The progressive nature of subaortic stenosis in congenital heart disease

Perioperative and Anesthetic Considerations in Pediatric Valvar and Subvalvar Aortic Stenosis

Aortic stenosis (AS) is a common form of left ventricular outflow tract obstruction (LVOTO) in children with congenital heart disease. This review specifically considers the perioperative features of valvar (VAS) and subvalvar AS (subAS) in the pediatric patient. Although VAS and subAS share some clinical features and diagnostic approaches, they are distinct clinical entities with separate therapeutic options, which range from transcatheter intervention to surgical repair. We detail the pathophysiology of AS and highlight the range of treatment strategies with a focus on anesthetic considerations for the care of these patients before, during, and after intervention.

A Case Report of Recurrent Subaortic Membrane in a 3-Year-Old Saudi Child

INTRODUCTION

While only a few cases have been reported in pediatrics, subaortic stenosis (SAS) is a gradually progressive disorder rarely seen at birth and infancy, however, it is the most common type of aortic stenosis. It obstructs the blood flow across the left ventricular outflow tract (LVOT). Although the cause is still not well known, different etiologies have been suggested by the literature. While surgical resection is the definitive treatment, recurrence is observed in many patients, nonetheless, LVOT gradient usually progresses over years of follow-up.

CASE PRESENTATION

We report the clinical and diagnostic course of a 41-months-old Saudi boy, asymptomatic child who was found to have progressive recurrent subaortic stenosis within a few months which required two redo sternotomy for sub-aortic membrane resection throughout a period of two years.

DISCUSSION

SAS is usually detected incidentally in asymptomatic patients requiring an echocardiogram to assess other accompanying congenital heart defects (CHD), or rather potentially arising after repair of CHD. Patient close monitoring is important aspect given the nature of disease progression, re-operation for recurrence demonstrate significant increase over years, re-resection rate was 0 % after one year, 6 % after five years, and 8 % after 10 years.

CONCLUSION

Recurrence of LVOT obstruction following sub-aortic membrane resection is common. Long-term follow-up care in postoperative patients is crucial. Majority of patients will need re-operation for recurrence at certain point during course of the disease.

Subvalvular aortic stenosis: a review of current literature

Subvalvular aortic stenosis (SAS) is one of the common adult congenital heart diseases, with a prevalence of 6.5%. It is usually diagnosed in the first decade of life. Echocardiography is the test of choice to diagnose SAS. Surgical correction is the best treatment modality, and the prognosis is usually excellent. In this review, we describe the pathophysiology, diagnosis, prognosis, and management of SAS with a focus on different pathophysiologic mechanisms, diagnostic approach, and prognosis of the disease by reviewing the current literature.

Outcome in Children Operated for Membranous Subaortic Stenosis

Background:

The optimal surgical procedure for treatment of fibromembranous subaortic stenosis has been a subject of debate. We report our experience with patients treated for membranous subaortic stenosis using membrane resection alone and membrane resection plus aggressive septal myectomy.

Methods:

Patients followed in the pediatric cardiology clinic of a university hospital, who had undergone surgery for subaortic stenosis between 2002 and 2013 were reviewed. Recurrence of subaortic membrane, residual left ventricular outflow gradient, and aortic valve function were analyzed.

Results:

Forty-six patients underwent surgery for subaortic membrane. Of these, 19 had membrane resection plus aggressive septal myectomy, while 27 had membrane resection alone. Mean age at surgery for the membrane resection group was 7.7 ± 3.9 years and 10.9 ± 3.6 years for the membrane resection plus aggressive myectomy group. Preoperative subaortic gradient for the membrane resection group was 75.5 ± 26.7 mm Hg and 103.2 ± 39.7 mm Hg for the membrane resection plus aggressive myectomy group. The mean follow-up left ventricular outflow tract gradient was 42.3 ± 31.3 mm Hg in the membrane resection group, while it was 11.6 ± 6.3 mm Hg in the aggressive septal myectomy group. Nine patients from the membrane resection group had significant regrowth of the subaortic membrane during the follow-up period, while none of the aggressive septal myectomy group had detectable membrane on echocardiography. Seven of the nine patients with recurrence of the subaortic membrane underwent subsequent membrane resection plus aggressive septal myectomy. Intraoperative finding in all these redo cases was recurrence (growth) of a subaortic membrane.

Conclusion:

Aggressive septal myectomy offers less chance of recurrence, freedom from reoperation, and an improved aortic valve function. This is especially important in sub-Saharan settings where a chance of getting a second surgery is unpredictable.

Fixed subaortic stenosis: a clinical dilemma for clinicians and patients

Subaortic stenosis carries considerable morbidity and mortality. In most cases, patients have an underlying left ventricular outflow tract morphology that promotes turbulence at the outflow tract, which induces the development of subaortic fibromuscular tissue. A subset of patients will progress to develop severe stenosis and aortic regurgitation, but it has been difficult to determine which patients are at risk. While resection of the subaortic tissue improves immediate outcome, many patients have recurrence of both stenosis and regurgitation, questioning the efficacy of surgical intervention in asymptomatic patients. This review article describes the current understanding of the etiology, treatment, and prognosis of subaortic stenosis.

Surgical outcome of discrete subaortic stenosis in adults: a multicenter study

BACKGROUND

Discrete subaortic stenosis is notable for its unpredictable hemodynamic progression in childhood and high reoperation rate; however, data about adulthood are scarce.

METHODS AND RESULTS

Adult patients who previously underwent surgery for discrete subaortic stenosis were included in this retrospective multicenter cohort study. Mixed-effects and joint models were used to assess the postoperative progression of discrete subaortic stenosis and aortic regurgitation, as well as reoperation. A total of 313 patients at 4 centers were included (age at baseline, 20.2 years [25th-75th percentile, 18.4-31.0 years]; 52% male). Median follow-up duration was 12.9 years (25th-75th percentile, 6.2-20.1 years), yielding 5617 patient-years. The peak instantaneous left ventricular outflow tract gradient decreased from 75.7±28.0 mm Hg preoperatively to 15.1±14.1 mm Hg postoperatively (P<0.001) and thereafter increased over time at a rate of 1.31±0.16 mm Hg/y (P=0.001). Mild aortic regurgitation was present in 68% but generally did not progress over time (P=0.76). A preoperative left ventricular outflow tract gradient ≥80 mm Hg was a predictor for progression to moderate aortic regurgitation postoperatively. Eighty patients required at least 1 reoperation (1.8% per patient-year). Predictors for reoperation included female sex (hazard ratio, 1.53; 95% confidence interval, 1.02-2.30) and left ventricular outflow tract gradient progression (hazard ratio, 1.45; 95% confidence interval, 1.31-1.62). Additional myectomy did not reduce the risk for reoperation (P=0.92) but significantly increased the risk of a complete heart block requiring pacemaker implantation (8.1% versus 1.7%; P=0.005).

