Pediatric Complete Atrioventricular Septal Defects

Updated: Sep 13, 2019
Author: Michael D Pettersen, MD; Chief Editor: Syamasundar Rao Patnana, MD 

Overview

Background

Atrioventricular septal defects (AVSDs) are anatomic defects that arise from faulty development of the embryonic endocardial cushions. This spectrum ranges from a primum atrial septal defect and cleft mitral valve, known as a partial atrioventricular septal defect (partial AVSD), to defects of both the primum atrial septum and inlet ventricular septum and the presence of a common atrioventricular valve, referred to as complete atrioventricular septal defect (complete AVSD, CAVSD). The terms atrioventricular canal defect and endocardial cushion defect are used in reference to this group of defects; however, atrioventricular septal defect is now the preferred terminology. These defects, particularly the complete form, typically present in the fetal or neonatal period and are an important source of cardiac morbidity and mortality in this age group.

This article focuses on the complete form. Partial, intermediate, and unbalanced forms are reviewed in other chapters (see Pediatric Partial and Intermediate Atrioventricular Septal Defects and Pediatric Unbalanced Atrioventricular Septal Defects).

For patient education resources, see Heart Health Center.

Embryology

Faulty development of the endocardial cushions, which represent the primordia of the atrioventricular septum and atrioventricular valves, plays a central role in the development of atrioventricular septal defects.[1, 2] The superior and inferior endocardial cushions appear at 4-5 weeks' gestation. During this time, the common atrioventricular canal is positioned over the primitive left ventricle.

Mesenchymal cells invade these masses of tissue, and, during the fifth week of gestation, the cushions approach each other and fuse. This divides the common atrioventricular canal into right and left canals.[3] The right and left lateral endocardial cushions develop shortly after the appearance of the superior and inferior cushions, followed by the dextrodorsal conus cushion. These structures are involved in the development of the mitral and tricuspid valves and their support apparatus (see the image below).

Atrioventricular (A-V) valve leaflets viewed from Atrioventricular (A-V) valve leaflets viewed from the cardiac apex in normal valves (A) and in the Rastelli type A complete form of common A-V canal (B). In A, the normal tricuspid valve (TV) has anterior (AL), septal (SL), and posterior (PL) leaflets. A normal mitral valve (MV) has ALs and PLs.In B, the superior cushion–derived leaflet bridges the ventricular septum and attaches to the papillary muscle of the conus at its rightmost extent. A right superior leaflet (RSL) typically attaches to the papillary muscle of the conus and to the anterior papillary muscle of the right ventricle (RV), and a right lateral leaflet (RLL) attaches to the anterior papillary muscle of the RV and to the posterior papillary muscle of the RV. The inferior cushion–derived bridging leaflet is usually cleft, giving the appearance of a right inferior leaflet (RIL) and a left inferior leaflet (LIL).

The endocardial cushions do not directly form the valve components but play an essential role in the process by which undermining and delamination of the myocardium forms the valve leaflets and chordal attachments.[4] Complete failure of fusion of the endocardial cushions results in deficiency of the inlet portion of the interventricular septum, a common atrioventricular valve annulus and common AV valve, as well as deficiency of the inferior (primum) portion of the atrial septum. This constellation of features results in a large defect in communication with all four chambers of the heart.

Anatomy

In complete atrioventricular septal defect, a single atrioventricular valve annulus, a common atrioventricular valve, and a defect of the inlet ventricular septum are observed. The deficiency of the atrioventricular septum also results in the presence of a large primum atrial septal defect. Details of the anatomy, particularly the morphology of the atrioventricular valve are crucial in planning surgical repair of this lesion. The common AV valve consists of at least four leaflets. These include the anterior and posterior bridging leaflets and two lateral leaflets. The anterior leaflet may be further subdivided to produce a total of five leaflets. The classification system initially described by Rastelli et al is used to describe the morphology of the atrioventricular valve.[5]

With the Rastelli type A valve, the anterior leaflet is divided into two portions of approximately equal size. The lateral portions of this leaflet attach to the anterior papillary muscles in each ventricle. Chordae tendineae attach the medial portion of this leaflet to the crest of the ventricular septum or slightly to the right ventricular side. Interventricular communication may occur between the anterior and posterior bridging leaflets and underneath the anterior leaflet in the interchordal spaces.

In type B valves, the rarest type, the anterior bridging leaflet is divided but overhangs the ventricular septum more so than in type A valves. The chordae from the medial portion of the divided anterior leaflet have no direct insertion to the ventricular septum but rather insert onto an anomalous papillary muscle positioned in the right ventricle near the ventricular septum. Because of the lack of chordal insertions to the septum, free interventricular communication occurs beneath the anterior leaflet.

In a Rastelli type C valve, the anterior bridging leaflet is larger and overhangs the septum more so than with a type A and type B valves. It is not attached in its mid portion to the ventricular septum or elsewhere and is referred to as being “free floating." Free interventricular communication also occurs underneath this valve leaflet.

