Atrial Septal Defect The 5 Minute Pediatric Consult


	Atrial Septal Defect

Song-Gui Yang

Database
Differential Diagnosis
Data Gathering
Physical Examination
Laboratory Aids
Therapy
Follow-Up
Common Questions and Answers
Bibliography

DATABASE

DEFINITION

An opening in the atrial septum, other than a patent foramen ovale (PFO).

Three major types of atrial septal defects (ASDs):
- Ostium secundum
- Ostium primum
- Ostium venosus defect.
A PFO usually does not cause a significant intracardiac shunt.
Ostium secundum defects make up 50% to 70% of all ASDs; usually there is a shunt from the left atrium to the right atrium.
Ostium primum defects occur in about 30% of all ASDs. They are usually associated with a cleft left AV valve.
Sinus venosus defects (located at the SVC-RA junction) occur in about 10% of all ASDs. The right pulmonary vein may drain anomalously.

ASSOCIATED LESIONS

An ASD may be associated with partial or total anomalous pulmonary venous drainage, mitral valve anomalies including prolapse, transposition of the great arteries or tricuspid atresia.

PATHOPHYSIOLOGY

A left-to-right shunt occurs through the ASD, resulting in right atrial and right ventricular (RV) volume overload. There is usually increased pulmonary blood flow. The left-to-right shunt generally increases with time as pulmonary resistance drops and RV compliance normalizes. Moderate and large defects are associated with a Qp/Qs ratio of more than 2:1. The direction of atrial shunting is determined by the relative compliance of the RV and LV.

GENETICS

Although usually spontaneous, ASDs may occur as part of a syndrome (Holt-Oram [autosomal dominant]).

EPIDEMIOLOGY

ASDs usually occur sporadically in 5% to 10% of all congenital heart diseases. The ratio between female and male is 2:1.

PROGNOSIS

The prognosis of small ASDs seems excellent without specific therapy.
Spontaneous closure of some small secundum ASDs can occur in up to 87% of infants in the first 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 present in up to 13% of unoperated patients over 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.

DIFFERENTIAL DIAGNOSIS

Ventricular septal defect
Patent ductus arteriosus
AV canal defect

DATA GATHERING

HISTORY

Most infants are asymptomatic.
Older children with moderate left-to-right shunts are often asymptomatic, but may have mild fatigue or dyspnea.
Children with large left-to-right shunts may complain of fatigue and dyspnea, which may become noticeable when the child gets older.
Growth failure is uncommon. Older patients with large atrial shunts may develop atrial arrhythmias.

PHYSICAL EXAMINATION

Inspection and palpation of the precordium are usually normal.
Older children with a large shunt may have a hyperdynamic precordium.
Auscultation reveals three important features:
- Wide and “fixed” splitting of S2
- A soft systolic murmur at the upper left sternal border
- A diastolic rumble at the lower sternal border, indicating a Qp/Qs ratio of at least 2:1.

LABORATORY AIDS

ECG

Usually normal sinus rhythm with right axis deviation. There is often an rSr’ indicating RV volume overload. First-degree AV block may be present. A monophasic R wave in lead V1 may suggest pulmonary hypertension.

CXR

Cardiomegaly, increased pulmonary vascular markings, and a dilated pulmonary trunk in patients with significant left-to-right shunts.

ECHO

A two-dimensional echo study is diagnostic; it reveals the location, size, and associated defect, if any. It may demonstrate dilated right-heart structures. Color Doppler generally permits visualization of the direction of shunt flow.

Cardiac Catheterization

Generally unnecessary; it is indicated when pulmonary vascular disease is suspected (determination of pulmonary vascular resistance) or for associated cardiac defects.

THERAPY

Infants with congestive heart failure should be treated with digoxin and diuretics. Elective surgical repair is indicated for ASDs associated with large left-to-right shunts, cardiomegaly, or symptoms. Other indications may include: prevention of paradoxical emboli and cerebrovascular accidents or refractory supraventricular arrhythmias. High PVR (i.e., >8 Wu/M²) increases the morbidity and may worsen the prognosis. Sinus venosus and ostium primum defects require elective surgery regardless of the defect size. The timing of the repair is usually deferred until 3 to 4 years of age. The mortality of surgical repair for an uncomplicated ASD approaches 0%. For some secundum ASDs, device closure of the defect can be done in the cardiac catheterization laboratory.

FOLLOW-UP

Children with typical auscultation 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 RV volume overload. Restriction on activity is unnecessary. SBE prophylaxis is not indicated in isolated secundum ASDs.
SBE prophylaxis is indicated for the first 6 months (assuming no residual defect) after closure of a secundum defect.
Complications related to surgery include sinus node dysfunction. Venous obstruction (facial or pulmonary edema) may occur after a sinus venous ASD repair. Postpericardiotomy syndrome, which manifests with nausea, vomiting, abdominal pain or fever, may occur even weeks after the initial repair. Although a friction rub may not be present, CXR may demonstrate cardiomegaly, and ECHO may reveal a pericardial effusion. Residual ASD after surgery is rare and usually without significant hemodynamic consequence.

COMMON QUESTIONS AND ANSWERS

Q: When should a moderate secundum ASD be closed?
A: This can generally be performed in children prior to their starting grade school.

Q: What is the significance of a patient having gastrointestinal complaints (nausea and vomiting) 1 to 2 weeks after surgical closure of an ASD?
A: This may represent a pericardial effusion (post-pericardotomy syndrome).

ICD-9-CM 745.61

BIBLIOGRAPHY

Chang AC, Hanley FL, Wernovsky G, Wessel DL. Pediatric cardiac intensive care. Baltimore: Williams & Wilkins, 1998:207–211.

Garson A, Bricker J, McNamara D. The science and practice of pediatric cardiology. Philadelphia: Lea & Febiger, 1990:1023–1036.

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.

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