Incomplete subaortic stenotic rings in domestic animals--a newly described congenital anomaly

A newly described congenital heart anomaly, the incomplete subaortic stenotic ring was detected at necropsy in four dogs, one cat, one cow, one horse, one sheep and one pig. These structures were grossly and histologically similar to complete subaortic stenotic rings, being composed of variably dense interlacing bands and sheets of fibrous connective tissue. In all nine cases, their presence at necropsy was considered an incidental finding.

Comparison of the cardiac output and stroke volume response to upright exercise in children with valvular and subvalvular aortic stenosis

Cardiac output and stroke volume were evaluated in 17 children (mean age 11.5 +/- 3 years) with discrete, membranous subvalvular (Group I, n = 7) and valvular (Group II, n = 10) aortic stenosis during submaximal and maximal (greater than 75% predicted maximal oxygen consumption) upright cycle ergometry. Patients with valvular aortic stenosis were further subdivided on the basis of their aortic valve gradient at rest determined by cardiac catheterization (Group IIA, gradient less than 40 mm Hg; Group IIB, gradient greater than or equal to 40 mm Hg). These patients were matched with 17 control subjects on the basis of age, sex, height and intensity of exercise during maximal exertion. Cardiac and stroke indexes were determined by the acetylene rebreathing method at each exercise level. Stroke volume index in Group I was significantly greater at rest when compared with that in control subjects (69 +/- 13 versus 53 +/- 11 ml/m2, alpha = 0.01, p less than 0.05) and that in patients in Group II (69 +/- 13 versus 47 +/- 12 ml/m2, alpha = 0.01, p less than 0.05). Patients with subvalvular aortic stenosis were unable to increase their stroke volume index from rest to submaximal exercise and also decreased their stroke volume index at maximal exercise levels. In contrast, patients with mild valvular aortic stenosis (Group IIA) displayed a normal exercise response. Patients with severe valvular aortic stenosis (Group IIB) had a blunted stroke volume response at rest and at each level of exercise, as well as signs of myocardial ischemia (ST segment depression) during maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

[Percutaneous transluminal balloon dilatation of discrete membranous subvalvular aortic stenosis]

Discrete membranous subaortic stenosis (DMSS) which is localized immediately subvalvular and can be differentiated from fibromuscular stenosis of the left ventricular outflow tract, represents theoretically a well-suited lesion for uncomplicated balloon dilatation. The practical use of balloon dilatation for treatment of DMSS has been reported by two groups [6, 10]. In this overview, we will report our experience with balloon dilatation of DMSS in six children. Between June, 1986 and June, 1987, balloon dilatation of DMSS was carried out in six male children ranging in age from four to ten years (Table 2). In one child, coarctation of the aorta had been present and was previously treated successfully with balloon dilatation. In two children, the aortic valve was thickened with or without stenosis. All children had mild aortic regurgitation. After transvenous right heart catheterization and transarterial left heart catheterization including levocardiography and supraaortic angiography, 50 units of heparin per kilogram of body weight were administered and a guidewire advanced to the left ventricle for positioning of the balloon catheter in the left ventricular outflow tract. The choice of balloon diameter was based on measurement of the angiographically-determined aortic ring diameter (Table 1). Pressure measurements were obtained by means of a diagnostic catheter after the dilatation. No complications were observed either during or immediately after the intervention. After the dilatation, all children were discharged from the hospital to go home. Pressure in the left ventricle was reduced from 225 +/- 55 to 116 +/- 29 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

[Quantitative evaluation of left heart obstructions (including aortic isthmus stenosis) in children using Doppler echocardiography]

To assess the accuracy of pulsed and continuous-wave Doppler echocardiography (DE) in evaluating pressure drops across left heart outflow obstructions we examined 27 children with valvular aortic stenosis (n = 13), fixed subaortic stenosis (n = 14) and 16 children with coarctation. Doppler examination was performed within 24 hours of cardiac catheterization in 15 patients, in 17 patients 2-42 months (mean 13 months) after catheterization. Simultaneous blood pressure measurements in both upper and lower limbs with an automated oscillometer were taken in 12 cases with coarctation. Using three standard positions (suprasternal, high right parasternal and apical) we found a close Doppler-catheter correlation in patients with aortic and subaortic stenosis (r = 0.94). The correlation in cases with coarctation was poor (r = 0.17) because of one patient with severe stenosis and another with atresia and a huge collateral vascularization, in whom a poststenotic jet could not be located. Surprisingly the postoperative pressure gradient was much overestimated in one of these patients by DE. We conclude that a "multi-channel system" due to collateral vascularization excludes the use of the simplified Bernoulli equation. Apart from these anatomically related false Doppler estimates we found a good correlation (r = 0.90), with slight overestimation in mild stenosis. Thus, Doppler ultrasound provides an accurate noninvasive method for estimating pressure gradients in patients with aortic and subaortic stenosis and to a lesser extent in patients with coarctation. In particular DE is helpful for determining subsequent clinical management.