Because of the deficient atrioventricular septum, the atrioventricular valves are displaced apically. As a result, the left ventricular inlet distance (distance from mitral valve annulus to apex) is shorter than the outlet distance (apex to aortic valve annulus). In the normal heart, these distances are nearly equal. In addition, the left ventricular outflow tract is displaced anteriorly, as opposed to wedged between the two atrioventricular valves. These features lead to the characteristic "gooseneck" deformity seen on angiography in the anteroposterior view. Although this leads to a left ventricular outflow tract (LVOT) diameter that is smaller than normal, it usually does not cause clinically significant obstruction by itself. However, it may contribute to an LVOT obstruction when associated with a subaortic membrane or accessory atrioventricular valve tissue. Also, the LVOT obstruction may develop years after surgical correction.

Defects commonly seen in association with complete atrioventricular septal defect include patent ductus arteriosus, coarctation of the aorta, secundum atrial septal defects, absent atrial septum, and anomalous pulmonary venous return.[6] Abnormalities of the mitral valve also commonly occur, including single papillary muscle (“parachute mitral valve”) and double orifice mitral valve. Tetralogy of Fallot is also present in about 2.7-10% of cases. At least 75% of patients with tetralogy of Fallot and complete atrioventricular septal defect have Down syndrome.[7]

Pathophysiology

The pathophysiology of complete atrioventricular septal defect depends on the magnitude of blood flow through the ventricular septal defect (VSD) and the amount of atrioventricular valve regurgitation. Patients with little atrioventricular valve regurgitation and high pulmonary vascular resistance (PVR) are asymptomatic early in life, and their condition may be difficult to diagnose.

These patients occasionally remain relatively asymptomatic until their second or third decade, when they develop increasing cyanosis from advanced pulmonary vascular disease. In most cases, the PVR decreases normally over the first 6 weeks of life, and the patient develops a large left-to-right shunt through both the atrial and ventricular defects, resulting in congestive heart failure (CHF). Patients with clinically significant atrioventricular valve regurgitation may also have symptoms of CHF, such as tachypnea, excessive sweating, and failure to appropriately gain weight.

Epidemiology

United States

Atrioventricular septal defects account for 2-9% of congenital heart disease in various series. Most investigators report a prevalence rate in the range of 3-5%.[8] The male-to-female distribution of atrioventricular septal defect is approximately equal.[9] The incidence of atrioventricular septal defect is higher among stillborn infants, likely due to the higher number of chromosomal and other genetic anomalies in this group. The pooled frequency of atrioventricular septal defects from several series of congenital heart disease in stillborn infants was about 7%.[10]

Freeman et al reported a prevalence of 9.6 cases of Down syndrome per 10,000 live births.[11] Congenital heart disease is present in 44% of affected infants, and atrioventricular canal defects are present in 45% of infants with Down syndrome and congenital heart disease.

Familial clustering may occur with atrioventricular canal defects. About 14% of women with common atrioventricular canal pass on congenital heart disease to their children. In a pedigree analysis, 11.7% of probands had a family history of congenital heart disease.[12]

Race-, sex-, and age-related demographics

The occurrence does not appear to vary on the basis of race. Advanced maternal age is a risk factor for Down syndrome. Because at least two thirds of patients with uncomplicated complete atrioventricular septal defect have trisomy 21, ethnic groups in which advanced maternal age is common may have an increased incidence of complete atrioventricular septal defect.

The male-to-female ratio for complete atrioventricular septal defect is 1:1.

Patients with complete atrioventricular septal defect often present with symptoms early in life. CHF usually develops by 6 weeks as PVR decreases and pulmonary blood flow increases. A rare case of survival to the eighth decade with untreated complete atrioventricular septal defect was reported. In some patients, PVR never decreases, and symptoms of CHF do not develop. In these rare cases, patients may remain asymptomatic as their pulmonary vascular obstructive changes worsen until cyanosis develops because of a right-to-left shunt.

Prognosis

Without operation, the survival of patients with this lesion is poor. Death may occur during infancy secondary to heart failure or pneumonia. Death later in childhood results from progressive pulmonary vascular obstructive disease (PVOD). PVOD tends to develop more rapidly than in other congenital heart defects. Intimal fibrosis (Heath-Edwards grade 3 lesions) have been demonstrated to appear between age 6-12 months. Vascular dilation and plexiform lesions (Heath-Edward grade 4 lesions) may occur by age 1 year.[13] Evidence suggests that these changes develop earlier and progress more rapidly in infants with Down syndrome.

Risk factors for surgical and late mortality and morbidity are identified. Preoperative risk factors for mortality include small size, unbalanced ventricular size, New York Heart Association class IV, and severe atrioventricular valve insufficiency. The era of operation (before 1987), patient age at operation, presence of accessory atrioventricular valve orifices, and other congenital heart diseases also increase the surgical mortality risk. Down syndrome is surprisingly not an independent risk factor for morbidity and mortality and therefore should not limit intervention. In one retrospective study (2002-2010) that evaluated 53 consecutive patients aged 3 years and younger who presented with complete AVSD and underwent surgical repair, multivariate analysis revealed the only significant factor associated with moderate or severe left atrioventricular valve regurgitation was the absence of Down syndrome.[14]

Infants can successfully undergo surgery, with a published mortality rate of 3.6% and with minimal long-term morbidity. Late survival is approximately 96%, and the reoperation rate is approximately 11%. The need for reoperation affects long-term survival after congenital AVSD repair.[15]

