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Original Articles: Adult Cardiac

The Surgical History, Management, and Outcomes of Subaortic Stenosis in Adults

^a Department of Cardiothoracic Surgery, Great Ormond Street Hospital, London, United Kingdom
^b Department of Cardiothoracic Surgery/Cardiology, The Heart Hospital, London, United Kingdom
^c Heart Science Centre, Imperial College London, Harefield Hospital, London, United Kingdom

Accepted for publication December 28, 2011.

^_* Address correspondence to Mr Tsang, Level 7, Old Nurses Home, Cardiothoracic Department, Great Ormond Street Hospital, Great Ormond St, London WC1N 3JH, United Kingdom (Email: tsangv{at}gosh.nhs.uk).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background: Subaortic stenosis (SAS) is a curtain of tissue involving the subaortic region, the aortic and mitral valves, the septum, and the fibrous trigones. Little is known of its course or the outcomes of its surgical management in adults.

Methods: We reviewed our experience of the surgical management of SAS in adults from 1999 to 2010. We divided patients into three groups: (1) those presenting for first-time SAS resection (6 patients, 4 male, median age of 46.9 ± 17 years, mean follow-up of 5 ± 2.7 years); (2) those requiring redo resection of SAS without organic aortic valve dysfunction (8 patients, 3 male, median age of 25.3 ± 5 years, mean follow-up of 8 ± 3.08 years); and (3) those with SAS and aortic valve dysfunction (8 patients, 4 males, median age of 34.8 ± 12 years, mean follow-up of 4.5 ± 2.5 years; 5 had previous SAS surgery).

Results: Patients underwent extensive excision of the SAS, release of the fibrous trigones, and a septal myectomy if required. There was 1 early death in group 2 and 1 in group 3. In group 3, 1 patient underwent the Ross procedure and 7 patients had mechanical valve implantation. No patient required permanent pacemaker implantation. Overall follow-up was 3.3 ± 3 years (range, 6 months to 10 years). The preoperative left ventricular outflow tract gradient ranged from 40 to 120 mm Hg, and the postoperative left ventricular outflow tract gradient ranged from 0 to 16 mm Hg. At latest follow-up, no patient in groups 1 or 2 had greater than mild native aortic regurgitation.

Conclusions: Subaortic stenosis resection in adults can successfully relieve left ventricular outflow tract obstruction, with low mortality. The complexity of SAS increases with time; therefore a longer duration of follow-up is needed to further validate our conclusions.

	Introduction

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Subaortic stenosis (SAS) is responsible for 8% to 20% of left ventricular outflow tract (LVOT) obstruction in the young [1–3], and yet it is a commonly misunderstood lesion [2]. It is not simply a membrane that obstructs the LVOT but rather consists of an irregular ridge of fibroelastic tissue attached to the muscular septum, usually taking the shape of a crescent [1]. A detailed understanding of the multifactorial causes of SAS is critical to its proper surgical management, and it is important to acknowledge that it is not a true congenital lesion as it is not usually present at birth, but grows during postnatal life and may also recur after surgical correction [4].

Subaortic stenosis is commonly associated with congenital abnormalities such as ventricular septal defect, coarctation of the aorta, and patent ductus arteriosus. The subaortic–mitral angle appears to be important, as is malalignment of the outlet septum, resulting in turbulent flow patterns. These anatomic and morphologic factors lead to important surgical considerations including (1) it is an acquired, progressive lesion, (2) it occupies a short channel between the aortic valve (AV) and the left ventricular (LV) inflow tract, and (3) it is surrounded by important, dynamic structures. Such features suggest that early surgical management is the best option. The ideal SAS resection should therefore provide durable and predictable relief of LVOT obstruction, including freeing of the fibrous trigones, restoring the normal hinge mechanism of the LVOT (which shares a common orifice with the LV inflow tract) while preserving AV and mitral valve function, and it should not compromise the integrity of surrounding conduction tissues. Some of these features are incorporated into the surgical technique proposed by Yacoub and colleagues [5].

A number of factors appear to influence the risk of recurrence, including age at intervention, residual LVOT gradient, and the surgical technique used [4, 6, 7]. However, how these affect outcome, valve function, LVOT velocities, and recurrence is unclear, especially in the adult population. We therefore reviewed our experience of SAS surgery in adults with regard to their management and outcome.

	Material and Methods

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This study passed local ethical review at the Heart Hospital, and individual patient consent was waived.

