Management and outcome of atrioventricular (AV) canal defects

INTRODUCTION — Atrioventricular (AV) canal defects are a group of congenital cardiac defects involving, to varying extent, the AV septum and AV valves (ie, mitral and tricuspid valves) (figure 1).

The management and outcome of patients with AV canal defects will be reviewed here. The anatomy, pathophysiology, clinical features, and diagnosis of AV canal defects are discussed separately. (See "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects".)

TERMINOLOGY — The term "AV canal defect" refers to a broad range of AV septal and valve defects that result from failure of the superior and inferior endocardial cushions to fuse correctly during embryologic cardiac development (figure 2). They are also commonly called AV septal defects or endocardial cushion defects.

AV canal defects include the following (figure 1):

●Complete AV canal (CAVC) defect is characterized by a primum atrial septal defect (ASD) that is contiguous with a ventricular septal defect (VSD) and a common AV valve. CAVC defects can be further classified based upon the relative sizes of the ventricles:

•In balanced CAVC, the ventricles are relatively equal in size and are amenable to biventricular repair

•In unbalanced CAVC, there is hypoplasia of either the right or left ventricle (most commonly the left)

●Partial AV canal defect consists of a primum ASD and a common valvular annulus with two separate valve orifices. The anterior leaflet of the mitral valve is cleft (due to abnormal fusion of the left tubercle of the superior and inferior cushions), which is often associated with mitral valve regurgitation.

●Transitional AV canal defect consists of a large primum ASD, cleft mitral valve, and inlet VSD. However, dense chordal attachments to the ventricular septum result in small shunting at the ventricular level and delineate distinct left and right AV valve orifices, resulting in a defect that is similar to the physiology of a partial AV canal defect.

●Intermediate AV canal defect is a rare subtype of CAVC, in which a bridging tongue of tissue divides a common AV valve into two distinct orifices. This defect is physiologically similar to CAVC and usually has both a large primum atrial and large inlet VSDs. Due to natural division of the common AV valve into left and right AV valve components by the tongue of tissue, surgical division is not required.

The anatomy of AV canal defects is discussed in greater detail separately. (See "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects", section on 'Anatomy and pathogenesis'.)

OVERVIEW OF MANAGEMENT — The management approach for AV canal defects is based on the type of defect, determining whether there are other associated anatomic and hemodynamic abnormalities (eg, relative ventricular size, AV valve regurgitation, and right or left ventricular outflow tract obstruction [LVOTO]), and whether or not other cardiac conditions are present (eg, coarctation of the aorta).

In general, surgical correction is recommended because of the significant morbidity and mortality associated with the uncorrected defect.

●Complete AV canal defects (CAVC) – Infants with CAVC defects, including those with the intermediate type, generally develop heart failure by one year of age. If the defect is not repaired, unrestricted pulmonary blood flow and elevated pulmonary artery pressures cause pulmonary vascular changes, which can ultimately lead to irreversible pulmonary hypertension (PH), right-to-left intracardiac shunting, and systemic cyanosis (ie, Eisenmenger syndrome). For this reason, we recommend surgical intervention for most patients with CAVC by six months of age (ie, prior to the onset of irreversible PH). (See 'Complete atrioventricular canal defect' below and "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects", section on 'Complete atrioventricular canal defect'.)

●Partial and transitional AV canal defects – Even though many patients with partial and transitional AV canal defects are asymptomatic until adulthood, surgical repair is suggested in childhood because the primum atrial septal defect (ASD) will not close spontaneously and, without intervention, these patients are at risk for atrial arrhythmias (eg, atrial fibrillation), heart failure, and pulmonary hypertension later in life, similar to the late complications of ASD. Patients with significant mitral regurgitation (MR) are more likely to present earlier with heart failure symptoms. (See 'Partial and transitional atrioventricular canal defect' below and "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects", section on 'Partial and transitional atrioventricular canal defects'.)

COMPLETE ATRIOVENTRICULAR CANAL DEFECT — Management of complete AV canal (CAVC) defects encompasses initial medical management for heart failure, and either primary complete repair or palliative intervention.

Initial medical management — Infants with CAVC usually present with symptoms of heart failure by approximately six weeks of age and generally require medical management before surgical repair. The goal of medical management is to improve cardiac function and the patient's clinical status, thereby optimizing the patient's condition before surgery.