Subaortic obstruction in complex congenital heart disease: management by proximal pulmonary artery to ascending aorta end to side anastomosis

Six patients with univentricular heart and one patient with d-transposition of the great arteries had transection of the main pulmonary artery with an end to side anastomosis of the main pulmonary artery to the ascending aorta to relieve subaortic obstruction. Two operations were performed as a palliative procedure within the first 6 months of life and five were performed as part of a definitive repair (four modified Fontan procedures and one repair of transposition of the great arteries with ventricular septal defect). There was one surgical death (14%) occurring 1 day postoperatively from low cardiac output. The remaining six patients are doing well 1 to 19 months postoperatively (mean 11.4 months). The proximal pulmonary artery to ascending aorta end to side anastomosis is an effective means of bypassing subaortic obstruction associated with complex congenital heart disease.

The progressive nature of subaortic stenosis in congenital heart disease

Data derived from serial hemodynamic and angiocardiographic investigations on pediatric patients not subjected to intervening intracardiac operations support the view that subaortic stenosis in congenital heart disease tends to be a progressive disorder. Our data are obtained from two groups of patients. The first comprised 22 patients with discrete subaortic stenosis in relative isolation. The second was made up of 19 patients with the fibrous or fibromuscular forms of discrete subaortic stenosis associated with a perimembranous ventricular septal defect. The results from both groups support our initial contention. The progressive character of subaortic stenosis in these two situations illustrates the dynamic nature of congenital heart disease, and the tendency of a changing form and function.

Familial membranous subaortic stenosis

Familial occurrence of membranous subaortic stenosis (MSS) is described in three families. The defect was found in 2 siblings in two of these families, and in 3 siblings of the third family. The importance of early diagnosis and treatment of MSS is emphasized. We suggest early evaluation of first-degree relatives of patients with MSS for the possibility of this defect.

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.

Management of infants with left ventricular outflow obstruction by conduit interposition between the ventricular apex and thoracic aorta

On the basis of experience with older children, creation of a double-outlet ventricle by interposition of a valved conduit between the apex of the left ventricle and the thoracic aorta appeared to be an option for treating life-threatening left ventricular outflow tract obstruction even in the small heart of the infant. Over the recent 3 year period, nine infants ranging in age from 3 days to 13 months with various forms of left ventricular outflow tract obstruction underwent placement of an apical-aortic conduit to decompress the hypertensive left ventricle. There were two early and two late deaths. Five patients are clinically well and developing normally 5 to 23 months following the operation. This series demonstrates that this operation permits normal growth and development in infants previously failing to thrive. Echocardiographic and cardiac catheterization data suggest that left ventricular function need not be adversely affected by placement of a stent in the small infant ventricle; rather, ventricular function can be markedly improved. Although the mortality in this series is appreciable, it appears that apical-aortic conduit interposition can provide significant palliation for infants with otherwise lethal left ventricular outflow tract obstruction.

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.

The management of congenital aortic stenosis

The progress of 128 patients with congenital aortic stenosis has been followed from one to 28 (mean 14) years. Fifty-eight underwent cardiac catheterisation, and 46 (36% of the total) required surgical treatment. Of these, 42 were under 20 years old. Additional cardiac lesions were noted in five. Infective endocarditis was encountered in four. The onset of symptoms or increasing evidence of left ventricular hypertrophy on the electrocardiogram were the principal indications for catheterisation. Two-dimensional echocardiography is now important in this context. There were four deaths in the 46 surgically treated patients; three of these were early and the fourth was a late death three years after operation due to a massive cerebral embolus complicating infective endocarditis. The 42 survivors of operation and the 82 unoperated patients have remained under long-term supervision. Further surgery was necessary in 12 of the 42 surgically treated patients--valve replacement in seven of them two to eight years after valvotomy, replacement of a calcified xenograft valve in three, and repeat operation in two because of recurrence of subvalvar obstruction. Aortic stenosis is not a benign condition in childhood and adolescence. Close supervision is necessary and when any deterioration is detected further investigation as a prelude to probable surgery is mandatory. This should not be embarked on lightly in childhood unless there are pressing indications, particularly in view of the serious disadvantages of valve replacement in childhood.