Patient Population
We included all patients in our center with a diagnosis of SAS or who had a procedure involving SAS. This identified 22 patients who underwent surgery for SAS from 1999 to 2010. Data were collected prospectively and analyzed retrospectively. Patients were followed up by (at least annual) regular visits to the outpatient clinic, where they were assessed clinically using echocardiography. We considered these patients as belonging to one of three groups: (1) those presenting for first-time SAS resection (6 patients, 4 males, with median age of 46.9 years ± 17 years); (2) those presenting for redo resection of a subaortic membrane (8 patients, 3 males, with median age of 25.3 years); and (3) those presenting with SAS with or without previous surgery at the referring hospitals and significant AV dysfunction (8 patients, 4 males, median age of 34.8 ± 12 years).

Operative and midterm outcomes are available for all patients. Overall completeness of follow-up (assessed by the Clark method [8]) is 100%, with a mean length of follow-up after surgery of 3.3 ± 3.0 years (range, 6 months to 10 years).

Operative Technique
The technique for SAS resection has been described previously [5, 9]. Briefly, the conduct of cardiopulmonary bypass strategy is standard. The AV is then exposed by a hockey-stick excision and the subvalvular region is viewed by retracting the leaflets. The subaortic ring is excised deep into the fibrous trigones, restoring the proper hinge mechanism, which underlies the normal function of the LVOT. A wedge-shaped portion of the LV septum is removed if necessary. Cold antegrade blood cardioplegia through the coronaries and topical cooling with ice is our preferred technique for myocardial protection. No retrograde perfusion is used.

Statistical Analysis
Continuous variables are expressed as mean ± standard deviation, whereas discrete variables are expressed as a percentage. Nonparametric Student's t test was used to compare preoperative and postoperative LVOT velocities, as a Gaussian distribution was not found. A probability value of less than 0.05 was considered statistically significant.

	Results

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Patient Characteristics
The increasing complexity of the SAS lesion throughout the surgical history of individual patients is depicted in Figure 1 . The first group of patients presented with newly diagnosed SAS and required first-time resection of the fibrous lesion. The second group of patients presented with recurrent disease and required repeat resection of the fibrous SAS. The third group includes those patients who presented either with de novo SAS that required resection of the SAS and AV surgery, and those patients presenting with recurrence of SAS who initially underwent limited resection of an SAS and now have disease involving the aortic valve, which required valve replacement. Our patients underwent a total of 21 cardiac operations before the present subaortic membrane resection (Table 1). Previous operations are detailed in Table 2.

View larger version (7K): [in this window] [in a new window]   Fig 1. Increasing complexity of surgery through the surgical history of the patients. (AVR = aortic valve replacement; SAS = subaortic stenosis; 1 = subaortic ridge resection; 2 = redo subaortic ridge resection; 3 = subaortic ridge resection plus aortic valve replacement.)

There were no early deaths in this group. One patient died late of cancer, 3 years after surgery. This patient was a 42-year-old man who underwent first-time resection of a subaortic membrane and LV myectomy.

All patients had mild aortic regurgitation (AR) preoperatively, reduced to none in 3 patients, and 3 patients had trivial AR postoperatively. Mean preoperative LVOT velocity was 4.2 ± 0.9 m/s and was reduced to 1.6 ± 0.3 m/s postoperatively.

Group 2: Redo Subaortic Stenosis Resection
Redo SAS resection was required in 8 patients, 3 male, with a median age of 25.3 ± 5 years. Mean follow-up was 7.96 ± 3 years. Mean interval between first time and redo SAS was 14 ± 4 years. One patient underwent a third SAS resection. One patient underwent previous LV myotomy. Before surgery, 1 patient had no AR, 1 patient had trivial AR, 3 patients had mild AR, 2 patients had moderate AR, and 1 patient had severe AR. These lesions were not attributable to primary disease of the AV, and so did not require AV surgery. Mean cardiopulmonary bypass time was 80 ± 33 minutes, and mean aortic cross-clamp time was 61 ± 13 minutes.

There was 1 early death attributable to severe pulmonary hypertension on the third postoperative day in a 30-year-old man undergoing his fourth cardiac operation (second-time SAS resection). The patient had a previous history of patent ductus arteriosus ligation (age, 3 years) and repair of coarctation of the aorta (age, 4 years). At age 9 years, he underwent initial subaortic membrane resection. The patient presented again with mild to moderate AR and SAS. The pulmonary artery pressure was markedly elevated. The SAS surgery was uneventful, and after weaning from cardiopulmonary bypass, he experienced right heart failure with impaired LV function. Although it was possible to wean from cardiopulmonary bypass, his right heart pressure remained almost systemic, and ultimately the patient died of heart failure on the third postoperative day. There were no late deaths in this group.