Medical management includes the following:

●Diuretic therapy reduces volume overload and pulmonary congestion. Diuretic agents include loop (eg, furosemide) and thiazide diuretics. (See "Heart failure in children: Management", section on 'Diuretics'.)

●Inotropic agents (eg, digoxin) improve myocardial contractility. (See "Heart failure in children: Management", section on 'Digoxin'.)

●Angiotensin blockade reduces afterload, thereby decreasing left-to-right shunting and possibly mitral regurgitation (MR). In children, angiotensin-converting enzyme (ACE) inhibitors are the preferred agents as there is a paucity of data on the use of angiotensin receptor blockers in pediatric heart failure. (See "Heart failure in children: Management", section on 'ACE inhibitors'.)

●Promoting adequate nutrition, especially in patients with poor feeding and failure to thrive. In these patients, caloric supplementation is often needed and may require the use of nasogastric tube feeding or, rarely, gastric tube insertion before surgical repair. (See "Heart failure in children: Management", section on 'Nutritional support'.)

Surgical interventions — For most patients with CAVC, primary complete repair is the preferred surgical approach because of its overall low morbidity and mortality. (See 'Complete repair' below.)

However, primary complete repair may not be feasible for a subset of patients, including the following:

●Unbalanced CAVC – In patients with unbalanced CAVC (ie, one ventricle is hypoplastic) whose anatomy is deemed unfavorable for biventricular repair, surgical palliation is performed using interventions developed for other single ventricular cardiac defects, such as hypoplastic left heart syndrome (HLHS) and tricuspid atresia. (See 'Single-ventricle palliation' below and "Hypoplastic left heart syndrome: Management and outcome", section on 'Surgical management'.)

●Complex anatomy or early symptoms – Some patients with CAVC may not be optimal candidates for early primary complete repair, because of associated cardiac defects (eg, coarctation of aorta) or complex anatomy (eg, multiple ventricular septal defects [VSDs]) or because significant symptoms develop at a very early age when valve construction may not be feasible. In such patients, pulmonary artery banding may be used to protect the pulmonary circulation until complete repair can be performed. (See 'Timing of repair' below.)

Complete repair — The objectives of surgical repair are to close atrial and ventricular defects and to form two separate and competent AV valves.

Timing of repair — Surgical repair is generally performed in early infancy to avoid development of pulmonary vascular disease (PVD).

●Early repair for symptomatic infants – Infants with refractory heart failure symptoms despite medical management, significant AV valve regurgitation, or other defects that require early surgical correction (eg, aortic coarctation) may benefit from early surgical repair (ie, before the age of two to three months). However, valve construction may be technically challenging in very young infants and preterm infants due to size considerations and poor valve tissue maturation. The optimal age for valve construction is generally considered to be >6 weeks, though it varies by surgeon [1]. For infants who require intervention before six weeks of age, pulmonary artery banding may be used to protect the pulmonary circulation until the infant grows to an acceptable size for complete repair.

●Elective repair in infants with mild or no symptoms – For infants without heart failure symptoms and those whose symptoms are well controlled with medical therapy, elective surgical repair is generally performed between the age of three to six months. Elective repair is recommended in infancy for all patients regardless of whether symptoms are present because all patients with CAVC are at risk of developing PVD if repair is deferred. This is particularly important for patients with Down syndrome, who have a higher risk of developing PVD than those without Down syndrome. Patients with Down syndrome often remain asymptomatic throughout early infancy, likely due to persistently elevated pulmonary vascular resistance from birth. Surgical outcomes for patients with Down syndrome undergoing CAVC repair during infancy are similar to those of patients without Down syndrome [2,3]. (See 'Outcome' below.)

●Adults with unrepaired CAVC – Adults with unrepaired CAVC are rarely encountered and generally have irreversible PVD with associated right-to-left shunting (Eisenmenger syndrome). Such patients are generally not candidates for operative repair. This is discussed separately. (See "Pulmonary hypertension in adults with congenital heart disease: General management and prognosis".)

Surgical procedures — Surgical techniques for correction of CAVC have evolved since the first report of successful surgical repair in 1955 [4].

●Techniques for repair of CAVC – In the contemporary era, repair of CAVC is performed using one of the following techniques (figure 3) [5]:

•Single-patch repair – In the single-patch technique, prosthetic patch material is placed to close the ventricular and atrial communications. The common AV valve is divided and reattached to the patch (figure 3).

