AUTHOR AND EDITOR INFORMATION

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
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INTRODUCTION

Section 2 of 10  

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Background

An ostium primum atrial septal defect (ASD) is located in the most anterior and inferior aspect of the atrial septum. It is the simplest form of atrioventricular (AV) canal or AV septal defect. These defects are often associated with trisomy 21.

During fetal development, the rudimentary atrium is divided by the septum primum, except for an anterior and inferior space that is the ostium primum. The ostium primum is sealed by fusion of the superior and inferior endocardial cushions around 5 weeks' gestation. Failure to do so results in an ostium primum ASD. The endocardial cushions also contribute to the complete formation of 2 separate AV valves and the inlet interventricular septum. For this reason, ostium primum ASDs commonly are associated with malformations of these structures.

Ostium primum ASDs may occur in isolation but most commonly present with a cleft in the anterior leaflet of the mitral valve. This is sometimes termed a partial AV canal defect or a partial AV septal defect. In this case, a 5-leaflet AV valve is arranged so that separate right and left components (a tricuspid valve and a mitral valve) are present. The leaflets connect to each other and then adhere to the crest of the interventricular septum. This results in obligatory shunting at the atrial level with no ventricular level shunting. Generally, a commissure is observed between the left superior and inferior bridging leaflets because of abnormal fusion of the left tubercle of the superior and inferior cushions, which results in a cleft in the anterior leaflet of the mitral valve.

Pathophysiology

Shunting is predominantly left-to-right in the absence of pulmonary vascular disease or significant right ventricular outflow tract obstruction. This results in volume overload of the right atrium and ventricle and pulmonary overcirculation. If the mitral valve cleft causes significant mitral regurgitation, the left side of the heart also becomes volume overloaded. A left ventricle to right atrium shunt can be present, which further overloads both the right and left heart.

Frequency

United States

Ostium primum ASDs are most commonly associated with Down syndrome (trisomy 21). The incidence of trisomy 21 is 1 per 800 live births, with an increased prevalence noted in children born to older mothers.

• The overall risk of congenital heart disease in patients with Down syndrome is 40-50%. Approximately 65% of those affected have some form of AV septal defect.
• The inherited risk for children of parents who have an AV septal defect is reported as 9-14%.

Mortality/Morbidity

The presence and degree of associated mitral regurgitation and/or left ventricle to right atrium shunting generally determine symptoms.

Those with either no cleft or a cleft with a mild degree of mitral regurgitation are often asymptomatic. Patients typically are referred for evaluation of a heart murmur in childhood and generally survive well into adulthood. However, adults who have not had the condition repaired often become symptomatic from congestive heart failure (CHF) by age 45 years. Rarely, patients are reported to present in the seventh decade of life. Dyspnea on exertion and fatigue are usual adult complaints. Palpitations secondary to atrial fibrillation or flutter also are common.

Those with more severe mitral regurgitation or left ventricle to right atrium shunting often present in the first 2 years of life. Mortality has been reported to be as high as 30% in this subpopulation in the first year of life.

Although relatively rare, pulmonary vascular obstructive disease may occur in patients with long-standing substantial shunts and significant mitral regurgitation.

Children with trisomy 21 are at higher risk than the general population of developing pulmonary vascular obstructive disease at a younger age. Potential reasons for this include chronic upper airway disease, tonsillar and adenoid hypertrophy, and inadequate alveolarization of the terminal bronchioles, leading to a decreased surface area of the vascular bed.

Sex

The male-to-female ratio is 1:1.

Age

Patients with smaller defects and little or no mitral regurgitation may present at any age with a murmur and/or an abnormal ECG. Those with more severe mitral regurgitation typically present with CHF in the first 1-2 years of life.

CLINICAL

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History

Children with smaller ostium primum atrial septal defects (ASDs) and little or no mitral regurgitation or left ventricle to right atrium shunting are usually asymptomatic. Those with significant pulmonary overcirculation and/or significant mitral regurgitation tend to present in infancy with congestive heart failure (CHF). Tachypnea and tachycardia are noted at rest and are exacerbated with crying or exertion. Feeding is accompanied by dyspnea, diaphoresis, and an increased work of breathing. The combination of feeding difficulties and increased metabolic demands results in failure to thrive, which may be severe and/or intractable.

