Ostium Primum Atrial Septal Defects 

Updated: Aug 08, 2017
Author: Shannon M Rivenes, MD; Chief Editor: Syamasundar Rao Patnana, MD 

Overview

Background

An ostium primum atrial septal defect (ASD), as seen in the image below, 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.

Gross pathology specimen viewed from the opened le 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 two 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, and MV = mitral valve.

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. Observations by Anderson and colleagues suggest that failure of growth of the vestibular spine to complete atrial septation may result in the ostium primum atrial defect.[1]

The endocardial cushions also contribute to the complete formation of two separate AV valves and the inlet interventricular septum. For this reason, ostium primum ASDs are commonly associated with malformations of these structures. 

Ostium primum ASDs are most commonly seen with a cleft in the anterior leaflet of the mitral valve, but they may occur in isolation. This is sometimes termed a partial AV canal defect or a partial AV septal defect. In this case, a five-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 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.

For patient education resources, see Heart Health Center, as well as Palpitations.

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.

Etiology

The most common association of an ostium primum atrial septal defect (ASD) is genetic, associated with trisomy 21. Well-described associations have also 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 atrioventricular (AV) canal and AV septal defects is ongoing.

A study by Rana et al implicated the TBX1 gene in the development of ostium primum ASDs, among other congenital heart defects. According to these investigators, TBX1 -null embryos are impaired in the ability of second heart field cells (multipotent cardiovascular progenitor cells) to be added to the venous pole of the heart, causing ostium primum defects, as well as abnormal development of the dorsal mesenchymal protrusion.[2]

Epidemiology

United States statistics

Ostium primum atrial septal defects (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 observed in children born to older mothers. Note the following:

  • The overall risk of congenital heart disease in patients with Down syndrome is 40-50%. Approximately 65% of those affected have some form of atrioventricular (AV) septal defect.

  • The inherited risk for children of parents who have an AV septal defect is reported as 9-14%.

Sex- and age-related demographics

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

Patients with ostium primum ASD typically present at a young age. Patients very rarely reach adulthood without surgical correction.[3, 4, 5]

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

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—and those with Down syndrome are at the highest risk.[6]  The 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. Investigators at the Hospital for Sick Children in Toront evaluated the long-term outcome of 180 children with ostium primum atrial septal defects (ASDs) from 1982 to 1996 and found that age and preoperative moderate-to-severe left atrioventricular (AV) valve regurgitation were predictors of reoperation, and age at repair younger than 1 year was a predictor of death.[7]  Three patients (1.6%) suffered early mortality, two of whom were infants. Another 17 patients (9%) underwent reoperation (five infants); five patients underwent reoperation for subaortic obstruction, and 12 for left AV valve regurgitation (one required valve replacement, 11 were repaired). Actuarial survival was 98% at 10 years with no late deaths. At 10 years, the actuarial survival was 98% and no late deaths occurred.[7]

A study from Oregon Health Sciences University that assessed 38 consecutive patients aged 3-58 months who underwent surgical correction for partial AV septal defect between 1981 and 1997 concluded that an aggressive approach to early operative intervention is safe and effective, as well as provides good long-term results.[8]  Nearly all the patients (92%) underwent closure of the mitral cleft, with 28% of these patients also requiring mitral annuloplasty. Early 30-day mortality was 7.9%. At follow-up up to 14 years, late mitral regurgitation was present in 0.9% of the patients, and there was only one late reoperation. At last follow-up, 13% of the patients were symptomatic.[8]

Data from Italian investigators supported the conclusions of Oregon Health Sciences University researchers. Michielon et al documented 93.5% (±2%) freedom from reoperation at 12.3 years for partial AV canal defects.[9]  Reintervention was highest in patients with preoperative AV valve regurgitation and a double orifice left AV valve but was statistically lower for patients who underwent early repair using a bifoliate approach. Results were attributed to the prevention of progressive mitral annular dilatation.[9]

The Mayo Clinic reviewed the need for reoperation over a 45-year period (1962-2006) and found that when reoperation was required, overall late survival was significantly reduced.[10] Ninety-six patients underwent reoperation (median interval, 10 years), with a median age at first reoperation of 26 years (range, 10 months to 71 years). Indications included left AV valve (LAVV) regurgitation in 67% of patients, subaortic stenosis in 25% of patients, right AV valve regurgitation in 22% of patients, residual ASD in 11% of patients, and other indications in 6%. Of the five early deaths, three occurred prior to 1983. No significant difference was noted in 20-year survival after LAVV repair or replacement (69% vs 55%, P = 0.20). At last follow-up (median, 5.2 years; max, 34 years), 81 of 89 late survivors had New York Heart Association (NYHA) functional class I or II.[10]

