QUICK RECERTIFICATION SERIES
- Atrial septal defect (ASD) is a congenital heart defect that enables blood flow between the left and right atria through a defect in the interatrial septum.
- Occurs due to failure of foramen ovale to close despite change in pulmonary pressure at birth, a condition known as a patent foramen ovale
- Results in mixing of arterial (high oxygen content) and venous (low oxygen content) blood
- The mixing of blood can cause a left-to-right shunt that can reverse to a right-to-left shunt over time. This complication is known as Eisenmenger syndrome.
- Right-to-left shunts cause more complications, such as right heart failure and pulmonary hypertension.
- ASDs are present in 1.64 of every 1,000 live births.
- ASDs compose 35% to 40% of congenital heart defects, making them the second most common congenital heart defect.
- The male to female ratio is 1:2.
- Familial recurrence rate is about 10%.
- Ostium secundum, an opening in the atrial wall at the site of the foramen ovale, is the most common type of ASD.
- Most patients with ASDs are diagnosed in utero or early childhood due to advances in ultrasonography and auscultation during the physical exam.
- Symptoms of ASD are related to size of the defect.
- Small to medium ASDs may not cause symptoms in early childhood.
- Infants with large ASDs may have cyanosis, heart failure, recurrent respiratory infections, or failure to thrive.
- Adults who were not diagnosed in childhood typically present by their 30s or 40s with
- Dyspnea on exertion
- New-onset heart failure
- Atrial fibrillation
- In patients who have long-standing ASD, a switch to a right-to-left shunt may result in cyanosis evident on physical exam.
- The findings on physical examination depend on the size and location of the defect.
- Palpation of the precordium: right ventricular heave most noticeable on the left sternal border. A left upper sternal border impulse may be noted if the patient has pulmonary hypertension.
- Heart sounds: A wide, fixed, split S2 is characteristic of ASD and is best evaluated when the patient is sitting or standing.
- Additional murmurs that may be auscultated include:
- Mid-systolic pulmonary flow or ejection murmur, noted in larger left-to-right shunts
- A low-pitched diastolic murmur, which can be heard when the pulmonary artery has dilated
- A late apical or holosystolic murmur radiating to the axilla, found in patients with mitral regurgitation due to ASD
- A diastolic rumble increased with inspiration can be noted in patients with left-to-right shunts, and is caused by increased flow across the tricuspid valve.
- An S4 will be noted in patients with pulmonary hypertension due to ASD.
- Test of choice for diagnosis
- Transthoracic echocardiogram (TTE) with color Doppler will show jet of blood from left to right atrium.
- A bubble study can be conducted. Bubbles moving from right to left atrium indicate that right atrial pressure is higher.
- Transesophageal echocardiogram may be required if the ASD is not visualized on TTE or to aid in sizing and determining concomitant abnormalities.
- Chest X-ray
- May be normal
- Later in life, may show enlarged cardiac silhouette and pulmonary edema
- In patients with sinus venous defect (a defect close to the superior or inferior vena cava), the “scimitar sign” may be seen. This is a vertical, curved right-sided pericardiac linear density that increases in width as it approaches the right cardiophrenic angle.
- Prolonged PR interval in patients with first-degree heart block
- Incomplete right bundle branch block
- Notched R wave in inferior leads
- Left axis deviation of QRS, most commonly seen in primum ASDs, which are communications present at the level of the mitral or triscupid valves
- Right axis deviation of QRS (ostium secundum ASD)
- Left axis deviation of P wave (sinus venous defect)
- Treatment options are determined based on time of discovery and size and location of defect.
- Patients with significant pulmonary hypertension are best treated symptomatically for heart failure.
- Surgical correction is ideal before pulmonary hypertension develops, and has the lowest risk of complications when performed in patients<25y. Closure may be performed as open heart surgery or, more common, percutaneously.
© 2013 American Academy of Physician Assistants.
- Decompression sickness
- Paradoxical emboli
- Eisenmenger syndrome
- Pulmonary hypertension
- Right-sided heart failure
- Atrial fibrillation or flutter.