Atrioventricular Septal Defect Surgery 

Updated: Apr 12, 2017
Author: Richard G Ohye, MD; Chief Editor: Suvro S Sett, MD, FRCSC, FACS 

Overview

Background

Atrioventricular septal defects (AVSDs) represent approximately 5% of congenital cardiac abnormalities[1, 2] and are bound by a variable deficiency of the atrioventricular (AV) septum immediately above and below the AV valves. These defects are frequently associated with other cardiac malformations. About 30-40% of the cardiac abnormalities observed in patients with Down syndrome are AVSDs.[3] ​

The AV valves are invariably abnormal in patients with atrioventricular septal defects. At one end of the spectrum of atrioventricular septal defects, incomplete atrioventricular septal defects, also termed ostium primum atrial septal defects (ASDs), have only a deficiency in the inferior portion of the atrial septum immediately superior to the AV valves and have 2 valve orifices. The other end of the spectrum encompasses complete atrioventricular septal defects, with both ASDs and ventricular septal defects (VSDs) and a single common AV valve.

In addition to the term "atrioventricular septal defects," these congenital abnormalities have been described by several other terms, including AV canal defects, endocardial cushion defects, and AV communis.

History of the Procedure

In 1955, Lillehei and colleagues reported the first successful repair of an atrioventricular (AV) septal defect (AVSD) using the technique of cross circulation.[4] Early mortality rates for the repair of AVSDs were 50%. Complications, including complete heart block and AV valve regurgitation, were also common.

In 1958, Lev delineated the bundle of His, which helped decrease the incidence of heart block following surgery.[5] An improved understanding of the structure and function of the common AV valve and a realization of the importance of closing the mitral cleft led to refinements in surgical technique that have decreased the short-term and long-term incidence of AV valve regurgitation. By the 1970s, improvements in surgical techniques and cardiopulmonary bypass resulted in the ability to repair AVSDs with low morbidity and mortality rates in children. Further refinements have allowed successful repair of even complex variations of AVSDs in infancy.

Problem

Atrioventricular septal defects (AVSDs) represent a spectrum of defects involving varying degrees of deficiency of the atrial and ventricular septae. The common pathophysiology is right-to-left shunting at the atrial level, ventricular level, or both. These septal defects are accompanied by atrioventricular (AV) valve abnormalities, which may lead to regurgitation, further complicating the problem. The goals of surgical treatment are to close the atrial and ventricular defects while preserving or improving AV valve function in both the short term and the long term.

Pathophysiology

The embryologic abnormality in atrioventricular (AV) septal defects (AVSDs) is failure of the proper development of the endocardial cushions, which are responsible for the septation of the atria and ventricles. The exact causal factors are unknown.

In the absence of left AV valve regurgitation, the hemodynamic features are the result of left-to-right shunting at the atrial and ventricular levels. In the absence of ventricular level shunting, the hemodynamics resemble those of a typical secundum atrial septal defect (ASD) with right atrial (RA) and right ventricular (RV) volume overload. As with an uncomplicated ASD, the natural history of decades of chronic volume overload results in atrial dilatation and arrhythmias, ventricular dysfunction, and, potentially, pulmonary vascular disease.

Incomplete AVSD

Moderate or severe left AV valve regurgitation occurs in approximately 10% of patients with an incomplete atrioventricular septal defects. The regurgitant jet is often directed into the RA and is often termed a left ventricle (LV)–to–RA shunt. Although this term is not strictly accurate because the jet actually goes from the LV to the left atrium (LA) to the RA, the result is an increase in the magnitude of the left-to-right shunt.

Complete AVSD

Patients with a complete AVSD with both atrial and ventricular level shunting usually present early in infancy with signs and symptoms of congestive heart failure (CHF). In addition, moderate or severe left AV valve regurgitation occurs in approximately 10% of patients with a complete AVSD, worsening the clinical picture. According to Newfeld et al, as many as 90% of untreated individuals with a complete AVSD develop pulmonary vascular disease by age 1 year because of the large left-to-right shunt, potentially exacerbated by associated AV valve regurgitation.[6]

Epidemiology

 

 

Presentation

The clinical presentation of a patient with an incomplete atrioventricular (AV) septal defect (AVSD) with isolated atrial level shunting is similar to that observed in a patient with a typical secundum atrial septal defect (ASD). Upon physical examination, an active precordium, a pulmonary outflow murmur, and a fixed widely split second heart sound is present.