Physical

Characteristic features of trisomy 21 may be detected. These include the following:

• Hypotonia and hyperflexibility
• • Short, flat nose with a flat nasal bridge
  • Oblique palpebral fissures
  • Abundant neck skin
  • Large and protuberant tongue
  • Short, broad hands with a shorter fifth finger (clinodactyly)
  • Simian crease
  • Inner epicanthal fold extending onto the lower lid
  • Brushfield spots (speckled iris)

Infants and children with partial atrioventricular (AV) septal defects and significant mitral regurgitation have poor development and are tachypneic and tachycardic at rest. A hyperinflated thorax, bulging precordium, and Harrison grooves are often present. Most children, however, have a milder degree of mitral regurgitation and, in general, appear normally developed and thriving on examination.

The cardiac examination in isolated ostium primum ASDs or partial AV canal defects with minimal mitral regurgitation is similar to that in other forms of ASDs. Patients typically have an increased right ventricular impulse secondary to volume overload. The first heart sound is normal. The second heart sound is fixed or at least widely split. A systolic ejection murmur is heard loudest at the upper left sternal border, with radiation to both lung fields. A click is not present. A tricuspid mid-diastolic rumble is present in children with larger shunts (pulmonary-to-systemic flow ratio > 2:1) and is appreciated at the lower left sternal border.

The murmur of mitral insufficiency is typically high-pitched, holosystolic, and loudest at the apex. The murmur usually radiates to the axilla but may radiate preferentially to the sternal edge secondary to streaming of the regurgitant flow across the atrial septum.

If pulmonary hypertension is present, significant changes are noted in the physical examination. The pulmonary component of the second heart sound becomes loud. The splitting of the second heart sound narrows and eventually may become single. The diastolic tricuspid rumble disappears. A holosystolic murmur of tricuspid regurgitation becomes noticeable as the right ventricle dilates. This murmur is usually loudest at the lower left sternal border and becomes higher pitched as the right ventricular pressure increases. A short midsystolic murmur may be present secondary to flow into a dilated pulmonary artery. A Graham-Steell pulmonary insufficiency murmur may be appreciated as an early diastolic decrescendo murmur at the mid left sternal border.

Causes

The most common cause of an ostium primum ASD is genetic, associated with trisomy 21. Well-described associations have been reported with Holt-Oram syndrome, Noonan syndrome, and Ellis-van Creveld syndrome, among others. In children with normal chromosomes, however, the cause remains unknown. Research into the molecular genetic basis for AV canal and AV septal defects is ongoing.

DIFFERENTIALS

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WORKUP

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Imaging Studies

The following studies may be indicated in patients with ostium primum atrial septal defect (ASD):