CONCLUSIONS

Survival is excellent after surgery for discrete subaortic stenosis; however, reoperation for recurrent discrete subaortic stenosis is not uncommon. Over time, the left ventricular outflow tract gradient slowly increases and mild aortic regurgitation is common, although generally nonprogressive over time. Myectomy does not show additional advantages, and because it is associated with an increased risk of complete heart block, it should not be performed routinely.

Severe subaortic stenosis that progressed over a 12-year period after cardiac surgery

A 12-year-old girl who had undergone cardiac surgery for ventricular septal defect (VSD), atrial septal defect (ASD), and patent ductus arteriosus (PDA) in infancy was referred to our institution for fatigue and excessive sweating. Transthoracic and transesophageal echocardiographic studies revealed tunnel-type subaortic stenosis with aortic valvular stenosis, for which she underwent aortic valve replacement and myomectomy of left ventricular outflow tract. Progression of subaortic stenosis should be considered in patients with only mild aortic valve stenosis after previous cardiovascular surgery. Echocardiography contributed significantly to making the diagnosis and therapeutic decision in our patient.

Hypertrophic cardiomyopathy presenting as restrictive cardiomyopathy: a case complicated by biventricular apical aneurysms and papillary fibroelastoma

This report describes a 45-year-old male patient with nonobstructive hypertrophic cardiomyopathy, biventricular apical aneurysms, and papillary fibroelastoma. Histology revealed muscle fiber disarray, interstitial fibrosis, and mural vessel changes. The wall of the aneurysms showed fat infiltration, and loss and replacement of muscle fibers with fibrous tissues. A review of the literature suggests that this case is the first reported experience with the three pathologies occurring in combination.

Steepened aortoseptal angle may be a risk factor for discrete subaortic stenosis in adults

Discussion exists whether discrete subaortic stenosis (DSS) is a congenital or acquired cardiac defect. Currently, it is regarded an "acquired" cardiac defect presumably secondary to altered flow patterns due to morphological abnormalities in the left ventricular outflow tract, as have been shown by some studies in the pediatric population. In this report, we demonstrated a steepened aortoseptal angle in adults with DSS without previous cardiac surgery in comparison to controls. Our results strengthen the hypothesis that altered flow patterns due to a steepened aortoseptal angle are a substrate for development of DSS in adults.

Geometry of the left ventricular outflow tract in fixed subaortic stenosis and intact ventricular septum: An echocardiographic study in children and adults

OBJECTIVE

We compared the echocardiographic geometry of the preoperative and postoperative left ventricular outflow tract in children and adults with isolated fixed subaortic stenosis with age- and weight-matched controls to elucidate whether the geometry can be modified when surgical intervention is performed at a younger age.

METHODS

The mitral-aortic valve distance, aortic valve diameter, aorto-left ventricular septal angle, degree of aortic valve dextroposition, aortic valve-subaortic stenosis distance, width of left ventricular outflow tract, left ventricle wall thickness, and septal thickness were determined preoperatively and postoperatively in 21 patients and 21 controls. The measurements were indexed to body surface area. Patients were divided into 3 age groups: group 1 comprised 9 patients aged 1 to 10 years, group 2 comprised 8 patients aged 11 to 20 years, and group 3 comprised 4 patients aged 21 years or more.

RESULTS

Compared with controls, patients had a significantly wider mitral-aortic separation (group 1, P = .003; group 2, P = .02), a steeper aortoseptal angle (group 1, P = .02; group 3, P = .03), a smaller left ventricular outflow tract width (group 1, P = .003; group 2, P = .01), a marked aortic valve dextroposition (groups 1 and 3), an increased left ventricle wall thickness (group 1, P = .03), and an increased septal thickness (group 1, P = .01). There was a significant difference between preoperative and postoperative values in aortoseptal angle and left ventricular outflow tract width in patients up to 10 years of age (P = .02 and P = .01, respectively).

CONCLUSIONS

Hearts with isolated subaortic stenosis have abnormal left ventricular outflow tract geometry that postoperatively showed changes in left ventricular outflow tract width and aortoseptal angle. Compared with controls, the aortoseptal angle does not "normalize" when surgery is performed in older patients, suggesting that left ventricular outflow tract geometry may be remodeled in younger patients.

Echocardiographic follow-up of children with isolated discrete subaortic stenosis

This study evaluates the progression of stenosis, onset and progression of aortic regurgitation (AR), and the results of surgical outcomes in children with isolated discrete subaortic stenosis (SAS). The medical records of 108 patients (mean age, 5.5 +/- 3.8 years; range, 3 days to 18 years) with isolated discrete SAS were reviewed. Patients with lesions other than AR were excluded. Very mild stenosis was defined as Doppler peak systolic instantaneous gradient (PSIG) less than 25 mmHg, mild stenosis as 25-49 mmHg, moderate stenosis as 50-75 mmHg, and severe stenosis as more than 75 mmHg. Seventy-eight of 108 patients were followed for 2 months to 14 years (mean, 4.8 +/- 3.7 years; median, 5 years) with medical treatment alone. In these patients, the mean PSIG at last echocardiogram was higher than the mean PSIG at initial echocardiogram (39 +/- 19 vs 31 +/- 12 mmHg, respectively; p < 0.001). Among 24 patients with very mild stenosis at initial echocardiogram, 10 had mild and 2 had moderate stenosis after a mean period of 5.6 years. Among 46 patients with mild stenosis at initial echocardiogram, 11 had moderate and 5 had severe stenosis after a mean period of 4.1 years. Only 1 patient among the 8 patients with moderate stenosis at initial echocardiogram had severe stenosis after a mean period of 2.7 years. Thirty-nine patients (50%) had AR (13% trivial, 33% mild, and 4% moderate) at initial echocardiogram. After a mean period of 4.8 years, 77% of the patients had AR (10% trivial, 53% mild, 9% mild-moderate, and 5% moderate). Twenty-four patients underwent surgery. Preoperatively, mean Doppler PSIG and AR incidence were 64 +/- 17 mmHg and 91% (22/24), respectively. The mean Doppler PSIG was 30 +/- 19 mmHg and AR was present in all of the patients a mean period of 4.1 years after surgery. Two patients underwent reoperation for recurrent SAS and AR. Patients with very mild or mild stenosis may be followed noninvasively every year. One patient of the 8 patients with moderate stenosis progressed to severe stenosis, and moderate AR developed in 2 patients after a mean of 2.7 years. We recommend that patients with moderate stenosis undergo careful evaluation to determine whether surgery is necessary due to the severity of stenosis and AR.