Incomplete AVSD

Clinical presentation is complicated by a moderate or severe left AV valve regurgitation in approximately 10% of patients with an incomplete AVSD. The regurgitant jet is often directed into the right atrium (RA) and is often termed a left ventricular (LV)-to-RA shunt (although, more accurately, it is termed an LV-to-left atrium [LA]-to-RA shunt) and increases the magnitude of the left-to-right shunt. These patients may present early in life with symptoms of congestive heart failure (CHF), including pulmonary congestion and infection, dyspnea, tachycardia, and failure to thrive. Inability to medically control the CHF is an indication for earlier surgical intervention in these patients. However, symptoms in the first year of life may indicate the presence of associated left-sided anomalies, which exacerbate the left-to-right shunt and include LV hypoplasia, LV outflow tract obstruction, and aortic arch obstruction.

Complete AVSD

Patients with a complete AVSD with both atrial and ventricular level shunting usually present early in infancy with signs and symptoms of CHF. Clinical presentation is worsened by moderate or severe left AV valve regurgitation, which occurs in approximately 10% of patients with a complete AVSD. Upon physical examination, the precordium is hyperactive, often with a prominent thrill. Auscultatory findings include a systolic murmur along the left sternal border, a high-pitched murmur at the apex resulting from left AV valve regurgitation, and a mid-diastolic flow murmur across the common AV valve. In the presence of elevated pulmonary vascular resistance, a split first heart sound may be present.

Indications

Partial atrioventricular (AV) septal defect (AVSD)

For a partial AVSD, also termed a primum atrial septal defect (ASD), the hemodynamics resemble that of a typical secundum ASD with right atrial (RA) and right ventricular (RV) volume overload. As with an uncomplicated ASD, the natural history of decades of chronic volume overload results in atrial dilatation and arrhythmias, ventricular dysfunction, and, potentially, pulmonary vascular disease. Therefore, repair is indicated and is usually performed by age 2-4 years in a patient with partial AVSD.

Incomplete AVSD

Moderate or severe left AV valve regurgitation occurs in approximately 10% of patients with an incomplete AVSD. The regurgitant jet is often directed into the RA, resulting in an increase in the magnitude of the left-to-right shunt. These patients may present early in life with symptoms of congestive heart failure (CHF), including pulmonary congestion and infection, dyspnea, tachycardia, and failure to thrive. Inability to medically control CHF is an indication for earlier surgical intervention in these patients.

Complete AVSD

According to Newfeld et al, as many as 90% of untreated individuals with a complete AVSD develop pulmonary vascular disease by age 1 year as a result of the large left-to-right shunt, potentially exacerbated by the associated AV valve regurgitation.[6] Patients with trisomy 21 tend to develop pulmonary vascular obstructive disease earlier than infants with normal karyotypes because of small airway disease, chronic hypoventilation, and elevated partial pressure of carbon dioxide (PCO2). Undertake initial aggressive medical management to relieve symptoms of CHF. Perform elective surgical correction by age 3-6 months in infants with AVSD. Earlier intervention is indicated for failure of medical management.

Relevant Anatomy

From a surgical standpoint, the most useful classification subdivides atrioventricular (AV) septal defects (AVSDs) into incomplete and complete, based on AV valve morphology.

Incomplete AVSD

Incomplete or partial defects have 2 AV valve orifices as a result of the continuity between the left superior leaflet (LSL) and the left inferior leaflet (LIL). Although the development of the commissures varies, 6 leaflets are usually present (see the image below).

(a) An incomplete atrioventricular septal defect ( (a) An incomplete atrioventricular septal defect (AVSD) with right superior leaflet (RSL), right lateral leaflet (RLL), right inferior leaflet (RIL), left superior leaflet (LSL), left lateral leaflet (LLL), and left inferior leaflet (LIL). (b) A complete ASD with superior bridging leaflet (SBL), inferior bridging leaflet (IBL), LLL, RSL, and RIL. The locations of the atrioventricular (AV) node and bundle of His are indicated. All images are surgeon's-eye views with cranial leftward, caudad rightward, superior upward, and posterior downward.

The right-sided AV valve consists of the right superior leaflet (RSL), right lateral leaflet (RLL), and right inferior leaflet (RIL). The LSL, left lateral leaflet (LLL), and LIL form the left-sided AV valve. The commissure between the LSL and LIL represents the cleft of the left AV valve.

Although most incomplete AVSDs have no ventricular level shunting, classification of an AVSD as complete or incomplete depends only on the valve anatomy and not on the presence or absence of a ventricular septal defect (VSD). As in all AVSDs, the inlet septum in incomplete AVSDs is deficient. The continuity of the LSL and LIL forms a bridge of tissue, which obliterates the potential for shunting below the leaflets. Incomplete defects without associated ventricular level shunting have also been termed ostium primum atrial septal defects (ASDs), whereas those with a VSD have been described as intermediate or transitional AVSDs.

Complete AVSD

Complete AVSDs have a single common AV valve orifice resulting in a 5-leaflet valve (see the image below).

