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

Discrete subaortic membranes in adults--a clinicopathological analysis

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Aortic stenosis in the Dogue de Bordeaux

OBJECTIVES

To evaluate the occurrence of aortic stenosis and establish echocardiographic reference values in the Dogue de Bordeaux in Denmark.

METHODS

Fifty-three dogs were auscultated for evidence of a cardiac murmur and a full echocardiographic examination was performed. The criterion for the diagnosis of aortic stenosis was a peak aortic velocity greater than 2.5 m/s from a subcostal transducer location.

RESULTS

A left-basilar ejection murmur was detected in 38 (72 per cent) of the dogs. An aortic ejection velocity greater than 2.5 m/s was identified in 9 (17 per cent) of the dogs from a subcostal view. The aortic annulus in Dogue de Bordeaux was smaller than that considered normal in other breeds with comparable body size. Furthermore, a decreased aortoseptal angle was noticed in dogs with aortic stenosis.

CLINICAL SIGNIFICANCE

The Dogue de Bordeaux may be highly predisposed to aortic stenosis. The small aortic annulus noted in healthy and affected Dogue de Bordeaux and a decreased aortoseptal angle noted in affected dogs in this study might reflect key aetiological features in the development of aortic stenosis.

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.

Surgery for subvalvar aortic stenosis - resection of discrete subvalvar aortic membrane

Discrete subvalvar aortic membrane is characterized by a fibromuscular shelf located at the area of aortomitral continuity with the extension toward the interventricular septum. As compared to other congenital heart defects, discrete subvalvar aortic membrane is virtually never recognized in early infancy, but appears to be an 'acquired' lesion, typically seen in patients with a more acute angle between the long axis of the left ventricle and the aorta. This angulation leads to imbalance in shear forces, which causes the proliferation of tissue that forms the membrane. The surgical intervention is considered when the gradient across the left ventricular outflow tract is 30 mmHg or more. Surgery is also advocated in infants and children in the presence of aortic regurgitation even when there is no significant gradient. The circumferential excision of the fibrous ridge with septal myectomy is safe and provides efficient relief of obstruction. Aggressive resection of all structures causing flow turbulence and removal of pathological tissue from the valve leaflets might prevent development or progression of aortic regurgitation and might eliminate the substrate for recurrent obstruction. Nevertheless, recurrence still remains a problem, especially in the presence of a predisposing associated congenital heart defect.

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.

Recurrent discrete subaortic stenosis and small aortic annulus successfully repaired by the Konno procedure in a young woman

A 24-year-old woman who had undergone excision of the membrane for discrete subaortic stenosis when 6 years old displayed recurrent subaortic stenosis and had a small aortic annulus, with a peak pressure gradient of 60mmHg. We chose to perform the Konno operation with a mechanical valve. This released the left ventricular outflow tract obstruction adequately, and she recovered uneventfully with New York Heart Association functional class I. In our experience, an aggressive strategy such as myectomy is an appropriate initial procedure for preventing recurrence when the geometry of the problem may lead to recurrence in the left ventricular outflow tract. The Konno operation is a good option for recurrent subaortic stenosis with small aortic annulus.

Rapid progression of midventricular obstruction in adults with double-chambered right ventricle

OBJECTIVE

The purpose of this study was to determine the rate of progression of midventricular obstruction in adolescents and adults with double-chambered right ventricle.

METHODS

Clinical and echocardiographic findings in 45 patients (mean age 26 +/- 6 years, range 15-44) diagnosed with double-chambered right ventricle were retrospectively analyzed. Twenty patients underwent surgical repair before the age of 15 years. The relationship between Doppler midventricular pressure gradient and patient age was analyzed in 25 patients without previous repair. Sequential change in midventricular obstruction was determined for patients with 2 or more Doppler echocardiographic examinations performed within at least a 2-year interval.

RESULTS

Right midventricular pressure gradient in nonrepaired patients was 70 +/- 38 mm Hg (range 25-150). A significant relationship between midventricular obstruction and patient age (r = 0.64, P <.001) was found. Midventricular pressure gradient at initial evaluation was 32 +/- 27 mm Hg in 16 patients < 25 years and 73 +/- 45 mm Hg in 9 patients >/= 25 years (P <.03). After the initial study, 5 patients underwent surgical repair and 13 patients without repair were followed up for a period of 6.1 +/- 2.7 years (range 2-9), in which midventricular pressure gradient increased from 32 +/- 26 mm Hg to 67 +/- 35 mm Hg (P <.001). The slope of the change in midventricular pressure gradient was 6.2 +/- 3 mm Hg per year of follow-up. Seven more patients underwent surgical repair during follow-up due to progression of the obstruction. There was no mortality nor residual midventricular obstruction in surgically repaired patients.

CONCLUSIONS

Mild right midventricular obstruction shows a fast rate of progression in adolescents and young adults. Thus, close clinical and echocardiographic follow-up is advised, and surgical repair should be considered if significant progression of obstruction is detected.

Discrete subaortic stenosis: incidence, morphology and surgical impact of associated subaortic anomalies

BACKGROUND

The association between discrete subaortic stenosis and other subaortic anomalies is a well known but rarely reported occurrence. The aim of this study is to define the incidence, morphology, and surgical impact of associated anomalies of the left ventricular outflow tract in children operated on for discrete subaortic stenosis.

METHODS

Between 1994 and 2000, 45 consecutive children were operated on for discrete subaortic stenosis. Patients were divided in two groups according to the obstructive lesion detected by echocardiography.

