Discrete subaortic stenosis

Surgery for discrete subvalvular aortic stenosis: actuarial survival, hemodynamic results, and acquired aortic regurgitation

Discrete membranous subaortic stenosis (DMSS) accounts for 8 to 30% of congenital left ventricular outflow obstruction. The immediate effectiveness of surgical resection of this discrete obstructing membrane has been well documented, but little has appeared regarding late clinical and hemodynamic follow-up. Fifty-three patients with DMSS underwent operation at our institution from 1957 to 1983. Most (78%) were symptomatic, 79% had left ventricular hypertrophy (LVH) by electrocardiogram, and 92% had roentgenographic evidence of cardiomegaly preoperatively. Catheterization revealed a mean preoperative left ventricular-aortic gradient of 89 mm Hg. Twenty-eight patients had associated aortic insufficiency (AI) on the initial aortogram. Seven patients acquired AI in the interim between the first and second preoperative catheterization. Our patients have been followed for up to 12 years postoperatively. There have been 2 early and 3 late deaths. (Actuarial analysis revealed 5- and 10-year survival of 95% and 83%, respectively.) Seventy-one percent of the previously symptomatic patients noted relief of their preoperative complaints, and 45% of those with LVH had a regression in voltage. Cardiomegaly as determined by chest roentgenogram decreased in 45%. The left ventricular-aortic gradient fell to an average of 35 mm Hg a year postoperatively. Surgical treatment of congenital subvalvular aortic stenosis is effective in reducing the preoperative symptoms and the left ventricular-aortic gradient. It appears that DMSS causes AI.

Discrete subaortic stenosis

From 1971-1981, 18 patients with discrete subaortic stenosis were treated surgically at the Medical University of South Carolina. Echocardiography was diagnostic in 10 of 11 patients in whom it was used. Preoperative cardiac catheterization was performed in all patients. The preoperative left ventricular outflow systolic pressure gradient was 82.0 +/- 27.2 mmHg (mean +/- SD) (range 30-145). In 16 (88.8%) patients excision of the subaortic membrane was complete, and relief of left ventricular outflow obstruction was good. The excision was incomplete in 2 patients; one required reoperation for residual gradient and developed complete heart block, and the other had a residual gradient of 60 mmHg and was in New York Heart Association functional class II when lost to follow-up. These data suggest that complete excision of the discrete subaortic stenosis is important to achieve good relief of left ventricular outflow obstruction.

Ventricular septal defect and subaortic stenosis: an analysis of 41 patients

Forty-one patients with subaortic stenosis (SAS) and ventricular septal defect (VSD) were identified from the cardiac records of the Hospital for Sick Children, Toronto, Ontario. The diagnosis of an associated SAS was made clinically in only 1 patient, who had findings of left ventricular (LV) hypertrophy with strain on the electrocardiogram. There was a delay of 3.1 years between initial presentation and detection of SAS. The SAS was not diagnosed at initial catheterization in 17 patients and was confirmed at subsequent catheter studies in 8 patients, surgery in 5 and autopsy in 4. Associated defects included coarctation of the aorta in 12 patients, mitral valve abnormalities in 4, and right-sided obstructions, including anomalous right ventricular muscle bundles in 6 patients, tetralogy in 4 and pulmonic stenosis in 1 patient. The mean gradient across the LV outflow tract was 25 mm Hg. Nineteen patients had serial catheters without intervening surgery, and the outflow gradient increased from a mean of 9 to 36 mm Hg. The mechanism of SAS consisted of fibrous diaphragm and fibromuscular obstruction in 31 cases, muscular narrowing in 4, protruding tricuspid valve leaflet in 2, hypertrophic cardiomyopathy in 2, anterolateral twist in 1 patient and redundant tissue tag in 1. Thirty-eight patients had a perimembranous VSD, 19 of whom had an associated so-called aneurysm of the membranous septum; 2 had an infundibular VSD and 1 patient had a central muscular defect. Although the SAS was located below the VSD in 30 cases, the associated heart failure and reduced cardiac output can mask the presence or severity of associated SAS.(ABSTRACT TRUNCATED AT 250 WORDS)

