* 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.
* Decompression sickness
* Paradoxical emboli
* Eisenmenger syndrome
* Pulmonary hypertension
* Right-sided heart failure
* Atrial fibrillation or flutter.