(a) An incomplete atrioventricular septal defect ( (a) An incomplete atrioventricular septal defect (AVSD) with right superior leaflet (RSL), right lateral leaflet (RLL), right inferior leaflet (RIL), left superior leaflet (LSL), left lateral leaflet (LLL), and left inferior leaflet (LIL). (b) A complete ASD with superior bridging leaflet (SBL), inferior bridging leaflet (IBL), LLL, RSL, and RIL. The locations of the atrioventricular (AV) node and bundle of His are indicated. All images are surgeon's-eye views with cranial leftward, caudad rightward, superior upward, and posterior downward.

These leaflets are termed the left superior or superior bridging leaflet (SBL), left inferior or inferior bridging leaflet (IBL), LLL, RSL, and RIL. Alternatively, the superior and inferior leaflets also may be termed anterior and posterior, respectively.

Rastelli et al further subclassified complete AVSDs into types A, B, and C based on the morphology of the SBL (see the image below).[7]

Rastelli classification. (a) Rastelli type A. (b) Rastelli classification. (a) Rastelli type A. (b) Rastelli type B. (c) Rastelli type C.

In a Rastelli type A defect, the SBL is divided at the plane of the interventricular septum and attached to the crest of the VSD by numerous cordae. Type B complete AVSDs, which are rare, are characterized by cordal attachments from the left AV valve to papillary muscles in the right ventricle (RV). In a Rastelli type C defect, the SBL is said to be "free floating" because it is undivided and unattached to the crest of the VSD.

Aortic valve displacement

The aortic valve is displaced anterosuperiorly and to the right. As mentioned above, in all forms of AVSDs, the inlet portion of the left ventricle (LV) is deficient relative to the outflow tract. This decrease in the inlet-outlet ratio results in the characteristic gooseneck deformity observed on anteroposterior projection of a left ventriculogram. The LV outflow tract is elongated and horizontally oriented. According to Studer et al and Piccoli et al, although frequently narrow, the LV outflow tract causes obstruction in only 4-7% of individuals with AVSDs.[8, 9]

Ventricular balance

Both left and right AV valves may equally share the common AV valve orifice. This arrangement is termed a balanced defect. Occasionally, the orifice may favor the right AV valve (right dominance) or the left AV valve (left dominance). In marked right dominance, the left AV valve and LV are hypoplastic; frequently, they coexist with other left-sided abnormalities including aortic stenosis, hypoplasia of the aorta, and coarctation. Conversely, marked left dominance results in a deficient right AV valve with associated hypoplasia of the RV, pulmonary stenosis or atresia, and tetralogy of Fallot (TOF). Ventricular balance is based on the size of the ventricular inlet, not on the size of the ventricular chamber, and is assessed best on the 4-chamber view on echocardiography.

Conduction tissue location

Because the conduction tissue is at risk during repair, its location is of importance in the surgical treatment of AVSDs. The AV node is displaced posteriorly and inferiorly toward the coronary sinus in what has been termed the nodal triangle, which is bounded by the coronary sinus, the posterior attachment of the IBL, and the rim of the ASD (see the image below).

Rastelli classification. (a) Rastelli type A. (b) Rastelli classification. (a) Rastelli type A. (b) Rastelli type B. (c) Rastelli type C.

The bundle of His courses anteriorly and superiorly to run along the leftward aspect of the crest of the VSD, giving off the left bundle branch and continuing as the right bundle branch.

Other cardiac anomalies

According to Bharati et al, numerous other cardiac anomalies are associated with AVSDs including patent ductus arteriosus (found in 10% of individuals with AVSD) and TOF (found in 10% of individuals with AVSD).[10] Of the important abnormalities of the left AV valve, according to Draulans-Noe et al, 2-6% of patients with AVSD have a single papillary muscle (parachute mitral valve) and 8-14% of persons with AVSD have a double-orifice mitral valve.[11] Bharati et al state that a persistent left superior vena cava, with or without an unroofed coronary sinus, is encountered in 3% of patients with an AVSD.[10] Double-outlet RV, which is found in 2% of individuals with AVSD, significantly complicates or may even preclude complete surgical correction.

As mentioned previously, LV outflow tract obstruction from subaortic stenosis or redundant AV valve tissue occurs in 4-7% of individuals with AVSD, according to Studer et al and Piccoli et al.[8, 9] Associated transposition of the great arteries and LV inflow obstruction have rarely been reported.

Contraindications

The treatment of choice for an incomplete or complete atrioventricular (AV) septal defect (AVSD) is complete surgical repair. Pulmonary artery banding for palliation of symptoms of congestive heart failure (CHF) has a limited role in the management of these lesions. Indications for pulmonary artery banding may include patients with associated complex cardiac anomalies, severely unbalanced defects, or other functional single ventricle anatomy necessitating an ultimate Fontan procedure and a poor clinical condition precluding major cardiac surgery.