•Two-patch repair – In the two-patch technique, prosthetic patch material is used to close the VSD and the common AV valve is sutured to the top of the patch. The atrial component is closed with a pericardial patch that is sutured to the common AV valve and ventricular patch (figure 3).

•Modified (simplified) single-patch repair – In the modified single-patch technique, the common AV valve is directly sutured to the crest of the ventricular septum. Pericardium is used to close the atrial component and is sutured to the crest of the ventricular septum, separating the common AV valve into right and left components (figure 3) [6]. This newer technique simplified the one-patch repair and resulted in significantly shorter cardiopulmonary bypass and aortic cross-clamp time [7-10].

The choice of procedure is based largely upon surgeon and institutional preference and experience. Whether there are clinically meaningful long-term advantages of one approach over another remains uncertain. The available observational data comparing these three techniques are limited and suggest that major determinants of a successful outcome are surgeon and institution familiarity and experience with a specific technique, rather than the technique itself [7-9,11].

A meta-analysis of 15 observational studies evaluating outcomes in 1034 patients after modified single-patch repair or two-patch repair of CAVC did not detect significant differences between the two groups in early mortality (4.4 versus 5.2 percent, respectively; odds ratio [OR] 0.96, 95% CI 0.52-1.79), overall mortality (5.8 versus 5.5 percent; OR 1.18, 95% CI 0.64-2.19), complete heart block (1.6 versus 2.0 percent; OR 0.63, 95% CI 0.21-1.87), residual septal defects (3.3 versus 2.3 percent; OR 1.65, 95% CI 0.67-4.06), degree of AV valve regurgitation (standard mean difference -0.10, 95% CI -0.26 to 0.06), or reoperation rate (6.3 versus 7.5 percent; OR 0.84, 95% CI 0.48-1.47) [9]. Left ventricular outflow obstruction was less common in the modified single-patch repair group, but the difference was not statistically significant (0.6 versus 3.6 percent; OR 0.22, 95% CI 0.02-2.82). Compared with patients who underwent two-patch repair, those who underwent modified single-patch had shorter cardiopulmonary bypass time, shorter aortic cross clamp time, and shorter length of hospital stay. Of note, patients in the modified single-patch group had smaller VSD size compared with the two-patch repair group. The modified single-patch has been used preferentially in patients with a comparatively smaller VSD [5,8]. Thus, the utility of this technique remains unclear in patients with a large VSD, and in these patients, it is unclear whether the outcome of this procedure is comparable or better than the other two procedures.

In a multicenter observational study of 120 children who underwent repair of CAVC from June 2004 to 2006, two-patch, one-patch, and the modified single-patch repair were used in 72, 18, and 10 percent of cases, respectively [8]. Patients who underwent the modified single-patch repair were younger on average compared with those corrected by either the single- or double-patch repair (mean age 2.6 versus 4.4 and 3.8 months, respectively). The overall in-hospital mortality was 2.5 percent, and six-month mortality was 4 percent. The incidence of residual VSD or left AV valve regurgitation was not affected by the age at operation, presence of Down syndrome, or type of repair. There was a lower rate of additional annuloplasty modifications in patients who underwent the modified single-patch repair compared with either the single- or double-patch repairs (0 versus 14 and 30 percent, respectively).

●Closure of the cleft in the AV valve – With any of the three techniques, closure of the cleft in the mitral component of the valve is controversial. Our preferred approach is generally to close the cleft whenever the morphology of the left AV valve allows for closure without producing stenosis. The rationale is that residual left AV valve regurgitation through the cleft is a frequent reason for reoperation. However, other experts argue that the cleft in the left AV valve is a true commissure and should be left open so that the repaired valve functions as a three-leaflet valve [12].

Our approach is supported by a retrospective single-center study of 159 patients who underwent CAVC repair from 1984 to 1997, which found that patients who underwent left AV valve cleft repair had higher eight-year freedom from reoperation for left AV regurgitation compared with patients in whom the cleft was left open (98 versus 78 percent, respectively) [13]. In another small retrospective study, closure of the cleft also appeared to be beneficial even in the setting of a parachute left AV valve, where there would be a concern for producing left AV valve stenosis with closure of the cleft [14].

Single-ventricle palliation — The term "unbalanced AV canal defect" has been used when there is significant right ventricular (RV) or left ventricular (LV) hypoplasia associated with an unequally positioned common AV valve either over the right or over the left ventricle. The management of unbalanced AV canal defect remains difficult. In general, two-ventricle repair is better tolerated in patients with RV hypoplasia than in patients with LV hypoplasia.