RESULTS

A localized shelf was found as an isolated lesion in 31 patients (group A), whereas additional subaortic anomalies were found in 14 cases (31%) and were multiple in 5 cases (group B). The anomalies included anomalous septal insertion of mitral valve (7 cases); accessory mitral valve tissue (2 cases); anomalous papillary muscle (2 cases); anomalous muscular band (8 cases); and muscularization of the anterior mitral valve leaflet (1 case). Cardiopulmonary bypass and aortic cross-clamping times were significantly shorter in group A. There were no operative deaths nor major complications or deaths during follow-up. A gradient of 15 mm Hg or more was found at follow-up in 5 cases whereas aortic regurgitation was estimated to be not clinically significant in all but 1 patient. Six cases of recurrent subaortic stenosis were found in our series, 3 of them with other subaortic anomalies.

CONCLUSIONS

This study shows that discrete subaortic stenosis can often be associated with other subaortic abnormalities. Surgical treatment of these anomalies produces excellent early and mid-term relief of obstruction without any increase in mortality and morbidity.

Rheology of discrete subaortic stenosis

The discrete form of subaortic stenosis is thought to be an acquired lesion, the aetiology of which may be a combination of factors which include an underlying genetic predisposition, turbulence in the left ventricular outflow tract, and various geometric and anatomical variations of the left ventricular outflow tract. A review of hypotheses relating to its aetiology is provided

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.

Surgical management of complex and tunnel-like subaortic stenosis

BACKGROUND

Relief of primary or secondary subaortic stenosis (SAS) remains a surgical challenge. Heart block, aortic valve regurgitation and recurrent obstruction have been persistent problems.

METHODS

Forty six patients who underwent surgery for complex and tunnel-like SAS between January 1990 and November 1998 were reviewed. In 45 of the 46 patients SAS developed following repair of a primary congenital heart defect and only one patient presented with de novo tunnel-like SAS. Fifteen of the 45 patients had undergone repair of double-outlet right ventricle (DORV) and the remaining 30 had undergone repair of a variety of defects. The median age at the time of surgery was 5 years. The modified Konno procedure was performed in 15 patients, Konno procedure in three, Ross-Konno procedure in two and resection of the conal septum in 12 patients. Five patients with DORV underwent replacement of the intraventricular baffle and two patients underwent an aortic valve-preserving procedure in conjunction with mitral valve replacement.

RESULTS

There were no deaths. None of the patients had an exacerbation of aortic regurgitation and none developed complete heart block. The median follow-up was 3 years (range 1 month-8.5 years). Two patients developed recurrent SAS defined as a gradient of 40 mmHg or greater diagnosed by transthoracic echocardiography. Freedom from SAS at 1, 3 and 5 years was 100, 94 and 86%, respectively.

CONCLUSIONS

We favor the modified Konno procedure and conal resection to the Konno or the Ross procedure, since insertion of a prosthetic valve or homograft is avoided and aortic valve function is preserved. Excellent relief of tunnel-like SAS can be achieved without damage to the conduction tissue.

Echocardiographic, morphologic, and geometric variations of the left ventricular outflow tract: possible role in the pathogenesis of discrete subaortic stenosis

Although the clinical features and natural course of discrete subaortic stenosis (DSS) are well defined, the etiology remains speculative. The purpose of this study was to identify the echocardiographic, morphologic, and geometric variations of the left ventricular outflow tract associated with DSS in children and to determine whether these variations have a role in the pathogenesis of DSS. The aortoseptal angle (ASA), mitral-aortic valve separation (MAS), and the size of the aortic annulus were determined in two groups of children. Group 1 comprised 11 patients with isolated DSS, who were compared with an age- and body surface area- (BSA) matched healthy children (Group 1A, n: 20). Group 2 comprised 10 patients with DSS and ventricular septal defect (VSD). Group 2 was compared with an age- and BSA-matched patients with isolated perimembranous VSD (Group 2A, n: 22). Measurements were carried out from previously recorded echocardiographic studies. The ASA was steeper (119.3 +/- 6.1 degrees vs 137.5 +/- 5.6 degrees , p < 0.001), and the MAS was wider (6.1 +/- 1.6 vs 3.2 +/- 0.7 mm, p < 0.001) in patients with isolated DSS than in healthy control subjects. Similar differences were found between patients in Group 2 and Group 2A; the ASA was steeper (122.2 +/- 6.5 degrees vs 141.3 +/- 5.0 degrees, p < 0.001), and the MAS was wider (5.8 +/- 1.5 vs 3.8 +/- 1.1 mm, p < 0.001). The size of the aortic annulus was not different among the four study groups. Although the MAS was significantly wider in patients with DSS, there was significant overlap in MAS between patients and controls. However, if an ASA < or = 130 degrees was chosen as a predictive variable, it was found to be a highly sensitive, specific, and positive predictive marker for the development of DSS. This study demonstrates that DSS is associated with a steeper ASA, and a wider MAS, in patients with or without associated VSD. These morphologic abnormalities, especially a steeper ASA, may be risk factors for the development of DSS.

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.

Left ventricular outflow obstruction

Patients with LVOT obstruction require lifelong follow-up because the obstruction may be progressive or recurrent. Several procedures are usually required, either by surgery or by interventional cardiac catheterization, to repair or palliate the obstructive lesion. The treatment of these patients continues to evolve, and, despite the complexity of these patients' lesions, the morbidity and mortality rates have decreased and are expected to decrease further in the future.

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.