Fixed subaortic stenosis in the young: medical and surgical course in 83 patients

Eighty-three patients aged 11 months to 25 years were followed up a median of 6.1 years (range 8 days to 24 years) after diagnosis of fixed subaortic stenosis (SAS). Fourteen (17%) had significant noncardiac defects and 47 (57%) had additional cardiac malformations. The left ventricular (LV) outflow gradient increased in 25 of 26 patients catheterized more than once before surgery. Of 15 patients less than 12 years old with gradients less than or equal to 40 mm Hg, 10 ultimately underwent operation after developing severe obstruction; another has progressed to a gradient of 45 mm Hg at 6 years of age. Before surgery (at a median age of 12 years), 55% had aortic regurgitation (AR), which was usually mild. Infective endocarditis occurred in 12% of the group, with a frequency of 14.3 cases per 1,000 patient-years. Seventy-four patients were operated on, with 6 early (8%) and 7 late (9%) deaths. Twelve underwent reoperation to relieve residual obstruction. Surgery reduced gradients in patients with discrete SAS from 83 +/- 33 to 29 +/- 30 mm Hg, but in 6 patients with tunnel SAS the reduction was less satisfactory. AR was absent or mild in most patients postoperatively. When the gradient was reduced to less than 80 mm Hg, infective endocarditis did not occur unless there were other residual lesions. These data suggest that it is reasonable to resect discrete SAS in children less than 10 to 12 years old with LV outflow gradients greater than or equal to 30 mm Hg.

Discrete membraneous sub-aortic stenosis in adult patient obtained by echocardiography and not proved by catheterization

A case of a 60-year-old patient with discrete membranous sub-aortic stenosis is described. The diagnosis was established bases on echocardiographic evaluation by demonstration of a premature aortic valve closure and a sub-aortic membrane. No evidence of the sub-aortic membrane was noticed on cardiac catheterization. At operation, a discrete sub-aortic membrane was found 9 mm below the aortic valve, leaving an aperture of 1 cm diameter and a mildly deformed stenotic aortic valve. We stress the importance of careful pre-operative echocardiographic evaluation of every patient suspected of having any kind of left ventricular outflow tract obstruction, even if catheterization data are not contributory.

Left ventricular outflow tract obstruction coexisting with ventricular septal defect

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Late results after operations for left ventricular outflow tract obstruction

The late results were evaluated of operations for the relief of left ventricular outflow tract obstruction in young patients, 1 to 18 years old, from the National Heart Institute who were followed up for at least 5 years and from recently reported studies with an average follow-up duration of 5 or more years. The operative mortality rate for the combined series was low: 1.9 percent of 522 patients with valvular aortic stenosis, 6.0 percent of 222 patients with fixed subvalvular aortic stenosis and 5.5 percent of 18 patients with hypertrophic subaortic stenosis. From the National Heart Institute series, gradients early postoperatively were decreased to less than 50 mm Hg in 88 percent (30 of 34) of patients with valvular, in 68 percent (15 of 22) of patients with subvalvular and in 88 percent (8 of 9) of patients with hypertrophic subaortic stenosis. Late survival rates for patients in the combined series were 90 percent (472 of 522), 86 percent (190 of 222), and 82 percent (14 of 17) in the three respective groups after mean follow-up periods of 5 to 14.4 years. All late survivors in the current series have had symptomatic improvement; 95 percent (58 of 61) are asymptomatic. However, actuarial analysis in these patients predicts that 50 +/- 8 percent of those with valvular and 44 +/- 10 percent of those with subvalvular aortic stenosis after 10 years will be free from the adverse postoperative events of residual or recurrent left ventricular outflow tract obstruction, clinically significant aortic regurgitation, reoperation, endocarditis or late death. With use of the same adverse postoperative events to determine satisfactory late results from the combined series, it was found that 54 percent (281 of 522) of those operated on for valvular, 54 percent (120 of 222) of those operated on for subvalvular and 78 percent (14 of 18) of those operated on for hypertrophic subaortic stenosis had satisfactory late results 5 to 14 years after operation. Of the patients having unsatisfactory late results, major hemodynamic abnormalities were detected in 55 percent (23 of 42) within 1 year postoperatively. Thus it appears that operations for many children with left ventricular outflow tract obstruction are palliative. These patients should have early postoperative assessment and continuing long-term follow-up evaluation during childhood, adolescence and adulthood.