Echocardiography is used to measure the relative sizes of the ventricles in patients with an unbalanced AV canal defect and to determine whether or not a two-ventricle repair is feasible. Echocardiographic features put forth as measures to determine suitability for two-ventricle repair include:

●AV valve index – Derived by the ratio of the area of the AV valve apportioned to the LV over the combined area of the AV valve measured in the subcostal left anterior oblique view. Two-ventricle repair is typically successful when the AV valve index is between 0.4 and 0.6 [15,16].

●LV inflow index – Secondary inflow diameter into the LV indexed to the left AV valve annulus diameter. LV inflow index less than 0.5 was associated with no survival after two-ventricle repair [17].

●RV-LV inflow angle – The angle between the base of the RV and LV free wall using the crest of the ventricular septum as the apex of the angle. Increasing inflow angle was associated with successful two-ventricle repair. The morphologic significance of this angle has not been elucidated, but the smaller angle may relate to a larger VSD and a narrower angle of inflow into the LV [18].

However, in a multicenter study of 257 infants with CAVC, these echocardiographic measures of unbalance correlated poorly with one another, suggesting that they likely assess distinct morphologic and functional parameters [19]. Additional studies are needed to identify the best method for distinguishing balanced from unbalanced defects. In particular, data are lacking on which measures (if any) truly correlate with outcome. An ongoing multicenter prospective study of AV canal defects may better define the echocardiographic characteristics of balanced versus unbalanced defects and may better inform surgical decision-making [18,19].

When a two-ventricle repair is not possible, palliative intervention using a modified Fontan approach is performed based on techniques developed in patients with other single ventricular cardiac defects (eg, HLHS and tricuspid atresia). The success of this approach is dependent on the competency of the AV valve and the protection of the pulmonary vascular bed.

Surgical repair typically consists of three staged palliative procedures (see "Hypoplastic left heart syndrome: Management and outcome", section on 'Surgical management'):

●Stage 1 establishes a controlled source of pulmonary blood flow and provides blood flow from the "single ventricle," which can either be a dominant right or left ventricle, to the systemic circulation. In some cases, pulmonary artery banding is sufficient, but in others, banding of the pulmonary artery to lower pulmonary artery pressure may lead to worsening of AV valve regurgitation and/or subsequent distortion of the central pulmonary arteries. In these patients, an alternative approach directly shunts pulmonary blood flow from a systemic artery to pulmonary artery through a component of a divided main pulmonary artery.

●Stage 2 is performed when the patients begin to outgrow their original shunt. In general, a bidirectional Glenn shunt or a hemi-Fontan procedure is performed that results in direct drainage of blood from the superior vena cava into the pulmonary artery. This leads to improved systemic oxygenation and a decreased volume load on the heart.

●Stage 3 is performed after further growth. This stage entails a modified Fontan procedure that separates the venous and arterial circulations. This separation is obtained by baffling the blood return from the inferior vena cava directly to the pulmonary artery, usually with an extracardiac conduit.

Similar to HLHS, mortality is high in patients with unbalanced lesions who are not amenable to two-ventricular repair. The three-stage palliative approach reduces early mortality, but the long-term outcome remains uncertain. (See "Hypoplastic left heart syndrome: Management and outcome", section on 'Outcome'.)

PARTIAL AND TRANSITIONAL ATRIOVENTRICULAR CANAL DEFECT

Rationale for intervention — We suggest elective surgical repair in early childhood for all children with partial and transitional AV canal defects. The goal of surgery is to close the interatrial communication and restore and preserve left AV valve competence. The rationale for elective surgical repair in childhood is to prevent the long-term consequences of the left-to-right shunting (ie, pulmonary hypertension [PH], heart failure, and atrial fibrillation) and to preserve valve function [20]. Partial and transitional AV canal defects generally do not produce symptoms during infancy and early childhood; however, they are associated with a moderate to large left-to-right shunt that is unlikely to resolve spontaneously. Thus, with increasing age, patients are at risk for developing PH and symptoms of right heart failure, especially with exertion. Patients with left AV valve regurgitation are more likely to develop heart failure symptoms at an earlier age.

Timing of repair — For patients in whom the diagnosis of partial or transitional AV canal defect is made in infancy, surgical repair is usually performed in early childhood (typically between the age of 18 months to 3 years). Surgery at this age is associated with very low risk of morbidity and minimal mortality (<1 percent). For patients who are diagnosed later in childhood, surgery is performed whenever the diagnosis is made.

