Atrioventricular Septal Defect Surgery Treatment & Management
- Author: Richard G Ohye, MD; Chief Editor: John Kupferschmid, MD more...
Patients with incomplete atrioventricular 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 atrioventricular septal defects 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 ACE inhibitors (for afterload reduction).
The treatment of choice for an incomplete or complete atrioventricular septal defect is complete surgical repair. Pulmonary artery banding for palliation of symptoms of CHF has a very limited role in the management of these lesions. Indications for pulmonary artery banding may include patients with atrioventricular septal defect 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.
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.
Use a median sternotomy approach. Harvest a patch of autologous pericardium for the 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 septal defects with only atrial level shunting, and use moderate hypothermia (25-28°C) for complete atrioventricular septal defects. A right atriotomy provides access to the atrioventricular septal defect for repair.
Intraoperative transesophageal echocardiography (TEE) has been beneficial in the treatment of individuals with atrioventricular septal defects by helping identify left atrioventricular (AV) valve regurgitation, stenosis, and residual atrial or ventricular shunts, allowing for immediate surgical revision.
Traditional surgical technique for the repair of complete atrioventricular septal defect
Two techniques are widely used in the repair of complete atrioventricular septal defects, 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).
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).
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).
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).
For the 1-patch technique, divide the SBL and IBL along a line separating them into right and left components (see the image below).
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).
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).
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. 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.[11, 6]
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 atrioventricular septal defect 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).
Modified single patch repair of complete atrioventricular septal defect
Nunn described a modified single patch technique. This technique is particularly applicable to patients with an atrioventricular septal defects 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).
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 atrioventricular septal defect. 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).
Operative technique for the repair of incomplete atrioventricular septal defect
Repair of an incomplete atrioventricular septal defects 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 atrioventricular septal defect, take care to avoid injury to the conduction system, often by closing the coronary sinus into the left atrium.
Repair of complete atrioventricular septal defect with associated cardiac anomalies
Tetralogy of Fallot (TOF) complicates the repair of an atrioventricular septal defect in as many as 10% of individuals. Atrioventricular septal defect with TOF is differentiated from atrioventricular septal defect 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 atrioventricular septal defect 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 atrioventricular septal defects or TOF has lead to a reanalysis of this staged approach. Recently, several groups, including McElhinney et al and Najm et al, have reported excellent results with the primary repair of atrioventricular septal defect with TOF in infants.[13, 14] They cite equivalent results with a less complicated postoperative course and fewer repeat surgeries.
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 atrioventricular septal defect. 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 atrioventricular septal defects may also present with a severely unbalanced atrioventricular septal defect and a hypoplastic ventricle necessitating a single ventricle repair. 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. An initial pulmonary artery band or systemic-to-pulmonary artery shunt may be palliative in patients with pulmonary overcirculation or undercirculation.
Postoperative treatment in patients with atrioventricular septal defect 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 atrioventricular septal defect is repaired at a later age (>6-12 mo). Placement of a pulmonary artery catheter, in addition to routinely placed 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 FiO2, lowering of PCO2 (25-30 mm Hg), avoidance of acidosis, and use of inhaled nitric oxide (5-80 ppm). 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 TEE and, if necessary, cardiac catheterization.
Lifelong cardiologic follow-up care is indicated for patients with complete atrioventricular septal defects. Individualize follow-up care for patients with uncomplicated partial atrioventricular septal defects 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 Web site.
Most repeat surgeries following repair of atrioventricular septal defect (AVSD) are because of left atrioventricular (AV) valve regurgitation. According to Puga, Minich et al, and Hanley et al, significant postoperative AV valve regurgitation occurs in 10-15% of patients, necessitating additional surgery for valve repair or replacement in 7-12% of patients.[10, 15, 16]
With improved understanding of the conduction system in atrioventricular septal defects, incidence of permanent complete heart block is approximately 1%, as reported by Studer et al and Kadoba et al.[6, 17] 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%).
Outcome and Prognosis
Several factors have been associated with increased surgical risk. 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. However, more recent studies, such as those by Studer et al and Berger et al, have not found age to be a risk factor.[6, 19] In addition, Reddy et al have suggested that incidence of atrioventricular (AV) valve regurgitation is lower after earlier repair (patients < 4 mo).
Preoperative AV regurgitation has also been identified as a risk factor for surgical mortality in series by Studer et al and Stewart et al.[11, 6] Patients with complete atrioventricular septal defects (AVSDs) are at higher surgical risk than patients with incomplete atrioventricular septal defects.
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.[21, 22, 15] 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 atrioventricular septal defects ranges from 0-0.6%, whereas the addition of left AV valve regurgitation increases the mortality rate to 4-6%.[11, 6] In individuals with complete atrioventricular septal defects, the mortality rate without left AV valve regurgitation is approximately 5%, compared with 13% in patients with significant degrees of regurgitation.
The authors recently retrospectively evaluated outcomes in 116 patients with complete atrioventricular septal defects who underwent definitive repair from February 1997 through October 2002. Patients with unbalanced atrioventricular septal defects not suitable for biventricular repair, tetralogy of Fallot (TOF), or double-outlet right ventricle were excluded. 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 author's institution. Ninety two patients (79%) underwent repair before age 6 months, including 25 (22%) before age 3 months. Actuarial survival at 1, 3, and 5 years was 98%, 95%, and 95%, respectively. 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.
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.
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 AVSD 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 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.
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 atrioventricular septal defect. The optimal management must be tailored to the individual patient in the context of locally available resources.
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