Original study

Editorial note Fixed subaortic stenosis — a frequently misunderstood lesion☆

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.

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).

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.

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.

A discrete subaortic membrane (DSM) is one of the causes of subaortic stenosis in children. The incidence, characteristics, and the therapeutic options for such membranes in adults have not been well documented. This report documents the clinical and pathological features of DSM in adults.

DSMs, surgically excised over a 10-year period in a large adult tertiary care center, were reviewed with regard to the age and gender of the patients, clinical findings, and the morphological features.

Among the 19 adults, there were six males and 13 females, with age ranging from 26 to 75 years. The patients most often presented with dyspnea, fatigability, and palpitation for 3 months to 2 years. Four patients (21%) had other congenital heart disease in association with the DSM; in the rest, the membranes were isolated occurrences (79%). A cardiac murmur or the presence of membranes had been noted in childhood in four patients. Tissue growths over the ventricular surface of the anterior mitral leaflet were seen in 18 cases. Irrespective of the gross appearance, the stenosing lesions exhibited five tissue layers, beginning from the luminal aspect, endothelium, acid mucopolysaccharide-rich subendothelial layer, collagen-rich fibrous layer, fibroelastotic layer, and a smooth muscle layer. Twelve patients (63%) had aortic regurgitation, which necessitated repair or replacement in seven. Septal myectomy resulted in conduction abnormalities in nine.

The study describes the occurrence of DSM in adults. It is important to remember that it can occur following a repair of underlying congenital heart disease.

This study aimed to identify independent predictors of reoperation after successful resection of discrete subaortic stenosis (DSS).

Recurrence of DSS has been reported to range from 0% to 55% of patients. Factors associated with recurrence have not been adequately defined.

Patients were included if they had a diagnosis of DSS, normal segmental cardiac anatomy, previous resection of DSS, and at least 36 months’ follow-up. Demographic, surgical, and echocardiographic data were analyzed. Primary outcome was repeat resection of DSS in patients after successful primary resection.

Of 111 subjects who had successful surgical resection of DSS, 16 patients (14%) required reoperation. Median follow-up time was 8.2 years. Form of DSS and gender did not differ significantly between those with reoperation and those without. In multivariate analysis, independent predictors of reoperation that would be available before first surgery were <6 mm distance between the aortic valve (AoV) and the obstruction (hazard ratio [HR] 5.1; p = 0.013) and peak gradient by Doppler ≥60 mm Hg (HR 4.2; p = 0.016). If intraoperative variables are also considered, peeling of the membrane from the AoV or mitral valve at first surgery, <6 mm distance between the DSS and AoV, and peak gradient by Doppler ≥60 mm Hg were independent predictors of reoperation.

Proximity of the obstructive lesion to the AoV and severe obstruction determined by preoperative echocardiography, as well as involvement of valve leaflets requiring surgical peeling, predict recurrent DSS requiring reoperation.

The clinical course of discrete subaortic stenosis (DSS) varies considerably between patients. This study was performed to identify echocardiographic characteristics of DSS that distinguish progressive from nonprogressive disease. The study included 100 patients from 2 institutions and was performed in 2 stages. In phase I, a prediction model was developed based on multivariate analysis of morphometric and Doppler variables obtained from the initial echocardiogram in 52 children with DSS from Texas Children’s Hospital. In phase II, the performance characteristics of the prediction model were tested in 48 patients with DSS followed at Children’s Hospital in Boston. Patients were divided into 3 outcome groups: nonprogressive, progressive, and intermediate progression. In phase I, multivariate analysis identified 3 independent predictors of progressive disease: indexed aortic valve to subaortic membrane distance, anterior mitral leaflet involvement, and initial Doppler gradient. The logistic regression equation—Probability = [1 + e^{−(−3.22+0.334X}₁^+4.06X₂^−0.708X₃⁾]⁻¹, where X = initial gradient in mm Hg; X₂ = absence (0) or presence (1) of mitral leaflet involvement; and X₃ = indexed distance between aortic valve and subaortic membrane in mm/body surface area^0.5 were used to predict progression. When the prediction model was applied to phase II study patients, none of the patients with nonprogressive DSS had a prediction value >0.29 and none of the patients with progressive DSS had a prediction value <0.58. Thus, a prediction value >0.55 yielded a 100% sensitivity and 100% specificity for distinguishing progressive from nonprogressive DSS. Patients with intermediate progression were indistinguishable from progressive DSS but were clearly separable from nonprogressing patients. We conclude that progressive subaortic obstruction in children with DSS can be predicted from morphologic, morphometric, and Doppler echocardiographic analysis of left ventricular outflow.