According to Newfeld et al, as many as 90% of untreated patients with a complete AVSD develop pulmonary vascular obstructive disease.[6] As with a secundum atrial septal defect (ASD), patients with a partial AVSD are at risk for developing pulmonary vascular obstructive disease in the third, fourth, and fifth decades of life. Cardiac catheterization is recommended for patients presenting later in life for repair. A pulmonary vascular resistance of greater than 10 Wood units is a contraindication to surgical repair.

 

Workup

Laboratory Studies

Routine preoperative studies (eg, complete blood cell [CBC] count, platelet counts, electrolyte levels, blood urea nitrogen [BUN] levels, creatinine levels) are indicated. Typing and crossmatching blood are necessary for cardiopulmonary bypass preparation.

Arterial blood gas (ABG) determinations are not routinely warranted; however, cyanosis alerts the physician to the possibility of pulmonary vascular obstructive disease in older patients or concurrent right-sided obstructive lesions.

Imaging Studies

Chest radiography

In incomplete atrioventricular (AV) septal defects (AVSDs), chest radiographs usually reveal mild cardiomegaly and increased pulmonary vascular markings. In complete AVSDs, Significant cardiomegaly and pulmonary overcirculation are depicted on chest radiographs.

Doppler echocardiography

In incomplete AVSDs, Doppler echocardiography findings are diagnostic of the atrial defect, the absence of ventricular level shunting, and the presence of any AV valve abnormalities. In complete AVSDs, Doppler echocardiography findings are diagnostic, defining the atrial and ventricular level shunting, valvular anatomy, and any associated anomalies.

Other Tests

Electrocardiography

In incomplete atrioventricular (AV) septal defects (AVSDs), electrocardiography (ECG) reveals left axis deviation, prominent P waves associated with atrial enlargement, and a prolonged PR interval. In complete AVSDs, ECG reveals biventricular hypertrophy, atrial enlargement, prolonged PR interval, leftward axis, and counterclockwise frontal plane loop.

Diagnostic Procedures

Cardiac catheterization

In incomplete atrioventricular (AV) septal defects (AVSDs), cardiac catheterization is indicated only in adults with a diagnosis of incomplete AVSDs or in patients manifesting physical or radiologic signs of decreased pulmonary blood flow. Decreased pulmonary artery blood flow may be a result of pulmonary vascular disease or concurrent right-sided obstructive lesions. High fraction of inspired oxygen (FiO2) and nitric oxide may be needed to assess the reversibility of increased pulmonary vascular resistance.

In complete AVSD, perform cardiac catheterization for patients older than 1 year, patients with signs or symptoms of increased pulmonary vascular resistance, or in some individuals to further evaluate other associated major cardiac anomalies. High FiO2 and nitric oxide may be needed to assess the reversibility of increased pulmonary vascular resistance.

 

Treatment

Medical Therapy

Patients with incomplete atrioventricular (AV) septal defects (AVSDs) present with signs and symptoms similar to those of secundum atrial septal defects (ASDs) and, as such, rarely require medical therapy. Medical therapy in patients with complete AVSDs consists of aggressive anticongestive treatment for the signs and symptoms of congestive heart failure (CHF). The mainstays of medical therapy are furosemide (for diuresis for the volume-overloaded heart), digoxin (as a mild inotrope), and angiotensin-converting enzyme (ACE) inhibitors (for afterload reduction).

Surgical Therapy

The treatment of choice for an incomplete or complete atrioventricular septal defect (AVSD) is complete surgical repair. Factors for a favorable outcome in patients who undergo repair of complete AVSD appear to include younger patient age and better preoperative common AV valve function.[12]  Surgical technique does not appear to affect outcomes.

Pulmonary artery banding for palliation of symptoms of congestive heart failure (CHF) has a very limited role in the management of these lesions. Indications for pulmonary artery banding may include patients with AVSD and associated complex cardiac anomalies, severely unbalanced defects or other functional single ventricle anatomy necessitating an ultimate Fontan procedure, and poor clinical condition precluding major cardiac surgery.

Preoperative details

Recognized standard pediatric cardiac methods of premedication, anesthesia, and preparation for surgery are used for both complete and incomplete atrioventricular septal defects. Routine screening using cervical spine radiography has been suggested prior to cervical manipulation for intubation in patients with Down syndrome.

Intraoperative Details

Use a median sternotomy approach. Harvest a patch of autologous pericardium for the atrial septal defect (ASD) closure and treat with glutaraldehyde (0.6%), according to surgeon preference. Perform aortic and bicaval cannulation with routine cardiopulmonary bypass in most patients. Rarely, deep hypothermic circulatory arrest may be required during the repair in very low birth weight neonates.

