Atrioventricular Canal Type Research Articles

The association of congenital heart disease with down's syndrome (mongolism)

Between 1957 and 1964 in California there were 7,625 known deaths due to congenital heart disease; in 367 of these cases the subjects had Down's syndrome. Autopsy records from 14 hospital centers allowed more specific anatomic diagnoses in 139 of the 367 cases. Five types of defects, with some overlap, accounted for 91.4 per cent of the cases: ventricular septal defect in 55 cases (32.4 per cent), atrioventricularis communis in 34 (24.5 per cent), atrial septal defect in 28 (20.1 per cent), patent ductus arteriosus in 16 (11.5 per cent) and tetralogy of Fallot in 15 (10.8 per cent). It was not possible to ascertain how many of the atrial septal defects were of the ostium primum variety, nor how many of the ventricular septal defects were of the atrioventricular canal type. The 139 cases are compared with 172 documented anatomic findings from four other studies. The major difference in this, the largest single study, is the larger number with ventricular septal defect as opposed to atrioventricularis communis. Many of the ventricular septal defects were associated with other defects, however.

ENDOCARDIAL CUSHION DEFECTS

1. Maldevelopment of the endocardial cushions in the embryonic heart can result in varying degrees of persistence of the common atrioventricular canal or in isolated septal defects between the two ventricles or between the left ventricle and right atrium. 2. Selective left ventricular angiocardiography is the most sensitive and accurate technique for the identification of endocardial cushion defects, especially those of the persistent atrioventricular canal type. 3. Characteristic deformities of the left ventricular outflow tract and the mitral valve can be identified, which directly reflect the cleft in the mitral valve and the abnormality of the atrioventricular and muscular septa. These findings appear to be unique for this group of defects.

Ventricular septal defect of atrioventricular canal type with straddling right atrioventricular valve and mitral valve deformity.

At the Mayo Clinic, four patients were seen in whom a ventricular septal defect (VSD) of the atrioventricular (A-V) canal type was associated with an angle of nearly 90° between the intact atrial septum and the ventricular septum. The right atrium overrode the ventricular septum and communicated with both ventricles. A complex, straddling right A-V valve had some attachments in the left ventricle and resembled the common A-V valve of persistent common A-V canal. In three of the patients, a congenital mitral valve deformity also existed. Mild cyanosis probably is not a contraindication to surgical repair in such patients because right atrial blood may enter the left ventricle directly.

Complete transposition of the great vessels with anatomic obstruction of the outflow tract of the left ventricle: Surgical implications of anatomic findings

Twenty-three specimens with complete transposition of the great vessels and left ventricular outflow tract obstruction were studied. Two groups emerged: Group I, 12 specimens with an intact ventricular septum, and Group II, 11 specimens with a ventricular septal defect. In Group I valvular stenosis was present in 4, subvalvular fibrous ring in 3 (1 associated with valvular stenosis), and bulging of the septum into the cavity of the left ventricle in 7 (1 associated with valvular stenosis). In Group II pulmonary valvular stenosis was present in all. In addition, 7 specimens also showed bulging of the septum into the cavity of the left ventricle; three showed severe subvalvular fibromuscular obstructions (tunnel type); and 1, a subvalvular fibrous ring or shelf. Whereas a subvalvular fibrous ring or bulging of the septum into the cavity of the left ventricle occurred in those with an intact ventricular septum or with a ventricular septal defect, a subvalvular fibromuscular obstruction (tunnel type) was observed only in those with a ventricular septal defect when this defect was situated at some distance from the pulmonary valve. Bulging of the ventricular septum into the cavity of the left ventricle was thought to be acquired as a result of either hypertrophic reaction of the left ventricle to pulmonary valvular or subvalvular stenosis, or septal hypertrophy secondary to right ventricular hypertrophy. Sufficient hemodynamic data are not available to evaluate the functional significance of bulging of the ventricular septum into the cavity of the left ventricle. Limited hemodynamic data, coupled with anatomic data, suggest that the obstruction is mild to moderate in the majority of cases. In all patients with a ventricular septal defect the pulmonary artery was smaller than the aorta, and it was small enough to create a problem in relation to surgical correction in 5. In those with an intact ventricular septum the pulmonary artery was larger than the aorta in 3, smaller than the aorta in 5, and of equal size in 4. The ventricular septal defect was anterior in 3, posterior in 3, and of the atrioventricular canal type in 5. The anatomy of the coronary artery has been studied in each case, and it was found that the left circumflex artery coursed in front of the outflow tract of the left ventricle in 16 specimens. Left ventricular angiocardiography is of help in demonstrating the type of left ventricular outflow tract obstruction as well as the size of the pulmonary artery. The surgical approach to the associated defects is discussed. For cases with a small pulmonary artery an initial anastomosis between the superior vena cava and the pulmonary artery is recommended. Patients with juxtaposition of the atrial appendages are believed to require a graft or prosthesis to enlarge the right atrium. When the left circumflex artery courses in front of the outflow tract of the left ventricle, relief of the obstruction should be undertaken, preferably through the pulmonary artery or the apex of the left ventricle.