• Chest radiography
• • With an isolated primum defect and no significant mitral regurgitation, findings of right heart enlargement and of a variable degree of pulmonary overcirculation are noted. In children with hemodynamically significant mitral regurgitation, radiographic evidence of left heart enlargement is also seen.
  • In patients with relatively small shunts, radiographic evidence of mild-to-moderate right atrial and right ventricular enlargement is seen. A mild degree of pulmonary congestion also may be noted.
  • With larger left-to-right shunts, radiographic signs of congestive heart failure (CHF) are manifest. The heart size is enlarged, with a cardiothoracic ratio greater than 50%. Pulmonary vascular markings are increased in proportion to the pulmonary-to-systemic flow ratio (Qp:Qs). The pulmonary trunk and proximal right pulmonary artery are dilated, and the aortic knob appears proportionally small. The right atrium and right ventricle are significantly enlarged.
  • Superimposed mitral regurgitation results in left atrial and left ventricular dilation, further enlarging the cardiac silhouette.
• Echocardiography
• • Echocardiography confirms the diagnosis of a primum ASD or partial atrioventricular (AV) canal defect. Anatomy is delineated by 2-dimensional imaging, and shunt flow and AV valve regurgitation are assessed by color and pulsed Doppler.
  • Two-dimensional imaging
  • • The apical 4-chamber view and subcostal imaging planes readily demonstrate a primum ASD, showing an area of "drop-out" in the inferior atrial septum. Care must be taken to differentiate this from the drop-out noted in the region of the coronary sinus. This may be particularly difficult when the coronary sinus is dilated from drainage of a left superior vena cava.
    • In the apical imaging plane in a normal heart, the tricuspid valve is more apically positioned than the mitral valve. In AV canal defects, both valves are visualized at the same horizontal level, and the crux of the heart is absent. In a partial canal defect, distinct left and right AV valves are identified. The leaflets are attached to the crest of the interventricular septum and no defect of the interventricular septum is visualized. A tricuspid valve cleft or other abnormalities of the valve leaflets also may be noted.
    • When present, a cleft is visualized in the anterior mitral valve leaflet pointing toward the interventricular septum. This is best seen in a parasternal or subcostal short-axis view. A double orifice mitral valve or single papillary muscle may be noted. Since the aortic root is not wedged between the mitral and tricuspid annuli, the aortic valve is anteriorly positioned, resulting in a long, narrow, left ventricular outflow tract with a so-called "gooseneck" appearance. Left ventricular outflow tract obstruction may occur from mitral valve tissue crossing the subaortic area.
  • Color Doppler: The direction of atrial level shunting is readily detected by color Doppler and is best seen from the long-axis subcostal imaging plane. AV valve regurgitation is quantifiable by color Doppler, particularly well seen in the apical 4-chamber view but best evaluated in multiple planes. Tricuspid regurgitation typically is mild in the absence of pulmonary hypertension, whereas mitral regurgitation may range from trivial to severe. A left ventricle to right atrium shunt should be interrogated, and lack of interventricular shunting should be confirmed. Differentiation of a primum ASD from a dilated coronary sinus is also aided by color and spectral Doppler.
  • Pulsed or continuous wave Doppler: The presence and degree of left ventricular outflow tract obstruction as well as relative pulmonary stenosis from increased flow across the pulmonary valve may be detected. The peak velocity (v) of the tricuspid regurgitant jet can be used to estimate right ventricular pressure. In the absence of right ventricular outflow tract obstruction, the pulmonary artery systolic pressure will approximate (4 X v X v) + right atrial pressure. Pulmonary artery systolic pressure higher than 25 mm Hg indicates the presence of pulmonary hypertension. Estimation of the pulmonary artery pressure by continuous wave Doppler technique is not reliable in patients with left ventricle to right atrial shunting; this high velocity jet may be misinterpreted for the tricuspid regurgitant jet, resulting in an overestimation of the pulmonary artery pressure.
  • Three-dimensional echocardiography: Although rarely used, 3-dimensional echocardiography may offer a more accurate reconstruction of the AV valve(s) and the atrial septum, providing a more complete preoperative picture for the surgeon.
  • Transesophageal echocardiography (TEE): TEE generally is reserved for anatomical definition in older patients with poor acoustic windows and for intraoperative assessment during surgical repair. Postoperative assessment is particularly helpful while weaning from cardiopulmonary bypass. Mitral stenosis, residual AV valve regurgitation, left ventricular outflow tract obstruction and residual atrial level shunting may be identified. Pulmonary artery pressure may be estimated by the peak velocity of the tricuspid regurgitation jet. Optimally, residual problems can be identified and corrected before leaving the operating room.

Other Tests

• Diagnosis of a primum ASD or a partial AV canal defect often can be made based on physical examination findings and the ECG alone. The ECG abnormalities are predominantly caused by abnormalities of the conduction system. Specifically, the AV node is displaced posteriorly and inferiorly, and atrial and/or AV nodal conduction often is delayed.
• Displacement of the AV node results in a counterclockwise loop in the frontal plane in 95% of cases. The QRS axis is outside the normal range for age, demonstrating either a left or far left axis, and Q waves are present in leads I and aVL.
• Delayed conduction through the atria or through the AV node may lead to prolongation of the PR interval (ie, a first degree AV block).
• Abnormalities in the right precordial leads are similar to those in secundum-type ASDs. The QRS pattern typically is either an rSr' or an rsR' resulting from dilation and hypertrophy of the right ventricular outflow tract caused by volume overload of the right heart.
• Right atrial enlargement is often detected, demonstrated by a peaked P wave measuring more than 2.5 mm (standard 10 mV/mm). It is best seen in leads II, III, V1, and V3R.
• With significant mitral regurgitation, left atrial enlargement may be present, demonstrated by a P wave duration of more than 0.08 sec and/or terminal and deep inversion of the P wave in lead V1 or V3R.