Arrest the heart with antegrade cardioplegia, with additional doses every 20-30 minutes during the period of aortic cross-clamping. Place a left atrial (LA) vent through the right upper pulmonary vein to help maintain a bloodless operative field and to assist in de-airing of the heart after the cross-clamp is removed.

Use mild systemic hypothermia (>32°C) for the repair of incomplete atrioventricular (AV) septal defects (AVSDs) with only atrial level shunting, and use moderate hypothermia (25-28°C) for complete AVSDs. A right atriotomy provides access to the AVSD for repair.

Intraoperative transesophageal echocardiography (TEE) has been beneficial in the treatment of individuals with AVSDs by helping identify left AV valve regurgitation, stenosis, and residual atrial or ventricular shunts, allowing for immediate surgical revision.

Traditional surgical technique for the repair of complete AVSD

Two techniques are widely used in the repair of complete AVSDs, namely, a 1-patch technique and a 2-patch technique.

Regardless of which approach is selected, first elevate the common AV valve to its closed position by injecting cold isotonic sodium chloride solution into the ventricles to assess valvular competence and structure.

The central apposition of the superior bridging leaflet (SBL) and inferior bridging leaflet (IBL) is the area where the 2 leaflets meet at a point separating the left and right AV valves. Identify and mark these points with fine polypropylene sutures (see the image below).

The common atrioventricular (AV) valve is floated The common atrioventricular (AV) valve is floated to a closed position using isotonic sodium chloride solution. The central apposition points of the superior and inferior bridging leaflets are identified and marked with fine polypropylene sutures.

For the 2-patch technique, fashion a patch of polytetrafluoroethylene (PTFE, Gore-Tex) into a crescent shape to match the dimensions of the ventricular septal defect (VSD). Secure this patch along the ventricular septal crest slightly on the rightward aspect, particularly inferiorly, to avoid the conduction system. The authors use a running technique with polypropylene sutures, although interrupted sutures may also be used (see the image below).

Two-patch technique. A patch of polytetrafluoroeth Two-patch technique. A patch of polytetrafluoroethylene (Gore-Tex) is fashioned and secured along the crest of the ventricular septal defect.

Septate the common AV valve into right and left valves along the line overlying the ventricular septal crest defined by the point of central apposition and the hinge points at which the VSD meets the AV valve annulus beneath the SBL and IBL.

Place interrupted horizontal mattress sutures through the crest of the VSD patch and then the SBL and IBL (see the image below).

Two-patch technique. Interrupted horizontal mattre Two-patch technique. Interrupted horizontal mattress sutures are placed through the crest of the ventricular septal defect (VSD) patch and the inferior and superior bridging leaflets, dividing the common atrioventricular (AV) valve into right and left components.

Pass these same sutures through the edge of the autologous pericardial patch for the closure of the ASD, and tie them (see the image below).

Two-patch technique. The pericardial patch is secu Two-patch technique. The pericardial patch is secured to the crest of the prosthetic ventricular septum with the superior and inferior bridging leaflet sandwiched between the 2 patches.

For the 1-patch technique, divide the SBL and IBL along a line separating them into right and left components (see the image below).

One-patch technique. The superior and inferior bri One-patch technique. The superior and inferior bridging leaflets are divided into right and left components.

Tailor a single polyethylene terephthalate (Dacron) or PTFE patch to close both the VSD and ASD.

Similar to the technique for the 2-patch repair, secure the patch to the crest of the ventricular septum. Then, resuspend the leaflets to the patch by passing interrupted sutures through the cut edge of the left AV valve leaflet, the patch, and the cut edge of the right AV valve, and tie the sutures (see the image below).

One-patch technique. The leaflets are resuspended One-patch technique. The leaflets are resuspended to the patch by passing sutures through the cut edge of the left atrioventricular (AV) valve leaflet, the patch, and the cut edge of the right AV valve and tying the sutures.

Whichever technique is used to close the ASD and VSD, reassess the AV valves for adequate orifice size and competence by filling the respective ventricles with cold isotonic sodium chloride solution. Although earlier reports recommended that the cleft in the left AV valve not be closed and the valve be treated as a trileaflet structure, most authors currently believe that closure of the cleft is an important mechanism in preventing postoperative left AV valve regurgitation (see the image below).

The cleft of the mitral valve between the superior The cleft of the mitral valve between the superior and inferior bridging leaflets is closed.

