eMedicine Specialties > Cardiology > Congenital Heart Disease in the Adult

Atrial Septal Defect

Bekir Hasan Melek, MD, Assistant Professor of Clinical Medicine, Department of Medicine, Section of Cardiology, Tulane University School of Medicine
James V Talano, MD, MM, FACC, Director of Cardiovascular Medicine, SWICFT Institute; Jeffrey C Milliken, MD, Chief, Division of Cardiothoracic Surgery, University of California at Irvine Medical Center; Clinical Professor, Department of Surgery, University of California at Irvine School of Medicine; Peter B Smulowitz, BA, University of California at Irvine School of Medicine

Updated: Jul 11, 2006

Introduction

History of the Procedure

F. John Lewis successfully performed the first open heart closure of an atrial septal defect (ASD) on September 5, 1952, in Minneapolis, Minnesota. He used direct vision with hypothermia and inflow occlusion. Subsequent development of the cardiopulmonary bypass machine widely expanded the treatment of this and other congenital heart diseases more complex than ASD and spurred rapid expansion in the field of thoracic surgery.

In terms of establishing normal anatomy and eliminating sequelae, early repair of ASDs may well be the most successful application of open heart surgery of any congenital heart lesion. For nearly 50 years, surgical closure of ASDs has been almost exclusively accomplished with direct suture or patch repair on cardiopulmonary bypass. In recent years, use of a variety of transcatheter occlusion devices inserted through the defect in the septum has become common. For some patients, these devices have become an alternative to surgical procedures for the repair of the ostium secundum ASD. Surgical innovators have simultaneously developed minimally invasive techniques involving small incisions and even robotically assisted thoracoscopic approaches.

Problem

ASD is one of the most commonly recognized congenital cardiac anomalies in adults, but it is rarely diagnosed and even less commonly results in disability in infants. It is characterized by a defect in the interatrial septum that allows pulmonary venous return to pass from the left to the right atrium, resulting in right atrial and right ventricular chamber dilation, the extent of which depends on the size of the shunt. Patients, especially those with small or isolated defects, are usually asymptomatic through the first 3 decades of life, though more than 70% become impaired by the fifth decade. Early surgical closure of most types of ASD is recommended.

Frequency

ASD accounts for 10% of all congenital heart disease and for 22-40% of congenital heart disease in adults.

Ostium secundum defect is the most common type and accounts for 60-70% of all cases, for approximately 7% of all congenital cardiac defects and for 30-40% of all congenital heart disease in patients over age 40.

Ostium primum type accounts for 15-20% of all ASDs.

Sinus venosus type ASDs are seen in 5-15% of all patients.

Sex: ASD occurs with a female-to-male ratio of approximately 2:1.

Age: Patients with ASD are usually asymptomatic through infancy and childhood. Symptoms become more common with advancing age. By the age of 40 years, 90% of untreated patients have symptoms of exertional dyspnea, fatigue, palpitation, or sustained arrhythmia.

Etiology

ASD is a congenital cardiac disorder caused by the spontaneous malformation of the atrial septum.

• Ostium secundum ASDs: incomplete adhesion between the original flap of the valve of the foramen ovale and the septum secundum after birth causes the probe-patent foramen ovale. The patent foramen ovale usually results from abnormal resorption of the septum primum during the formation of the foramen secundum. Resorption in abnormal locations causes a fenestrated or netlike septum primum. Excessive resorption of the septum primum results in a short septum primum that does not close the foramen ovale. An abnormally large foramen ovale can occur as a result of defective development of the septum secundum. The normal septum primum does not close this type of abnormal foramen ovale at birth. A combination of excessive resorption of the septum primum and a large foramen ovale produces a large ostium secundum ASD. About 10-20% of patients have associated mitral valve prolapse.
• Ostium primum ASDs: These defects are caused by incomplete fusion of septum primum with endocardial cushion. The defect lies immediately adjacent to the atrioventricular (AV) valves, either of which may be deformed and incompetent. In most cases, only the anterior or septal leaflet of the mitral valve is displaced, and it is commonly cleft. The tricuspid valve is usually not involved. The defect is often large.
• Sinus venosus ASDs: Abnormal fusion between the embryologic sinus venosus and the atrium causes these defects. In most cases, the defect lies superior, high in the atrial septum near the entry of superior vena cava, and it is associated with partial anomalous drainage of the right superior pulmonary vein. The relatively uncommon inferior type is associated with partial anomalous drainage of the right inferior pulmonary vein. Anomalous drainage can be into the right atrium, the superior vena cava, or the inferior vena cava.
• Coronary sinus defect: Coronary sinus defect is characterized by unroofed coronary sinus and persistent left superior vena cava that drains into the left atrium. A dilated coronary sinus often suggests this defect. The diagnosis can be made by injecting contrast agent into left upper extremity; coronary sinus opacification precedes right atrial opacification.
• Other ASDs
  • Certain ASDs may occur on a familial basis. Holt-Oram syndrome is characterized by an autosomal dominant pattern of inheritance, deformities of the upper limbs (most often, absent or hypoplastic radii), and ECG abnormalities, such as right bundle-branch block or first-degree AV block. A single gene defect with a penetrance of nearly 100% is the apparent cause of Holt-Oram syndrome. Approximately 40% of cases are due to new mutations; the rest are inherited from a parent.
  • Another example is the syndrome of familial ASD with prolonged AV conduction. This syndrome is an autosomal dominant trait with a high degree of penetrance but no associated skeletal abnormalities.
  • Both Holt-Oram syndrome and familial ASD with prolonged AV conduction affect nearly 50% of first-degree relatives of the patient.

