Atrial Septal Defect Treatment & Management

Atrial septal defect (ASD) is a disorder to be addressed surgically or through interventional catheterization. No specific or definitive medical therapy is available. However, patients with significant volume overload or atrial arrhythmias may require specific drug therapy.

Criterion standard

The criterion standard in the treatment of atrial septal defect (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 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 an ostium primum defect, surgical closure is more 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 a sinus venosus defect, 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 venous 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 pulmonary venous hypertension.

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, secundum ASD 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 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 allows closure of large orifices with excellent success rates in most cases. It was first used in humans 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 method, the static diameter of the defect is first assessed by using TEE. The diameter is then measured with a sizing balloon using the “stop-flow” technique to select the proper diameter of the device. Using this technique, the sizing balloon is inflated until no flow is visible through the defect using TEE. The margins of the orifice must be wide enough (≤5 mm) 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 has been used for the same purpose.

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 more than 96%. Transcatheter closure has been associated with fewer complications, shortened hospitalization, and reduced need for blood products.

At any age, ASD closure is followed by symptomatic improvement and regression of positive airway pressure (PAP) and right ventricle size; however, the best outcome is achieved in patients with less functional impairment and less elevated PAP.^[5] Considering the continuous increase in symptoms, right ventricle remodelling, and PAP with age, ASD closure must be recommended irrespective of symptoms early after diagnosis, even in adults of advanced age.

Furthermore, transcatheter closure appears to have additional benefits regarding hemodynamic improvement compared with surgery. In one study, transcatheter closure with ASO improved the left atrial volume index, the left ventricular myocardial performance index, and the right ventricular myocardial performance index.^[6] The last was unimpressive after surgery, possibly because of cardiopulmonary bypass.

Another group compared atrial function in 45 patients with a mean age of 9 years after surgery and after percutaneous closure by using strain-rate imaging.^[7] 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 or intraoperative myocardial damage might have altered the deformation properties of the left atrium.

Postoperative management after atrial septal defect (ASD) repair is usually standard. Patients are expected to be awake and often 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, patients are generally discharged the next day. Six months of treatment with aspirin with or without clopidogrel is recommended to prevent thrombus formation.

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 cardiologist with congenital experience 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, in large part to follow and evaluate for arrhythmia complications.

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

Surgery may be associated with a long-term risk of atrial fibrillation or flutter. The risk of infective endocarditis exists during the first 6 months after surgery. The following complications are also associated with atrial septal defect (ASD):

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

The following complications are specifically 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 less than 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. The incidence of arrhythmia appears to be related to the size of the device.
• Thrombus formation: A study of 1000 patients was performed to investigate the incidence of thrombus by performing TEE at 4 weeks and 6 months after the procedure.^[8] 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 one study of 37 patients.^[9]
• 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, the patient should be hospitalized for 24-48 hours of observation and follow-up echocardiography.^[10]
• Device erosion: Erosion of septal occluder devices occurs in 0.1-0.15% of implants.^[11] 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.^[12]
• Residual shunts: As many as 20% of patients may have a residual shunt persisting for 24 hours after the procedure; >90% of such residua are small. During follow-up, the incidence approaches 0% at 3 years for most series.^{[13, 14]}
• Other complications include pericardial effusion, transient ischemic attack, and sudden death.

Natural history

Although life expectancy is not normal for patients with atrial septal defect (ASD), 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 is less than 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 less than 1% for patients younger than 45 years without heart failure and who have systolic pulmonary artery pressures less than 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 completed at 2-4 years of age. Early surgical repair is considered in a few infants and young children with clinically significant symptoms or congestive heart failure (CHF).

Surgery before the age 25 years results in a 30-year survival rate comparable to that of age- and sex-matched control subjects. However, at age 25-40 years, surgical survival is reduced, though not significantly if pulmonary artery pressures are normal. If pulmonary artery systolic pressure is higher than 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 pulmonary artery 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, and heart 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 long-standing 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 atrial flutter

  • These conditions are uncommon in young patients, though they are 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.

With increased experience over the years, transcatheter closure of suitable secundum atrial septal defects (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 near future.