Surgical outcome following treatment of isolated subaortic obstruction

Surgical and nonsurgical patients with isolated subaortic stenosis (SAS) were compared to determine the important factors contributing to the timing of surgical intervention. This study reviews 49 consecutive patients (27 surgical and 22 nonsurgical) aged 1.8 to 15.9 years with isolated SAS. The preoperative peak left ventricular outflow tract (LVOT) gradient in surgical patients was significantly higher than the gradient in nonsurgical patients (59.0 +/- 30.4 vs 22.77 +/- 13.9 mm Hg, P = .0001). The progression in LVOT gradient analyzed by echo Doppler was significantly higher in the surgical group compared with the nonsurgical group (10.48 +/- 9.7 vs 1.56 +/- 6.5 mm Hg/y, P = .007). Repeat surgical intervention was required in 22% of patients in the surgical group for recurrence of SAS, and 4% needed a third surgery. The progression in the severity of aortic regurgitation (AR) was not significantly different in the surgical and nonsurgical groups. There was a significant association between the development of AR and patients undergoing surgery (P = .045). AR may not be a reliable indication for early operative intervention in isolated SAS as there was no significant difference in its progression with surgical and nonsurgical patients. Asymptomatic patients with isolated SAS may warrant surgical intervention on the basis of progression of LVOT gradient, rather than the development or progression of AR.

Discrete subaortic stenosis in adults: increased prevalence and slow rate of progression of the obstruction and aortic regurgitation

OBJECTIVES

We sought to determine the prevalence and rate of progression of left ventricular outflow tract obstruction (LVOTO) and aortic regurgitation (AR) in adults with discrete subaortic stenosis (DSS).

BACKGROUND

Discrete subaortic stenosis is an uncommon form of LVOTO, with rapid hemodynamic progression in children, but the prevalence and rate of progression in adults have not been studied so far.

METHODS

The prevalence of DSS was determined in 2,057 consecutive adults diagnosed with congenital heart disease (CHD). The relationship between LVOTO on Doppler echocardiography and patient age was analyzed. Sequential changes in LVOTO and AR were determined for patients with two or more Doppler echocardiograms obtained with at least a two-year interval.

RESULTS

A total of 134 adults (mean age 31 +/- 17 years) were diagnosed with DSS. The prevalence was 6.5% for all adults with CHD. Sixty patients (44%) had other associated CHD. The mean age of 29 patients who had undergone an operation for DSS during their adult life (56 +/- 15 years) was significantly higher than that of 64 patients (27 +/- 13 years) who had not required a surgical intervention (p < 0.0001). A significant relationship between LVOTO and patient age (r = 0.61, p < 0.0001) was found: 21 +/- 16 mm Hg in patients <25 years old, 51 +/- 47 mm Hg for those between 25 and 50 years old, and 78 +/- 36 mm Hg for those >50 years old. The LVOTO increased from 39.2 +/- 28 to 46.8 +/- 34 mm Hg (p = 0.01) during a mean follow-up of 4.8 +/- 1.8 years in 25 patients. The slope of the change in LVOTO was 2.25 +/- 4.7 mm Hg per year of follow-up. Aortic regurgitation was detected by color Doppler imaging in 109 patients (81%), but it was hemodynamically significant in <20%. An increase in the mean degree of AR over time was not significant (baseline: 1.3 +/- 0.8; follow-up: 1.5 +/- 0.9; p = 0.096).

CONCLUSIONS

The prevalence of DSS is increasing in adults due to the greater number of repaired CHDs that develop into evolutive DSS. In contrast to infants and children, adults with DSS show a slow rate of LVOTO progression. Aortic regurgitation is a common but usually mild and nonprogressive consequence. The current indications for surgical intervention should be revised.

Subaortic membrane excision: Mid-term results

BACKGROUND

Subaortic membrane (SAM) is a form of fixed subaortic obstruction in which a fibrous membrane is located below the aortic valve.

AIM

To determine the role of surgical treatment for patients with a discrete SAM.

PATIENTS AND METHODS

The hospital records of 45 patients (age range: 2-23 years; median 8 years) undergoing surgery for SAM between 1990 and 1998 at the All India Institute of Medical Sciences, New Delhi, India, were analysed. Preoperative echocardiographically calculated gradients across the left ventricular outflow tract ranged from 50 to 154 mmHg (mean: 86.5 +/- 33.2 mmHg). Nine patients had trivial aortic regurgitation (AR), 10 had mild AR and five had moderate-severe AR. The left ventricular ejection fraction (LVEF) ranged from 20 to 68% (mean 48 +/- 15%). Nineteen patients had significant left ventricular dysfunction (LVEF <50%). Transaortic resection of SAM was done in all patients along with excision of a wedge-shaped segment of septal muscle underlying the membrane.

RESULTS

There were no early or late postoperative deaths. On follow up (up to 113 months), only four patients had gradients >30 mmHg. LVEF improved to 45-70% (mean 58 +/- 7.7%). AR reduced to mild in four patients and trivial in four patients, and did not progress further.

CONCLUSION

Resection of SAM carries long-term benefits. Routine septal myectomy appears to be associated with a low risk of recurrence.

Subvalvular Aortic Stenosis

Subvalvular aortic stenosis (SAS) is a congenital heart defect that causes fixed form of hemodynamically significant left ventricular outflow tract (LVOT) obstruction with progressive course. It has a spectrum of anatomy. It appears usually beyond infancy, causes left ventricular hypertrophy and myocardial dysfunction, and tends to involve the aortic and mitral valves in its progressive course. Although most of the patients are asymptomatic, careful monitoring is essential. Moderate to severe SAS requires surgical resection and septal myomectomy. There is a high rate of postoperative recurrence of the lesion. Recurrent lesions and the complex type of lesions with aortic valve involvement should have aortoseptoplasty (to enlarge the outflow tract) and Ross procedure (removal of the damaged aortic valve and placement of a pulmonary autograft in the aortic position and a pulmonary homograft in the pulmonary position).