Procedures

• Because of the excellent information generally provided by echocardiography, cardiac catheterization is rarely warranted in the diagnosis and management of partial AV canal defects. The exception is a hemodynamic evaluation in a patient with suspected pulmonary vascular obstructive disease.
• • In the hemodynamic assessment, systemic and pulmonary venous saturations are generally normal but may be somewhat low in trisomy 21 patients secondary to upper airway obstruction. A step-up in oxygen saturation is noted at the right atrial level secondary to left-to-right shunting across the atrial septum. A step-up in saturations at the right ventricular level should be notably absent. A calculated Qp:Qs ratio of 2:1 is hemodynamically significant.
  • In the hemodynamic assessment, intracardiac and pulmonary artery pressures are directly measured. Pulmonary vascular resistance is calculated, but note that results may be affected by the presence of upper airway obstruction or congestion. If significant upper airway obstruction resulting in carbon dioxide retention is present, placement of an airway or even intubation with mechanical ventilation may be required in order to get an accurate assessment of pulmonary vascular resistance. If pulmonary vascular disease is suspected or confirmed, administration of 100% oxygen or inhaled nitric oxide is warranted to assess pulmonary vascular reactivity.
• A left ventricular injection is performed to rule out ventricular level shunting, determine the degree of AV valve regurgitation, and assess the left ventricular outflow tract for evidence of obstruction. A right upper pulmonary vein contrast injection allows visualization of the ostium primum ASD and assesses for additional ASDs. A right ventricular injection delineates the right ventricular outflow tract and pulmonary arteries. Aortic or pulmonary artery injections may be warranted if patent ductus arteriosus, coarctation of the aorta, or anomalous pulmonary venous connections are suspected. Pulmonary arterial wedge angiography may be indicated in the patient with suspected pulmonary vascular obstructive disease.

TREATMENT

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Medical Care

Catheter intervention: Unlike a ostium secundum atrial septal defect (ASD), the ostium primum form of ASD is not amenable to device closure in the cardiac catheterization laboratory. The device is unable to be adequately seated secondary to an inadequate inferior rim of atrial septal tissue and the proximity of the defect to the atrioventricular (AV) valves.

Surgical Care

Definitive management of hemodynamically significant primum ASDs and partial AV canal defects is operative repair. Timing has been debated over the years; more recent reports encourage a trend toward earlier repair.

• Patients with an isolated ostium primum ASD are typically referred for elective repair between the ages of 2 and 5 years. Occasionally, repair may be recommended at an earlier age because of significant congestive heart failure (CHF) or failure to thrive, especially if associated with significant mitral regurgitation. Repair is preferred in patients younger than 10 years to decrease the risk of persistent atrial arrhythmias or pulmonary vascular disease in later life.
• The most important consideration in timing is the incompetency of the mitral valve. Once regurgitation develops, the leaflets tend to thicken, making valve repair less successful. Most surgeons prefer referral upon presentation of all patients with documented mitral regurgitation, regardless of symptoms, because earlier age of repair has been shown to reduce the development of late mitral regurgitation. Recurrent severe mitral regurgitation may require further reconstruction of the mitral valve and/or eventual prosthetic mitral valve replacement, with its inherent anticoagulation risks.
• Adults have tolerated surgery well as a whole. Case reports of surgical repair as late as the seventh decade of life have documented successful outcomes and a notable improvement in symptoms. Pulmonary hypertension and elevated pulmonary vascular resistance do not appear to be contraindications and generally improve postoperatively. A small but significant number of adults develop long-term difficulties despite repair. These difficulties generally include atrial arrhythmias, complete heart block, subaortic stenosis, recurrent mitral regurgitation, and mitral stenosis. Long-term follow-up is requisite.
• Repair is performed through a right atrial incision. The mitral valve is repaired first through the ASD. Complete repair of the cleft is preferred, moving the sutures centrally from the annulus until chordal attachments are reached (bifoliate approach). Central regurgitant jets are addressed by placing sutures at the bases of the commissures to reduce the annulus circumference. The ASD is then closed with a pericardial patch. Successful primary suture closure of smaller primum ASDs has been reported. Less invasive surgical access has been utilized with success, including a transxiphoid approach, right submammary minithoracotomy, and ministernotomy.
• Symptomatic patients with severely malformed valves and significant preoperative mitral regurgitation often have less optimal long-term results than those patients with competent mitral valves. Results have improved with more aggressive attempts at complete closure of the mitral cleft, bearing in mind that mitral stenosis is a poorly tolerated alternative. A Japanese study noted postoperative mitral regurgitation grade II or higher at hospital discharge to be the only independent variable related to late mitral regurgitation;¹ age of operation, preoperative grade of mitral insufficiency, and method of repair of the cleft were not significant risk factors. Efforts to eliminate even mild postoperative mitral regurgitation were encouraged. Late development of moderate-to-severe mitral regurgitation warrants repeat mitral valve repair or, occasionally, mechanical valve replacement.
• Other patients at risk of reoperation include those with left ventricular outflow tract obstruction that is related to accessory mitral chordal attachments to the interventricular septum or to muscular subaortic stenosis from the inherent "gooseneck" deformity of the sprung aorta. Late mitral stenosis is a rare, late cause of reoperation, with its incidence reduced by routine use of intraoperative TEE. Severe associated defects, particularly those with aortic arch abnormalities, may also warrant further repair.
• Systolic function may be depressed in the immediate postoperative period in the patient who has a marked volume-overloaded heart preoperatively. Inotropic support is important to avoid the tendency to volume resuscitate, which may result in dilation of the mitral annulus and worsening of mitral valve regurgitation. Diuretics and judicious fluid use are beneficial, as atrial-filling pressures should be kept low. Afterload reduction may be helpful. Some patients, particularly those with trisomy 21 may develop a junctional escape rhythm postoperatively. Atrial pacing restores AV synchrony and may be beneficial to reduce AV valve insufficiency and increase cardiac output.
• Intraoperative TEE is requisite in all forms of atrioventricular canal defects. Important information is gleaned with respect to residual atrial level shunting, residual mitral regurgitation, the presence of new or worsening mitral stenosis, and potential left ventricular outflow tract obstruction. The risk-to-benefit ratio of performing TEE must be weighed in the setting of a tenuous airway, gastroesophageal abnormalities, or prior surgeries.
• Complications related to cardiopulmonary bypass and anesthesia inherent in all forms of congenital heart surgery also are potential risks.