Pathophysiology

The magnitude of the left-to-right shunt depends on defect size and relative compliance of the ventricles and the relative resistance in both pulmonary and systemic circulation. In patients with small ASDs, left atrial pressure may exceed right atrial pressure by several millimeters of mercury, whereas mean atrial pressures are nearly identical if the defect is large. Left-to-right shunting occurs predominantly in late ventricular systole and in early diastole, with some augmentation during atrial contraction. The shunt results in diastolic overload of the right ventricle and increased pulmonary blood flow.

Resistance in the pulmonary vascular is commonly normal or low in older infants or children with ASD, and the volume load is usually well tolerated though pulmonary blood flow may be 2-5 times more than systemic blood flow. A transient and small right-to-left shunt that occurs with the onset of left ventricular contraction, especially during respiratory periods of decreasing intrathoracic pressure, is common in patients with ostium secundum ASD, even in absence of pulmonary hypertension.

Pregnancy can increase shunt volume and lead to congestive heart failure (CHF). Pulmonary artery pressure usually remains normal and well tolerated.

A chronic left-to-right shunt fixes pulmonary hypertension and eventually reverses the direction of the shunt, resulting in Eisenmenger syndrome.

Presentation

History:

• The malformation often goes unnoticed for decades because symptoms may be absent and because physical signs are subtle.
• Even isolated defects of moderate-to-large size do not generally cause symptoms in infancy and childhood. Occasional cases of CHF and recurrent pneumonia are seen in infancy. Most children are asymptomatic, though some may have easy fatigability and exertional dyspnea. They may be somewhat underdeveloped and prone to respiratory infections. In childhood, the diagnosis is often considered after a heart murmur is detected on routine physical examination or after an abnormal finding is observed on chest radiographs or ECGs.
• Symptoms usually take 30-40 years to develop. They are mainly consequences of pulmonary hypertension, atrial tachyarrhythmias, and, sometimes, associated mitral valve disease. Virtually all patients with ostium secundum ASD who survive beyond the 6th decade are symptomatic.
• Clinical deterioration in older patients occurs by means of several mechanisms.
  • First, an age-related decrease in left ventricular distensibility augments the left-to-right shunt.
  • Second, atrial arrhythmias, especially atrial fibrillation, but also atrial flutter or paroxysmal atrial tachycardia, increase in frequency after the 4th decade and precipitate right ventricular failure.
  • Third, most symptomatic adults older than 40 years of age have mild-to-moderate pulmonary hypertension in the presence of a persistent large left-to-right shunt; therefore, the aging right ventricle is burdened by pressure and volume overload.
• Another mechanism for symptoms is related to clinically significant mitral regurgitation that is seen in about 15% of patients. Its incidence, extent and degree of dysfunction increases with age. These abnormalities have been attributed mainly to the effects of left ventricular cavity deformity on mitral apparatus.
• Most common presenting symptom is dyspnea and easy fatigability. Other symptoms include palpitations, syncope, and CHF.
• The development of palpitations related to atrial arrhythmias is the most common symptom in adults.