Published 10-year survival rates are 81-91%. In one retrospective study (1974-2000) comprising 198 patients who underwent surgical repair, the overall estimated survival for the entire cohort was 85% at 10 years, 82% at 20 years, and 71% at 30 years after initial congenital AVSD repair.[15] The estimated freedom from reoperation was 88% at 10 years, 83% at 20 years, and 78% at 30 years after initial congenital AVSD repair.[15]

Risk factors strongly associated with early death or the need for repeat operation include operation before 1987, postoperative pulmonary hypertensive crisis, immediate postoperative severe left atrioventricular valve regurgitation, and double-orifice left atrioventricular valve. In the past, death was significantly most common when complete atrioventricular septal defect with RV outflow tract obstruction was corrected in children younger than 5 years or weighing less than 15 kg. In the current era, most centers operate by age 6 months.[16, 17]

Mortality/morbidity

Patients with complete atrioventricular septal defect typically develop tachypnea and failure to thrive in the first few months of life. Tachypnea hampers normal feeding. In addition, respiratory tract infections, such as those due to respiratory syncytial virus (RSV), are poorly tolerated.

Patients may survive past the first few years of life without surgical intervention if the PVR remains elevated, although they may develop irreversible pulmonary vascular obstructive disease (PVOD) at a rapid rate. Surgical morbidity and mortality rates associated with this defect have dramatically improved over the years. A recent multicenter study demonstrated an in-hospital mortality rate of 2.5% and an overall 6-month mortality rate of 4%.[18] About 3% of patients with a surgical heart block require a pacemaker, and about 7% may require repeat operation for residual defects or surgically induced mitral insufficiency. Actuarial survival at 13 years is 81%.

In patients with a nonrestrictive VSD component, pulmonary vascular disease (Eisenmenger syndrome) eventually occurs unless the VSD component is surgically closed. Rare cases have occurred even when surgical repair is successfully accomplished in infants younger than 6 months. Cyanosis occurs when patients develop some degree of right-to-left shunt at either atrial or ventricular levels. Although patients' quality of life may be impaired at this point, their life expectancy may be 20-50 years.

Treatment for the complete atrioventricular septal defect is primarily surgical. Operative morbidity and mortality for this procedure has dramatically improved over the past 20 years. Tweddell et al identified risk factors for surgical and late mortality and morbidity; these are the era of operation, patient's age at operation, severity of left atrioventricular valve regurgitation, magnitude of preoperative heart failure, presence of accessory atrioventricular valve orifices, other congenital heart disease, and Down syndrome.[19]

Miller et al reviewed the long-term survival of infants with all types of atrioventricular septal defects with Down syndrome (n = 177) and without Down syndrome (n = 161).[20] In this cohort, born from 1979-2003, overall survival probability through 2004 was 70% in those with Down syndrome and 69% in those without. Mortality was higher in children with a complex atrioventricular septal defect and in those with two or more major noncardiac malformations, but was lower in children born in 1992-2003.

In infants, the published mortality rate for complete atrioventricular septal defect repair is 3.6% with minimal long-term morbidity; the 10-year survival rate is 81%. Bando et al found similar results while identifying risk factors for early death and the need for repeat operation.[21] Risk factors included postoperative pulmonary hypertensive crisis, immediate postoperative severe left atrioventricular valve regurgitation, and a double-orifice left atrioventricular valve. McElhinney et al described an occasional anomalous attachment or tissue of the atrioventricular valve, which may complicate operative repair.[22]

Complications

Postoperative complications include arrhythmias, low cardiac output, pulmonary hypertension, atrioventricular valve stenosis, and mitral insufficiency. Arrhythmias include heart block and junctional tachycardia; the latter usually subsides within 3-7 days after surgery. Postoperative left ventricular dysfunction may result in low cardiac output and even renal insufficiency. Inotropic drugs may be needed for several days after surgery.

In patients with pulmonary hypertension, sedation, paralysis, and mild hyperventilation with 100% oxygen may be required to prevent pulmonary hypertensive crisis and decreased right ventricular (RV) afterload. For pulmonary hypertension refractory to these measures, nitric oxide may be used to achieve pulmonary vasodilatation.

On occasion, patients may require long-term therapy, which might include phenoxybenzamine, calcium-channel–blocking drugs or sildenafil to manage an elevated pulmonary vascular resistance (PVR).

Severe mitral regurgitation may occur postoperatively and is ideally recognized on intraoperative transesophageal echocardiography (TEE). Residual mitral regurgitation is the most common indication for late reoperation after repair of complete atrioventricular septal defect. Approximately 5-10% of patients ultimately require mitral valve repair or replacement.[23, 24]

Anomalous attachment of atrioventricular valve tissue occasionally causes left ventricular (LV) outflow tract (LVOT) obstruction, in addition to the known tendency for patients with atrioventricular septal defect to have a small LVOT.[25] Such anomalous attachments may prevent complete relief of subaortic obstruction without mitral-valve replacement. Resection of some discrete obstructing tissue or, in some patients, a modified Konno procedure for tunnel-like LVOT obstruction or for obstruction caused by anomalous attachments of the mitral-valve apparatus may be performed. This procedure may complicate outflow-tract reconstruction and has had varied results.

A rare complication of the complete atrioventricular canal is subacute bacterial endocarditis. Successful repair during active endocarditis is reported.

