commissure between the left and right coronary leaflets. A second myotomy has been made parallel to and to the right of the first to remove a rectangular bar of septal muscle. The resulting channel has begun beneath the aortic annulus, extended over the "hump," and ended on the trabeculated portion of the septum. Its width has been approximately one half of the length of the right aortic leaflet at its attachment to the annulus, and its depth has been slightly less than the width. The distinction between a fibromuscular collar and tunnel stenosis has been the long, tubular narrowing characteristic of the latter. Thick fibrous scar has covered the ventricular free wall anteriorly, extended onto the anterior leaflet of the mitral valve at both ends, and
extended onto the papillary muscles toward the apex. The septum and free wall have been concentrically thickened to a greater degree than with the fibromuscular collar, and the narrowing of the left ventricular outflow tract has been longer and more severe. Idiopathic hypertrophic subaortic stenosis has been differentiated from the congenital stenoses by disproportionate thickening of the septum relative to the free wall. Late evaluation. Immediately following discharge, the patients have been evaluated by the surgical staff and subsequently by the staff of the pediatric cardiology department. Generally, each patient has been evaluated annually or at longer or shorter intervals chosen on the basis of the clinical assessment. Selection for a postoperative catheterization has been based on the presence of a systolic thrill, on a concern about having measured an unsatisfactory gradient operatively, or on persistent left ventricular hypertrophy. Recently, the trend has been to repeat the catheterization in every patient at an interval of 1 to 2 years following operation.
Results Preoperative considerations. The accurate clinical identification of isolated subvalvular aortic stenosis has been good, but on occasion a ventricular septal defect and subvalvular stenosis have been confused. Valvular aortic stenosis has been differentiated from the subvalvular type by the presence of a systolic click and a point of maximal intensity at the high right sternal border occurring with the valvular type. The presence of a
Volume 74
Number3 September, 1977
Fig. 4. Left ventricular angiogram in right anterior oblique projection showing a thin, membranous subvalvularobstruction. systolic thrill at the mid-left sternal border has been the common indication for an initial catheterization. Fourty-nine percent of the patients (17/35) having a gradient from the left ventricle to the aorta of at least 50 torr had no evidence of left ventricular hypertrophy on the electrocardiogram. The age of the patient and the magnitude of the gradient have not correlated with the presence or absence of left ventricular hypertrophy (Fig. I). Symptoms, occurring in 17 percent (6/35), have included dyspnea, fatigue, syncope, and chest pain. Those children having symptoms have been the same age and have had the same gradient as the mean (Table I); those having the largest gradients have been asymptomatic. Progression of the gradient has been documented in seven instances over an interval of 2 to 6 years (Fig. 2) when a mild gradient has been identified initially or operative therapy has been delayed. The 35 children who were selected for operation had a resting peak systolic gradient (Fig. 3) ranging from 40 torr to 145 torr (mean 80 torr). Their ages ranged from 3 to 16 years (mean 7 years). Retrospectively, the obstructions could all be accurately recognized and classified into the categories of thin (Fig. 4) or thick membranes (Fig. 5), fibromuscular collars (Fig. 6), and tunnel (Fig. 7). Prospectively, nine of the thirteen fibromuscular collars had been accurately identified. Associated valvular stenosis has been accurately identified from the cineangiogram in each of the eight children with combined lesions.
Discrete subvalvular aortic stenosis
355
Fig. 5. Left ventricular angiogram in the posteroanterior projection demonstrating a thick, membranous subvalvular obstruction.
Fig. 6. Left ventricular angiogram in the lateral viewshowing a fibromuscular collar.
The Journal of Thoracic and Cardiovascular
356 Hardesty et al.
Surgery
Fig. 8. Distribution of types of subvalvular aortic stenosis and incidence of valvular aortic stenosis encountered among 35 children treated operatively.
Fig. 7. Left ventricular angiogram in a lateral projection demonstrating a tunnel subvalvular stenosis.