Physical:

• The findings depend on the hemodynamic consequences of the left-to-right shunt, which in turn depends on the size of the defect, the diastolic properties of both ventricles, and the relative impedance in pulmonary and systemic circulation.
• Blood flow across the ASD does not cause a murmur at the site of the shunt because no substantial pressure gradient is present between the atria.
• The patient often has a hyperdynamic right ventricular impulse due to increased diastolic filling and a large stroke volume.
• Palpable pulsation of the pulmonary artery and an ejection click can be detected because of a dilated pulmonary artery.
• S₁ is typically split, and the second component may be increased in intensity, reflecting forceful right ventricular contraction and delayed closure of the tricuspid leaflets.
• ASDs with moderate-to-large left-to-right shunts produce a pulmonary outflow murmur that begins shortly after the S₁, peaks in early-to-mid systole and that ends before the S₂. An associated thrill indicates a large shunt or pulmonic stenosis.
• S₂ is widely split and fixed because of greatly reduced respiratory variation due to delayed pulmonic valve closure (seen only if pulmonary artery pressure is normal and pulmonary vascular resistance is low). This characteristic abnormality is found in almost all patients with large left-to-right shunts.
• Increased right ventricular stroke volume across the pulmonary outflow tract and valve creates a crescendo-decrescendo midsystolic (ejection) murmur. This murmur is usually grade 2 or 3 and is heard in the second interspace at the left sternal border.
• Patients with large left-to-right shunts often have a rumbling middiastolic murmur at the lower left sternal border because of increased flow across the tricuspid valve.
• In patients with an ostium primum defect and an associated cleft mitral valve, an apical pansystolic murmur of mitral regurgitation may be present. This murmur can be heard along the left sternal border as the jet is directed into the right atrium through the low ASD. Mitral regurgitation murmur can also be heard if valve prolapse is present.
• In patients who develop pulmonary hypertension and right ventricular hypertrophy, a right ventricular S₄ may be present. In such cases, the midsystolic pulmonic murmur is softer and shorter, the tricuspid flow murmur is not present, the splitting of S₂ is narrowed with accentuated pulmonic component and murmur of pulmonic regurgitation may become apparent.
• In case of shunt reversal (Eisenmenger syndrome), cyanosis and clubbing may become evident.
• Auscultatory findings of the ASD may resemble those of mild valvular, or infundibular, pulmonic stenosis and idiopathic dilatation of the pulmonary artery. These disorders all manifest as a midsystolic (ejection) murmur, but they differ from the ASD by movement of the S₂ with respiration, a pulmonary ejection click, or the absence of a tricuspid flow murmur.

Indications

The decision to repair any kind of ASD is based on clinical and echocardiographic information, including the size and location of the ASD, the magnitude and hemodynamic impact of the left-to-right shunt, and the presence and degree of pulmonary hypertension. Elective closure is advised for all ASDs with echocardiographic evidence of right ventricular overload or with a clinically significant shunt (pulmonary vascular resistance [Qp]–to–systemic vascular resistance [Qs] ratio >1.5). Lack of symptoms is not a contraindication for repair. In patients with interatrial septal aneurysm and secundum ASD, spontaneous closure may occur, and patients may be followed up relatively conservatively for a period before repair is advised.

For both children and adults, surgical mortality rates for uncomplicated secundum ASDs are approximately 1-3%. Because of the risk of paradoxical embolization, closure may be recommended, even for patients with small shunts in whom the incidence of CHF, pulmonary hypertension, and arrhythmias is low. However, such closure remains controversial because patients with small defects generally have a good prognosis, and the risk of cardiopulmonary bypass may not be warranted. The benefit of catheter closure of small secundum defects remains to be determined.

Long-term prevention of death and complications is best achieved when the ASD is closed before the age of 25 years and when the systolic pressure in the main pulmonary artery is less than 40 mm Hg. Even in elderly patients with large shunts, surgical closure can be performed at low risk and with good results in reducing symptoms.

Contraindications

Closure of an ASD is not recommended in patients who have severe pulmonary hypertension or severe pulmonary vascular disease (Qp-Qs ratio 0.7 or above) without a clinically significant shunt or in patients who have a reversed shunt with at-rest arterial oxygen saturations of <90% with little or no residual left-to-right shunt. In addition to the high surgical mortality and morbidity risk, closure of the defect may worsen the prognosis. Whether patients whose condition is diagnosed well in the sixth decade of life benefit from surgical closure remains of controversial.

Workup

Laboratory Studies

• No specific laboratory blood tests are indicated in the workup of ASDs.
• The following routine laboratory studies should be performed in patients undergoing surgical correction of ASD under general anesthesia:
  • CBC count
  • Determination of electrolyte levels
  • Coagulation studies (prothrombin time [PT], activated partial thromboplastin time [aPTT])
  • Routine urinalysis