In a retrospective multicenter study of 87 patients who underwent repair of a partial or transitional defect at a mean age of 1.8 years, there was one perioperative fatality (a four-day-old infant who also underwent arch reconstruction) and no interim deaths at six-month follow-up [21]. One-third of patients in this study had preoperative moderate or severe left AV valve regurgitation and 20 percent had growth failure, indicating that this cohort was a more symptomatic and severely affected than is typical for these defects. Weight gain improved after surgery, especially in underweight children. Left AV valve regurgitation was the most common residual defect, occurring more frequently in children repaired after four years of age. These results suggest that surgical repair before preschool age may be advantageous in preventing left AV valve regurgitation.

Surgical procedure — Surgical repair of partial and transitional AV canal defects involves patch closure of the ostium primum defect and mitral valvuloplasty to eliminate or to minimize mitral regurgitation (MR). For moderate or severe MR, surgeons suture the mitral valve cleft closed and perform a mitral annuloplasty when associated annular dilatation is present. Surgical closure of the cleft in the presence of mild or no MR is controversial. For transitional AV canal defects, the ventricular septal defect (VSD) may be closed primarily or with a patch, depending on its size.

POSTOPERATIVE COMPLICATIONS

Pulmonary hypertension — Without repair, the natural history of complete AV canal (CAVC) defect is that of progressive pulmonary vascular disease (PVD), pulmonary hypertension (PH), heart failure, and premature death [22]. Surgical repair in early infancy substantially reduces the risk of developing PVD; however, it does not eliminate it. Major risk factors for developing PH after surgical repair of CAVC include underlying Down syndrome and delayed repair (ie, after the age of six months, with the risk increasing incrementally with age thereafter) [23]. For children with Down syndrome, the development of PH is multifactorial and other noncardiac issues likely contribute to the risk (eg, obstructive sleep apnea, hypoventilation, recurrent aspiration, genetic predisposition). Thus, even with early complete repair of CAVC, the risk of developing PH may persist. (See "Down syndrome: Clinical features and diagnosis", section on 'Pulmonary disorders' and "Pulmonary hypertension in children: Classification, evaluation, and diagnosis", section on 'Syndromes'.)

Nonsyndromic children with partial and transitional AV canal defects who undergo repair in childhood are at low risk of developing PH.

When PH is identified postoperatively, it is important to rule out secondary causes of PH such as severe mitral regurgitation (MR), stenosis, or residual ventricular septal defect (VSD).

The evaluation and management of PH are discussed in greater detail separately. (See "Pulmonary hypertension in children: Classification, evaluation, and diagnosis" and "Pulmonary hypertension in children: Management and prognosis".)

Arrhythmias — Arrhythmias in the immediate postoperative setting may include sinus node dysfunction, complete heart block, supraventricular tachycardia, junctional ectopic tachycardia, and ventricular arrhythmias. In the available case series, postoperative arrhythmias occurred in approximately 10 to 15 percent of patients, with roughly equivalent rates in complete and partial AV defects [8,24]. Late postoperative arrhythmias were less common, occurring in 2 to 3 percent of patients. Bradyarrhythmias, particularly complete heart block, are the most common long-term rhythm problems following surgical repair of AV canal defects, with approximately 3 to 4 percent of patients requiring permanent pacemaker implantation [24-27]. (See "Atrial arrhythmias (including AV block) in congenital heart disease".)

Mitral valve regurgitation — Following initial surgical correction of partial and CAVC defect, postsurgical AV valve regurgitation is a common complication and the most common reason for reoperation after repair (movie 1) [5,8,21,28,29]. The left AV (mitral) valve is most commonly involved.

Moderate to severe MR occurs in approximately 20 to 30 percent of patients who undergo surgical repair of AV canal defects, of whom approximately one-half (ie, 10 to 15 percent overall) require reoperation [21,30,31]. In one report, patients with CAVC were more likely to have MR due to technical failures at the time of repair, whereas patients with partial AV canal defects were more likely to have valve regurgitation due to residual anatomic anomalies [30]. In another report of 165 patients who underwent repair of CAVC, moderate or severe MR was noted in 37 percent of patients in the early postoperative period and in 32 percent at ≥6 months after repair [32]. Late MR was associated with more widely spaced papillary muscles, in distinction with the more closely spaced papillary muscles often seen with AV canal defect.

