An opening in the atrial septum, other than a patent foramen ovale (PFO)
4 major types of atrial septal defects (ASDs)
Secundum ASD
Primum ASD
Sinus venosus ASD
Coronary sinus ASD
A PFO usually does not cause a significant intracardiac shunt. A probe-patent PFO can be found in up to 15-25% of normal hearts at pathologic exam.
Secundum defects make up 60-70% of all ASDs. Usually, there is a shunt from the left atrium to the right atrium.
Primum defects occur in ~30% of all ASDs. They are usually associated with a cleft mitral valve. This defect is the result of an abnormality of the endocardial cushions and therefore is also referred to as an incomplete atrioventricular (AV) canal defect.
Sinus venosus defects can be of the superior or inferior vena caval type and occur in ~5-10% of all ASDs. In ASDs of the superior vena caval type, the right pulmonary veins (usually right upper lobe) may drain anomalously to the superior vena cava or right atrium.
Coronary sinus ASDs are rare and occur in <1% of all ASDs. They are often associated with absence of the coronary sinus and a persistent left superior vena cava that joins the roof of the left atrium (also known as an "unroofed coronary sinus"¯).
Epidemiology
Females > males (2:1)
Incidence
Difficult to determine
Represents 6-10% of all cardiac anomalies encountered
Pathophysiology
A left-to-right shunt occurs through the ASD. For large defects, this results in right atrial and right ventricular volume overload.
There is usually increased pulmonary blood flow.
The left-to-right shunt generally increases with time as pulmonary resistance drops and right ventricular compliance normalizes.
Moderate and large defects are associated with a Qp/Qs ratio of >2:1.
The direction of atrial shunting is determined by the relative compliance of the right and left ventricles.
Etiology
ASDs may be associated with partial or total anomalous pulmonary venous drainage, mitral valve anomalies, transposition of the great arteries, or tricuspid atresia.
Although usually isolated, ASDs may occur as part of a syndrome (Holt-Oram [autosomal dominant]).
Diagnosis
History
Most infants are asymptomatic.
Older children with moderate left-to-right shunts are often asymptomatic but may have mild fatigue or dyspnea, especially with exercise.
Children with large left-to-right shunts may complain of fatigue and dyspnea, which may become noticeable as the child gets older.
Growth failure is uncommon.
Older patients with large atrial shunts may develop atrial arrhythmias.
Physical Exam
Inspection and palpation of the precordium are usually normal, although older children with a large ASD may have a hyperdynamic precordium, right ventricular heave, or precordial bulge.
Auscultation reveals 3 important features:
Wide and "fixed"¯ splitting of S2. Splitting of S2 (A2 and P2 components) is caused by a delay in emptying of a volume-loaded right ventricle.
A systolic ejection murmur at the upper left sternal border. This murmur is caused by an increase in blood flow across a normal pulmonary valve. It may be differentiated from the murmur of pulmonary stenosis because there is no click.
A diastolic murmur at the lower sternal border, indicating a Qp/Qs ratio of at least 2:1. This murmur is caused by increased flow across the tricuspid valve.
Diagnostic Tests & Interpretation
Lab
ECG
Usually normal sinus rhythm with an rSR' (incomplete right bundle branch block pattern) in leads V1, V3R, and V4R, indicating right ventricular volume overload. For larger shunts, ECG may show evidence of right atrial enlargement as well as 1st-degree AV block. A late finding suggestive of pulmonary hypertension is right ventricular hypertrophy.
Chest radiograph
Cardiomegaly (right atrium and right ventricle), increased pulmonary vascular markings, and a dilated pulmonary trunk are seen in patients with significant left-to-right shunts.
Echocardiogram
A 2-D echo study is diagnostic; it reveals the location, size, and associated defects, if any. It may demonstrate dilated right heart structures. Color Doppler generally permits visualization of the direction of shunt flow. Older children and adolescents may require transesophageal echo to best define the ASD.
Cardiac catheterization
Generally unnecessary. It is indicated when pulmonary vascular disease is suspected (determination of pulmonary vascular resistance) or for associated cardiac defects.
Differential Diagnosis
Ventricular septal defect
Patent ductus arteriosus
AV canal defect
Valvar pulmonary stenosis
Treatment
Additional Treatment
General Measures
Infants with congestive heart failure should be treated with diuretics.
Elective closure is indicated for ASDs associated with large left-to-right shunts, cardiomegaly, or symptoms.
The timing of closure is usually deferred until 3-5 years of age.
For most secundum-type ASDs, device closure of the defect can be performed in the cardiac catheterization laboratory, thus avoiding surgery.
Prevention of paradoxical emboli and cerebrovascular accidents is an uncommon but possible indication for closure of ASDs or PFO.
Irreversible pulmonary hypertension from a long-term left-to-right shunt usually does not occur until adolescence or young adulthood.
Sinus venosus, primum, and coronary sinus-type ASDs require surgical closure. The mortality of surgical repair for an uncomplicated ASD approaches 0%.
There is some anecdotal evidence suggesting that PFOs are a cause of migraine headaches in certain populations. Prospective adult studies are currently ongoing to further investigate this question, but to date no study has found an indication for PFO closure in migraine patients.
Ongoing Care
Follow-up Recommendations
Patient Monitoring
Children with typical auscultation, chest radiograph, and ECG findings should undergo an echocardiographic evaluation to determine the location and size of the ASD.
Children with ASDs should have regular follow-up to assess for signs of congestive heart failure or right ventricular volume overload. Restriction of activity is unnecessary. Subacute bacterial endocarditis (SBE) prophylaxis is not indicated for an isolated secundum ASD. Residual ASD after surgery is rare.
SBE prophylaxis is indicated for the first 6 months (assuming no residual defect) after closure of a secundum defect.
Complications related to surgery include the following:
Sinus node dysfunction
Venous obstruction (facial or pulmonary edema) may occur after a sinus venosus ASD repair.
Postpericardiotomy syndrome, which manifests with nausea, vomiting, chest pain, abdominal pain, or fever, may occur a few weeks after surgical repair. Although a friction rub may not be present, the chest radiograph may show cardiomegaly and the echocardiogram may reveal a pericardial effusion.
Prognosis
The prognosis for small ASDs seems excellent without specific therapy.
Spontaneous closure of small secundum ASDs can occur in up to 80% of infants in the 1st year of life. Isolated secundum ASDs of moderate and large size do not typically cause symptoms in most infants and children.
Pulmonary hypertension is rare in childhood.
Atrial flutter and fibrillation occur in up to 13% of unoperated patients older than 40 years of age.
Bacterial endocarditis is rare in children with isolated ASD.
Paradoxical emboli may occur and should be considered in patients with cerebral or systemic emboli.
Additional Reading
Horton SC, Bunch TJ. Patent foramen ovale and stroke. Mayo Clin Proc. 2004;79(1):79-88. [View Abstract]
Kharouf R, Luxenberg DM, Khalid O, et al. Atrial septal defect: spectrum of care. Pediatr Cardiol. 2008;29(2):271-280. [View Abstract]
Meijboom F, Roos-Hesselink J, Sievert H. The role of the atria in congenital heart disease. Cardiol Clin. 2002;20(3):351-366. [View Abstract]
Ohye RG, Bove EL. Advances in congenital heart surgery. Curr Opin Pediatr. 2001;13(5):473-481. [View Abstract]
Radzik D, Davignon A, van Doesburg N, et al. Predictive factors for spontaneous closure of atrial septal defect diagnosed in the first 3 months of life. J Am Coll Cardiol. 1993;22:851-853. [View Abstract]
Zanchetta M, Rigatelli G, Pedon L, et al. Role of intracardiac echocardiography in atrial septal abnormalities. J Interv Cardiol. 2003;16(1):63-77. [View Abstract]
Codes
ICD09
745.5 Ostium secundum type atrial septal defect
745.61 Ostium primum defect
745.8 Other bulbus cordis anomalies and anomalies of cardiac septal closure
ICD10
Q21.1 Atrial septal defect
Q21.2 Atrioventricular septal defect
SNOMED
70142008 Atrial septal defect (disorder)
17718000 Ostium primum defect
95268002 Sinus venosus atrial septal defect
FAQ
Q: When should a moderate secundum ASD be closed?
A: This can generally be electively performed in children prior to their starting grade school.
Q: What is the significance of a patient having gastrointestinal complaints (nausea and vomiting) 2-3 weeks after surgical closure of an ASD?
A: This may represent a pericardial effusion (postpericardiotomy syndrome).