Consultations

Consultation with a geneticist is advisable for children with trisomy 21 or any suspected chromosomal abnormality or syndrome.

Diet

For asymptomatic patients, no specific dietary recommendations are warranted. For infants or very young children with CHF, caloric supplementation may be needed. Despite pulmonary overcirculation, it generally is not advisable to fluid-restrict children with CHF who are able to feed orally. Adequate intake of fluids must be maintained in order to achieve caloric goals. Fluid intake can be balanced with diuresis to offset volume overload.

Activity

• No activity restriction is imposed on patients with small defects and without evidence of pulmonary hypertension.
• A right-to-left shunt and/or a significant pulmonary hypertension warrant restriction to low-intensity competitive sports only (class IA).
• Associated mitral regurgitation may affect exercise recommendations.
• No restriction is placed on patients in sinus rhythm with normal left ventricular size. However, mild ventricular enlargement warrants restriction of low and moderate static and dynamic competitive sports, provided systolic function is normal.

MEDICATION

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Asymptomatic patients with ostium primum atrial septal defects (ASDs) require no medications. Those with evidence of congestive heart failure (CHF) warrant diuresis, traditionally using furosemide. Afterload reduction with an ACE inhibitor may also be prudent and may aid in the management of mitral regurgitation. Digitalis was traditionally thought to improve CHF by improving cardiac output and by increasing renal blood flow, with effects primarily related to an increase in cardiac contractility. Recently, its use has generally fallen out of favor for the management of CHF.

According to 2007 American Heart association (AHA) guidelines, subacute bacterial endocarditis prophylaxis is no longer warranted preoperatively; however, antibiotics for endocarditis prophylaxis are required for 6 months postoperatively. Patients with persistent atrioventricular (AV) valve abnormalities and/or significant mitral regurgitation adjacent to suture or patch material may require long-term prophylaxis before performing procedures that may cause bacteremia. For more information, see Antibiotic Prophylactic Regimens for Endocarditis.

Drug Category: Diuretic

These agents are used to relieve volume overload and pulmonary congestion in patients with CHF.

Drug Category: Angiotensin-converting enzyme inhibitors

The primary indication for ACE inhibition for CHF and/or significant mitral regurgitation is to decrease afterload. These drugs cause a decrease in blood pressure with a concomitant decrease in systemic arteriolar resistance. Cardiac output, cardiac index, stroke volume, and stroke work increase, and the heart rate generally decreases. At the same time, renal blood flow increases and aldosterone secretion decreases, resulting in a beneficial natriuresis.

FOLLOW-UP

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Further Inpatient Care

• Low-risk patients with ostium primum atrial septal defects (ASDs) who undergo successful intracardiac repairs generally do well after surgery. Fluid restriction is liberalized and diuretic therapy weaned over a period of 3-5 days after surgery. Initially, electrolytes are closely monitored, with frequency decreasing as diuretic therapy is weaned. Patients on preoperative ACE inhibition may remain on continued therapy for a period of time. Activity and diet are advanced. A postoperative transthoracic echocardiography is generally performed before discharge or at the first postoperative visit. Care must be taken to avoid trauma to the chest for 8-12 weeks postoperatively.
• Some patients may develop a postpericardiotomy syndrome manifested by chest pain, fever, pericardial inflammation with a rub, and pericardial effusion. High-dose salicylates or nonsteroidal anti-inflammatory drugs (NSAIDs) generally improve symptoms. Hemodynamically significant effusions may require pericardiocentesis. Failure to respond to salicylates may warrant pulsed steroid therapy.