Preoperative severe AV valve regurgitation is an important risk factor for requiring reoperation for MR. However, in one study, one-third of the patients with moderate or severe MR at ≥6 months after repair did not have significant MR in the early postoperative period, raising the likelihood that different mechanisms may be involved in some patients [32].

Transesophageal echocardiogram in the operating room immediately before and after initial repair can assess the degree of MR. If significant MR or stenosis is noted after initial repair, further surgery on the valve may be performed before leaving the operating room. However, it is important to recognize that transesophageal echocardiogram performed while the patient is still on cardiopulmonary bypass (or immediately after) may not accurately reflect the true severity of MR [33,34]. Nonetheless, it is the best immediate method to assess the repair.

Age at the time of repair may also be a risk factor for needing reoperation for MR, but the available reports have reached conflicting conclusions, with some reporting higher rates of reoperation in patients repaired at a young age [28], while others report lower risk of reoperation in patients operated on at a young age [21,31,35,36].

For patients with persistent or severe MR who require reoperation, surgery generally aims to repair the valve but may require valve replacement. Valve surgery should be performed by a surgeon with experience in congenital cardiac surgery.

Mitral valve stenosis — Reoperation for mitral stenosis after AV canal defect repair is much less common compared with MR [37-39]. Reoperation for mitral stenosis may be necessary if the valve orifice is hypoplastic or restrictive due to parachute valve morphology. Assessment of valve morphology prior to surgical repair and avoiding aggressive cleft closure in cases with small left mural leaflet decreases the incidence of postoperative mitral stenosis. Reoperation for AV valve stenosis or inflow obstruction should be performed by a surgeon with experience in congenital cardiac surgery. The operation usually requires valve replacement. Balloon mitral valvotomy can rarely be utilized as a temporizing method to delay the need for replacement [40].

Left ventricular outflow tract obstruction — Relief of left ventricular outflow tract obstruction (LVOTO) is the second most common reason for reoperation after initial repair of partial and CAVC defect, occurring in 3 to 7 percent of patients [11,28,30,41]. LVOTO may develop from combination of anatomic characteristics associated with AV canal defects, including elongation and narrowing of the LVOT and crowding of the LVOT by AV valve tissue that may be accentuated over time by patient growth or development of subaortic membrane. (See "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects", section on 'Left ventricular outflow tract'.)

If LVOTO is severe or if turbulent flow results in increasing aortic valve regurgitation, reoperation for enlargement of the LVOT or resection of subaortic tissue may be performed.

LONG-TERM MANAGEMENT

Follow-up — Longitudinal follow-up care is required in all patients with AV canal defects, in conjunction with a cardiologist with expertise in congenital heart disease (CHD). Follow-up visits should include an interval history, physical examination, and cardiac testing (electrocardiography and echocardiography). The assessment focuses on identifying patients with ventricular dysfunction (eg, heart failure or outflow obstruction), arrhythmia, and worsening mitral regurgitation (MR).

●Frequency of follow-up – Follow-up visits typically occur annually, though the frequency will vary depending on the child's course. Use of a technical performance score may help identify patients who need more frequent follow-up and testing. Based on the findings on postoperative echocardiography, patients can be categorized as having no residual defects (class 1), minor residual defects (class 2), or major residual defects (class 3, including moderate or worse mitral valve regurgitation or stenosis, residual shunt, any residual defect requiring unplanned surgical or catheter-based reintervention during the hospitalization, or need for permanent pacemaker) [41]. Patients with major residual defects are more likely to require unplanned reintervention after discharge and may benefit from more frequent follow-up [42].

●Clinical assessment – The history and physical examination focus on the cardiac status of the patient. The following findings are suggestive of cardiac dysfunction:

•Dyspnea or decreased exercise tolerance is suggestive of ventricular dysfunction or worsening MR

•Episodes of palpitations or syncope suggest an underlying arrhythmia

•Irregular pulse suggests an underlying arrhythmia

•Gallop rhythm or new murmur may suggest residual shunt, MR, mitral stenosis, or subaortic stenosis

•Signs of heart failure include crackles, jugular venous distension, peripheral edema, and hepatomegaly

●Tests – The following tests are routinely performed:

•Electrocardiography is performed yearly to detect and diagnose arrhythmias. Holter or event recorder monitoring may be periodically useful tests and are particularly helpful in patients with a history suggestive of arrhythmia.

•Routine echocardiography is initially performed annually or if there are any concerning clinical findings. It is used to evaluate ventricular function, residual shunts, AV valve regurgitation/stenosis, and subaortic stenosis.