Imaging Studies

• Chest radiography
  • In the presence of a clinically significant left-to-right shunt, chest radiographs most often show cardiomegaly because of dilatation of the right atrium and right ventricular chamber.
  • The pulmonary artery is prominent, and pulmonary vascular markings are increased in the lung fields.
  • Left atrial enlargement is rare only if clinically significant mitral regurgitation or atrial fibrillation is present. On occasion, proximal dilatation of the superior vena cava can be seen in sinus venosus defect.
• Transthoracic echocardiography
  • Transthoracic echocardiography has been suggested as the initial investigation in patients thought to have an ASD. An uncertain diagnosis can be clarified with transthoracic 2-dimensional echocardiography, which provides direct noninvasive visualization of most types of ASDs, especially from the subcostal view. One exception is the diagnosis of sinus venosus defects, for which transesophageal echocardiography (TEE) is the procedure of choice.
  • Two-dimensional echocardiography is also useful in demonstrating enlargement of the right atrium, right ventricle, and pulmonary arteries, as well as other associated abnormalities (eg, single papillary muscle, left ventricular hypoplasia and aortic coarctation).
  • In young patients with good echocardiographic windows, anomalies of systemic venous connection should be sought. These can be clearly identified by 2-dimensional imaging.
  • Real-time echocardiography is helpful for identifying additional abnormalities, such as mitral valve prolapse and a double-orifice mitral valve (seen in 3% of patients with ostium primum defect).
  • Doppler echocardiography may be helpful in demonstrating flow across the atrial septum. It typically shows biphasic (systolic and diastolic) pattern with a small right-to-left shunt at the beginning of systole. Largest shunt flow occurs in late systole.
  • Two-dimensional color Doppler studies are usually required for a reliable assessment of pulmonary venous connections.
  • Transthoracic echocardiography may be suboptimal in some patients with poor echocardiographic windows. In such patients, TEE can provide excellent definition of the atrial septum. TEE is also useful in guiding device placement during catheter ASD occlusion procedures and in providing immediate intraoperative assurance that defect closure is accomplished.
  • Continuous-wave Doppler echocardiography is valuable for estimating right ventricular–pulmonary arterial systolic pressure when a tricuspid regurgitant jet is present. This technique is also useful in estimating the pressure gradient across the atrial septum in patients with left atrial hypertension and restrictive atrial septal effects and in evaluating patients for obstruction to pulmonary venous return.
  • Contrast echocardiography can provide additional confirmation. A right-to-left shunt can be detected by visualizing microcavitation bubbles in the left atrium and the left ventricle. A left-to-right shunt can be detected as a negative contrast washout effect in the right atrium.
• MRI: MRI has successfully been used to identify the size and position of ASDs, facilitating appropriate referral for catheter occlusion or surgery.

Other Tests

• Electrocardiography
  • ECG usually shows a normal sinus rhythm unless an atrial arrhythmia has developed. Characteristic findings in patients with secundum ASD are right-axis deviation and an rSR' pattern in V₁ or a right bundle-branch block (which represents delayed posterobasal activation of the ventricular septum and enlargement of the right ventricular outflow tract).
  • Left-axis deviation and an rSR' pattern in V₁ or a right bundle-branch block suggest an ostium primum defect or an ostium secundum defect with associated mitral valve prolapse.
  • Left-axis deviation and negative P wave in lead III suggest sinus venosus defect.
  • Increasing pulmonary hypertension can cause loss of the rSR' pattern in V₁ and a tall monophasic R wave with a deeply inverted T wave.
• A prolonged P-R interval is most common in ostium primum and is due to left atrial enlargement and an increased distance for internodal conduction produced by the defect itself. Displacement of the AV node in a posteroinferior direction in some patients or an enlarged right atrium has also been reported.

Diagnostic Procedures

• When noninvasive techniques demonstrate the presence of an uncomplicated ASD in a child, routine cardiac catheterization is unnecessary.
• Cardiac catheterization may be useful if the clinical data are inconsistent, if clinically significant pulmonary hypertension or associated malformations are suspected, or if concurrent CAD must be assessed in patients older than 40 years.
• The diagnosis of ASD may be confirmed by directly passing the catheter through the defect.
  • Serial oxygen saturation measurements may be used to estimate the magnitude of the shunt
  • In young patients, right heart pressures are often normal despite a large shunt.
  • If high oxygen saturation is present in the superior vena cava or if the catheter enters pulmonary vein directly from the right atrium, sinus venosus type is likely.
  • Partial anomalous pulmonary venous return is usually associated with sinus venosus defect, but it may also accompany the ostium secundum type.

Treatment

Medical Therapy

ASD is a surgical disorder, and no specific medical therapy is available. However, patients with CHF may require digitalis and diuretics, and those with arrhythmias may require specific drug therapy.

Surgical Therapy

Criterion standard

The criterion standard in the treatment of ASD is direct closure of the defect by using an open approach with extracorporeal support. John Gibbon performed the first successful ASD closure by applying this method in 1953. Surgical techniques and equipment have since improved to the point that the mortality rate from this repair approaches zero.