The mean LVOT velocity was reduced from a preoperative value of 4.4 ± 0.89 m/s to 1.67 ± 0.62 m/s (Fig 2). Three patients had mild AR at latest follow-up, whereas the remaining 4 had no AR.

View larger version (2K): [in this window] [in a new window]   Fig 2. Effect of subaortic stenosis surgery on left ventricular outflow tract (LVOT) velocity. (A) Group 1 (first-time subaortic stenosis resection). (B) Group 2 (redo subaortic stenosis resection). Left ventricular outflow tract velocities are significantly reduced after surgery (p < 0.001). (Post-Op = postoperatively; Pre-Op = preoperatively.)

One patient underwent the Ross procedure, and 5 patients underwent mechanical valve implantation (23-mm St. Jude's AV in 4 patients and 25-mm in 1 patient). One patient underwent root enlargement. Their mean interval between last and present operations was 25.3 ± 15 years.

Mean cardiopulmonary bypass time was 108 ± 49 minutes, and mean aortic cross-clamp time was 79 ± 34 minutes. All patients had at least moderate to severe AR preoperatively, which was abolished with no paravalvular leak.

There was 1 early death in a 59-year-old man with bicuspid AV stenosis and regurgitation. This patient underwent second-time sternotomy for redo fibrous ridge resection and first-time 23-mm St. Jude's mechanical AV replacement. This patient had a history of subaortic resection repair at age 12 years. After difficulty accessing the right femoral vessels for institution of cardiopulmonary bypass, a successful cannulation was achieved using the left femoral vessels. During the operation, poor venous return and hypotension required increasingly large volumes of fluid replacement to maintain tissue perfusion. There was increasing abdominal distension, and a retroperitoneal bleed was thought highly likely. The patient died on the second postoperative day of multiorgan failure.

There was 1 late death attributable to postoperative renal failure, 223 days after surgery. This was a 34-year-old man who presented for redo AV replacement owing to a calcified homograft. He underwent mechanical valve implantation.

Operative Morbidity
Postoperative complications are listed in Table 3.

	Comment

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Group 1
There were no deaths for patients undergoing first-time SAS resection. Other studies also report that SAS surgery has a very low mortality [7, 10–13].

Importantly, no patient required a permanent pacemaker. The LVOT velocity was significantly reduced in this group, and no patient in this group had more than trivial AR. These results were maintained at latest follow-up. Early surgery at a lower gradient (30 mm Hg) has been recommended to prevent the development of AR and improve results [7, 12]. We also believe that a tailored surgical approach that takes into account all of the aspects underlying SAS may prevent progression of the lesion. Although no patients who have undergone SAS resection in our center have required reoperation, owing to the limited follow-up of this study it remains to be seen whether our surgical approach will be successful in limiting the recurrence of SAS.

Group 2
Review of the records of the first SAS resection that patients in group 2 had undergone showed that they were limited operations, not taking into account all the aspects of the anatomy as we have described. These patients required reoperation because of a recurrence of the SAS, but did not have significant AV dysfunction. This means that group 2 patients may have AR without organic disease of the AV and therefore do not require AV surgery. In these patients, we believe that comprehensively addressing the true anatomic basis of the lesion is adequate, without AV replacement. Indeed, this appears to be borne out in that AV function was improved postoperatively and no patient has required AV replacement subsequently.

Because septal myectomy involves the risk of damage to the conducting tissue and the integrity of the interventricular septum, we reserve its use for those patients in whom there is a prominent septal bulge. Therefore, although we have a low threshold for performing septal myectomy, we do not perform it in all patients (Table 2).

There was 1 early death (described earlier) in this group, which was also associated with longer cardiopulmonary bypass and aortic cross-clamp times compared with first-time SAS resection. The LVOT velocity was significantly reduced by surgery in this group, and AV function was significantly improved. This group has a follow-up that extends to 11 years, and no patient has required AV surgery after SAS resection in our center. Greater follow-up is required to test this hypothesis more fully.

Group 3
This group of patients includes those who present with de novo SAS with significant AV dysfunction (with significant AR preoperatively and high LVOT velocities), as well as patients who underwent previous SAS resection but in whom the disease has progressed to compromise the AV. There was 1 early death (described earlier) in this group, and cardiopulmonary bypass and aortic cross-clamp times were the highest of all the groups, indicating the complex surgical challenge. Because of the number of cardiac operations this group had already undergone, we elected to use mechanical AV replacement for most patients, as it provides the most durability and should reduce the need for early valve replacement owing to structural valve deterioration.