Puga has identified significant AV valve regurgitation at the conclusion of surgery, severe dysplasia of the left AV valve, and failure to close the cleft of the left AV valve as important risk factors for repeat surgery.[13]  According to Studer et al and Stewart et al, significant postoperative left AV valve regurgitation is also a risk factor for surgical and long-term mortality.[8, 14]

Use fine tailoring of the valve by cleft closure, eccentric annuloplasty, and commissuroplasty on an individual basis to ensure valve competency while avoiding valve stenosis. Special considerations are necessary for patients with an AVSD and an associated single papillary muscle to the left AV valve or a double-orifice valve. Do not completely close the cleft in the presence of a single papillary muscle to avoid causing left AV valve stenosis. In a double-orifice valve, do not divide the bridging tissue to create a single opening in the valve.

Close the ASD with the autologous pericardial patch in the 2-patch technique or with the atrial component of the single patch using a running suture technique. The authors generally maintain the coronary sinus on the RA side. Running the suture line down into the mouth of the coronary sinus where no conduction system tissue is present may help decrease the risk of heart block. Other surgeons elect to leave the coronary sinus in the LA side of the repair to avoid injuring the conduction system (see the image below).

The atrial septal defect (ASD) is closed with an a The atrial septal defect (ASD) is closed with an autologous pericardial patch. The coronary sinus is placed in the left atrium to avoid injury to the conduction system. The rim of the ASD, the atrioventricular (AV) node, and the bundle of His are indicated. The dashes represent the proposed suture line.

Modified single patch repair of complete AVSD

Nunn described a modified single patch technique.[15]  This technique is particularly applicable to patients with an AVSDs and a small-to-moderate VSD component.

As with the other approaches, first elevate the common AV valve to its closed position by injecting cold isotonic sodium chloride solution into the ventricles to assess valvular competence and structure.

The central apposition of the SBL and IBL is the area where the 2 leaflets meet at a point separating the left and right AV valves. Identify and mark these points with fine polypropylene sutures (see the image below).

The common atrioventricular (AV) valve is floated The common atrioventricular (AV) valve is floated to a closed position using isotonic sodium chloride solution. The central apposition points of the superior and inferior bridging leaflets are identified and marked with fine polypropylene sutures.

A series of sutures are then placed along the right ventricular aspect of the crest of the VSD, as in the repair of an incomplete AVSD. These sutures are then passed through the SBL and IBL along the line demarcating their right and left components, and subsequently through the edge of a single PTFE patch. The sutures are then tied down, sandwiching the SBL and IBL between the patch and the crest of the septum.

The patch is then used to close the ASD using a running suture technique. The authors generally maintain the coronary sinus on the RA side. Running the suture line down into the mouth of the coronary sinus where no conduction system tissue is present may help decrease the risk of heart block. Other surgeons elect to leave the coronary sinus in the LA side of the repair to avoid injuring the conduction system (see the image below).

The atrial septal defect (ASD) is closed with an a The atrial septal defect (ASD) is closed with an autologous pericardial patch. The coronary sinus is placed in the left atrium to avoid injury to the conduction system. The rim of the ASD, the atrioventricular (AV) node, and the bundle of His are indicated. The dashes represent the proposed suture line.

Operative technique for the repair of incomplete AVSD

Repair of an incomplete AVSDs with only atrial level shunting is similar to the approach use for ASD closure in the 2-patch technique.

First inspect the valves for orifice size and competence by filling the ventricles with cold isotonic sodium chloride solution.

Close the cleft in the left AV valve and perform any other tailoring of the AV valves to ensure competence without causing stenosis.

Make interrupted sutures along the base of the tricuspid valve, pass them through an autologous pericardial patch, and tie them.

Use the patch to close the ASD with a running suture technique. As in complete AVSD, take care to avoid injury to the conduction system, often by closing the coronary sinus into the left atrium.

Repair of complete AVSD with associated cardiac anomalies

Tetralogy of Fallot (TOF) complicates the repair of an AVSD in as many as 10% of individuals. AVSD with TOF is differentiated from AVSD with pulmonary valve stenosis by the anterior malalignment of the conal septum. The result is an extension of the VSD to include a malalignment component, with overriding aorta and crowding of the pulmonary outflow tract as observed with isolated TOF. The complete repair of AVSD with TOF remains challenging, and the optimal management strategy is controversial.

The basic repair requires a modification of the usually crescent-shaped patch to include an extension to sew around the annulus of the overriding aorta to maintain it on the left side of the repair. Many groups have used an initial palliative systemic-to-pulmonary artery for significant cyanosis in neonates and young infants. The definitive repair is then delayed until the child is aged 1-2 years. The success of the early and complete repair of isolated AVSDs or TOF has lead to a reanalysis of this staged approach.