Left ventricular-right atrial communication in complete transposition of the great vessels

The pathologic features in three cases of complete transposition of the great vessels with a left ventricular-right atrial communication have been presented. This combination of malformations has not, to our knowledge, been reported before. Our three cases emerged from among 60 instances of complete transposition of the great vessels studied at necropsy. Clinical data were available in two of the three; both of these patients presented certain features which, when present in a cyanotic infant with congestive cardiac failure, should lead the clinician to suspect complete transposition of the great vessels with a left ventricular-right atrial communication. These features were in the auscultatory and electrocardiographic findings (which are similar to those observed in patients with a persistent common atrioventricular canal type of defect). They include a loud holosystolic and a diastolic murmur, accompanied by a thrill, and left axis deviation with a counterclock-wise QRS loop oriented around the mean manifest electrical axis, associated with right or combined ventricular hypertrophy. By conventional roentgenography and by venous angiocardiography, these patients could not be distinguished from those with the usual type of complete transposition of the great vessels. A selective left ventriculogram, however, would be expected to define the peculiar communication between the left ventricle and the right atrium, when present.

Isolated ventricular septal defect of the persistent common atrioventricular canal type.

Among 60 necropsy specimens of isolated ventricular septal defects and more than 300 cases of ventricular septal defect observed at operation, 15 cases demonstrating unusual anatomic positions of the defect were found. The ventricular defect differed from the ordinary ventricular septal defect in that it usually occupied the position of the ventricular component of the defect in persistent common atrioventricular canal. For this reason it was named ventricular septal defect of the persistent common atrioventricular canal type. Deformities of one or both atrioventricular valves were common (nine of 15 cases). No atrial septal defects of the ostium primum type were present. Anatomic studies of the conduction tissue revealed that this tissue skirted the posterior and inferior aspects of the ventricular septal defect and that, as in persistent common atrioventricular canal, the course taken by the conduction tissue was unusually long, as a result of the peculiar posteroinferior position of the lower edge of the defect. The electrocardiographic features were striking. In all cases the mean electrical axis of the QRS lay above the isoelectric point; the vector loop obtained in the frontal plane from the scalar electrocardiogram was directed counterclockwise, and its main mass was above the zero line. In addition, in all cases there were signs of right ventricular overload, and in some cases of left ventricular overload as well. Electrocardiographic findings of this pattern have been thought by some authors to be diagnostic of persistent common atrioventricular canal, but we observed that they also occurred in each of the cases of isolated ventricular septal defect of the variety described herein. We recognize that in the usual variety of ventricular septal defect this electrocardiographic pattern occurs, but it does so uncommonly. We have not studied its exact incidence. The anatomy, hemodynamics, and surgical considerations are different in cases with this defect from those with persistent common atrioventricular canal. The surgical risk in these cases has been higher than that in the usual type of ventricular septal defect. In the discussion of the electrophysiologic theories that seek to explain the unusual electrocardiographic patterns in this group of cases, a new theory is offered, based on studies of the conduction system. In our opinion, the different orientation of the advancing fronts of depolarization is the result of congenital displacement of the bundle of His in its relation to the ventricular septal defect.

Clinical problems related to surgical repair of intracardiac defects with the aid of an extracorporeal pump-oxygenator.

The medical problems in the selection of patients for direct-vision reconstructive operations utilizing the pump-oxygenator of the Gibbon type are discussed. The evaluation of the pulmonary vascular changes is one of the most important medical tasks in many cases. The operative risk for such lesions as ventricular septal defect with high pulmonary flow, tetralogy of Fallot, pulmonary stenosis with intact ventricular septum, and atrial septal defect of the partial atrioventricular canal type is constantly decreasing and is 15 per cent or less at the present time. Heart block and cardiac arrhythmias are still, on occasion, serious postoperative complications. During 1 period of 3 months, subacute bacterial endocarditis ( Pseudomonas ) occurred in 4 patients but it has not recurred since.