Natural history and surgical outcomes for isolated discrete subaortic stenosis in children

OBJECTIVE

To document the natural history and surgical outcomes for discrete subaortic stenosis in children.

DESIGN

Retrospective review.

SETTING

Tertiary care paediatric cardiology centres.

PATIENTS

92 children diagnosed between 1985 and 1998.

MAIN OUTCOME MEASURES

Echocardiographic left ventricular outflow gradient (echograd), and aortic insufficiency (AI).

RESULTS

The mean (SEM) age at diagnosis was 5.3 (0.4) years; the mean echograd was 30 (2) mm Hg, with AI in 22% (19/87) of patients. The echograd and incidence of AI increased to 35 (3) mm Hg and 53% (36/68) (p < 0.05) 3.6 (0.3) years later. The echograd at diagnosis predicted echograd progression and appearance of AI. 42 patients underwent surgery 2.2 (0.4) years after diagnosis. Preoperatively echograd and AI incidence increased to 58 (6) mm Hg and 76% (19/25) (p < 0.05). The echograd was 26 (4) mm Hg 3.7 (0.4) years postoperatively, with AI in 82% (31/38) of patients. Surgical morbidities included complete heart block, need for prosthetic valves, and iatrogenic ventricular septal defects. Eight patients underwent reoperation for recurrent subaortic stenosis. The age at diagnosis of 44 patients followed medically and 42 patients operated on did not differ (5.5 (0.6) v 5. 0 (0.6) years, p < 0.05). However, the echograd at diagnosis in the former was less (21 (2) v 40 (5) mm Hg, p < 0.05) and did not increase (23 (2) mm Hg) despite longer follow up (4.1 (0.4) v 2.2 (0. 4) years, p < 0.05). The incidence of AI at diagnosis and at last medical follow up was also less (14% (6/44) v 34% (13/38); 40% (17/43) v 76% (19/25), p < 0.05).

CONCLUSIONS

Many children with mild subaortic stenosis exhibit little progression of obstruction or AI and need not undergo immediate surgery. Others with more severe subaortic stenosis may progress precipitously and will benefit from early resection despite risks of surgical morbidity and recurrence.

Surgical treatment of subaortic stenosis: a seventeen-year experience

OBJECTIVE

The aim of the study was to analyze the long-term results of subaortic stenosis relief and the risk factors associated with recurrence and reoperation.

METHODS

One hundred sixty patients with subaortic stenosis underwent biventricular repair. Before the operation the mean left ventricle-aorta gradient was 80 +/- 35 mm Hg, 57 patients had aortic regurgitation, and 34 were in New York Heart Association functional class III or IV. Median age at repair was 10 years. For discrete subaortic stenosis (n = 120), 39 patients underwent isolated membranectomy, 67 underwent membranectomy with associated septal myotomy, and 14 underwent septal myectomy. Tunnel subaortic stenosis (n = 34) was treated by myotomy in 10 cases, myectomy in 12, septoplasty in 7, Konno procedure in 3, and apical conduit in 2. Aortic valve replacement was performed in 6 cases, mitral valve replacement in 2 cases, and mitral valvuloplasty in 4 cases.

RESULTS

There were 5 early (3.1%) and 4 late (4.4%) deaths. Within 3.6 +/- 3.3 years a recurrent gradient greater than 30 mm Hg was found in 42 patients (27%), 20 of whom had 26 reoperations. According to multivariable Cox regression analysis survival was influenced by hypoplastic aortic anulus (P =.01) and mitral stenosis (P =.048); recurrence and reoperation were influenced by coarctation and immediate postoperative left ventricular outflow tract gradients. At a median follow-up of 13.3 years, mean left ventricle-aorta gradient was 20 +/- 13 mm Hg. Relief of the subaortic stenosis improved the degree of aortic regurgitation in 86% of patients with preoperative aortic regurgitation. Actuarial survival and freedom from reoperation rates at 15 years were 94% +/- 1.3% and 85% +/- 6%, respectively.

CONCLUSION

Although surgical treatment provides good results, recurrence and reoperation are significantly influenced by previous coarctation repair and by the quality of initial relief of subaortic stenosis.

Detection of cardiovascular abnormalities in the nursery of a general hospital in the Amazon region: correlation with potential risk factors

Congenital heart diseases have been studied much more extensively in children than in neonates. In this study, we report on the findings from 57 neonates seen from June of 1995 through June 1996 in the nursery of a large public hospital in Belém, Pará, Brazil. All were routinely examined by a paediatrician just after birth, and, when indicated, these babies were referred to the cardiology unit of our Hospital for assessment by a paediatric cardiologist. Most of the diagnoses were made by means of Doppler and cross-sectional echocardiography with color flow mapping. Several abnormalities of the cardiovascular system were diagnosed. The most frequent was patency of the arterial duct. But, since many ducts closed spontaneously, ventricular septal defect was the most frequent lesion seen even in the nursery. Four defects (patent arterial duct, ventricular septal defect, atrial septal defect and pulmonary stenosis) together accounted for two thirds of all cardiac abnormalities. Associated non-cardiac anomalies were more frequent in those with simple lesions within the heart. All the babies with complex heart disease, and the majority of those designated as having significant lesions, died before they could be discharged. Several risk factors were investigated. Among maternal drugs, misoprostol emerged as having a possible teratogenic effect.

Development and validation of an echocardiographic model for predicting progression of discrete subaortic stenosis in children

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-(-322+0.334X1+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 area0.5 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.

Benefits of early surgical repair in fixed subaortic stenosis

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 < or = 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.

Potential role of mechanical stress in the etiology of pediatric heart disease: septal shear stress in subaortic stenosis

OBJECTIVES

The objective of this study was to show elevations in septal shear stress in response to morphologic abnormalities that have been associated with discrete subaortic stenosis (SAS) in children. Combined with the published data, this critical connection supports a four-stage etiology of SAS that is advanced in this report.

BACKGROUND

Subaortic stenosis constitutes up to 20% of left ventricular outflow obstruction in children and frequently requires surgical removal, and the lesions may reappear unpredictably after the operation. The etiology of SAS is unknown. This study proposes a four-stage etiology for SAS that I) combines morphologic abnormalities, II) elevation of septal shear stress, III) genetic predisposition and IV) cellular proliferation in response to shear stress.