Objectives. We sought to determine whether early resection can improve outcome in fixed subaortic stenosis.

Background. The diagnosis of subaortic stenosis (SAS) is often made before significant gradients occur. Whereas resection is the accepted treatment, it remains uncertain whether surgical intervention at this early stage can reduce the incidence of recurrence or influence the progression of aortic valve damage.

Methods. Follow-up was available for 75 of 83 consecutive patients operated on for fixed SAS; the average duration of follow-up was 6.7 years. The lesion was discrete in 68 patients (91%) and of a tunnel type in 7, with associated ventricular septal defect in 28 (37%). All underwent transaortic resection.

Results. There were no deaths. There were 18 recurrences of SAS in 15 patients (20%). Thirteen patients (17%) underwent 17 reoperations for recurrence or aortic valve disease. The cumulative hazard of recurrence was 8.9%, 16.1% and 29.4% ± 2.3% (mean ± SEM), and the hazard of events, including recurrence and reoperation, was 9.2%, 18.4% and 35.1% ± 3.5% at 2, 5 and 10 years, respectively. Residual end-operative left ventricular outflow tract (LVOT) gradients (>10 mm Hg, n = 8) and tunnel lesions were univariate predictors of recurrence (p = 0.0006 and p = 0.003, respectively). Multivariate predictors included higher preoperative LVOT gradient (p < 10⁻⁴) and younger patient age (p = 0.002). Only two recurrences (0.87 per 100 patient-years of follow-up) were noted in patients with a preoperative peak LVOT gradient ≤40 mm Hg (n = 40), whereas higher gradients (n = 35) were associated with a greater than sevenfold recurrence rate (6.45 events per 100 patient-years, p = 0.002). The aortic valve required concomitant repair in 17 cases in the high gradient group (48.6%) but in only 8 in the low gradient group (20%, p = 0.018). Despite relief of the obstruction, progressive aortic regurgitation was noted at follow-up after 14 procedures in the high gradient group (40%) but after only 5 procedures in the low gradient group (12.5%, p = 0.014).

Conclusions. The data suggest that surgical resection of fixed subaortic stenosis before the development of a significant (>40 mm Hg) outflow tract gradient may prevent recurrence, reoperation and secondary progressive aortic valve disease.

Objectives. The purpose of this study was to examine the echocardiographic abnormalities of the left ventricular outflow tract associated with subaortic stenosis in children.

Background. Considerable evidence suggests that subaortic stenosis is an acquired and progressive lesion, but the etiology remains unknown. We have proposed a four-stage etiologic process for the development of subaortic stenosis. This report addresses the first stage by defining the morphologic abnormalities of the left ventricular outflow tract present in patients who develop subaortic stenosis.

Methods. Two study groups were evaluated—33 patients with isolated subaortic stenosis and 12 patients with perimembranous ventricular septal defect and subaortic stenosis—and were compared with a size- and lesion-matched control group. Subjects ranged in age from 0.05 to 23 years, and body surface area ranged from 0.17 to 2.3 m². Two independent observers measured aortoseptal angle, aortic annulus diameter and mitral-aortic separation from previously recorded echocardiographic studies.

Results. The aortoseptal angle was steeper in patients with isolated subaortic stenosis than in control subjects (p < 0.001). This pattern was also true for patients with ventricular septal defect and subaortic stenosis compared with control subjects (p < 0.001). Neither age nor body surface area was correlated with aortoseptal angle. A trend toward smaller aortic annulus diameter indexed to patient size was seen between patients and control subjects but failed to achieve statistical significance (p = 0.08). There was an excellent interrater correlation in aortoseptal angle and aortic annulus measurement. The mitral-aortic separation measurement was unreliable. Our results, specifically relating steep aortoseptal angle to subaortic stenosis, confirm the results of other investigators.

Conclusions. This study demonstrates that subaortic stenosis is associated with a steepened aortoseptal angle, as defined by two-dimensional echocardiography, and this association holds in patients with and without a ventricular septal defect. A steepened aortoseptal angle may be a risk factor for the development of subaortic stenosis.

(J Am Coll Cardiol 1997;30:255–9)