Physical activity — After recovering from surgery, normal daily activities should be allowed. Most patients remain asymptomatic with a normal functional status. The 2015 scientific statement of the American Heart Association and American College of Cardiology provides competitive athletic participation guidelines for patients with CHD [43]. These guidelines do not provide specific recommendations for patients with AV canal defects; however, activity recommendations can be inferred from those of similar CHD lesions. Patients who have no residual defects, normal ventricular function, and have no evidence of atrial or ventricular tachyarrhythmias may participate in all competitive sports without restrictions. Patients who have arrhythmias or residual cardiac lesions are addressed on an individual basis.

Physical activity and exercise in children with CHD are discussed in greater detail separately. (See "Physical activity and exercise in patients with congenital heart disease".)

Endocarditis prophylaxis — For patients undergoing procedures likely to result in bacteremia (eg, dental work) within six months of complete repair, prophylactic antibiotics are recommended for prevention of endocarditis. After six months, antibiotics are recommended at the time of such procedures if the patient had a repair involving use of prosthetic material for valve repair, if there is a residual shunt or valvular regurgitation at the site or adjacent to the site of the prosthetic patch or prosthetic device, or if the patient has had a prior episode of endocarditis. Antimicrobial prophylaxis for the prevention of bacterial endocarditis is discussed in greater detail separately. (See "Prevention of endocarditis: Antibiotic prophylaxis and other measures".)

Pregnancy — A comprehensive cardiovascular evaluation by a congenital cardiac specialist is recommended prior to pregnancy in a patient with repaired AV canal defect to confirm that there are no cardiovascular features that would be best treated before a pregnancy or to suggest that a pregnancy would be high risk and not advised. (See "Pregnancy in women with congenital heart disease: Specific lesions", section on 'Atrioventricular septal defect'.)

OUTCOME

Survival — In the contemporary era, early mortality (ie, within six months) following repair of complete AV canal (CAVC) defect is approximately 3 to 4 percent [5,8,21,26]. Major risk factors for early mortality include young age at time of repair (ie, age <2 months), presence of other cardiac defects, and need for univentricular palliation. Mortality rates do not appear to be different in patients with Down syndrome compared with nonsyndromic patients [2,3]. Ten-year survival after CAVC repair exceeds 90 percent [44-46].

For children with partial and transitional AV canal defects, surgical outcomes are excellent, with minimal perioperative mortality (<1 percent) and with long-term survival that is similar to that of the general population [21,47,48]. In a single-center report of 249 consecutive patients who underwent repair of partial AV canal between 1975 to 2012, survival was 96 percent at 10 years and 94 percent at 30 years [48].

Reintervention — Reoperation is required in 15 to 20 percent of patients [44-46]. Worsening mitral regurgitation (MR) is the leading reason for reoperation and is necessary in 10 to 15 percent of patients [21,30,31]. All patients require long-term follow-up after repair to monitor for MR, atrial arrhythmias, left ventricular outflow tract obstruction (LVOTO), and ventricular dysfunction [49,50]. (See 'Long-term management' above.)

Neurodevelopmental outcome — Neurodevelopmental outcomes depend on the type of defect and whether the child has Down syndrome.

●CAVC – Children who undergo repair of CAVC in infancy are at risk for developmental delays. Early developmental surveillance is warranted in all children with CAVC, with referral to early intervention and/or neurodevelopmental specialists as appropriate [51]. (See "Developmental-behavioral surveillance and screening in primary care".)

•Children with Down syndrome – Nearly all children with Down syndrome have some degree of cognitive impairment, though the range is wide. It is uncertain what impact undergoing cardiac surgery in infancy has on long-term neurodevelopment in children with Down syndrome. Observational studies have demonstrated that patients with Down syndrome who underwent cardiac surgery in infancy scored lower on developmental testing in early childhood compared with children with Down syndrome without congenital heart disease (CHD) [52-54]. However, in one study, differences did not persist to school age [52]. (See "Down syndrome: Clinical features and diagnosis", section on 'Intellectual disability'.)

•Nonsyndromic children – Nonsyndromic children with CAVC have an increased risk of long-term neurodevelopmental impairment compared with healthy peers, though the risk is less than for children with Down syndrome [55-57]. When developmental delays are identified in this setting, they are generally mild and usually improve over time. However, patients with unbalanced CAVC who undergo univentricular palliation are at risk for more severe neurodevelopmental impairment. (See "Management of complications in patients with Fontan circulation", section on 'Neurologic complications'.)