 

Presentation

History

Tachypnea, repeated respiratory infections, poor feeding, and failure to thrive are frequent symptoms in patients with complete atrioventricular septal defect (AVSD) and large left-to-right shunts. These symptoms are usually present by 6-8 weeks and due to blood flow through the large interventricular communication with or without incompetence of the common atrioventricular valve.

Pulmonary vascular disease results from damage caused by excessive pulmonary flow and elevated pulmonary artery pressure due to the large ventricular septal defect (VSD). Irreversible pulmonary vascular disease may be present by age 2 years or, in rare cases, earlier. The pulmonary vascular disease may occur earlier in infants with Down syndrome.

Physical

General physical examination may show characteristics of Down syndrome, including flat facial profile, upslanting palpebral fissures, prominent inner epicanthal folds, Brushfield spots, protuberant tongue, abnormal palmar creases, and fifth finger clinobrachydactyly. Inspection may reveal pallor or Harrison grooves (horizontal depression along lower border of chest at diaphragm insertion site due to chronic tachypnea).[26] Failure to thrive is common due to excessive metabolic cardiovascular requirements and poor caloric intake (due to tachypnea).

The cardiac examination is remarkable for and overactive precordium. The volume and pressure overload on the right ventricle result in a prominent systolic heave along the left sternal border and subxiphoid regions. The pulmonary component of the second heart sound may be palpable at the left second intercostal space. Regurgitation of the atrioventricular valve may uncommonly result in a palpable apical thrill.

The first heart sound is single and often accentuated. The second heart sound is narrowly split, with an accentuated pulmonary component. A crescendo-decrescendo murmur may be audible at the upper left sternal border due to increased blood flow through a normal pulmonary valve. A mid diastolic rumble may be audible at the lower left sternal border and apex due to the increased flow across the common atrioventricular valve. A holosystolic murmur is often appreciated at the apex due to atrioventricular valve insufficiency. Because the VSD in complete atrioventricular septal defect is large and unrestrictive, it is not usually associated with a separate murmur.

When pulmonary vascular resistance (PVR) is elevated, the systolic murmur may not be prominent, and the diastolic rumble may disappear, reflecting less left-to-right shunt. This finding can occur in the infant in whom PVR has never fallen or in the older child with developing pulmonary vascular obstructive disease (PVOD), for whom the improvement in congestive heart failure (CHF) symptoms is an ominous finding.

In patients with advanced PVOD, the left parasternal impulse is prominent, S2 may be palpable, and the systolic murmur may be soft and short or even may be absent. A high-pitched decrescendo diastolic murmur of pulmonary insufficiency (Graham Steell murmur) may be detected at the left upper sternal border, reflecting severely elevated PVR.

Factors that can influence hemodynamics in Down syndrome include chronic nasopharyngeal obstruction, relative hypoventilation, carbon dioxide retention, and sleep apnea. Nonspecific CHF signs that may be seen include hepatosplenomegaly, pulmonary rales, and tachypnea. Skull erosion and striations have been noted from venous distension and increased blood volume.

Causes

The exact cause atrioventricular septal defects is not known. The majority of the defects may be explained by multifactorial inheritance hypothesis.[27]

Trisomy 21 (Down syndrome) is the most frequently associated genetic abnormality with complete atrioventricular septal defect, although it may also occur in association with trisomy 13 and trisomy 18. In patients without trisomy 21 who have common atrioventricular canal (CAVC) defects, a genetic locus on chromosome 1 can account for the disorder in some families.[28]

Interstitial deletion on chromosome 16 may be associated with atrioventricular septal defect. Endocardial cushion tissue seems to function as an adhesive for myocardial structures. Fibroblasts of endocardial cushions in trisomy 21 tend to be more adhesive, possibly leading to cardiac malformations. Atrioventricular septal defect may be seen with other less common syndromes, such as Dandy-Walker malformation, Joubert syndrome, and Ritscher-Schintal (craniocerebellocardiac) syndrome. An orocardiodigital syndrome consisting of tongue hamartomas, polysyndactyly, and atrioventricular septal defect has been described.

Atrioventricular septal defect is one of several cardiac abnormalities commonly seen with heterotaxy syndromes (asplenia and occasionally with polysplenia). Other rare combinations include atrioventricular septal defect with total anomalous pulmonary venous return and atrioventricular septal defect with Ebstein anomaly. Uncommon associations with atrioventricular septal defect include DiGeorge syndrome and coloboma of the eye, heart defects, atresia of the choanae, renal anomalies and retardation of growth and/or development, genital anomalies in males such as micropenis or cryptorchidism, and ear abnormalities or deafness (CHARGE) syndrome.

The presence of vascular endothelial growth factor (VEGF) gene mutations has been associated with atrioventricular septal defect.[29] The prevalence of the VEGF +405C allele was higher in patients with CHD than in control subjects (0.42 vs 0.21; P < .05). The presence of VEGF +405C presented increased risk for CHD (odds ratio [OR], 1.72; 95% CI, 1.32–2.26).

Advanced maternal age is a risk factor for Down syndrome, and at least two thirds of patients with uncomplicated atrioventricular septal defect have trisomy 21.