METHODS

Morphologic structures of a left ventricular outflow tract were modeled based on measurements in patients with and without SAS. Septal shear stress was studied in response to changes in aortoseptal angle (AoSA) (120 degrees to 150 degrees), outflow tract convergence angle (45 degrees, 22.5 degrees and 0 degree), presence/location of a ventricular septal defect (VSD) (3-mm VSD; 2 and 6 mm from annulus) and shunt velocity (3 and 5 m/s).

RESULTS

Variations in AoSA produced marked elevations in septal shear stress (from 103 dynes/cm2 for 150 degrees angle to 150 dynes/cm2 for 120 degrees angle for baseline conditions). This effect was not dependent on the convergence angle in the outflow tract (150 to 132 dynes/cm2 over full range of angles including extreme case of 0 degree). A VSD enhanced this effect (150 to 220 dynes/cm2 at steep angle of 120 degrees and 3 m/s shunt velocity), consistent with the high incidence of VSDs in patients with SAS. The position of the VSD was also important, with a reduction of the distance between the VSD and the aortic annulus causing further increases in septal shear stress (220 and 266 dynes/cm2 for distances of 6 and 2 mm from the annulus, respectively).

CONCLUSIONS

Small changes in AoSA produce important changes in septal shear stress. The levels of stress increase are consistent with cellular flow studies showing stimulation of growth factors and cellular proliferation. Steepened AoSA may be a risk factor for the development of SAS. Evidence exists for all four stages of the proposed etiology of SAS.

Abnormalities of the left ventricular outflow tract associated with discrete subaortic stenosis in children: an echocardiographic study

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.

Subaortic septal bulge simulates hypertrophic cardiomyopathy by angulation of the septum with age, independent of focal hypertrophy. An echocardiographic study

Focal hypertrophy of the basal anterior septum occurs not infrequently in elderly patients and is considered by some to be a significant form of hypertrophic cardiomyopathy; others consider it to be an unimportant anatomic variant associated with an angulated septum, called a septal bulge (SB). We analyzed 94 cases of SB collected prospectively and compared them with 88 patients with extensive hypertrophic cardiomyopathy (HCM), 20 patients with hypertrophic cardiomyopathy limited to the entire septum (ASH), and 20 age-matched controls. The SB cases were also divided into three groups, with marked, moderate, or no basal septal hypertrophy associated with the occurrence of an SB. All groups of SB patients had increased fractional shortening compared with controls (0.48 +/- 0.07 versus controls 0.40 +/- 0.07), comparable with HCM (0.48 +/- 0.12), and increased left ventricular outflow tract velocity both at rest and especially after amyl nitrite inhalation (3.42 +/- 1.35 versus 1.55 +/- 0.60 m/sec [controls]). Other features of HCM were not present: normal wall thickness except for the basal septal hypertrophy, no anterior malposition in SB patients, no age-independent reversal of ratio of early to late mitral inflow velocity (E/A), and no decrease in end-diastolic dimension. It is concluded that outflow tract narrowing by an angulated septum is the primary mechanism responsible for the increased outflow tract velocity, rather than the hypertrophic septum. The resultant increase in convective acceleration simulates the dynamics of hypertrophic cardiomyopathy. The focal hypertrophy may be secondary and contributory to the enhanced ventricular dynamics, but it does not appear to be a primary cardiomyopathy.

The Usefulness of Transesophageal Echocardiography in the Surgical Management of Older Children with Subaortic Stenosis

Subaortic stenosis is a complex lesion that often presents in older children and adolescents. A clear depiction of the lesion is required for optimization of surgery. Due to the large size of these patients, is not always possible from surface echocardiography. Intraoperative multiplane echocardiography (MTEE) has been performed at our institute in older children for several different congenital heart lesions including many patients with subaortic stenosis. A retrospective analysis of our experience with MTEE in patients with subaortic stenosis was performed to assess its usefulness in the preoperative diagnosis and postoperative assessment of repair. Our results show that intraoperative MTEE was useful preoperatively by correcting or confirming suspected diagnosis, and giving additional details of the lesion in many patients. Postoperatively, MTEE was highly useful in the assessment of repair. We strongly recommend the use of intraoperative MTEE in older children and adolescents with subaortic stenosis. (ECHOCARDIOGRAPHY, Volume 13, November 1996)

Malalignment-type ventricular septal defect in double-chambered right ventricle

Double-chambered right ventricle (DCRV) is commonly associated with ventricular septal defect (VSD). In this study, an assessment was made of the relevance of a malalignment-type VSD to hemodynamic and morphologic features in DCRV. During an 8.5-year period, 53 patients with DCRV were enrolled after study with echocardiography, catheterization, and angiography. Patients were divided into 2 groups: group I included 40 patients, aged 3.7 +/- 3.2 years, with a malalignment-type VSD; group II consisted of 13 patients, aged 8.6 +/- 2.7 years, without a malalignment-type VSD. History of congestive heart failure in infancy was present in 21 group I and 2 group II patients (53% vs 15%, respectively, p <0.05). The mean pulmonary-to-systemic flow ratio was significantly higher in group I than in group II (1.89 +/- 0.74 vs 1.14 +/- 0.21, respectively, p <0.05). The mean pressure gradient across the right ventricular outflow tract was lower in group I than in group II (41 +/- 16 vs, 73 +/- 33 mm Hg, respectively, p <0.05). Among 42 patients who had a series of echocardiograms recorded, progression of pressure gradient was evident in 35: 28 in group I and 7 in group II. A subaortic ridge was present exclusively in 29 group I patients (73%). Prolapse of the aortic valve was present in 26 (49%): 20 group I (50%) and 6 group II (46%) patients. Aneurysm formation of the septal defect was found in 17 (43%) and 7 (54%) group I and II patients, respectively. It can be concluded that a history of congestive heart failure was more common in DCRV patients with a malalignment-type VSD. Malalignment-type VSD is significantly associated with a larger pulmonary-to-systemic flow ratio and subaortic ridge.

Fibrous obstruction within the left ventricular outflow tract associated with ventricular septal defect: a pathologic study

OBJECTIVES

We examined the nature of ridges within the left ventricular outflow tract associated with ventricular septal defects that might be found by echocardiography.

BACKGROUND

Echocardiography displays even small ridges well. Surgical removal of such ridges at the time of defect closure is recommended.

METHODS

We examined 37 heart specimens with ventricular septal defects with a ridge, noting its nature and relation to the defect and adjacent valves. We excluded left ventricular outflow tract obstruction associated with complex lesions.