Table II. Information regarding three reoperations for subvalvular aortic stenosis _ _ _ _ _1
Case 1
Preop. gradient Operation
85
Postop. gradient Reoperation
70
torr Membrane
torr Valve + membrane 100 torr Myomectomy
Postop. gradient
No thrill
45
torr Valve
Case 3
1--c-a-s-e-2-100
torr
torr Valve + membrane 80 torr Valve + myomectomy 35 torr 145
Associated anomalies have included an atrial septal defect (one), ventricular septal defects (three), patent ductus arteriosus (three), coarctation (two), valvular pulmonic stenosis (one), and infundibular pulmonic stenosis (two). Operative considerations. The types of subvalvular obstruction have been categorized according to the anatomy described intraoperatively (Fig. 8). These have consisted of fifteen thin membranes (43 percent), six thin membranes having valvular stenosis (17 percent), eleven fibromuscular collars (31 percent), two fibromuscular collars with associated valvular stenosis
(6 percent), and one tunnel-like obstruction (3 percent). Excision of the membrane alone has been accomplished in 15 instances and combined with an aortic valvulotomy in six. In one boy who had a residual intraoperative gradient of 60 torr, asystole developed very early in the postoperative period. Excision of an unrecognized membrane was necessary once as a second procedure one year following an aortic commissurotomy (Table II). Two injuries of the anterior leaflet of the mitral valve were repaired; in no case has the aortic leaflet been damaged. Removal of the thick fibrous ridge and scarring combined with a left ventricular myomectomy has been executed as a primary procedure II times. Ventricular myomectomy has been performed as a second procedure twice and has resulted in a satisfactory reduction of the residual gradient. Both patients had a concomitant valvulotomy with the first procedure; although a repeat commissurotomy was done on one occasion at the time of myomectomy, the subvalvular component was believed to be dominant (Table II). One girl died, but the cause of her low cardiac output remained obscure. The mitral and aortic leaflets have not been injured, and in no case has an iatrogenic ventricular septal defect been created. Complete heart block necessitating insertion of a permanent pacemaker developed in one girl. The single child having a tunnel-like subvalvular obstruction has had the fibrous component excised but has not undergone myomectomy. Left ventricular pressures have been measured trans-
Volume 74
Discrete subvalvular aortic stenosis
Number 3 September, 1977
......
120
o MEMBRANE o MEMBRANEtVALVE • COLLAR o COLLAR +VALVE
.2 100 I-
~
Cl
357
80
a: <.:>
60
:..::
40
~
20
I
OL..---+------------~
Fig. 9. Reduction of the left ventricular-aortic (LV-Ao) gradients from measurements made at the conclusion of the procedures (Op).
6
-
o RE-OPERATION o RE -OPERATION
PLANNED
5 •
o NO RE-OPERATION
PLANNED
>
I-
u; 4 ----<----t-----CD---+--------+--THRILL z
UJ I-
Z
3
I
-
2
PRE -OP
1111
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---<><>
POST-OP 1-6 YEARS POST-OP 6-14YEARS
Fig. 10. Reduction in the intensity of aortic stenosis murmurs postoperatively except in instances where the residual gradients have been unacceptable.
septally and simultaneously with that in the brachial artery during 60 percent of the procedures (21/35). Two children had significant residual gradients (Fig. 9).
The operative mortality rate was 6 percent (2/35). Late evaluations. Thirty-three survivors (100 percent) have been evaluated during an interval of 1 to 13 years following their operations (mean, 6 years). Although one patient changed residence after 7 years of evaluation and no subsequent information has been obtained, her postoperative result has been a good one with no suggestion of any potential problem. Seven children have had a residual thrill leading to
suspicion of a significant residual gradient. Two had had a fibromuscular collar for which they were treated by resection of the fibrous ridge and a myomectomy; one of these had had a valvulotomy as well. Reduction of the gradients from 100 to 46 torr 1 year later and from 70 to 47 torr 9 years postoperatively has been considered to be acceptable. A boy in whom the operative description was that of a thin membrane and valvular stenosis had a residual gradient of 80 torr 1 year later, for which another procedure has been suggested. The single child whose obstruction of 110 torr was due to a tunnel deformity had a persistent gradient of 100 torr when studied 4
The Journal of
358
Hardesty et ai.
......