Clinical presentation and natural history of mild discrete subaortic stenosis. Follow-up of 1--17 years

We report 21 patients with discrete subaortic stenosis (DSS) causing mild obstruction with a peak systolic left ventricular outflow pressure gradients less than 50 mm Hg. They were followed 1--17 years (mean 6.5 years), and eight were recatheterized before surgery, 2--17 years after the first cardiac catheterization. Three patients (14%) had subacute bacterial endocarditis. Ten (48%) had aortic insufficiency, one of whom had no pressure gradient across the left ventricular outflow tract. In three of the 10 patients, aortic insufficiency was found only at the second catheterization. Nine patients (43%) had hyperactive, asymmetric left ventricular contraction; in three, this finding was present only at the second catheterization. Seven of the eight patients who were recatheterized (33% of the entire group) showed an increase in gradient. The increase was from a mean gradient of 35.2 mm Hg to 76.7 mm Hg. Seventeen patients (81%) had at least one of these four features. In view of these data, we suggest that surgical indications for DSS might be expanded, although definitive recommendations are not possible. All cases of DSS should be carefully followed. Surgery should be performed if signs of progressive complications develop.

Ventricular septal defect with silent discrete subaortic stenosis

Subaortic stenosis is rarely mentioned as a lesion that may be associated with a ventricular septal defect. We have encountered 4 patients with discrete subaortic stenosis adjacent to a ventricular septal defect, all of whom posed significant problems in diagnosis. In all 4 patients the subaortic stenosis was silent clinically and in 3 cases the obstruction was also not detected at the initial cardiac catheterization and angiocardiography. In the latter 3 cases, after surgical closure of the ventricular septal defect, there was a loud systolic murmur initially thought to be due to a small residual ventricular septal defect. In time, the clinical findings became more typical of isolated subaortic stenosis. In each of these cases the obstruction was verified at cardiac catheterization with peak systolic pressure gradients of 145, 45, and 70 mmHg. During reoperation, a discrete subaortic shelf was found opposite the patch used to close the ventricular septal defect. In the 4th case, the subaortic stenosis was unsuspected by clinical evaluation but was diagnosed by echocardiography as well as at cardiac catheterization, and both the ventricular septal defect and subaortic stenosis were corrected at the initial operation. A discrete subaortic shelf situated adjacent to a ventricular septal defect may be "silent," producing minimal, if any, pressure gradient and may pose diagnostic difficulties. Failure to recognize such a shelf and to remove it at the time of surgical closure of the ventricular septal defect, may result in the creation of a severe subaortic obstruction.

Discrete subaortic stenosis

Data concerning 17 consecutive patients with discrete subaortic stenosis are recorded. Twelve patients underwent operative resection of the obstructing lesion. Of these all except one were symptomatic and all had electrocardiographic evidence of left ventricular hypertrophy or left ventricular hypertrophy with strain. They had a peak resting systolic left ventricular outflow tract gradient of greater than 50 mmHg as predicted from the combined cuff measurement of systolic blood pressure and the echocardiographically estimated left ventricular systolic pressure and/or as determined by cardiac catheterisation. The outflow tract gradient as predicted from M-mode echocardiography and peak systolic pressure showed close correlation with that measured at cardiac catheterisation or operation. During the postoperative follow-up from one month to 11 years, of 11 patients, one patient required a further operation for recurrence of the obstruction four years after the initial operation. All patients are now asymptomatic. Five patients have not had an operation. The left ventricular outflow tract gradient as assessed at the time of cardiac catheterisation was greater than 50 mmHg. One patient has been lost to follow-up. The remaining four have been followed from four to eight years and have remained asymptomatic and the electrocardiograms have remained unchanged. Careful follow-up of all patients is essential with continuing clinical assessment, electrocardiograms, M-mode and two-dimensional echocardiograms, and if necessary cardiac catheterisation. Prophylaxis against bacterial endocarditis is also essential.