The Mayo Clinic also previously reviewed the adult experience of 31 patients aged 40-71 years at the time of repair at their institution from 1958 to 1990[11] ; 23 had repair of the mitral cleft, two required mitral valve replacements, and six warranted mitral reoperation. Early mortality was 6%; 19 patients were followed for a mean of 14 years, with 14 reporting a sustained postoperative improvement.[11]

The Pediatric Heart Network evaluated the need for reoperation for partial versus other forms of ASDs in 215 patients from seven North American centers and found that the subtype of AV septal defect was significantly associated with preoperative patient characteristics and clinical status as well as influenced the age at repair.[12] Patients were subtyped as partial (n = 60), transitional (n = 27), complete (n = 120), and canal-type ventricular septal defect (VSD) (n = 8). The highest preoperative prevalence of moderate or severe LAVV regurgitation occurred in those with transitional ASD (P = 0.01).[12]

Significant postoperative LAVV regurgitation was the most common sequela (similar prevalence across all centers at 6 months).[12] At 6-month follow-up, older age at repair was an independent predictor of moderate or severe LAVV regurgitation (P = 0.02) but not annuloplasty, subtype, or center (P >0.4). After accounting for age at repair, there was no association seen between AV septal defect subtype and postoperative LAVV regurgitation severity or growth failure at 6 months.[12]  Annuloplasty failed to decrease the postoperative prevalence of moderate or severe LAVV regurgitation at 6 months

Morbidity/mortality

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

Patients 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.[13] Rarely, patients are reported to present in the seventh decade of life.[14] Dyspnea on exertion and fatigue are the usual adult complaints, as are palpitations secondary to atrial fibrillation or flutter.

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.

As noted earlier, 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.

Complications

Infective endocarditis remains both a preoperative and a postoperative complication. In a study from Oregon Health Sciences University, the 30-year postoperative incidence of infective endocarditis was 2.8% among patients with ostium primum ASDs.[15] ​

 

 

Presentation

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 Examination

Characteristic features of trisomy 21 may be detected, such as hypotonia and hyperflexibility, and include the following:

  • 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 atrial septal defects (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 sometimes 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.

 

DDx

 

Workup

Imaging Studies

The following imaging 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 may not be seen. An increase in pulmonary vascular markings also may not be noted.

With larger left-to-right shunts, 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 dilatation, further enlarging the cardiac silhouette.

Echocardiography 

Echocardiography confirms the diagnosis of a primum ASD or partial atrioventricular (AV) canal defect. The anatomy is delineated by two-dimensional imaging, and shunt flow and AV valve regurgitation are assessed by color, pulsed, and continuous wave Doppler.[16]

Two-dimensional imaging

The apical four-chamber view and subcostal imaging planes readily demonstrate a primum ASD, showing an area of "drop-out" in the inferior atrial septum. Use care to differentiate this from the drop-out noted in the region of the coronary sinus, which may be particularly difficult to do when the coronary sinus is dilated from drainage of a persistent 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. Because 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 ultrasonography

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 four-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 and continuous wave Doppler ultrasonography

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/pulmonary arterial systolic pressure. In the absence of right ventricular outflow tract obstruction, the pulmonary artery systolic pressure will approximate (4 × v × 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, three-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

Transesophageal echocardiography (TEE) is generally reserved for anatomic 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.

  • Two-dimensional, apical, four-chamber echocardiogr Two-dimensional, apical, four-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 two-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. LA = left atrium, LV = left ventricle, RA = right atrium, and RV = right ventricle.

     

Other Tests

Electrocardiography

Diagnosis of a primum atrial septal defect (ASD) or a partial atrioventricular (AV) canal defect can often be made based on physical examination findings and the electrocardiogram (ECG) alone. The ECG abnormalities (see the image below) 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 is often delayed.

Electrocardiogram from a patient with a partial at Electrocardiogram 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 are also noted.

Note the following:

  • 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 is typically either an rSr' or an rsR' resulting from dilatation 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 longer than 0.08 sec and/or terminal and deep inversion of the P wave in lead V1 or V3R.

Procedures

Cardiac catherization

Because of the excellent information generally provided by echocardiography, cardiac catheterization is rarely warranted in the diagnosis and management of partial atrioventricular (AV) canal defects. The exception is a hemodynamic evaluation in a patient with suspected pulmonary vascular obstructive disease. Note the following:

  • 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 owing to left-to-right shunting across the atrial septum. A step-up in saturations at the right ventricular level should be notably absent. However, a step-up at the right ventricular level may be seen because of better mixing distally. A calculated pulmonary-to-systemic flow ratio (Qp:Qs) 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 the 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 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.

Contrast injection

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. Goose-neck deformity of the left ventricular outflow tract is classic for endocardial septal defects, including ostium primum atrial septal defects (ASDs).

A right upper pulmonary vein contrast injection allows visualization of the ostium primum ASD and assessment for additional ASDs. A right ventricular injection delineates the right ventricular outflow tract and pulmonary arteries, but it is not necessary routinely.