 

DDx

Diagnostic Considerations

Important considerations

Early recognition/diagnosis of common atrioventricular canal is important. Common atrioventricular septal defect is often recognized early in the life of the patient, especially in an infant with Down syndrome, only because of abnormal precordial activity, a loud, single S2, or both.

Because data from most studies suggest that approximately 50% of children with Down syndrome have congenital heart disease and because the physical findings are often subtle, early referral of a patient with Down syndrome to a pediatric cardiologist or performing an echocardiogram to exclude endocardial cushion defects is recommended.

Special concerns

Women who undergo successful repair of common atrioventricular canal should be able to tolerate pregnancy well if they are asymptomatic. If the patient has clinically significant residual atrioventricular valve insufficiency, a clinically significant residual ventricular septal defect (VSD), or poor ventricular function, the risks to both the mother and the fetus rise. The risk of a fetal congenital heart disease may be as high as 14% (range, 10-15%).

Data from some studies suggest that patients with congenital heart disease have substantially more stress in their lives than patients without chronic diseases. Even if this is true, findings suggest that children who have congenital heart disease have educational and occupational rates higher than those of age-matched control patients. Children with Down syndrome or other syndromes that affect cognitive function perform less well than other children.

Common atrioventricular canal defect is an endocardial cushion malformation resulting in an atrial septal defect, a VSD, and a common atrioventricular valve. Causes are multifactorial. Although the natural history is somewhat ominous, technologic advances over the past 20 years have greatly aided diagnosis and surgical correction of this complex malformation, yielding promising results.

Differential Diagnoses

 

Workup

Laboratory Studies

Although basic chemistry panels and the CBC count may aid in overall care, complete atrioventricular septal defect (AVSD) requires no specific laboratory tests.

If Down syndrome or another chromosomal abnormality is suspected, chromosome studies are indicated.

Electrocardiography

Electrocardiography reveals many typical findings and may provide clues to the presence of complete atrioventricular septal defect. The underlying rhythm most is often sinus. The PR interval may be prolonged secondary to atrial enlargement and increased atrial conduction time. The p-wave may be indicative of right atrial, left atrial, or biatrial enlargement.

The QRS complex reveals the most characteristic findings of atrioventricular septal defect. Posterior displacement of the atrioventricular node and His bundle results in left axis deviation with a superiorly oriented QRS frontal plane axis and counterclockwise depolarization pattern. The QRS frontal axis is usually between -30º and -90º. Right ventricular volume and pressure overload leads to evidence of right ventricular hypertrophy and the presence of an rsR’ or RSR’ pattern in the right precordial chest leads. Left ventricular hypertrophy may be present in the setting of significant mitral or common atrioventricular valve regurgitation.

Imaging Studies

Chest radiography shows enlargement of the cardiac silhouette. Enlargement of the right atrium and right ventricle is most apparent. Evaluation of the left ventricle may be difficult because it is often displaced by the enlarged right ventricle. The main pulmonary artery segments are prominent, as well as the overall pulmonary vascular markings. In the setting of pulmonary vascular disease, the distal pulmonary vessels may have a lucent, pruned appearance.

Echocardiography reveals defects of the atrial and ventricular septae[30, 31, 32] and is the most useful study in the identification, diagnosis, and evaluation of most important aspects anatomy and physiology.

The subcostal 4-chamber and long axial oblique (modified left oblique) views reveal many important aspects of complete atrioventricular septal defect, including the size of the atrial and ventricular defects, the nature of the atrioventricular valve attachments, the distribution of atrioventricular valve tissue, and the left ventricular (LV) outflow tract (LVOT).

The videos below demonstrate echocardiographic findings:

Apical 4-chamber echocardiographic image demonstrating a complete atrioventricular septal defect. A large primum atrial septal defect, a large inlet ventricular septal defect, and a single common orifice atrioventricular valve are noted.
Apical 4-chamber echocardiographic image with color Doppler demonstrating moderately-severe insufficiency of the common atrioventricular valve.
Parasternal long axis echocardiographic image of a complete atrioventricular septal defect. A large inlet ventricular septal defect is seen. Accessory atrioventricular valve tissue is visualized within the left ventricular outflow tract.
Subcostal sagittal echocardiographic image demonstrating the common atrioventricular valve. The anterior bridging leaflet inserts onto the interventricular septum consistent with a Rastelli type A valve.

Other anatomic features, such as ventricular size, atrioventricular valve insufficiency, aortic arch anatomy, and a patent ductus arteriosus (PDA), may be accurately assessed with echocardiography, especially in the infant.

Echocardiography also can reveal a single LV papillary muscle, which may influence the success of mitral reconstruction.

In some centers, 3-dimensional (3D) reconstructions of echocardiographic images are used to evaluate atrioventricular valve morphology, and proponents claim increased diagnostic accuracy with this technique compared with transthoracic echocardiography.[33, 34, 35]

Abnormal atrioventricular valve leaflets may be classified into the following three types:

  • Rastelli type A involves minimal bridging of the superior cushion-derived leaflet and attachment of the leftward component of the anterior bridging leaflet to the crest of the interventricular septum.

  • Rastelli type B is rare and involves chordal support of the anterior bridging leaflet attaching to the body of the right ventricle (RV).