Further Outpatient Care

• Follow-up is warranted within 1-2 weeks of surgery. Vital signs, history, and physical examination are assessed, and sutures are removed. An ECG generally is obtained to rule out conduction abnormalities or arrhythmias. Chest radiography is performed to assess potential pleural or pericardial fluid and to assess heart size and pulmonary vasculature. Echocardiography may be performed as a limited study to assess function and effusion or performed on an inpatient basis as a complete postoperative study. Further outpatient care is dictated by findings from the initial visit.
• Long-term follow-up is required for all patients. Both the tricuspid and mitral valves tend to be abnormal, with the potential for deterioration with advancing age. Subacute bacterial endocarditis (SBE) prophylaxis is warranted for a minimum of 6 months postoperatively and may be prudent for life because of the abnormal atrioventricular (AV) valve tissue adjacent to suture/patch material. The development and/or progression of AV conduction abnormalities also warrant continued observation.
• In patients who have not undergone repair for isolated small-to-moderate ASDs, follow-up in clinic is usually every 6 months to a year. Exercise intolerance, increasing fatigue, palpitations, and frequent lower respiratory infections or wheezing may merit referral for earlier repair. Palpitations may need to be evaluated with a Holter monitor and ECG. Chest radiography is warranted to follow heart size and pulmonary vascular markings.
• For patients with mitral regurgitation, closer follow-up is usually necessary. In addition to the above, monitoring for progression of mitral regurgitation via physical examination, chest radiography, and echocardiography is important. It is important to time surgery before a deterioration in ventricular function if ventricular dilatation is noted. Remember that left ventricular function may appear near normal in the setting of moderate-to-severe mitral regurgitation because of the reduced afterload related to mitral regurgitation. Ventricular function may worsen significantly when a competent mitral valve is in place.

In/Out Patient Meds

• Immediately following surgery, patients generally receive intravenous (IV) diuretic therapy, traditionally furosemide. During recovery, IV preparations are changed to oral (PO) formulations and the dose is decreased. Patients are typically discharged on twice-daily dosing. Diuretics are weaned over a period of weeks to months, dictated by physical findings and roentgenographic assessment.
• Patients often require inotropic support and/or afterload reduction in the early postoperative period. Ongoing support may be warranted with oral ACE inhibition following discharge. As heart size and systolic function normalize, ACE inhibition may be reduced or discontinued in the outpatient setting. With persistent or evolving significant mitral regurgitation, afterload reduction should be continued. 

Deterrence/Prevention

• Prevention of congenital heart defects lies in continued research at the molecular genetics level. No effective preventive therapies are available at this time.

Complications

• Infective endocarditis remains both a preoperative and a postoperative complication. In a study from the Oregon Health Sciences University, the 30-year postoperative incidence of infective endocarditis was 2.8% among patients with ostium primum ASDs.²