In the usual procedure, a median sternotomy incision is made, and the sternum is split in the midline. Direct arterial and double venous (superior vena cava and inferior vena cava) cannulation are performed. By applying cardiopulmonary bypass, the aorta is clamped, and the heart is arrested with a cardioplegia solution. The caval snares are tightened, and the right atrium is opened. Most secundum defects can be closed by using a direct continuous suture of 3-0 or 4-0 polypropylene (Prolene).

Caution must be taken when large defects are directly closed because this closure can distort the atrium. Large defects that rise superiorly can distort the aortic anulus if closed directly. These ASDs are also best closed by using autologous pericardium or synthetic patches made of polyester polymer (Dacron) or polytetrafluoroethylene (PTFE). Care must be taken to completely remove any air or debris from the left atrium and ventricle before cardiopulmonary bypass is discontinued. Temporary pacing wires are left in place on the right ventricle before the chest is closed over the drains.

In patients with ostium primum defects, surgical closure is relatively complicated. The patch must be attached to the septum at the juncture of the mitral and tricuspid valves. Mitral valve repair, including closure of the cleft mitral leaflet and, possibly annuloplasty, may be necessary to correct or prevent mitral insufficiency. In rare cases, mitral valve replacement may be required.

In sinus venosus defects, partial anomalous pulmonary venous return is typical. One or more of the pulmonary veins primarily drains into the right atrium. The ASD must be patched in such a way as to ensure that the anomalous pulmonary venous drainage is diverted into the left atrium. This patching may be simple or complex, depending on where the anomalous drainage enters. Many innovative techniques have been developed to redirect pulmonary flow, and the surgeon should be familiar with several approaches. Pulmonary venous return must not be compromised with the redirection because this invariably causes localized venous hypertension and pulmonary complications.

Minimally invasive approaches

In recent years, minimally invasive approaches to the repair of ASD have garnered significant interest. In most cases, the size of the incision is simply decreased with different approaches to cardiopulmonary bypass. Examples include partial or full submammary skin incision, hemisternotomy, and limited thoracotomy. The goal is to improve better cosmetic results because these approaches are not associated with decreased morbidity or mortality.

Percutaneous transcatheter closure

In recent times, ASDs have been closed by using a variety of catheter-implanted occlusion devices rather than by direct surgical closure with cardiopulmonary bypass. These devices are placed through a femoral venous approach and are deployed like an umbrella to seal the septal defect. These devices work best for small, centrally located secundum defects. Although surgical closure is associated with low morbidity and mortality and excellent long-term results, sternotomy and cardiopulmonary bypass are required.

Drs King and Mills performed the first transcatheter closure of a secundum ASD in the mid-1970s. William Rashkind pioneered the development of percutaneous ASD closure technique in late 1970s. Jim Lock developed the clamshell method in 1989. Around the same time, Sideris started clinical trials with buttoned device.

Although many devices have been studied, over the last few years, 4 major devices have become available: CardioSEAL (NMT Medical, Inc, Boston, Mass), Amplatzer septal occluder (ASO) (AGA Medical Corporation, Golden Valley, Minn), HELEX septal occluder (Gore Medical [WL Gore & Associates, Inc], Flagstaff, Ariz), and Sideris patch (Custom Medical Devices, Amarillo, Tex). The ASO is currently the most widely used device because it is easy to implant and because it allows closure of large orifices with excellent success rates in most cases. It was first used in human in 1995. Selection of a particular device is difficult because no randomized trials have been conducted. Furthermore, devices are currently not amenable to percutaneous closure of ostium primum and sinus venosus defects.

With this technique, the static diameter of the defect is first assessed by using TEE first, and the stretched diameter is then measured with a sizing balloon to select the proper diameter of the device. The margins of the orifice must be wide enough to accommodate the edges of the closing device. TEE has been the mainstream technique for device sizing, positioning, and deployment, but it can cause discomfort. In addition, airway protection and general anesthesia are required. Intracardiac echocardiography was recently found to be superior for the same purposes and has largely replaced TEE.

Transcatheter closure of ASDs is now established practice at most cardiac centers. It is proven safe in experienced hands, it is cost-effective, and it favorably compares to surgical closure with successful implantation rates of >96%. One group compared the surgical technique and percutaneous transcatheter technique for ASD closure in 91 children. Closure rates were similar (95% in the surgery group, 97% in the percutaneous group); however, the transcatheter group had fewer complications, shortened hospitalization, and reduced need for blood products.