Fate of patients with fixed subaortic stenosis after surgical removal

Thirty-nine consecutive patients, aged 5 to 57 years, were followed for two to 15 years with serial haemodynamic studies after removal of fixed subaortic stenosis, which was never a "membrane". Two late deaths occurred, one sudden and one in congestive failure. Of 37 survivors, 25 were asymptomatic and could be classified as good or excellent if judged by well-being. Seven were symptomatic, two having had reoperation for fixed subaortic stenosis, and four needed long-term pacing. Evaluation, including the effect of isoprenaline, showed important dynamic obstruction in 17, five of whom redeveloped fixed obstruction. Seven had congestive features without outflow gradients, and 14 had neither congestion nor outflow obstruction. Complete assessment therefore confirmed that only 14 (36%) were haemodynamically satisfactory; two of them had permanent pacing, and four had had aortic valve surgery. Fixed subaortic stenosis should be removed early, when diagnosed, and completely before secondary myocardial changes occur. Patients however "well" need regular supervision and early haemodynamic assessment. The aortic valve, whether repaired, replaced, or untouched, remains a site for infective endocarditis for life. The fixed subaortic stenosis removed at operation may not be present in that form at birth, but acquired secondary to other congenital abnormalities which remain in the patient.

Subendocardial ischaemia in patients with discrete subvalvar aortic stenosis

The evidence for subendocardial ischaemia was studied in 12 patients with discrete subvalvar aortic stenosis. Symptomatology, electrocardiographic criteria, and pressure difference across the left ventricular outflow tract were compared with the subendocardial flow index (diastolic pressure time index systolic pressure time index). All symptomatic patients had a large pressure difference and abnormal index, but 4 asymptomatic patients had pressure differences greater than 60 mmHg and a low index. One of these 4 patients had a normal resting electrocardiogram. In patients with borderline accepted indications for surgery, calculation of the subendocardial flow index may be an additional useful variable in the timing of surgery.

Discrete subaortic stenosis in Newfoundland dogs: association of infective endocarditis

Necropsy findings are described in eight Newfoundland dogs from the same colony with discrete subaortic stenosis. Infective endocarditis involving the aortic valve occurred in four dogs and in each it proved fatal. Damage to the aortic valve cusps by the jet of blood ejected through the discretely narrowed left ventricular outflow tract predisposes to the development of infective endocarditis in both dogs and human beings with discrete subaortic stenosis. Severe abnormality of the intramural coronary arteries in the ventricular septum, which also occurs in patients with hypertrophic cardiomyopathy, was present in all eight dogs. Myocardial fiber disorganization and asymmetric septal hypertrophy, two other findings observed in patients with hypertrophic cardiomyopathy, were absent in each of the eight Newfoundland dogs with discrete subaortic stenosis.

Discrete membranous subaortic stenosis. Report of 31 patients, review of the literature, and delineation of management

The presentation, management, and follow-up of 31 patients with discrete membranous subaortic stenosis (DMSS) is presented. DMSS comprised 16% of 185 patients with congenital left ventricular (LV) obstruction. Only one patient was older than 40 years. The rarity of DMSS in older patients in both our population and in the literature is noted, and possible explanations are discussed. One-quarter of these patients had dyspnea, chest pain, or syncope combined with electrocardiographic left ventricular hypertrophy (LVH) and strain, and these all had peak LV outflow gradients (PSG) greater than 85 mm Hg. One-quarter had neither symptoms nor electrocardiographic abnormalities and all had PSG less than 90 mm Hg. Bacterial endocarditis was found in 13%, and in 13% an immediate family member also had congenital LV obstruction. Following surgical resection (25 patients), 18 were asymptomatic, two had residual fibromuscular obstruction, and four developed new fibromuscular obstruction after from one to six years (leading in one to late sudden death). Thus, even after resection, these patients require continued re-evaluation for residual or new LV obstruction.