Prognosis

• Pediatric patients with small left-to-right shunts and no significant mitral regurgitation who have not undergone surgery are at relatively low risk for complications. In these patients, adult survival is expected, but complications can develop as age advances. Untreated patients with large shunts and/or significant mitral regurgitation are at significant risk of morbidity and mortality. Death, arrhythmia, heart block, refractory heart failure, and advanced pulmonary vascular disease are the most common complications and tend to increase with advancing age. Pulmonary vascular obstructive disease may develop in a subset of patients, with patients with Down syndrome at highest risk. Prognosis is guarded, and morbidity and mortality are high regardless of therapy.
• Surgical repair generally improves life expectancy and alters the natural course of the disease. Long-term outcome of 180 children with ostium primum ASDs from 1982-1996 was assessed by the group at the Hospital for Sick Children in Toronto.³ Mean age at repair was 4.6 years, with 23 patients younger than 1 year. Absent or mild symptoms were reported in 145 patients (80%), and severe symptoms or congestive heart failure (CHF) were reported in 34 patients (20%). Follow-up ranged from 2 months to 14.5 years (mean, 6 ± 4.2 y). Early mortality occurred in 3 patients (1.6%); 2 were infants. Seventeen patients (9%) underwent reoperation (5 infants). Five patients underwent reoperation for subaortic obstruction, 12 for left AV valve regurgitation (1 required valve replacement). Actuarial survival was 98% at 10 years with no late deaths. Age and preoperative moderate-to-severe left AV valve regurgitation werepredictors of reoperation. Age at repair younger than 1 year was a predictor of death.
• A smaller study from the Oregon Health Sciences University assessed 38 consecutive patients aged 3-58 months who underwent correction between 1981 and 1997. Moderate-to-severe mitral regurgitation was present in 45% of patients, and CHF was present in 41%. Closure of the mitral cleft was performed in 92% of patients, and 28% underwent a mitral annuloplasty. The early 30-day mortality was 7.9%. A low incidence of late mitral regurgitation (0.9%) with only one late reoperation was noted on a follow-up lasting 14 years. Eighty-seven percent of patients remained asymptomatic at the last follow-up visit. The study concluded that an aggressive approach to operating at an early age is safe, effective, and yields excellent long-term results.
• The conclusions of the Oregon Health Sciences University study were supported by Italian data, which documented 93.5% (±2%) freedom from reoperation at 12.3 years for partial AV canal defects.⁴ Rates were highest in patients with preoperative AV valve regurgitation and a double orifice left AV valve and were statistically lower for patients who had early repair using a bifoliate approach. Results were attributed to the prevention of progressive mitral annular dilatation.
• The experience in Sapporo, Japan was more recently reviewed, spanning the years of 1983-2002.¹ Repair was performed in 61 patients with AV canal defects, including 7 with a transitional form. Age of operation ranged from 1 month to 62 years, with a median age of 5.3 years. All patients underwent patch closure of the ASD. The cleft was left at least partially open prior to 1995 and completely closed after 1996. The 10-year actuarial survival rate was 91%. Actuarial freedom from reoperation for mitral regurgitation was 91% at 10 years, notably decreased to 89% at 5 years and 78% at 10 years in patients with grade III or higher postoperative mitral insufficiency. Age at operation, preoperative degree of mitral regurgitation, and method of cleft repair (all previously assumed to be significant) were found not to be significant risk factors.
• The adult experience was reviewed from 1958-1990 at the Mayo Clinic, encompassing 31 patients aged 40-71 years at the time of repair;⁵ 23 had repair of the mitral cleft, 2 required mitral valve replacements, and 6 warranted mitral reoperation. Early mortality was 6%; 19 patients were followed for a mean of 14 years, with 14 reporting a sustained postoperative improvement.

Patient Education

• For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education article Palpitations.

MULTIMEDIA

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Media file 1:  ECG from a patient with a partial atrioventricular septal defect. The PR interval is mildly prolonged. Left axis deviation with Q waves in leads I and aVL are present, consistent with a counterclockwise loop in the frontal plane. Right atrial enlargement and an rsR' pattern in the right chest leads also are noted.
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Media type:  ECG

Media file 2:  Two-dimensional, apical, 4-chamber echocardiogram of a partial atrioventricular (AV) canal defect. The asterisk (*) delineates an area of dropout in the inferior atrial septum at the site of the primum atrial septal defect. The AV valves are separate but aligned at the same horizontal level, consistent with a 2-orifice common AV valve. In systole, the medial leaflets of the right- and left-sided AV valves demonstrate attachments to the crest of the interventricular septum, allowing no ventricular level shunting. RA = Right atrium; LA = Left atrium; RV = Right ventricle; LV = Left ventricle.
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Media type:  Echo

Media file 3:  Gross pathology specimen viewed from the opened left atrium and left ventricle, demonstrating a partial atrioventricular (AV) canal defect. An ostium primum atrial septal defect (ASD) marked by an asterisk (*) is visualized in the inferior aspect of the interatrial septum. An ostium secundum ASD marked by 2 asterisks (**) is also noted. The mitral valve is cleft and the leaflets are thickened and rolled, suggestive of chronic mitral regurgitation. LA = Left atrium; LV = Left ventricle; MV = Mitral valve.
	View Full Size Image
Media type:  Photo