Furthermore, transcatheter appears to have additional benefits regarding hemodynamic improvement compared with surgery. In 1 study, transcatheter closure with ASO improved the left atrial volume index, the left ventricular myocardial performance index, and the right ventricular myocardial performance index. The last was unimpressive after surgery, possibly because of cardiopulmonary bypass.

Another group compared atrial function in 45 patients with mean age of 9 years after surgery and after percutaneous closure by using strain-rate imaging. They found that both atrial functions were preserved after transcatheter closure, whereas the same was not seen after surgery. A potential explanation was that an atriotomy scar might have negatively influenced right atrial functio, whereas perioperative hypoxia o intraoperative myocardial damage might have altered the deformation properties of the left atrium.

Postoperative Details

Postoperative management after ASD repair is usually standard. Patients are expected to be awake and are extubated shortly after the operation. Drainage tubes are removed from the chest the first morning after surgery, and, except when rhythm problems occur, the pacing wires are removed shortly thereafter. Most patients can eat and ambulate without difficulty on the first or second postoperative day, and most are discharged by the third or fourth postoperative day. After transcatheter occlusion, 6 months of treatment with aspirin with or without clopidogrel is recommended to prevent thrombus formation.

Follow-up

Surgical follow-up care is maintained until the patient's wounds are completely healed and normal activities are resumed. This period rarely exceeds 1-2 months. All complications must be clearly resolved before the patient is discharged from surgical care.

Obtain at least 1 follow-up echocardiogram to confirm complete closure of the ASD. A pediatric cardiologist should continue patient care to monitor for recurrence of the shunt and to ensure that the patient has returned to normal activities and cardiac function. For most patients, a yearly appointment after the immediate postoperative period is adequate.

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

Complications

Surgery may be associated with a long-term risk of atrial fibrillation or flutter. The risk of infective endocarditis is highest during the first 6 months after surgery. The following complications are also associated with ASDs:

• Congestive heart failure
• Arrhythmias
• Pulmonary hypertension
• Cyanosis
• Paradoxical embolization
• Stroke
• Infective endocarditis

The following complications are associated with the use of transcatheter occlusion devices:

• Device embolization and malpositioning: The incidence significantly varies among devices and is related to operator experience and appropriate case selection. With experienced clinicians, the incidence is <1%. Device embolization and malpositioning happens as a result of inadequate sizing of the defect or incorrect device placement.
• Postimplantation arrhythmias: The incidence is 1-4% and varies from first- to third-degree AV block and atrial fibrillation. These arrhythmias are usually short-lived and do not require medical treatment. Patients who develop complete heart block are typically hemodynamically stable and do not require pacing. Complete heart block is most common with ASO and has been transient in all cases. The incidence of arrhythmia appears to be related to the size of the device.
• Thrombus formation: A study of 1000 patients was done to investigate the incidence of thrombus by performing TEE at 4 weeks and 6 months after the procedure. The overall incidence was 1.2%; 70% were found at 4 weeks. The lowest incidence was with ASO. Thromboembolic events were seen in 20% of patients with thrombus. In 80-85%, thrombus resolved with heparin and warfarin. Risk factors for thrombogenesis on the device were the type of device, postprocedural atrial fibrillation, incomplete neoendothelialization of the surface of the device, insufficient antithrombotic treatment, and previously undiagnosed hypercoagulability disorders (including aspirin resistance and persistent interatrial septal aneurysm). For prophylaxis, aspirin given for 6 months is a common practice. When combined with clopidogrel, no thrombus was noted at 4 weeks and 6 months in 1 study of 37 patients.
• Cardiac perforation: the incidence is 0.1-0.4% for various devices. Oversizing of the device and deficient anterosuperior rims are risk factors for perforation. Technique-related perforation during the procedure is amenable to intervention. Device-related perforations occur after technically adequate procedure in approximately 70% of patients after hospital discharge. A retrospective review of 24 patients revealed that all presented with chest pain, shortness of breath, hemodynamic collapse or sudden death. About 76% were female patients, and 70% of the perforations were late. If pericardial effusion is present on predischarge echocardiography, hospitalize the patient for 24-48 hours of observation and follow-up echocardiography.
• Device erosion: Erosion of septal occluder devices occurs in 0.1-0.15% of implants. Nearly all erosions occur at the dome of atria near the aortic root. Risk factors are a deficient aortic rim and/or superior rim and use of an oversized device. Aortic – right atrial fistula may be the consequence. Although device erosion is rare, the mortality rate is 10%.
• Increased levels of cardiac troponin I: Transcatheter closure induces minor myocardial lesions, the extent of which depends on the size of the ASO. The patient's age is not a factor.
• Residual shunts: As many as 25% of patients may have a residual shunt after the procedure; >90% of such residua are small. During follow-up, the incidence drops to 10% at 1 month, 1% at 1 year, and 0% at 3 years.
• Relatively common complications: Other complications include pericardial effusion, transient ischemic attack, and sudden death.