  • Rastelli type C valve has a free-floating anterior bridging leaflet that is attached at its rightmost extent to the anterior papillary muscle of the RV.

Doppler echocardiography can reveal common atrioventricular valve regurgitation as well as the flow through the atrial and ventricular septal defects (VSDs).

Hemodynamic information, such estimated RV and pulmonary artery pressure, may be obtained.

Many clinicians believe that a preoperative echocardiogram with Doppler and color flow mapping provides sufficient anatomic and functional information for young infants undergoing repair and that cardiac catheterization may yield little additional information. Other diagnostic tools are occasionally used to diagnose atrioventricular canal defects.

The complete form of atrioventricular canal can be prenatally diagnosed by performing fetal echocardiography. Because two thirds of neonates with complete atrioventricular septal defect also have trisomy 21, this finding by fetal echocardiography should prompt a search for associated chromosomal abnormalities, especially Down syndrome. Fetuses with complete atrioventricular septal defect may develop hydrops fetalis if insufficiency of the common atrioventricular valve is severe.

Transesophageal echocardiography (TEE) is extremely valuable in the large child or adult patient in whom transthoracic echocardiographic windows are limited. It is also ideal for intraoperative evaluation at the time of repair in infancy. TEE provides detailed anatomic information regarding the atrioventricular valves, ventricular function, residual shunts, LVOT obstruction, and atrioventricular valve insufficiency or stenosis.

MRI has been used to identify complete atrioventricular septal defect, but is not routinely required.

Procedures

Cardiac catheterization is no longer routine for anatomic delineation in many centers. However, when used, it is performed to verify whether the VSD component is nonrestrictive, to determine if additional VSDs are present, to calculate the pulmonary vascular resistance (PVR), and to determine if the pulmonary vascular bed is responsive to pulmonary vasodilators.

The most frequent use of catheterization in common atrioventricular canal is to accurately measure the PVR and, if it is elevated, to evaluate its response to vasodilators, such as oxygen, sodium nitroprusside, calcium-channel blockers, or inhaled nitric oxide.

PVR is calculated as the mean pulmonary artery pressure minus the mean left atrial pressure, divided by the pulmonary blood flow.

Response in the PVR (with oxygen, nitric oxide, or other pulmonary vasodilators) may suggest that a child with high PVR may still benefit from surgery to close atrial and ventricular communications, as outlined above.

Patients with a calculated PVR of 10 Wood units/m2 or greater that does not fall below 5-7 Wood units/m2 in response to vasodilators are at increased risk for death after surgical repair.

In patients younger than 1 year, irreversible pulmonary vascular obstructive disease (PVOD) is rare; hence, PVR data are often ignored.

The second most frequent use for cardiac catheterization is LV angiography to rule out coexisting muscular VSDs.

Histologic Findings

Complete atrioventricular septal defect is associated with high flow at systemic pressure, which leads to severe hypertrophy of the media of the small arteries of the lung. Intimal fibrosis may also be seen.

Acute fibrous proliferation and atrophy of the peripheral pulmonary arterial media are associated with aging and Down syndrome, which, in addition, reduces the total cross sectional area of the pulmonary vascular bed.

Chronic hypoxemia, upper airway obstruction, and Down syndrome may hasten these vascular changes.

Except in rare cases, surgery within 6 months prevents irreversible PVOD. In Down syndrome babies, most centers perform surgical correction around the age of 3 months.

 

Treatment

Medical Care

Although their effectiveness in complete atrioventricular septal defect (AVSD) has been questioned, diuretics, digoxin, and ACE inhibitors have all been used to alleviate tachypnea and failure to thrive.

In many medical centers, the surgical mortality rate at age 2-3 months is 5% or less. Therefore, unless symptoms are dramatically relived, medical treatment for children with symptoms of congestive heart failure (CHF) is not pursued for more than a few weeks before definitive repair.

Some children who have survived surgical repair of complete atrioventricular septal defect (AVSD) require prolonged hospitalization. Causes are multifactorial but may include sepsis, pulmonary hypertension, residual left-to-right shunts through ventricular septal defects (VSDs), or significant atrioventricular valve insufficiency.

Associated noncardiac problems, including feeding difficulties, renal insufficiency, or pulmonary insufficiency, may require ongoing management and delayed discharge.

Postoperative medications range from none to many of the medications used to treat CHF (see Medication).

Almost every child who has survived surgical repair of complete atrioventricular septal defect has some abnormality of an atrioventricular valve.

Antibiotic prophylaxis is recommended for patients during the first 6 months after complete repair and for patients who have a residual intracardiac shunt associated with prosthetic patch material and residual atrioventricular valve insufficiency.

Consultations

Given the complexity of atrioventricular septal defect, a multidisciplinary team is usually required. This could include pediatric cardiologists, pediatric cardiothoracic surgeons, pediatricians, neonatologists, and pediatric intensivists, as well as a nurse coordinator and supportive ancillary staff

Additional consultants might include a geneticist for genetic counseling and a nutritionist.

Transfer

Patients with complete atrioventricular septal defect should be transferred to an institution skilled in successfully treating patients with complex congenital heart disease.

Diet and activity

A high-energy diet is needed because cardiac shunting results in high metabolic demands. Even at 125 kcal/kg/d, children still may not appropriately gain weight. Some children have such high metabolic demands that extraordinary energy intake, exceeding 150 kcal/kg/d, is necessary for growth.