●Partial and transitional AV canal defects – For children with partial and transitional AV canal defects, surgical repair generally is deferred until after infancy and, therefore, the impact of surgery on long-term neurodevelopment is likely minimal. In the absence of underlying Down syndrome, these children generally do not require any additional screening or intervention beyond the routine screening recommended for all children. (See "Developmental-behavioral surveillance and screening in primary care".)

SUMMARY AND RECOMMENDATIONS

●Anatomy – Atrioventricular (AV) canal defects are a group of congenital cardiac defects involving the AV septum and AV valves (ie, mitral and tricuspid valves). Failure of the superior and inferior endocardial cushions to fuse correctly during cardiac embryology results in complete (both atrial and ventricular septal defects [ASDs/VSDs]) and partial (only ASD) anatomic forms (figure 1). They are also commonly called AV septal defects or endocardial cushion defects. (See 'Terminology' above and "Clinical manifestations and diagnosis of atrioventricular (AV) canal defects", section on 'Anatomy'.)

●Surgical repair – AV canal defects require surgical repair because they are associated with considerable morbidity and mortality if left uncorrected. The management approach is based on the type of defect, whether there are other associated anatomic and hemodynamic abnormalities (eg, relative ventricular size, AV valve regurgitation, and right or left ventricular outflow obstruction), and whether there are other cardiac defects (eg, coarctation of the aorta). Our approach is as follows (see 'Overview of management' above):

•Complete AV canal (CAVC) defects – Management of CAVC encompasses initial medical management for heart failure and either primary complete repair or palliative intervention.

-The goal of medical management is to improve cardiac function in patients with heart failure, thereby optimizing the patient's condition before surgery. Therapeutic interventions include diuretic therapy, inotropic support, angiotensin blockade, and provision of adequate nutrition. (See 'Initial medical management' above and "Heart failure in children: Management".)

-For patients with a balanced CAVC defect (two ventricles similar in size), we recommend primary surgical repair before six months of age rather than deferring repair until later in childhood (Grade 1B). Surgical intervention during early infancy is associated with low mortality and avoids later morbidity associated with development of pulmonary hypertension (PH). Repair of CAVC is performed using single-patch, two-patch, or modified single-patch approaches (figure 3). The choice of approach is based largely on surgeon preference and institutional experience. (See 'Complete repair' above and 'Pulmonary hypertension' above.)

-For patients in whom a two-ventricle repair is not feasible (ie, patients with unbalanced lesions wherein one of the ventricles is hypoplastic), we suggest surgical palliation using interventions developed for other univentricular cardiac conditions, such as hypoplastic left heart syndrome (HLHS) or tricuspid atresia (Grade 2C). (See 'Single-ventricle palliation' above.)

•Partial and transitional AV canal defects – For patients with partial and transitional AV canal defects, we recommend elective surgical repair in early childhood rather than observation or deferring repair until later in childhood (Grade 2C). Repair is typically performed between the age of 18 months to 3 years, or, for patients diagnosed later in childhood, surgery is performed whenever the diagnosis is made. The rationale for surgical repair in these patients is to reduce morbidity later in life, including heart failure and atrial fibrillation. Elective surgical repair in early childhood is associated with low morbidity and mortality. (See 'Partial and transitional atrioventricular canal defect' above.)

●Postoperative complications – Postoperative complications after repair of AV canal defects include PH, arrhythmias, mitral regurgitation (MR), mitral stenosis, and left ventricular outflow obstruction. Patients with preoperative AV regurgitation are likely to have postoperative MR, which often requires reoperation. (See 'Postoperative complications' above.)

●Outcome – The overall mortality rate for surgical repair of CAVC is approximately 3 percent, and the 10-year survival rate exceeds 90 percent. Outcomes following repair of partial and transitional AV canal defects are excellent, with minimal perioperative mortality (<1 percent) and long-term survival that is similar to that of the general population. (See 'Outcome' above.)

●Long-term follow-up – Longitudinal follow-up care is required in all patients with AV canal defects in conjunction with a cardiologist with expertise in congenital heart disease (CHD). Follow-up visits should include an interval history, physical examination, and cardiac testing (electrocardiography and echocardiography) that are focused on identifying patients with ventricular dysfunction, arrhythmia, and worsening MR. (See 'Long-term management' above.)