Membranous subaortic stenosis and patent ductus arteriosus

Six children (five of them girls) each initially had a large patent ductus arteriosus with auscultatory, radiologic, and electrocardiographic findings typical of that lesion. After surgery for the lesion, an ejection-type basal systolic murmur led to detection of discrete membranous subaortic stenosis, which became worse in late childhood. The murmur became louder, the systolic pressure gradient increased from slight to significant, and hypertrophic subaortic stenosis or aortic insufficiency (or both) developed in the older children. Surgical excision of the membrane afforded improvement, except in one patient with the most severe involvement. Because of the unexpected finding of discrete membranous subaortic stenosis in these infants and young children who had undergone surgery for a large patent ductus arteriosus and because of the treacherous worsening of the effects of the discrete membranous subaortic stenosis as childhood progressed, it is important that those patients with a persistent systolic murmur after ductal ligation not be discharged from cardiac follow-up as cured. Serial cardiac catheterization during the growing years appears to be the most accurate way of detecting worsening discrete membranous subaortic stenosis, so that the membrane can be excised before severe complications occur.

Left ventricle to aorta valved conduit for relief of diffuse left ventricular outflow tract obstruction

Operative relief of congenital tunnel subaortic stenosis by means of local incision or excision, or both, has generally been unsatisfactory. The use of a valve-bearing conduit between the left ventricular apex and thoracic aorta offers a predictable means of bypassing the left ventricular outflow obstruction. The procedure was used in a 17 year old girl with an excellent hemodynamic result. The history of operative management with diverting plantation of valved conduits in this position have not been defined, but use of these prostheses appears advisable in severe subvalvular, valvular and supravalvular obstructions that are not readily amenable to predictable and safe surgical palliation. The operation may prove useful in selected cases of idiopathic hypertrophic obstructive cardiomyopathy.

Angiocardiography in congenital subvalvular aortic stenosis: prognosis and operative indications

Twenty-three patients with congenital subvalvular aortic stenosis are reviewed. The importance of classifying this stenosis into four types based on angiocardiographic findings is stressed, as are the indications for left heart catheterization during the preoperative and postoperative course of the disease. The type of congenital subvalvular aortic stenosis should be an important consideration during the discussion of operative indications in both asymptomatic and symptomatic patients.

Discrete subvalvular aortic stenosis in childhood. Study of 51 patients

Fifty-one children with discrete subvalvular aortic stenosis were studied between 1951 and 1974. The three anatomic types of obstruction found were the thin membranous type (43 cases), the fibromuscular collar type (5 cases) and the tunnel type (3 cases). The obstruction was usually severe, and the median left ventricular to aortic systolic pressure gradient was 90 mm Hg. Progressive obstruction with an increasing gradient was documented in 10 patients by serial cardiac catherizations. Significant associated cardiac defects, present in 57 percent of patients, often masked the typical clinical and cardiac catheterization features of subaortic stenosis. The stenosis was often not discovered until after surgery for the associated defect. Forty patients underwent surgical resection of the discrete subaortic obstruction. After surgery significant left ventricular to aortic pressure gradients can be found at postoperative cardiac catheterization. These gradients may reflect inadequate resection of the more complex discrete obstructions or represent proliferation and regrowth of the previously resected subvalvular fibrous tissue. The criteria for operability of discrete subaortic stenosis should be the angiographic demonstration of a discrete subvalvular diaphragm and the presence of a resting left ventricular to aortic systolic pressure gradient of 40 mm Hg or more.

Congenital discrete subvalvar aortic stenosis. Surgical experience and long-term follow-up in 20 paediatric patients

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