REFERENCES

Section 10 of 10

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• References

1. Murashita T, Kubota T, Oba J, et al. Left atrioventricular valve regurgitation after repair of incomplete atrioventricular septal defect. Ann Thorac Surg. Jun 2004;77(6):2157-62. [Medline].
2. Morris CD, Reller MD, Menashe VD. Thirty-year incidence of infective endocarditis after surgery for congenital heart defect. JAMA. Feb 25 1998;279(8):599-603. [Medline].
3. Najm HK, Williams WG, Chuaratanaphong S, et al. Primum atrial septal defect in children: early results, risk factors, and freedom from reoperation. Ann Thorac Surg. Sep 1998;66(3):829-35. [Medline].
4. Michielon G, Stellin G, Rizzoli G, Milanesi O, Rubino M, Moreolo GS, et al. Left atrioventricular valve incompetence after repair of common atrioventricular canal defects. Ann Thorac Surg. Dec 1995;60(6 Suppl):S604-9. [Medline].
5. Bergin ML, Warnes CA, Tajik AJ, Danielson GK. Partial atrioventricular canal defect: long-term follow-up after initial repair in patients > or = 40 years old. J Am Coll Cardiol. Apr 1995;25(5):1189-94. [Medline].
6. Agny M, Cobanoglu A. Repair of Partial Atrioventricular Septal Defect in Children Less than Five Years of Age: Late Results. Ann Thorac Surg. May 1999;67(5):1412-4. [Medline].
7. Arky, Ronald. Physicians' Desk Reference. 52^nd ed. Montvale, NJ: Medical Economics Co Inc; 1998:784-7, 1051-1062, 1219-1221.
8. Castaneda AR, Jonas RA, Mayer JE. Atrioventricular canal defect. In: Cardiac Surgery of the Neonate and Infant. 1994:167-86.
9. Cheitlin MD, Douglas PS, Parmley WW. 26th Bethesda conference: recommendations for determining eligibility for competition in athletes with cardiovascular abnormalities. Task Force 2: acquired valvular heart disease. J Am Coll Cardiol. Oct 1994;24(4):874-80. [Medline].
10. Del Nido PJ, Bichell DP. Minimal-access surgery for congenital heart defects. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 1998;1():75-80. [Medline].
11. Garson A Jr, Bricker JT, Fisher DJ. The Science and Practice of Pediatric Cardiology. 2nd ed. Williams & Wilkins; 1998:1158-179.
12. Giamberti A, Mazzera E, Di Chiara L, Ferretti E, Pasquini L, Di Donato RM. Right submammary minithoracotomy for repair of congenital heart defects. Eur J Cardiothorac Surg. Dec 2000;18(6):678-82. [Medline].
13. Gilman AG, Goodman LS, Nies AS. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 8^th ed. 1990:721-5, 749-63, 814-839.
14. Graham TP Jr, Bricker JT, James FW, Strong WB. 26th Bethesda conference: recommendations for determining eligibility for competition in athletes with cardiovascular abnormalities. Task Force 1: congenital heart disease. J Am Coll Cardiol. Oct 1994;24(4):867-73. [Medline].
15. Kaur A, Srivastava S, Lytrivi ID, Nguyen K, Lai WW, Parness IA. Echocardiographic evaluation and surgical implications of common atrioventricular canal defects with absent or diminutive ostium primum defect. Am J Cardiol. Jun 1 2008;101(11):1648-51. [Medline].
16. Lange A, Mankad P, Walayat M, et al. Transthoracic three-dimensional echocardiography in the preoperative assessment of atrioventricular septal defect morphology. Am J Cardiol. Mar 1 2000;85(5):630-5. [Medline].
17. Marino B, Digilio MC, Toscano A, et al. Congenital heart diseases in children with Noonan syndrome: An expanded cardiac spectrum with high prevalence of atrioventricular canal. J Pediatr. Dec 1999;135(6):703-6. [Medline].
18. Perloff JK. The Clinical Recognition of Congenital Heart Disease. 4^th ed. WB Saunders; 1994:349-80.
19. Pretre R, Dave H, Kadner A, Bettex D, Turina MI. Direct closure of the septum primum in atrioventricular canal defects. J Thorac Cardiovasc Surg. Jun 2004;127(6):1678-81. [Medline].
20. Sadler TW. Langman's Medical Embryology. 5^th ed. Baltimore, MD: Williams & Wilkins; 1985:176-84.
21. Snider AR, Serwer GA, Ritter SB. Echocardiography in Pediatric Heart Disease. 2^nd ed. Harcourt Health Sciences Group; 1997:277-89.
22. Zanchetta M, Rigatelli G, Pedon L, et al. Role of intracardiac echocardiography in atrial septal abnormalities. J Interv Cardiol. Feb 2003;16(1):63-77. [Medline].

Article Last Updated: Nov 7, 2008