RESULTS

Defects were perimembranous in 25 specimens, muscular in 8 and part of an atrioventricular septal defect in 5. Some hearts had multiple defects. Many of the original reports had not mentioned ridges. Three distinct ridge patterns were found. The first (n = 18) was a fold of endocardial tissue related to the membranous septum. The second (n = 12) was a defect of a fibrous nature; in 8 this was a discrete, protuberant fibrous ridge, and in 4 the obstruction was diffuse, which we termed keloidal. The third pattern (n = 7) lay circumferentially around the ventricular septal defect, seemingly associated with the defect's attempted spontaneous diminution in size. Endocardial folds were not found in specimens from patients > 5 years old. Fibrous and keloidal lesions, which may represent a continuum of progression, generally were found in specimens from older patients. Histologic studies of 17 specimens confirmed the morphologic findings. The endocardial folds were endothelial tissue, whereas the fibrous and keloidal ridges were of fibrous tissue, as were circumferential lesions. All specimens had mitral-semilunar valvular continuity.

CONCLUSIONS

Endocardial fold and circumferential lesions appear to be benign. The endocardial folds arose from the membranous ventricular septum, were not protuberant and usually were found in younger patients. The fibrous ridges, in contrast, were protuberant and were always associated with the underlying muscle of the outlet septum. These pathologic distinctions may facilitate echocardiographic diagnosis and prognosis.

Postoperative follow-up of fibromuscular subaortic stenosis

OBJECTIVES

This study attempted to determine whether early subaortic resection at lower levels of obstruction reduces the rate of recurrence of subaortic stenosis or reduces secondary damage to the aortic valve, or both.

BACKGROUND

Fibromuscular subaortic stenosis is a progressive condition, and at present it is unclear whether early operation reduces the recurrence rate along with decreasing the incidence of aortic insufficiency.

METHODS

Thirty-seven patients with fibromuscular subaortic stenosis and no other significant cardiac abnormality who underwent open subaortic resection were evaluated. The preoperative, early and late postoperative catheterization or echocardiographic findings as well as the operative reports were reviewed. The median age at operation was 6.4 years (range 1.1 to 17.3). The entire group has been followed up postoperatively for a median of 5.2 years (range 1.1 to 11). Mean systolic gradients across the left ventricular outflow tract were used for the purpose of this study.

RESULTS

There was a significant correlation between the preoperative mean systolic gradient and the incidence of preoperative aortic regurgitation and late postoperative aortic valve thickening as well as the incidence and degree of late postoperative aortic regurgitation. Late postoperative gradient and degree of aortic regurgitation correlated significantly with the follow-up interval. Aortic regurgitation was progressive in some patients despite subaortic resection. A preoperative mean gradient > 30 mm Hg provided a reasonable cutoff for the likelihood postoperatively of needing a reoperation, having a postoperative shelf, a thickened aortic valve, moderate aortic regurgitation or a gradient of > 10 mm Hg.

CONCLUSIONS

Our results suggest that although early subaortic resection may not reduce the rate of recurrence of fixed subaortic stenosis, it is likely to reduce acquired damage to the aortic valve.

Morphology of left ventricular outflow tract structures in patients with subaortic stenosis and a ventricular septal defect

OBJECTIVE

To compare the incidence and prognosis of subaortic stenosis associated with a ventricular septal defect and to define the morphological basis of subaortic stenosis.

DESIGN

Presentation and follow up data on 202 patients with subaortic stenosis seen at the Royal Liverpool Children's Hospital between 1 January 1960 and 31 December 1991 were reviewed. Survivors were traced to assess their current clinical state. Necropsy specimens of 291 patients with lesions associated with subaortic stenosis were also examined.

RESULTS

In the clinical study; 65 (32.1%) of the 202 patients with subaortic stenosis had a ventricular septal defect (excluding an atrioventricular septal defect). 32 of these patients had a short segment (fibromuscular) subaortic stenosis. 33 had subaortic stenosis produced by deviation of muscular components of the outflow tracts. In 17 patients (51.5%) this was caused by posterior deviation or extension of structures into the left ventricular outflow tract, resulting in obstruction above the ventricular septal defect. In the other 16 patients (48.5%) there was over-riding of the aorta with concordant ventriculoarterial connections, (without compromise to right ventricular outflow) producing subaortic stenosis below the ventricular septal defect. Additional fibrous obstruction occurred in 39% of the patients with deviated structures. The age at presentation was lower (P < 0.01) in patients with deviated structures (median (range) 0.4 (0 to 9.2) months) than in those with short segment obstruction (median (range) 4.2 (0 to 84.9) months). The incidence of aortic arch obstruction was higher (P < 0.002) in patients with deviated structures than in those with short segment obstruction (38%). In the morphological study 35 pathological specimens showed obstructive muscular structures in the left ventricular outflow tract either above or below the ventricular septal defect. 16 had either posterior deviation of the outlet septum or extension of the right ventriculoinfundibular fold, or both of these together into the left ventricle. 19 had anterior deviation of the outlet septum into the right ventricle with overriding of the aorta (without compromise to right ventricular outflow). The earliest age at which additional fibrous obstruction was seen was 9 months. The aortic valve circumference was small in 18% of specimens.

FOLLOW UP

The median (range) duration of follow up in survivors from the clinical study was 6.6 (1 to 25.7) years. 16 patients with deviated musculature (49%) and 16 with short segment fibromuscular stenosis (50%) underwent operation for subaortic stenosis. Patients with deviated structures were younger at operation than those with short segment stenosis (P < 0.005). Patients with posterior deviation or extension of structures into the left ventricular outflow tract underwent operation for subaortic stenosis more frequently (P < 0.05) than those with anterior deviation of the outlet septum and aortic override. The ventricular septal defect required surgical closure more frequently (P < 0.005) in patients with deviation (93.9%) than in those with short segment obstruction (21.9%). There was no significant difference in the mortality between patients with deviation (27%) and those with short segment obstruction (12%).

CONCLUSIONS

32% of patients in the clinical study with subaortic stenosis had a ventricular septal defect. Only 51% of these had obstructive and deviated muscular structures in the left ventricular outflow tract. These patients had a significantly higher incidence of aortic arch obstruction and required surgery for subaortic stenosis at a younger age than those with short segment obstruction. The ventricular septal defect also required surgical closure more frequently in those patients with deviation. The morphological study defined the two sites of obstruction. The presence or absence and type of deviation should be clearly defined in all patients with a ventricular septal defect,

Echocardiographic morphometry and geometry of the left ventricular outflow tract in fixed subaortic stenosis

OBJECTIVES

This study was designed to identify, by echocardiography, morphometric abnormalities of the left ventricular outflow tract in children with fixed subaortic stenosis and to determine whether these abnormalities precede the development of subaortic obstruction.