Outcome and Prognosis

Natural history

Although life expectancy is not normal, patients generally survive into adulthood without surgical or percutaneous intervention, and many patients live to advanced age. However, natural survival beyond age 40-50 years <50%, and the attrition rate after 40 years of age is about 6% per year. Advanced pulmonary hypertension seldom occurs before the third decade. Late complications are stroke and atrial fibrillation.

Postsurgical prognosis

The mortality rate of surgical repair is <1% for patients younger than 45 years without heart failure and who have systolic pulmonary artery pressures <60 mm Hg. The morbidity rate is low. The surgical mortality rate increases with increasing age and pulmonary artery pressures.

Surgical repair should be considered for all patients with uncomplicated ASDs with a clinically significant left-to-right shunt. Such repair is ideally done at 2-4 years of age. Early surgical repair is considered in a few infants and young children with clinically significant symptoms or CHF. Surgery before the age of 25 years results in a 30-year survival rate comparable to that of age- and sex-matched control subjects. However, at 25-40 years of age, surgical survival is reduced, though not significantly if pulmonary artery pressures are normal. If pulmonary artery systolic pressure is >40 mm Hg, late survival is 50% less than control rates, though life expectancy in surgically treated older patients is better than that of medically treated patients. Even in select patients older than 60 years with no serious comorbidities, ASDs should be closed as early as possible if an indication is present because surgery improves symptoms–at least in the short term–regardless of pulmonaryartery pressure or

functional class, as long as the left-to-right shunt remains large. Although surgical closure of ASDs in adulthood is associated with a significant mortality benefit, its benefit is limited in preventing atrial arrhythmias. The patient's age at the time of closure is the most important predictor of the development of atrial arrhythmia.

Surgery for sinus venosus ASD is also associated with low morbidity and mortality, and postoperative subjective clinical improvement occurs irrespective of the patient's age at surgery. However, in contrast to ostium secundum ASD, surgery for sinus venosus defect is relatively complex and poses the risks of stenosis of the superior vena cava or pulmonary veins, residual shunting, and dysfunction of the sinoatrial node.

In childhood, right ventricular dimensions decrease, often strikingly, after surgery. However, when adults undergo surgery, the dimensions remain abnormal in approximately 80% of patients. If right ventricular failure and tricuspid regurgitation are present before surgery, late postoperative right atrial and ventricular enlargement is typical, and right ventricular systolic function seldom normalizes. Patients in this situation improve, but they usually remain symptomatic, and their preoperative pulmonary vascular resistance influences their long-term outcome.

A few patients who undergo surgical closure during childhood have late-onset supraventricular arrhythmias, which are believed to be related to patchy fibrosis of the right atrium secondary to dilatation and perhaps dysfunction of the sinus node. In adults, chronic preoperative atrial fibrillation usually persists after surgical repair, but cardioversion followed by antiarrhythmics treatment may be effective. If surgery is performed in patients older than 40 years, 50% of those with preoperative normal sinus rhythm have late postoperative atrial fibrillation. Intracardiac electrophysiologic studies have shown a high incidence of intrinsic dysfunction of the sinoatrial and AV nodes that persists after surgical repair. These nodal abnormalities are most common in the sinus venosus type than in the secundum type.

Late events, including atrial fibrillation, stroke, heat failure, are most common in patients undergoing repair in adulthood. This observation emphasizes the benefit of early repair of secundum ASDs in symptomatic patients. The unfavorable prognosis of late repairs is presumably related to longstanding deleterious effect of volume overload on the chambers on the right side, of pulmonary hypertension, and of right atrial enlargement with increased vulnerability to atrial arrhythmias and stroke. About 22% of late deaths are attributed to cerebrovascular events. Older age at repair and preoperative New York Heart Association class III or IV heart failure are independent predictors of late mortality. They are also predictive of atrial fibrillation, for which sinus node dysfunction with bradycardia-dependent atrial arrhythmias, scar-dependent multiple reentries, and atrial enlargement or atrial fibrosis due to increased pulmonary venous pressure with exercise are implicated as potential mechanisms.

Prognosis after transcatheter closure

See Treatment above.