Pulmonary edema can lead to tachypnea that makes oral intake of nourishment too difficult. A nasogastric tube may be needed in severe cases of congestive heart failure (CHF) with failure to thrive.

After the patient recovers from surgery, normal daily activities should be allowed.

Surgical Care

Treatment for a complete atrioventricular septal defect is surgical.

Single-stage complete repair is currently preferred, but occasional cases of refractory CHF in a low-birth-weight infant may be palliated with the placement of a pulmonary artery band.

Some patients with complete atrioventricular septal defect have additional muscular ventricular septal defects (VSDs); in such patients banding may be performed initially. Initial banding is also used in patients with mild hypoplasia of the right or left ventricle. Banding of the pulmonary artery may alleviate their CHF for 6-12 months, during which time the VSDs may spontaneously close and thus simplify eventual complete repair.

The surgical mortality rate should be low. In a published review of surgical outcomes of 363 patients with atrioventricular septal defects who were treated between 1982 and 1995, the early mortality rate was 10.3%, and the 10-year survival rate was 83%.[36]

The Pediatric Heart Network Investigators recently published a multicenter observational study on the contemporary results after repair of complete atrioventricular septal defect. In this series of 120 children, in-hospital and 6-month mortality rates were 2.5% and 4%, respectively. The incidence of residual septal defects and the degree of left atrioventricular valve regurgitation was independent of repair type, presence of trisomy 21, and age of operation, although younger age of operation was associated with a longer hospital stay.[18]

Another study, also from the Pediatric Heart Network Investigators, assessed the influence of AVSD subtype on outcomes after repair. Preoperatively, transitional patients showed the highest prevalence of moderate or severe left atrioventricular valve regurgitation (LAVVR). In data obtained 1 and 6 months post AVSD repair, the results noted that complete atrial VSD and canal-type VSD patients showed the highest prevalence of trisomy 21 and were younger, had lower weight-for-age z scores, and had more associated cardiac defects. Annuloplasty was similar among all subtypes, while complete atrial VSD showed a longer duration of ventilation and hospitalization. At 6 months, weight-for-age z scores improved and improvement was similar in all subtypes.[37]

A pulmonary artery band, placed on the main pulmonary artery by means of a small lateral or anterior thoracotomy incision, obviates cardiopulmonary bypass in a premature neonate or small infant. However, it has the risks of distorting the origins of the branch pulmonary arteries if it migrates and of complicating the eventual definitive surgery if it erodes through the media and intima. Pulmonary artery banding is best used, when deemed necessary, for only a few months in a patient who then undergo complete intracardiac repair and pulmonary artery band takedown.

A major aspect of atrioventricular septal defect repair involves creating a competent mitral valve. A pericardial patch can be used for this augmentation and for tricuspid valve repair. Single patch technique to close both the atrial and ventricular septal defects is used by most surgeons. Repair is occasionally done with two patches: a pericardial patch for the atrial septal defect and a polytetrafluoroethylene patch (Gore-Tex patch; W.L. Gore & Associates, Inc, Newark, DE) for the VSD, with routine closure of the mitral valve cleft. The 2-patch technique with routine cleft closure and atrial septal incision may lower the incidence of residual mitral regurgitation.

Ten Harkel et al reported intermediate follow-up results in patients who underwent surgical repair of atrioventricular septal defects.[38] During a mean follow-up of 66 months, 19% had severe mitral valve regurgitation, and 9% required reoperation. Of note, 13% of patients with severe mitral valve regurgitation in the immediate postoperative period had significantly improved mitral valve function. For this reason, the authors cautioned against reoperation in the early postoperative period unless it is absolutely necessary. The study from the Pediatric Heart Network Investigators reported the incidence of moderate or greater mitral valve regurgitation to be 22% at 6 months.[18]

Left ventricular outflow tract obstruction (LVOTO) is the second most common cause for reoperation after atrioventricular septal defect repair. Five years postoperatively, 10% of patients required reoperation for LVOTO.[39] This rises to 24% among patients who demonstrated LVOTO at the time of initial repair.[40] LVOTO after repair of atrioventricular septal defect is complex and multifactorial, and the ideal surgical approach remains to be defined.

Patent ductus arteriosus (PDA) ligation, removal of a previously placed pulmonary artery band, repair of stenosis of a pulmonary arterial branch, or relief of aortic arch obstruction are also frequently performed at the time of complete repair. Recent data suggest that children with atrioventricular septal defects and Down syndrome have a prognosis better than that of children with the same cardiac lesion but not Down syndrome.

Residual atrioventricular valve insufficiency or stenosis is a major determinant of long-term outcome.

Total circular annuloplasty is a simple procedure to help reduce atrioventricular valve regurgitation, although most patients with severe atrioventricular valve insufficiency or stenosis require more complex mitral valvuloplasty techniques. The need for mitral-valve replacement is not rare over the course of long-term follow-up but is ideally delayed until an adult-size prosthetic valve can be implanted.