Thoracic and Cardiovascular Surgery
o MEMBRANE o MEMBRANE + VALVE
100
• COLLAR
o COLLAR + VALVE
0
f-
z w
80
Ci
a:
~
60
:><::
40
0
> .....J
20
a
t
PRE-OP
2
3
4 5 6 7 YEARS POST-OP
8
9
Fig. 11. Reduction of the left ventricular-aortic (LV-Ao) gradients ascertained by postoperative catheterizations. years following operation; his parents had refused a myomectomy 7 years following the initial procedure. In two children, a myomectomy performed as a second procedure has reduced the gradients from 100 to 46 torr and 80 to 35 torr, respectively, 1 year later. The child whose gradient was 46 torr continued to have a thrill. A thin membrane that was not recognized at the time of valvulotomy resulted in a persistent gradient of 70 torr 1 year thereafter; 8 years following resection of that membrane, the boy had no thrill. Twenty-six patients have had persistent systolic murmurs without a thrill from 1 to 6 years postoperatively. Twelve patients have had no thrill 6 to 13 years after operation (Fig. 10). Seven of these without a thrill' have been restudied, and each has a residual gradient of less than 35 torr (Fig. II). Catheterization values have exceeded intraoperative figures by 5 to 25 torr. Three children who had no aortic insufficiency prior to the operation have acquired a faint diastolic murmur (Grade 1/6). All murmurs had been evident immediately after operation, and none had progressed over a 1 to 6 year period. A faint murmur present in four instances preoperatively, and confirmed as a trace of aortic insufficiency by cineaortograms, progressed (Grade 2/6) in the 1 to 6 years of evaluation. One had progressed to a murmur of moderate intensity (Grade 3/6) 10 years postoperatively, but the patient had not shown radiographic evidence of left ventricular enlargement, and she was not symptomatic. All seven patients with new or progressive aortic regurgitation had an aortic commissurotomy in addition to treatment of the subvalvular obstruction (Fig. 12).
Six patients with isolated subvalvular obstruction had a faint diastolic murmur (Grade 1/6) prior to operation which did not progress; 22 continue to have none (Fig. 12). Symptoms have abated immediately (6/6), and no one has been symptomatic subsequently. Left ventricular hypertrophy has resolved in 64 percent (11/ 17). The remaining six have unacceptable residual gradients (2 patients) or an acceptable gradient of 40 to 47 torr. One injury of the mitral valve has not progressed, but another led to a late death. Acute bacterial endocarditis, not related to the operative procedure, resulted in one late death, and malfunction of a pacemaker resulted in the third (Table III). Discussion
The pathological anatomy of congenital valvular stenosis includes a broad spectrum of abnormalities which narrow and obstruct the outflow tract of the left ventricle. At one end of this spectrum is' the thin (discrete) subvalvular membranous stenosis, which is characterized by a relatively thin (1 to 2 em.) crescent-shaped or circumferential fibrous diaphragm extending across the anterior portion of the outflow tract beneath the aortic annulus and attaching to the anterior leaflet of the mitral valve. At the opposite end of the spectrum is the diffuse tubular narrowing of tunnel subvalvular stenosis, which is characterized by a thick and irregular ridge of fibrous tissue covering the ventricular septum and the left ventricular free wall anteriorly and extending onto the aortic leaflet of the mitral valve. Toward the apex it involves the papillary
Volume 74 Number 3
Discrete subvalvular aortic stenosis
359
September. 1977
• SUBVALVULAR + VALVULAR
4
a::
• SUBVALVULAR
~
~
a:: 3 ~ ~
H
0
2
I.I..J
a a::
Ot...,Hii"'
PRE-OP
~
...L-
------J
POST OP 1-6 YEARS POST-OP 6-14YEARS
Fig. 12. Intensity of aortic insufficiency (AI) murmur during postoperative evaluations.
muscles. The septum and free wall are concentrically thickened, the aortic annulus may be small, the mitral orifice is of normal size, and the mitral valve is positioned normally in the left ventricular cavity. 4 Arbitrarily, an anatomic abnormality may be selected midway in the spectrum and labeled a fibromuscular collar. 3 Such a subdivision is justified to compare the effectiveness of current operative methods. This spectrum of abnormalities can be differentiated by angiocardiography. 5. 6 The significance of distinguishing between a thin, membranous diaphragm and a thick, annular fibrous band located at a greater distance below the valve (Types I and II of Deutsch and associates") is dubious. Delineating a fibromuscular collar (Type III of Deutsch and associates") is of great import in assessing the efficacy of the operative method. A thin membrane and the tubular narrowing of tunnel stenosis are readily apparent to the surgeon at operation. The distinction between a thick membrane and a fibromuscular collar necessarily invokes judgement as to whether or not the outflow tract remains narrow because of concentric thickening of the septum and free wall after the thick fibrous ridge is excised. Our current operative method is to excise a thin membrane or thick fibrous ridge, and, if a fibromuscular collar is identified by angiocardiogram or operative inspection, to effect a left ventricular myomectomy as described by Morrow and colleagues" for hypertrophic subaortic stenosis. Our data show that this approach is effective and safe. Operative and postoperative measurements of gradients indicate a substantial reduction and acceptable residual obstruction when the appropriate operative method is selected, and the successive
Table III. Causes of operative and late deaths _ _ _ _ _ _ _ _ _ _ _ _ _ _I_ _y_e_ar
Operative deaths Asystole Low cardiac output Late deaths Mitral insufficiency Bacterial endocarditis Pacer malfunction
_
1966 1967 1963-1967 1962-1964 1971-1974
clinical evaluation affirm that amelioration of the obstruction endures. Tunnel stenosis is a severe malformation, and the operative treatment is not as uniformly effective. Substantial reduction of the outflow gradient can be achieved, but a significant residual may rernain.s- 4. 6-8 The adequacy of treatment of the fibromuscular collar depends on the severity of the malformation and the operative method. Our results with a left ventricular myomectomy and excision of the thick fibrous ridge establish that the gradient can be reduced significantly and abolished frequently. An effective operation during childhood must convert the fixed stenotic orifice to an unobstructed one which can continue to increase as growth occurs. Hemodynamic studies of fixed subvalvular aortic stenosis indicate that the outflow gradient progresses because of increasing flow across a fixed obstruction and that, in rare instances, a decreasing orifice area is an additional factor in the progression. 9 Recurrence after satisfactory alleviation of the obstruction has not been evident in our experience. An unacceptable residual obstruction is
The Journal of Thoracic and Cardiovascular Surgery
3 60 Hardesty et al.