BACKGROUND

Fixed subaortic stenosis typically develops and progresses after the 1st year of life and is therefore often regarded as an acquired lesion. Although it has been speculated that there may be an underlying anatomic substrate, there are no data to support this hypothesis.

METHODS

The size of the aortic annulus, mitral-aortic valve separation, aorto-left ventricular septal angle and degree of aortic override were determined in two groups of children. Group 1 comprised 35 patients with isolated subaortic stenosis noted on initial echocardiogram who were compared with an age- and weight-matched normal control group (Group 1A). Group 2 comprised 23 patients with ventricular septal defect or coarctation of the aorta, or both, who had no subaortic stenosis on initial echocardiogram but who developed it subsequently. This group was compared with an age-, weight- and lesion-matched control group (Group 2A).

RESULTS

Compared with control subjects, patients with isolated subaortic stenosis had a significantly wider mitral-aortic separation ([mean +/- SD] 5.1 +/- 1.3 vs. 3.4 +/- 0.9 mm, p < 0.001), a steeper aortoseptal angle (131 +/- 6 degrees vs. 144 +/- 5 degrees, p < 0.001) and an exaggerated aortic override (p < 0.05). Similar differences were found on initial echocardiogram in Group 2 patients before development of subaortic stenosis: wider mitral-aortic separation (4.2 +/- 1.2 vs. 2.5 +/- 0.7 mm, p < 0.001), a steeper aortoseptal angle (132 +/- 7 degrees vs. 145 +/- 7 degrees, p < 0.001) and an exaggerated aortic override (p < 0.05).

CONCLUSIONS

A left ventricular outflow tract malformation characterized by a wider mitral-aortic separation, an exaggerated aortic override and a steeper aortoseptal angle are present in children with ventricular septal defect or coarctation of the aorta, or both, who subsequently develop subaortic stenosis. These morphometric features can be used to identify by echocardiography patients who are at risk for developing fixed subaortic stenosis.

Optimum treatment of discrete subaortic stenosis

Discrete subaortic stenosis typically appears as a well-defined membrane beneath the aortic valve. To assess the merits of alternative approaches to this problem, we have reviewed the results of operations for discrete subaortic stenosis from 1978 through 1990. Excision of the subaortic membrane alone was performed in 16 patients (group I). Excision of the membrane with resection of septal muscle was performed in 24 patients (group II). The groups were similar in age at operation, duration of follow-up, and preoperative and postoperative transvalvar gradients. There were no operative or late deaths. Reoperations for recurrent subaortic stenosis were performed in 4 group I patients (25%; 70% confidence limits, 16% to 38%) and 1 group II patient (4%; 70% confidence limits, 2% to 11%). Pacemakers were inserted for postoperative complete heart block in 1 group I patient (6%; 70% confidence limits, 2% to 16%) and 2 group II patients (8%; 70% confidence limits, 4% to 16%). We conclude that muscle resection combined with membrane excision in patients with discrete subaortic stenosis does not increase the risk of death or heart block, and does lower the risk of reoperation for recurrent subaortic stenosis.

Fixed subaortic stenosis in atrioventricular canal defect: a Doppler echocardiographic study

OBJECTIVES

The objectives of this retrospective study were to describe the Doppler and echocardiographic features of fixed subaortic stenosis in the setting of atrioventricular (AV) canal defect and to document the de novo occurrence of subaortic stenosis and progression of this lesion over time on the basis of sequential echocardiographic studies.

BACKGROUND

The coexistence of fixed subaortic and AV canal defect has been sporadically noted, but no single or multicenter experience with this constellation of abnormalities has been previously described.

METHODS

All patients with a diagnosis of subaortic stenosis and complete or partial AV canal defect who had one or more Doppler echocardiographic examinations were identified from a computer data bank. Retrospective analysis was performed, including review of patients' charts, operative notes, recorded videotapes and hard copy recordings when available.

RESULTS

Twenty-one patients with both subaortic stenosis and AV canal defect were identified over a 13-year period. Fifteen were female and the mean age at diagnosis of subaortic stenosis was 16 years. Fifteen patients had partial AV canal defect with prior repair in 10; 6 patients had complete AV canal defect with prior repair in 4. The mean interval from prior repair to recognition of subaortic stenosis was 6.8 years. In six patients, serial examinations demonstrated the de novo occurrence of subaortic obstruction over a period of 10 to 87 months. In five patients, progression of known subaortic stenosis was documented over a 10- to 59-month period. Surgical resection of subaortic stenosis was performed in 16 patients; the echocardiographic diagnosis was confirmed in 15 of the 16.

CONCLUSIONS

In the largest reported echocardiographic series of this lesion complex, it is concluded that subaortic stenosis can occur de novo, is often recognized only after repair of the canal defect and is progressive. Doppler echocardiography is the method of choice for diagnosis and serial follow-up of these patients.

Management of fixed subaortic stenosis: a retrospective study of 57 cases

Although recommended by several investigators, the benefit of early surgery in patients with fixed subaortic stenosis has not been proved. Findings were reviewed of 57 patients with isolated fixed subaortic stenosis, including 27 surgically treated patients, with special emphasis on the occurrence of aortic regurgitation during a mean follow-up period of 6.7 years. The number of patients with aortic regurgitation increased preoperatively in the total group (23% at diagnosis to 54% after 3.7 years of follow-up). The prevalence of aortic regurgitation in the 27 surgically treated patients was higher (81%) than that in the nonsurgically treated group but remained unchanged after a mean postoperative period of 4.7 years. In all patients but one, aortic regurgitation remained of minor hemodynamic significance. One patient died during follow-up. After surgery, 15 patients (55%) showed a relapse; 11 redeveloped a subvalvular pressure gradient greater than 30 mm Hg and discrete subvalvular ridges (range 6 months to 24 years after surgery, mean 7 years). In those patients with fixed subaortic stenosis, follow-up did not reveal any benefit from early surgery. The unpredictable course and sometimes very severe progression of this disease make frequent and careful follow-up necessary.