Mechanisms of Disease
The mechanisms underlying SAS remain debated, but include developmental abnormalities resulting in small or long aortic roots [14, 15], displacement of the ventricular septum, malalignment between the muscular and membranous parts of the interventricular septum [16], persistence of the endocardial cushion tissue in this region, and anterior displacement of the mitral valve apparatus toward the LVOT. Turbulence produced by any of these factors may drive fibrous proliferation, which can progress and worsen the disease [17]. In this series, we had data to suggest a role for each of these factors, with patients exhibiting ventricular septal defects, AV and mitral valve disease, and with small aortic annulus sizes.

The mechanisms that specifically mediate the late presentation of first-time SAS in adults are only partially understood [18]. There appear to be a number of causes, which can be broadly classified into those secondary to congenital heart disease and those not related to congenital heart disease. The altered septoaortic angle generates turbulent blood flow at the interventricular septum, stimulating cellular proliferation, which can lead to SAS. In addition, in a small number of cases, acquired cardiac diseases such as rheumatic mitral valve disease can lead to SAS [18]. The elucidation of the exact relationship between LVOT anatomy, acquired cardiovascular disease, and late presentation of de novo SAS in adults requires further studies, in a larger series.

Left Ventricular Outflow Tract Velocity and Recurrence
Our results show maintained low LVOT velocities, with no recurrence of SAS after the resection performed in our center. However, it is well established that subaortic membranes do recur after surgical resection, including 12 patients undergoing surgery in this series. There is some evidence that the addition of septal myectomy reduces the rate of increase in LVOT obstruction and therefore reduces the need for reoperation [19, 20]. Significant immediate postoperative LVOT gradients are risk factors for recurrence, reoperation, and mortality [11]. This stresses the importance of addressing the obstructive as well as the dynamic anatomy of the whole LVOT. Long-term follow-up studies show that reoperation for SAS is required in up to 50% of patients [4, 6]. Brauner and associates [12] report that 20% of patients required reoperation during 6.7 years, especially those with high postoperative gradients. Long-term follow-up of this series will directly address this issue.

Aortic Valve Function
There have been multiple mechanisms proposed for AR in SAS including a direct interaction between the subaortic shelf and the AV leaflets and leaflet distortion by turbulent blood flow [21–23]. Of note, AR was improved after SAS resection in group 1 patients, supporting a direct role in the subaortic lesion in triggering AR.

Some authors have suggested that AR is stagnant after surgery, or that it progresses [3, 18]. The evidence in adults is that LVOT obstruction in SAS does not progress rapidly, and neither does AR [18]. Progressive AR was noted in 40% of those with LVOT gradients greater than 40 mm Hg, but only in 12.5% of those with LVOT gradients less than 40 mm Hg, suggesting that early intervention or more extensive surgery might prevent recurrence [12]. In this study, there were no patients with a preoperative gradient less than 40 mm Hg, suggesting that their AR would have progressed; there were also no patients with postoperative gradients greater than 40 mm Hg, suggesting that the good valve function may be maintained in the long term. Importantly, patients presenting for redo surgery with AV dysfunction have a higher interval between first and second operations. This supports the notion that early intervention can limit the progression of AV dysfunction.

Conclusions
This paper shows that SAS resection can be undertaken safely and with durable valve and LVOT function in the midterm. Redo resection and resections including AV replacement are more risky and technically challenging. We believe that our approach addresses each element of this disease, including the whole subaortic ridge, the septum, and the fibrous trigones, and that this can limit the progression of the disease. Long-term durability of this effect should be assessed by studies with longer follow-up.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
We thank Juliet Aghion and Rebecca Tulk for assistance with obtaining clinical data for these patients.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