a consequence of an inadequate operative methodincomplete excision of a membrane, nonrecognition of a fibromuscular collar, or confinement to a meager excision and myomectomy by the anatomic boundaries. Scant evidence is available to support the thought that proliferation and regrowth of fibromuscular tissue occurs. An associated valvular stenosis does not alter the effectiveness of the operation in reducing the left ventricular-aortic gradient and obtaining a satisfactory residual. In the short and long term, its presence is associated with iatrogenically acquired and augmented aortic regurgitation which is slowly progressive. In the absence of a commissurotomy, aortic insufficiency is neither worsened by treatment of the subaortic stenosis nor made progressive. Fixed subvalvular aortic stenosis is progressive ,9 and current operative methods are effective and safe. It is reasonable to accept a 40 to 50 torr gradient": 6. 10. 11 as a criterion for operative treatment even when valvular stenosis occurs concomitantly. A membrane can be removed readily, the fibrous ridge of a fibromuscular collar or tunnel excised, and a left ventricular myomectomy executed. The outflow gradient can be reduced and a satisfactory residual attained. The best result will occur on the thin membrane end of the spectrum and substantial improvement will ensue toward the tunnellike side. Hypoplasia of the aortic annulus occurring concomitantly justifies application of a peak systolic gradient of more than 75 torr" as the criterion for operative intervention. In a young child having a gradient of more than 75 torr, associated with the severe form of tunnel deformity and severe hypoplasia of the aortic annulus, palliation can be achieved by using resection of the fibrous ridge and myomectomy as a means of preserving left ventricular function. When growth permits, a left ventricular-aortic prosthesis coupled to a Dacron conduit containing a porcine xenograft can be interposed between the left ventricular apex and the descending thoracic'! or abdominal aorta.P: 14 Symptoms, progressive left ventricular hypertrophy, or left ventricular strain indicate a need for operative treatment.
2 Morrow, A. G., Reitz, B. A., Epstein, S. E., Henry, W. L., Konkle, D. M., Itscoitz, S. B., and Redwood, D. R.: Operative Treatment in Hypertrophic Subaortic Stenosis, Circulation 52: 88, 1974. 3 Newfeld, E. A., Muster, A. J., Paul, M. H., Idriss, F. S., and Riker, W. L.: Discrete Subvalvular Aortic Stenosis in Childhood, Am. J. Cardio!. 38: 53, 1976. 4 Maron, B. 1., Redwood, D. R., Roberts, W. c., Henry, W. L. Morrow, A. G., and Epstein, S. E.: Tunnel Subaortic Stenosis, Circulation 54: 404, 1976. 5 Deutsch, V., Shem-Lov, A., Yahini, J. H., and Newfeld, H. N.: Subaortic Stenosis (Discrete Form): Classification and Angiocardiographic Features, Radiology 101: 275, 1971. 6 Heoffel, J. c., Gengler, L., Henry, M., and Pernat, c.: Angiocardiography in Congenital Subvalvular Aortic Stenosis: Prognosis and Operative Indications, Ann. Thorac. Surg. 23: 122, 1977. 7 Reis, R. L., Peterson, L. M., Mason, D. L., Simon, A. L., and Morrow, A. G.: Congenital Fixed Subvalvular Aortic Stenosis, Circulation 43: II, 1971 (Suppl. I). 8 Kelly, D. L., Wulfsberg, G. A., and Raive, R. D.: Discrete Subaortic Stenosis, Circulation 46: 309, 1972. 9 EI-Said, G., Galioto, F. M., Mullins, C. E., and McNamara, D. G.: Natural Hemodynamic History of Congenital Aortic Stenosis in Childhood, Am. J. Cardio!. 30: 6, 1972. 10 McGoon, D. C., Geha, A. S., Scofield, E. L., and DuShane, J. W.: Surgical Treatment of Congenital Aortic Stenosis, Chest 55: 388, 1969. II Cohen, L. S., Friedman, W. F., and Braunwald, E.: Natural History of Mild Congenital Aortic Stenosis Elucidated by Serial Hemodynamic Studies, Am. J. Cardio!' 30: I, 1972. 12 Bernhard, W. F., Poirer, V., and LaFarge, C. G.: Relief of Congenital Obstruction to Left Ventricular-Aortic Prosthesis, 1. THORAc. CARDIOVASC. SURG. 69: 223, 1975. 13 Cooley, D. A., Norman, J. C., Mullins, C. E., and Grace, R. R.: Left Ventricle to Abdominal Aorta Conduit for Relief of Aortic Stenosis, Cardiovasc. Dis. 2: 376, 1975. 14 Dembitsky, W. P., and Weldon, C. S.: Clinical Experience With the Use of a Valve-Bearing Conduit to Construct a Second Left Ventricular Outflow Tract in Cases of Unresectable Intra-ventricular Obstruction, Ann. Surg. 184: 317, 1976.