Atrioventricular septal defect may be associated with other surgical conditions, including subaortic stenosis, coarctation of the aorta, tetralogy of Fallot (TOF), and total anomalous pulmonary venous return. Each associated lesion may complicate complete repair and make it difficult to achieve a good hemodynamic result. In addition, these defects may add potential risk over follow-up (eg, recoarctation after coarctation of the aorta repair or pulmonary insufficiency after repair of TOF).

Surgically induced atrioventricular block is a known complication of atrioventricular septal defect repair. Permanent pacing is required if atrioventricular conduction does not return postoperatively.

For complex cardiac lesions involving an unbalanced atrioventricular septal defect, staged total cavopulmonary connection, otherwise known as a Fontan operation, may be indicated.

In the presence of TOF, an aortic monocusp is used to compensate for deficient right atrioventricular valve tissue. Right-dominant, unbalanced biventricular repair can be successfully completed in patients with mild LV hypoplasia. However, careful preoperative evaluation of the adequacy of the LV to support the systemic circulation is imperative.

De Oliveira et al reported their experience with 2-ventricular repair of patients with unbalanced atrioventricular septal defect and small right ventricles (RVs). Patients with a small RV had a high mortality rate, with an 87% 10-year survival, compared with a 100% survival rate in surgical patients with balanced atrioventricular septal defect. Although a median sternotomy is the usual surgical approach, the thoracotomy approach was safely used for common atrioventricular canal repair in some centers.

Long-Term Monitoring

As needed, outpatient care for nonsurgical patients with atrioventricular septal defect should focus on providing adequate nutrition and medications to lessen congestive heart failure (CHF) symptoms.

Outpatient care should prepare the child for surgical intervention at the age appropriate for the institution where the operation will be performed.

Postoperative outpatient care depends on any clinically significant residual problems.

 

Medication

Medication Summary

Medical treatment of complete atrioventricular septal defect (AVSD) is similar to treatment of any cardiac defect with volume overload. Digoxin is frequently used to decrease the heart rate and to increase inotropy, although little evidence (if any) suggests that it is effective in patients with congestive heart failure (CHF) due to left-to-right shunt lesions. At the present time, it is not the first line of therapy. Diuretics may decrease preload and ACE inhibitors decrease afterload. Care must be taken when administering ACE inhibitors to reproductive-age females, given their teratogenic effects. More recent, but limited, data suggest that the use of beta blockers in patients with left-to-right shunts who have CHF improves symptoms.[41]

The daily dosage of digoxin is approximately 5-10 mcg/kg/d. The diuretic used most frequently in the author's institution is furosemide 1-2 mg/kg/d. In children with clinical signs of CHF, 58% improved with enalapril. The mean maximal dose was 0.3 mg/kg/d. The most significant adverse effect observed was renal failure, particularly in young infants with large left-to-right shunts. Most of the older patients in the author's institution who need ACE inhibitors are treated with lisinopril because of its lower cost and long half-life. The dose generally is 0.5 mg/kg/d, but is individualized for each patient. Data about the efficacy of beta-blockers in patients with large left-to-right shunts is sparse. In small studies, beta-blockers appear to decrease renin levels and heart rates in infants with CHF due to left-to-right shunts.

Antibiotics for endocarditis prophylaxis are no longer recommended for most patients with congenital heart disease. Some significant exceptions are noted, including patients who have previously had endocarditis or patients within 6 months of their surgical repair. Current American Heart Association guidelines also recommend subacute bacterial endocarditis (SBE) prophylaxis for patients who have a complete repair and those who have a jet lesion aimed at a patch to impair the growth of endothelial cells on the patch.[42] This situation may occur in patients with atrioventricular septal defects and can only be discovered by the use of imaging modalities such as echocardiography.

Inotropic agents

Class Summary

The agents provide symptomatic improvement for CHF. Positive inotropic agents increase the force of contraction of the myocardium and are used to treat acute and chronic CHF. Positive or negative chronotropic agents may also increase or decrease the heart rate, provide vasodilatation, or improve myocardial relaxation. These additional properties influence the choice of drug for specific circumstances.

Digoxin (Lanoxicaps, Lanoxin)

Acts directly on cardiac muscle, increasing myocardial systolic contractions. Indirect actions increase carotid sinus nerve activity and enhance sympathetic withdrawal for any given increase in mean arterial pressure.

Diuretic agents

Class Summary

These agents provide symptomatic improvement for CHF and promote the excretion of water and electrolytes by the kidneys. They are indicated to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites.

Furosemide (Lasix)

Increases excretion of water by interfering with chloride-binding cotransport system, which inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule.

ACE inhibitors

Class Summary

These drugs are indicated for treatment of symptomatic CHF. ACE inhibitors are beneficial in all stages of chronic heart failure. Pharmacologic effects result in a decrease in systemic vascular resistance, reducing blood pressure, preload, and afterload.

Captopril (Capoten)

Short-acting ACE inhibitor. Predominant action is suppressing the renin-angiotensin aldosterone system. Prevents conversion of angiotensin I to angiotensin II (potent vasoconstrictor), increasing levels of plasma renin and reducing aldosterone secretion.

Enalapril (Vasotec)

Competitive ACE inhibitor. Reduces angiotensin II levels, decreasing aldosterone secretion.

Lisinopril (Prinivil, Zestril)

Prevents conversion of angiotensin I to angiotensin II (potent vasoconstrictor), reducing aldosterone secretion.