Common comorbidities

Common comorbidities include the following:

• Pulmonary hypertension
  • Pulmonary hypertension (mean pulmonary artery pressure >20 mm Hg or systolic pulmonary artery pressure >50 mm Hg) occurs in 15-20% of patients with ASD.
  • This condition is unusual in young patients, but it is observed in 50% of patients older than 40 years.
  • In Eisenmenger syndrome—a late and rare complication of isolated secundum ASD that occurs in 5-15% of patients—extreme pulmonary obstruction may result in a reversal of the shunt of blood to a right-to-left flow. Desaturated blood entering the systemic circulation results in systemic hypoxemia and cyanosis.
• Right-sided heart failure
  • Heart failure is due to the cardiac volume overload experienced on the right side of the heart because of left-to-right shunting.
  • In patients of all ages, substantial relief of such a complication is generally observed after the defect is closed.
• Atrial fibrillation or flutter
  • This condition is uncommon in young patients, though it is reported in as many as 50-60% of patients older than 40 years. Therefore, these arrhythmias occur most frequently with age, and they may become a major cause of morbidity and mortality.
  • The use of anticoagulants is indicated in patients with atrial fibrillation because of the high risk of stroke. Although atrial fibrillation may be present in patients before surgery, surgery may also cause it.
• Stroke
  • Regardless of their surgical status, 5-10% of patients have thromboembolic events (including stroke and transient ischemic attacks) on long-term follow-up.
  • Even with small defects, paradoxical emboli may occur. Therefore, the presence of an ASD should be considered in any patient with a cerebral or other systemic embolus in whom no left-sided source is demonstrable.

Future and Controversies

With increased experience over the years, transcatheter closure of suitable ASDs has now become preferable to surgical repair. Limitations currently include size and location of the defect.

Perhaps the most innovative approach to surgical closure in many years was recently accomplished in the form of robotically assisted closure of ASD. Current technology allows for excellent visualization and magnification of internal anatomy, and the ability to perform surgery at a remote distance from the patient is now a reality. However, even with this amazing technology, today's devices will seem crude compared with future computer robots. Improved access and cardiopulmonary bypass technology will most likely make robotically assisted heart surgery a routine procedure in the foreseeable future.

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Keywords

atrial septal defect, atrial septum, ASD, ostium secundum ASD, sinus venosus defect, ostium primum defect, ostium secundum defect, congenital heart disease, congenital cardiac disorder, ventricular dilatation, thoracic surgery, pulmonary hypertension, Eisenmenger syndrome, Holt-Oram syndrome, transcatheter occlusion devices, dyspnea, fatigue, palpitations, syncope, congestive heart failure, CHF

Contributor Information and Disclosures

Author

Bekir Hasan Melek, MD, Assistant Professor of Clinical Medicine, Department of Medicine, Section of Cardiology, Tulane University School of Medicine
Bekir Hasan Melek, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, American Society of Echocardiography, and Louisiana State Medical Society
Disclosure: Nothing to disclose.

Coauthor(s)

James V Talano, MD, MM, FACC, Director of Cardiovascular Medicine, SWICFT Institute
James V Talano, MD, MM, FACC is a member of the following medical societies: American College of Cardiology, American College of Chest Physicians, American College of Physician Executives, American College of Physicians, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, and Society of Geriatric Cardiology
Disclosure: Nothing to disclose.

Jeffrey C Milliken, MD, Chief, Division of Cardiothoracic Surgery, University of California at Irvine Medical Center; Clinical Professor, Department of Surgery, University of California at Irvine School of Medicine
Jeffrey C Milliken, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for Thoracic Surgery, American College of Cardiology, American College of Chest Physicians, American College of Surgeons, American Heart Association, American Society for Artificial Internal Organs, California Medical Association, International Society for Heart and Lung Transplantation, Phi Beta Kappa, Society of Thoracic Surgeons, Southwestern Oncology Group, and Western Surgical Association
Disclosure: Nothing to disclose.

Peter B Smulowitz, BA, University of California at Irvine School of Medicine
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Medical Editor

Park W Willis IV, MD, Sarah Graham Distinguished Professor of Medicine and Pediatrics, University of North Carolina at Chapel Hill School of Medicine
Park W Willis IV, MD is a member of the following medical societies: American Society of Echocardiography
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Steven J Compton, MD, FACC, FACP is a member of the following medical societies: Alaska State Medical Association, American College of Cardiology, American College of Physicians, and Heart Rhythm Society
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CME Editor

Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital
Amer Suleman, MD is a member of the following medical societies: American College of Physicians, American Heart Association, American Institute of Stress, American Society of Hypertension, Federation of American Societies for Experimental Biology, Royal Society of Medicine, and Society of Cardiac Angiography and Interventions
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Michael E Zevitz, MD, Assistant Professor of Medicine, Finch University of the Health Sciences, The Chicago Medical School; Consulting Staff, Private Practice
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