Several groups, including McElhinney et al and Najm et al, have reported excellent results with the primary repair of AVSD with TOF in infants.[16, 17]  They cite equivalent results with a less complicated postoperative course and fewer repeat surgeries. Similarly, Ong et al reported an actuarial survival of 76% at 5 years and 71% at 20 years in patients with AVSD and TOF or double-outlet right ventricle, with a 33% reoperation rate (an overall freedom from operation of 55% at 5 and 20 years).[18]

The long-term outcomes of cyanotic and very young children with complete AVSD and TOF tetralogy of Fallot who require urgent treatment appear to be similar following staged repair compared with primary repair.[19]  However, the presence of preoperative AV valve regurgitation increases the risk for reoperation over the long term.

LV outflow tract obstruction from fibromuscular subaortic stenosis, redundant AV valve tissue, abnormal attachment of mitral valve cordae, or tunnel-type outflow also can complicate the repair of an AVSD. Tailor surgical correction of the obstruction to the specific cause. Often, a resection of the subaortic membrane or redundant AV valve tissue combined with a septal myomectomy is sufficient. Occasionally, a septoplasty, preserving the aortic valve, is necessary. Rarely, a mitral valve replacement or a picoaortic conduit is required.

Patients with AVSDs may also present with a severely unbalanced AVSD and a hypoplastic ventricle necessitating a single ventricle repair. Mortality is high in these patients, with a reported survival at 25 years that is below 60% (66.5% at 5 years; 64.4% at 15 years).[20] If medical treatment is possible until patients are older than 4-6 months, a bidirectional Glenn operation or hemi-Fontan procedure may be performed as a stage to an eventual Fontan procedure. Long-term survival following Fontan procedure has been reported to be 82.4% at 25 years (94.9% at 5 years; 92.0% at 15 years).[20] An initial pulmonary artery band or systemic-to-pulmonary artery shunt may be palliative in patients with pulmonary overcirculation or undercirculation.

Potential aids to surgical decision making for biventricular operation in patients with right-dominant unbalanced AVSD include the use of echocardiographic measurements of the right ventricular/left ventricular (RV/LV) inflow angle in systole and the AV valve index, in conjunction with other echocardiographic indices such as LV dimensions and volumes, and VSD size.[21]

Postoperative Details

Postoperative treatment in patients with atrioventricular (AV) septal defect (AVSD) is similar to that in all patients undergoing corrective repair of congenital heart defects, with the exception of patients with elevated pulmonary vascular resistance or those prone to pulmonary vascular hypertensive crises. Patients at risk are primarily those in whom the AVSD is repaired at a later age (>6-12 mo). Placement of a pulmonary artery catheter, in addition to routinely placed left atrial (LA) line, aids in the diagnosis and management of pulmonary hypertensive crises.

These patients remain sedated and are usually paralyzed in the immediate postoperative period. Ventilator maneuvers include high fraction of inspired oxygen (FiO2), lowering of partial pressure of carbone dioxide (PCO2) (25-30 mm Hg), avoidance of acidosis, and use of inhaled nitric oxide (5-80 ppm). More recently, sildenafil has shown promise as a pulmonary vasodilator either alone, in combination with nitric oxide, or to prevent the rebound phenomenon seen during discontinuation of nitric oxide. Some authors routinely use phenoxybenzamine (1 mg/kg) at the initiation and conclusion of cardiopulmonary bypass, as well as every 8-12 hours postoperatively (0.5 mg/kg) in patients at high risk.

Intravenous nitroglycerin, nitroprusside, aminophylline, and prostacyclin all have been advocated for the management of pulmonary hypertensive crises. Generally, avoid high-dose dopamine and alpha-adrenergic agents if possible. Carefully evaluate low cardiac output with transesophageal echocardiography (TEE) and, if necessary, cardiac catheterization.

Follow-up

Lifelong cardiologic follow-up care is indicated for patients with complete atrioventricular (AV) septal defects (AVSDs). Individualize follow-up care for patients with uncomplicated partial AVSDs without AV valve regurgitation.

Major causes of long-term morbidity include left AV valve regurgitation and subaortic stenosis. Subacute bacterial endocarditis prophylaxis is indicated at times of identified risk. Details of the recommendations for prophylaxis for subacute bacterial endocarditis can be found on the American Heart Association Website.

For patient education resources, see the Heart Health Center and Tetralogy of Fallot.

Complications

Most repeat surgeries following repair of atrioventricular (AV) septal defect (AVSD) are because of left AV valve regurgitation (LAVVR).[13, 22, 23, 24, 25, 26] Significant postoperative AV valve regurgitation occurs in 10-15% of patients, necessitating additional surgery for valve repair or replacement in 7-12% of patients.[13, 22, 23, 25]

With improved understanding of the conduction system in AVSDs, the incidence of permanent complete heart block is approximately 1%, as reported by Studer et al and Kadoba et al.[8, 27]  Heart block encountered in the immediate postoperative period may be transient and result from edema of or trauma to the AV node or bundle of His. However, according to Kadoba et al, right bundle branch block is common (22%).[27]

Outcome and Prognosis

Several factors have been associated with increased surgical risk.[28] Improvements in perioperative management and experience with younger patients have led to improvement in results over time. Earlier studies, such as that by Najm et al, had suggested that age younger than 2 years at the time of surgery put patients at risk for death.[17] However, more recent studies, such as those by Studer et al and Berger et al, have not found age to be a risk factor.[8, 29] In addition, Reddy et al have suggested that incidence of atrioventricular (AV) valve regurgitation is lower after earlier repair (patients 30</ref>

Preoperative AV regurgitation has also been identified as a risk factor for surgical mortality in series by Studer et al and Stewart et al.[8, 14] Patients with complete atrioventricular septal defects (AVSDs) are at higher surgical risk than patients with incomplete AVSDs.

Although trisomy 21 has been reported to be a risk factor for surgical mortality in some series, Michielon et al, Vet and Ottenkamp, and Minich et al have found that Down syndrome does not affect or may improve outcome.[22, 31, 32]  Some authors note that AV valve dysfunction is less prevalent in patients with Down syndrome, and significantly fewer associated cardiac anomalies are found. In addition, infants with Down syndrome have been reported to have relatively larger left AV and aortic valves than infants with normal karyotypes, perhaps accounting for the improved outcome.

Surgical mortality is largely related to associated cardiac anomalies and left AV valve regurgitation. According to Studer et al and Stewart et al, the mortality rate in patients undergoing repair of uncomplicated incomplete AVSDs ranges from 0% to 0.6%, whereas the addition of left AV valve regurgitation increases the mortality rate to 4-6%.[8, 14] In individuals with complete AVSDs, the mortality rate without left AV valve regurgitation is approximately 5%, compared with 13% in patients with significant degrees of regurgitation.

In a retrospective evaluation of outcomes in 116 patients with complete AVSDs who underwent definitive repair from February 1997 through October 2002, actuarial survival at 1, 3, and 5 years was 98%, 95%, and 95%, respectively.[33]  Seventy five (68%) of patients had trivial-to-mild left AV valve regurgitation at discharge. Moderate or severe left AV valve stenosis developed in 3 patients (3%). Actuarial freedom from reoperation for left AV valve dysfunction at 1, 3, and 5 years was 94%, 89%, and 89%, respectively. Actuarial freedom from reoperation for left ventricular outflow tract obstruction at 1, 3, and 5 years was 100%, 93%, and 90%, respectively.[33]

Patients with unbalanced AVSDs not suitable for biventricular repair, tetralogy of Fallot (TOF), or double-outlet right ventricle were excluded.[33] Median age and weight at surgery were 4.8 months (range, 9 d to 5.4 y) and 4.8 kg (range, 2.1-23 kg), respectively. Follow-up was 93% complete at a mean of 27 months (range, 1-73 mo). Early definitive repairs were performed in 110 patients (98%) who initially presented to the institution. Ninety two patients (79%) underwent repair before age 6 months, including 25 (22%) before age 3 months.[33]

The Pediatric Heart Network Investigators published results from a multicenter observational study on the contemporary results after repair of complete AVSD in 120 children, in which in-hospital and 6-month mortality rates were 2.5% and 4%, respectively. The incidence of residual septal defects and the degree of left AV 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.[34]

Another study from The Pediatric Heart Network Investigators assessed the influence of AVSD subtype on outcomes after repair.[35] Preoperatively, transitional patients showed the highest prevalence of moderate or severe left AV valve regurgitation (LAVVR).[35] In data obtained 1 and 6 months post AVSD repair, patients with complete AVSD and canal-type VSD 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, whereas those with complete AVSD showed a longer duration of ventilation and hospitalization. At 6 months, weight-for-age z scores improved and improvement was similar in all subtypes.[35]

A more recent study from the Society of Thoracic Surgeons Congenital Heart Surgery Database that evaluated early outcomes in 2399 patients from 101 centers who underwent repair of complete AVSDs found that patients with Down syndrome had lower rates of mortality and morbidities than other patients, but the postoperatve length of stay was similar among patients.[36] In addition, weight less than 3.5 kg and age of 2.5 months or younger were associated with higher mortality, longer postoperative length of stay, and increased frequency of major complications. 

Future and Controversies

Overall, the trend in the management of an atrioventricular septal defect (AVSD), even in the presence of associated anomalies, has been toward early and complete repair. However, an initial palliative pulmonary artery band or systemic-to-pulmonary artery shunt remains an important option in the repair of very complex forms of AVSD. The optimal management must be tailored to the individual patient in the context of locally available resources.