[Heart with criss-cross ventricles associated with an obstruction of the ejection pathway of the left ventricle and a mitral anomaly]

A case of criss-cross heart with situs inversus associated with subvalvular aortic stenosis and mitral regurgitation in a 9 year old boy is reported. Surgical correction of the valvular abnormalities gave an excellent clinical and haemodynamic result. A review of the literature shows that this abnormality of rotation of the ventricles coexists with a concordant atrioventricular connection in 70 % cases; the ventriculoarterial connection is only discordant in 12 % cases. The right ventricle is always situated above the left ventricle. The most common associated lesions are usually accessible to surgery; ventricular septal defect (98 % cases); stenosis or atresia of the pulmonary artery (70% cases). However, right ventricular hypoplasia is also common (65 % cases). Six patients underwent surgical correction of the associated lesions with 4 successes and 2 deaths. Surgery is possible in these complex cardiac malformations with good results providing a precise preoperative anatomical diagnosis is made.

Supernumerary mitral valve producing subaortic stenosis

A ten-year-old girl with severe subaortic stenosis was found to have relatively mature valvular endocardial cushion tissue (fibromyxomatous sheets with a chorda tendinea attached to a left ventricular papillary muscle) immediately beneath the aortic valve. This structure behaved like a valve mechanism, obstructing the left ventricular outflow tract during ventricular systole. This anomaly is an extreme on the spectrum of obstructive endocardial cushion malformations.

Increased mitral-aortic separation in discrete subaortic stenosis

We recently speculated that mitral-aortic separation (MAS) might be increased in discrete subaortic stenosis (DSS). We have examined this hypothesis in 22 heart specimens in which the subaortic obstruction originated on the muscular ventricular septum below the right aortic sinus, either as a discrete band, an accumulation of several bands or a diffuse ridge, and extended posteriorly into the MAS or anterior leaflet of the mitral valve or both, with a variable relationship to the aortic cusps and sinuses. No specimen had ventricular septal defect, supravalvular aortic stenosis or other features of Shone syndrome. The mean MAS was nearly twice that of 80 normal specimens (4.9 vs 2.5 mm), the range of MAS was increased from normal (0.11 vs 0.7 mm) and the mean diameter of the aortic annulus was decreased compared with the normal specimens, data that will be of interest to echo- and angiocardiographers in the clinical description of DSS, and to the surgeon who must resect these lesions.

Aortoventriculoplasty for tunnel subaortic stenosis and other obstructions of the left ventricular outflow tract. Clinical and hemodynamic results

A new therapeutic concept of enlarging the outflow tracts of both ventricles with a patch and inserting an aortic prosthesis has been developed for the treatment of tunnel subaortic stenosis. This operation has been applied clinically since June 1974 on several types of obstruction in the outflow tract of the left ventricle. Twenty-one operations have been performed on 20 patients under the age of 18 years, with an overall mortality of 24% and no late deaths. Seven patients developed complete right bundle branch block or left anterior hemiblock or both as a result of this operation; transient atrioventricular block and complete left bundle branch block occurred in one patient each. In no case, however, did rhythm disturbances contribute to death. In one patient, the septal incision injured a septal coronary artery, with fatal result. Fourteen patients had catheterization studies postoperatively. Although previous conventional surgery had been unsuccessful, aortoventriculoplasty (AoVPI) reduced the mean gradient across the left ventricular outflow tract significantly (p less than or equal to 0.01), from 94.7 +/- 25.5 mm Hg to 14.4 +/- 17.2 mm Hg, leaving the end-diastolic pressure practically unchanged. No significant defect remained in the patch-covered septal incision. Thus, we consider AoVPI to be the operation of choice for tunnel subaortic stenosis, for valvular aortic stenosis with a narrow annulus and in cases where an artificial aortic valve has become too small because of the patient's growth.

Discrete fibromembranous aortic stenosis in middle age. Natural history and case report

Discrete fibromembranous subaortic stenosis may be severe at birth, progress in severity irrespective of the initial degree of obstruction, and morphologically change during the course of its natural history. Initial status, progression of the lesion and perhaps later development of fibromuscular (tunnel) and/or asymmetric septal hypertrophy may all contribute to a shortened life span and account for the different incidence of fibromembranous subaortic stenosis in children and adults. In the case reported here, a patient survived into the sixth decade with a discrete fibromembranous subaortic stenosis, which led to typical as well as unusual echocardiographic findings.

Discrete subvalvular aortic stenosis. An evaluation of operative therapy

Angiocardiographic and operative observations support the validity of classifying the spectrum of congenital subvalvular aortic stenosis into a membrane, fibromuscular collar, and tunnel. Our current operative method is to excise a thin membrane or thick fibrous ridge, and, if a fibromuscular collar or tunnel is identified, to effect a left ventricular myomectomy as described by Morrow for hypertrophic subaortic stenosis. Data from experience with 35 children indicate that this approach is effective and safe. Gradients are substantially reduced and residual obstruction acceptable. Successive clinical evaluations (100 percent of 33 survivors) over an interval of 1 to 13 years (mean of 6) affirm that amelioration of the obstruction endures.

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.