We express appreciation to Robert G. Pontius, M.D., for inclusion of his patients in this review.
Discussion DR. CLARENCES. WELDON St. Louis, Mo.
REFERENCES Schaffer, A. J., Kania, H., Cucci, C. E., and DePasquale, N. P.: New Technique for Angiographic Visualization of Membranous Subaortic Stenosis, Br. Heart J. 34: 743, 1972.
Subvalvular aortic stenosis is not an uncommon problem. Of all patients in a pediatric age group who require surgery for aortic stenosis in its various forms, about 20 percent will have subvalvular aortic stenosis. I wish to mention a very simple but, I think, a very useful
Volume74 Number 3 September, 1977
technique in doing this operation. Once the aortic valve has been opened and then retracted, a suture placed in the subvalvular membrane permits the surgeon or an assistant to apply traction at a distance. This maneuver puts the junctions of the membrane with the normal structures of the heart into very prominent relief. It also leaves the operative field totally unobstructed so that it is possible to do a very precise resection of the membrane. The maneuver even permits removal of the endocardium from the septum of the heart. As the incision is carried around in a circle, additional traction sutures can be placed to provide a precise definition of the junction of the membrane with the anterior leaflet of the mitral valve. Thus injury to the mitral valve can be avoided. With these maneuvers, it should always be possible to open the outflow tract of the left ventricle. DR. ANTHONYR. C. DOBELL Montreal, Quebec, Canada
I was struck by the statement in the abstract that aortic insufficiency remains after operation in a number of these patients. It seemed to me that the murmur of aortic insufficiency usually is gone after operation. In fact, I had decided that the murmur of aortic insufficiency was due to the slowing of aortic valve closure by eddy currents above the vascular ring. I would like Dr. Hardesty to expand on the postoperative murmur of aortic insufficiency. Can he explain why this murmur is present so often in those children with discrete subvalvular aortic stenosis?
Discrete subvalvular aortic stenosis
36 1
DR. JOHN C. NORMAN Houston, Texas
In regard to the creation of double-outlet left ventricles, in 14 patients we have used a rigid Pyrolite prosthesis which is inserted into the left ventricular apex and anastomosed to a valved conduit leading to the supraceliac abdominal aorta. All of the gradients have been markedly reduced. We have made similar conduits for about fifty groups in the country and the reported results are essentially the same. DR. ROB E R T L. H A R DES T Y (Closing) I would like to thank the discussers for their comments. Among the four patients who had aortic insufficiency murmurs preoperatively, there was no progression over a relatively short interval prior to the operation. Subsequent to the operation, among those who had isolated subvalvular aortic stenosis without concomitant valvular stenosis, there was no progression of the aortic insufficiency immediately following the operation or later. The only patients in whom aortic insufficiency progressed, based on the murmur alone (which are relatively soft data), were those who had concomitant valvulotomies. One of the explanations for the presence of the aortic insufficiency prior to operation is the fibrous scar which is frequently attached to the base of the leaflets. Whether this is acquired or not remains speculative.