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 patients with suspected pulmonary vascular obstructive disease.

 

Treatment

Approach Considerations

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 owing to an inadequate inferior rim of atrial septal tissue and the proximity of the defect to the atrioventricular (AV) valves. In addition, the cleft in the mitral valve can’t be addressed by catheter intervention.

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

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

Medical Care

Low-risk patients with ostium primum atrial septal defects (ASDs) who undergo successful intracardiac repairs generally do well after surgery. 

Immediately following surgery, patients usually receive intravenous (IV) diuretic therapy, traditionally furosemide. Fluid restriction is liberalized and diuretic therapy weaned over a  period of 3-5 days postoperatively. Initially, electrolyte levels are closely monitored, with the frequency decreasing as diuretic therapy is weaned. During recovery, IV preparations are changed to oral (PO) formulations and the doses are 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. Patients on preoperative angiotensin-converting enzyme (ACE) inhibition may remain on continued therapy for a period. 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.

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.

Diet and activity

For asymptomatic patients, no specific dietary recommendations are warranted. For infants or very young children with congestive heart failure (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 to achieve caloric goals. Fluid intake can be balanced with diuresis to offset volume overload.

No activity restriction is imposed on patients with small defects and without evidence of pulmonary hypertension. However, a right-to-left shunt and/or a significant pulmonary hypertension warrant(s) restriction to low-intensity competitive sports only (class IA). Note that 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 the systolic function is normal.

Surgical Care

Definitive management of hemodynamically significant primum atrial septal defects (ASDs) and partial atrioventricular (AV) canal defects is operative repair. Its 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 of the repair 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 an 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, ministernotomy, and axillary approach.[17]

It is important to recognize that mitral valve cleft should be addressed at the time of surgery, irrespective of the degree of preoperative mitral insufficiency.

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; age at operation, preoperative grade of mitral insufficiency, and method of the cleft repair were not significant risk factors.[18]  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 transesophageal echocardiography (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 patients with a marked preoperative volume-overloaded heart. Inotropic support is important to avoid the tendency to volume resuscitate, which may result in dilatation 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 provide benefit in reducing AV valve insufficiency and increasing cardiac output.

Intraoperative TEE is requisite in all forms of AV 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 are inherent in all forms of congenital heart surgery and, thus, are also potential risks.

Long-Term Monitoring

Follow-up is warranted within 1-2 weeks of surgery. At that time, assess the patient's vital signs, history, and physical examination, and remove sutures. In general, obtain an electrocardiogram (ECG) to rule out conduction abnormalities or arrhythmias. Perform chest radiography to evaluate potential pleural or pericardial fluid and to assess the heart size and pulmonary vasculature. Echocardiography may be performed as a limited study to assess function and effusion or 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. Postoperative prophylaxis against subacute bacterial endocarditis (SBE) is warranted for a minimum of 6 months, and it 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 atrial septal defects (ASDs), follow-up in a clinic is usually every 6 months to 1 year. The presence of 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 essential to time surgery before a deterioration in ventricular function if ventricular dilatation is noted. Keep in mind 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.

 

Medication

Medication Summary

Asymptomatic patients with ostium primum atrial septal defects (ASDs) do not require medications. Those with evidence of congestive heart failure (CHF) warrant diuresis, traditionally using furosemide. Afterload reduction with an angiotensin-converting enzyme (ACE) inhibitor may also be prudent and may aid in the management of mitral regurgitation. Digitalis was previously thought to improve CHF by improving cardiac output and by increasing renal blood flow, with effects primarily related to an increase in cardiac contractility. However, its use for the management of CHF has generally fallen out of favor.

In 2007, the American Heart association (AHA) guidelines changed its recommendations to no longer warrant preoperative subacute bacterial endocarditis prophylaxis[19, 20, 21] ; however, antibiotics for endocarditis prophylaxis are required for 6 months postoperatively.[19, 20] Patients with persistent atrioventricular (AV) valve abnormalities and/or significant mitral regurgitation adjacent to suture or patch material may require long-term prophylaxis before undergoing procedures that may cause bacteremia.

Diuretic

Class Summary

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

Furosemide (Lasix)

Loop diuretic, acting on the thick ascending limb of the loop of Henle. It increases renal blood flow without increasing filtration rate. Its onset of action generally is within 1 h. Potassium, sodium, calcium, and magnesium excretion is increased. Titratable acid and ammonium excretion also are increased, which, in combination with a contraction of extracellular fluid volume, results in a metabolic alkalosis.

Angiotensin-converting enzyme inhibitors

Class Summary

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.

Captopril (Capoten)

Rapidly absorbed, but bioavailability is significantly reduced with food intake. It achieves a peak concentration in an hour and has a short half-life. The drug is cleared by the kidney. Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion.