Basics
Description
A secundum atrial septal defect (ASD 2 °) is defined as the absence of septal tissue in the septum secundum, allowing for a free communication between the left and right atrium at or near the level of the fossa ovalis. A spectrum of defect size occurs, from a large fossa defect to multiple small perforations within the septum. The foramen ovale may or may not be included in the defect. A significant left-to-right shunt across the atrial septal defect causes enlargement of the right atrium and RV, usually associated with normal pulmonary artery pressures.
Epidemiology
- ASD 2 ° is common, reported to occur in 7-10% of children with congenital cardiac anomalies as the predominant cardiac lesion.
- Predominant sex: Female > Male, 2:1.
- The condition is associated with a lack of early symptoms and the subtlety of the physical exam, which may delay the diagnosis into adult life. Thus, ASD 2 ° is the most common form of congenital heart disease to present in the adult population.
Risk Factors
None
Pathophysiology
- The presence of an ASD results in left-to-right shunting of blood from left to right atrium during diastole. The degree of shunting depends on the size of the defect and the relative difference between the RV and LV compliance. The shunt is left to right because the RV is more compliant. On this basis, large left to right shunts can result in significant right atrial and ventricular enlargement.
- The left-to-right shunt is usually tolerated well, because pulmonary artery pressure and vascular resistance are almost always normal. However, symptoms may appear in adulthood as a consequence of increased left to right shunting if the LV compliance decreases as a result of age, HTN, coronary disease etc.
Etiology
- Isolated ASD 2 ° usually occurs sporadically and affects only 3% of 1st-degree relatives.
- However, familial inheritance occurs in certain conditions. The Holt-Oram syndrome is characterized by ASD 2 ° in association with upper limb skeletal malformations.
- Familial inheritance has also been described in secundum defects associated with prolonged atrioventricular conduction. Both conditions have a dominant mode of inheritance with a high degree of penetrance, therefore 50% of 1st-degree relatives are affected.
Associated Conditions
- Atrial septal defects may be associated with pulmonary valve stenosis, as well as with ventricular septal defects.
- The incidence of partial anomalous pulmonary venous return is 3% in patients with secundum defects, compared with 83% of those with a sinus venosus atrial septal defect.
- Atrial arrhythmias (most commonly atrial flutter or fibrillation) and more rarely pulmonary HTN and pulmonary vascular obstructive disease with right-to-left shunting may develop in patients with moderate to large sized ASD that have been left unrepaired into middle age.
Diagnosis
Signs and symptoms:
- Usually, no symptoms are related to an ASD in the pediatric age group. In rare instances, failure to thrive during infancy has been suspected. However, other causes to explain the symptoms should be excluded. In the presence of a very large defect, mild easy fatigability may be present, but often only appreciated in retrospect after repair of the ASD.
- Symptoms become manifest in the 4th, 5th decade, or beyond and include:
- Atrial arrhythmias
- Dyspnea on exertion
- Easy fatigability
- CHF
History
Most often asymptomatic
Physical Exam
- An abnormal 2nd heart sound that usually is split widely and fixed, or is persistently split, but varies somewhat with respirations.
- A medium-pitched short systolic ejection murmur is audible at the upper left sternal border, related to increased blood flow across the pulmonary valve.
- The murmur may be prominent at the base and throughout the lung fields due to increased flow over the distal pulmonary vessels.
- A soft, early diastolic murmur may be heard at the mid left sternal border related to increased flow across the tricuspid valve.
Tests
Lab
EKG:
- Usually shows right-axis deviation and a right bundle-branch block pattern over the right precordial leads. Complete RBBB is not present. A left superior axis is consistent with septum primum ASD.
Imaging
- CXR may show mild to moderate cardiomegaly with a large right atrium, RV, and pulmonary artery segment; pulmonary vascular markings are increased. Enlargement of the RV is often only noted on the lateral view. Many patients have a relatively normal radiograph.
- Echo is the optimal method of evaluating the anatomy of secundum ASD. It is also essential to rule out associated abnormalities. The exact location and size of the ASD is visualized, and enlargement of the right atrium and RV are defined. Visualization of the margins of the defect is important in determining plans for interventional/surgical management.
Surgery
Cardiac catheterization is not necessary to establish a diagnosis of ASD 2 ° in any age group. It is indicated only to evaluate suspected pulmonary HTN, or when interventional procedures are utilized as a form of therapy.
Differential Diagnosis
- The differential diagnosis for ASD includes mild pulmonary stenosis, because of similarities in the physical exam.
- Partial anomalous pulmonary venous connections without an associated ASD, although unusual, can be confused with an ASD 2 ° because both result in right-heart volume overload.
- The straight back syndrome, with a systolic ejection murmur at the upper left sternal border and a prominent pulmonary artery on CXR, may superficially suggest the presence of an ASD.
Treatment
Additional Treatment
General Measures
- Most children with an ASD 2 ° are asymptomatic.
- Children with ASD 2 ° should have no restrictions on their activity.
- No indication exists for drug therapy for this condition.
- Patients with evidence of volume overload of the RV on echo should be evaluated for definitive closure.
- Some small to moderate ASD may close spontaneously in the 1st 1-2 yr of life. For the vast majority of children, all approaches to closure should be delayed until patients are at least 2 yr of age.
- Antibiotic prophylaxis is not required.
Surgery
- The most common surgical form of ASD repair has been primary repair with suture closure or patch repair. Surgical mortality rate is <1% in experienced centers. Surgery is usually performed at 3-5 yr of age. Minimally invasive techniques have been developed that have improved cosmetic results and shortened hospital stay. The incidence of postpericardiotomy syndrome is higher following surgical repair of ASD, as compared to other cardiac surgical procedures.
- Transcatheter closure:
- In recent years, transcatheter closure of ASD 2 ° has gained acceptance as a valid alternative to surgical closure and has become the procedure of choice at most medical centers. An occasional ASD 2 ° is not amenable to closure with this technique because of size or position. Suitability for device closure is usually decided after careful evaluation by imaging cardiologists, and consultation with experienced interventional cardiologists.
- 2 FDA-approved devices are currently available, and each has unique advantages and risks. The recommended age for device closure in asymptomatic patients is similar to surgery (3-5 yr). The main advantages of transcatheter closure are the avoidance of cardiopulmonary bypass and sternotomy, and the brief time of recovery.
- The results of transcatheter technique are excellent, with complete closure rates of 90-95%. The rate of significant complications is comparable to that of open-heart surgery (<1%). Daily aspirin and antibiotic prophylaxis is recommended for 6 mo after device occlusion.
Ongoing Care
Diet
No dietary restrictions
Patient Education
Activity: Normal activity is recommended.
Prognosis
- Patients repaired in the pediatric years require minimal follow-up.
- A rare patient develops a late atrial arrhythmia, but this is a very unusual event when ASD closure has been performed within the 1st 2 decades of life.
- In older patients who have CHF and/or pulmonary HTN, require follow-up after surgery for possible progressive pulmonary HTN and/or arrhythmia.
- The rare unoperated patient who develops pulmonary vascular obstruction later in life receives symptomatic therapy. ASD closure is not indicated in this group of patients, and the prognosis is guarded.
- Long-term prognosis for children with a repaired ASD is excellent; a normal lifespan is expected. In the older patient who presents with symptoms, the lifespan may be shortened despite successful surgical closure.
- Antibiotic prophylaxis is not required.
- The presence of a large ASD does not adversely affect the outcome of pregnancy, but occasionally, patients have signs of mild CHF and, rarely, severe decompensation.
- An infrequent complication associated with ASD during pregnancy is paradoxical embolization across the ASD into the systemic circulation.
- Pregnancy is not associated with increased risk after closure.
Additional Reading
1Bergersen L, Foerster S, Marshall A Congenital Heart Disease: The Catheterization Manual. Springer Science, 2008.2Chessa M, Carminati M, Butera G. Early and late complications associated with transcatheter occlusion of secundum atrial septal defect. J Am Coll Cardiol. 2002;39:1061-1065. [View Abstract]3Hessling G, Hvca S, Brockmeier K. Cardiac dysrhythmias in pediatric patients before and 1 year after transcatheter closure of atrial septal defects using the Amplatzer septal occluder. Pediatr Cardiol. 2003;24:259-262; Epub 2003 Jan. 15. [View Abstract]4Kirklin JW, Barratt-Boyes BG. Atrial septal defect and partial anomalous pulmonary venous connection. Cardiac Surg. Second Edition, Volume I, 15:609-644.5Mandell V, Nimkin K, Hoffer FA. Devices for transcatheter closure of intracardiac defects. Am J Roentgen. 1993;160:179-184. [View Abstract]6Moss and Adams' heart disease in infants, children, and adolescents, 6th ed. 2005 Atrial Septal Defects.
Codes
ICD9
745.5 Ostium secundum type atrial septal defect
SNOMED
204315000 atrial septal defect within oval fossa (disorder)