Rheologic genesis of discrete subvalvular aortic stenosis: a Doppler echocardiographic study

To determine whether morphologic structures or abnormal flow patterns predispose to pathologic proliferation of subvalvular tissue, 26 patients (mean age 19.8 +/- 10.3 years) were studied greater than or equal to 6 months after operation for isolated discrete subvalvular aortic stenosis. The aortic root diameter and the mitral-aortic separation were measured with sector echocardiography. Flow patterns in the left ventricular outflow tract of these patients and control subjects were evaluated with a color flow mapping system optimized for the detection of turbulence. All control subjects had laminar flow throughout systole in the left ventricular outflow tract. By contrast, turbulence originating well below the site where the shelf had previously been resected was observed in 20 (77%) of the 26 patients. In 16 of these 20 patients turbulence was caused by a ridge, which in 13 patients could be identified as the offshoot of a ventricular band. In four patients the turbulence was caused by malalignment of the muscular and membranous septum, resulting in protrusion of the muscular septum into the outflow tract. Except for the latter four patients, the aortic root diameter was 84 +/- 10% of values predicted by body surface area, with values in six patients falling below the third percentile (p less than 0.01). The mitral-aortic separation was 9.7 +/- 3.5 mm, values in 21 patients falling above the 97th percentile (p less than 0.001). These data support the theory that discrete subvalvular aortic stenosis may be caused by a chronic flow disturbance, preferably in a small and long outflow tract. Left ventricular bands, if reaching the outflow tract, may be a factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac function after surgery for subaortic stenosis: non-invasive assessment of left ventricular performance

OBJECTIVE

To examine left ventricular function after surgical resection of subaortic stenosis during childhood.

DESIGN

Left ventricular performance was measured non-invasively in all patients who responded to an invitation for formal assessment.

SETTING

Outpatient study, tertiary referral centre.

PATIENTS

Twenty three (12 male and 11 female) patients (age range 3 to 31 years) of 43 consecutive patients with fixed subaortic stenosis undergoing surgical resection between 1975 and 1989 reattended for formal assessment 16 months to 15 years (median 4 years 4 months) after operation.

MAIN OUTCOME MEASURES

Left ventricular dimension, left ventricular wall thickness, left ventricular Doppler inflow velocities, and left ventricular diastolic pressure (measured from apexcardiograms). Results were compared with those in controls individually matched for age and sex.

RESULTS

All patients were symptom free. Left ventricular cavity dimensions were normal, as was the mean fractional shortening. Posterior wall thickness tended to be greater in the patients and there was a significant increase in septal thickness. Normalised peak rate of posterior wall thinning was significantly lower in the patients and the isovolumic relaxation time was significantly shorter. Doppler inflow velocity measurements showed that early diastolic mitral flow acceleration time was normal but deceleration time was significantly shorter in the patients. The ratio of mitral flow in early diastole (E) to E plus mitral flow in late diastole (A) was significantly higher in the patients and in two patients there was complete absence of A wave flow despite large A waves on the apexcardiogram.

CONCLUSIONS

Systolic function was well preserved in patients after operation for subaortic stenosis. A restrictive pattern of left ventricular filling was common, however, and presumably reflected a response to the chronic pressure load and to surgery in the paediatric heart.

Fixed subaortic stenosis: anatomical spectrum and nature of progression

Retrospective echocardiographic review identified 58 consecutive infants and children with fixed subaortic stenosis. Mean (SD) age at diagnosis was 4.8 (3.6) years (range two days to 14.7 years), and diagnosis occurred in infancy in eight. Associated cardiac abnormalities were present in 41 (71%) whereas fixed subaortic stenosis was an isolated lesion in 17 (29%). Four types of fixed subaortic stenosis were identified: short segment (47 (81%)), long segment (7 (12%)), posterior displacement of the infundibular septum with additional discrete narrowing of the left ventricular outflow tract (3 (5%)), and redundant tissue arising from the membranous septum (1 (2%)). Echocardiographic studies had been performed before the diagnosis of fixed subaortic stenosis in nine patients, all with associated abnormalities. These were performed in infancy in each and showed a "normal" left ventricular outflow tract in six and posterior deviation of the infundibular septum in three. In 16 patients serial echocardiographic studies had been performed after the diagnosis of fixed subaortic stenosis but before surgery of the left ventricular outflow tract. Rapid evolution of short segment to long segment narrowing was seen in one patient, and tethering of the aortic valve or mitral valve developed in a further four patients. Aortic valve or mitral valve involvement was not seen before the age of three years but was common thereafter (10/40 patients, 25%). Fixed subaortic stenosis may be an "acquired" lesion with the potential for changes in form as well as progression in severity of left ventricular outflow tract obstruction.

Subaortic obstruction: intraoperative echocardiography as an adjunct to operation

Fourteen patients undergoing operation for subaortic obstruction (membranous obstruction in 11 patients, tunnel obstruction in 2 patients, obstruction due to reduplicated mitral valve tissue in 1 patient) were evaluated by intraoperative epicardial echocardiography. In all 9 patients with "discrete" obstruction who underwent prebypass epicardial echocardiography, the septal and lateral attachments of the lesion were correctly demonstrated. The precise extent of tunnel stenosis was seen in both patients. The lateral attachment of the membrane in 4 patients and multiple extensions in another 2 were identified by the epicardial study (having been missed on precordial echocardiography). The discrete membrane was enucleated in 10 of the 11 patients and was partially resected in 1. One tunnel obstruction was completely relieved; the other was partially relieved. Reduplicated mitral valve tissue in the remaining patient was completely resected. Epicardial imaging after bypass showed remnants of the membrane in 2 patients. Intraoperative Doppler echocardiography and color flow imaging confirmed the absence of clinically significant residual gradients (less than 20 mm Hg) in all but 1 patient with tunnel obstruction. Epicardial imaging provided excellent morphological information about obstructive lesions of the left ventricular outflow tract and enabled immediate assessment of surgical repair.

Discrete subaortic stenosis. Surgery in children based on two-dimensional and Doppler echocardiography

Twenty pediatric patients underwent surgical resection of a "discrete" subaortic membrane. The diagnosis and the surgical indication were based on two-dimensional and Doppler echocardiography without cardiac catheterization and angiography. In all patients the echocardiographic diagnosis was confirmed at surgery in terms of presence, dimension and location of the membrane and in ten patients in terms of pressure gradients. Two-dimensional and Doppler echocardiography has proved to be a very reliable tool for the diagnosis and surgical indication in pediatric patients with a DSAS. Our criteria for the selection of surgical patients are the following: (1) isolated form of discrete subaortic stenosis with a short base of attachment to the ventricular septum; (2) pressure gradients higher than 25 mm Hg; (3) presence of significant aortic insufficiency. All of this information can be consistently obtained with two-dimensional and Doppler echocardiography.