1. Butany JW, David TE, Ojha M. Histological and morphometric analyses of early and late aortocoronary vein grafts and distal anastomoses Can J Cardiol 1998;14:671-677.[Medline]
2. Somerville J. Fixed subaortic stenosis—a frequently misunderstood lesion Int J Cardiol 1985;8:145-148.
3. Kelly DT, Wulfsberg E, Rowe RD. Discrete subaortic stenosis Circulation 1972;46:309-322.[Abstract/Free Full Text]
4. Barkhordarian R, Uemura H, Rigby ML, et al. A retrospective review in 50 patients with subaortic stenosis and intact ventricular septum: 5-year surgical experience Interact Cardiovasc Thorac Surg 2007;6:35-38.[Abstract/Free Full Text]
5. Yacoub M, Onuzo O, Riedel B, Radley-Smith R. Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction J Thorac Cardiovasc Surg 1999;117:126-133.[Abstract/Free Full Text]
6. Dodge-Khatami A, Schmid M, Rousson V, et al. Risk factors for reoperation after relief of congenital subaortic stenosis Eur J Cardiothorac Surg 2008;33:885-889.[Abstract/Free Full Text]
7. Parry AJ, Kovalchin JP, Suda K, et al. Resection of subaortic stenosis; can a more aggressive approach be justified? Eur J Cardiothorac Surg 1999;15:631-638.[Abstract/Free Full Text]
8. Clark TG, Altman DG, De Stavola BL. Quantification of the completeness of follow-up Lancet 2002;359:1309-1310.[Medline]
9. Tsang VT, de Leval MR. Surgery of the left ventricular outflow tractIn: Stark J, de Leval M, Tsang VT, editors. Surgery for congenital heart disease. London: Wiley; 2006. pp. 489-514.
10. Coleman DM, Smallhorn JF, McCrindle BW, Williams WG, Freedom RM. Postoperative follow-up of fibromuscular subaortic stenosis J Am Coll Cardiol 1994;24:1558-1564.[Medline]
11. Serraf A, Zoghby J, Lacour-Gayet F, et al. Surgical treatment of subaortic stenosis: a seventeen-year experience J Thorac Cardiovasc Surg 1999;117:669-678.[Abstract/Free Full Text]
12. Brauner R, Laks H, Drinkwater Jr DC, Shvarts O, Eghbali K, Galindo A. Benefits of early surgical repair in fixed subaortic stenosis J Am Coll Cardiol 1997;30:1835-1842.[Medline]
13. Vouhé PR, Poulain H, Bloch G, et al. Aortoseptal approach for optimal resection of diffuse subvalvular aortic stenosis J Thorac Cardiovasc Surg 1984;87:887-893.[Abstract]
14. Thilenius OG, Campbell D, Bharati S, Lev M, Arcilla RA. Small aortic valve annulus in children with fixed subaortic stenosis Pediatr Cardiol 1989;10:195-198.[Medline]
15. Rosenquist GC, Clark EB, McAllister HA, Bharati S, Edwards JE. Increased mitral-aortic separation in discrete subaortic stenosis Circulation 1979;60:70-74.[Abstract/Free Full Text]
16. Zielinsky P, Rossi M, Haertel JC, Vitola D, Lucchese FA, Rodrigues R. Subaortic fibrous ridge and ventricular septal defect: role of septal malalignment Circulation 1987;75:1124-1129.[Abstract/Free Full Text]
17. Gewillig M, Daenen W, Dumoulin M, Van der Hauwaert L. Rheologic genesis of discrete subvalvular aortic stenosis: a Doppler echocardiographic study J Am Coll Cardiol 1992;19:818-824.[Medline]
18. Oliver JM, González A, Gallego P, Sánchez-Recalde A, Benito F, Mesa JM. Discrete subaortic stenosis in adults: increased prevalence and slow rate of progression of the obstruction and aortic regurgitation J Am Coll Cardiol 2001;38:835-842.[Medline]
19. Lupinetti FM, Pridjian AK, Callow LB, Crowley DC, Beekman RH, Bove EL. Optimum treatment of discrete subaortic stenosis Ann Thorac Surg 1992;54:467-471.[Abstract/Free Full Text]
20. Rayburn ST, Netherland DE, Heath BJ. Discrete membranous subaortic stenosis: improved results after resection and myectomy Ann Thorac Surg 1997;64:105-109.[Abstract/Free Full Text]
21. Newfeld EA, Muster AJ, Paul MH, Idriss FS, Riker WL. Discrete subvalvular aortic stenosis in childhood. Study of 51 patients. Am J Cardiol 1976;38:53-61.[Medline]
22. Freedom RM, Pelech A, Brand A, et al. The progressive nature of subaortic stenosis in congenital heart disease Int J Cardiol 1985;8:137-148.[Medline]
23. Leichter DA, Sullivan I, Gersony WM. "Acquired" discrete subvalvular aortic stenosis: natural history and hemodynamics J Am Coll Cardiol 1989;14:1539-1544.[Medline]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Michael Ibrahim Martin Kostolny Magdi H. Yacoub Victor T. Tsang Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ibrahim, M. Articles by Tsang, V. T. Search for Related Content PubMed PubMed Citation Articles by Ibrahim, M. Articles by Tsang, V. T. Related Collections Congenital - cyanotic