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Atrial Septal Defect
Edlira Yzeiraj, DO, MS
Edward A. Gotfried, DO, FACOS
image BASICS
  • Anatomy
    • Opening in the atrial septum allowing flow of blood between the two atria
    • Patent foramen ovale is also an open communication between the atria, but it is not considered an ASD because no septal tissue is missing.
  • Types (by location in the interatrial septum) (1)
    • Classified based on their different anatomic location and abnormal embryogenesis: secundum ASD, primum ASD, sinus venosus ASD, coronary sinus ASD.
    • 70%: Ostium secundum defect occurs in the fossa ovalis region.
    • 15-20%: Ostium primum defect occurs in the inferior septum; often associated with cleft mitral valve and failure of endocardial cushion development.
    • 5-10%: Sinus venosus defect occurs in the superior-posterior septum near the orifice of the superior vena cava; usually associated with partial anomalous right upper pulmonary venous return.
    • Less than 1%: Coronary sinus defect: part of the entire common wall between the coronary sinus and the LA is absent.
  • Hemodynamic effects
    • Left-to-right shunting in late ventricular systole and early diastole
    • Degree depends on size of the defect and relative pressures of the two ventricles.
    • Causes excessive blood flow through the rightsided circulation, ultimately leading to reactive pulmonary hypertension and heart failure
  • Systems affected: cardiovascular; pulmonary
Pediatric Considerations
  • Most cases of ASD are detected and corrected in the pediatric population.
  • The smaller the defect and the younger the child, the greater the chance of spontaneous closure.
  • Predominant age: present from birth, may be diagnosed at any age
  • Slight female predominance (2)
  • No race predilection
  • 2/1,000 live births (3)
  • ASDs account for 13% of congenital heart disorders (3)
  • Flow across ASD usually left-to-right shunt because of higher left-sided pressures:
    • Minimal right-to-left shunting in early ventricular systole, especially during inspiration
    • Increased right-sided pressure/pulmonary hypertension can cause reversal of shunt flow (Eisenmenger syndrome) with resulting cyanosis and clubbing.
  • Symptoms typically occur due to right ventricular and pulmonary vascular volume overload and rightsided heart failure.
  • Most cases are spontaneous.
  • 5% with chromosomal abnormalities; other rare mutations exist
  • 25% prevalence in Down syndrome
  • Other congenital heart defects
  • Family history (˜7-10% recurrence)
  • Thalidomide, alcohol exposure in utero, smoking, maternal age >35 years, and elevated blood glucose have been associated with increased risk (2).
  • ASDs may occur as a component of other complex cardiac structural defects.
  • Important to exclude anomalous pulmonary venous return
  • Occasionally can indicate underlying genetic syndromes, for example: Holt-Oram (ASD present in 66%), Ellis-van Creveld, VACTERL syndrome, or Noonan syndrome.
  • Overall, ˜70% isolated (1)
  • Signs vary according to extent of shunting.
  • Cardiac auscultation
    • Fixed, widely split S2 (key physical finding)
    • May also have
      • Systolic ejection murmur (pulmonic flow murmur)
      • Low-pitched diastolic rumble (tricuspid flow murmur)
      • Diastolic murmur (pulmonic regurgitation)
      • Systolic murmur (mitral regurgitation)
  • Right ventricular heave
  • Palpable pulmonary artery pulse at left upper sternal border
  • If heart failure has developed, may hear a 4th heart sound (right-sided)
  • Signs of Eisenmenger syndrome:
    • Cyanosis and clubbing
    • Jugular venous distention and edema
  • Other congenital heart disease
  • Right bundle branch block (for widely split S2)
Initial Tests (lab, imaging)
  • Echocardiography is the test of choice (1)[C].
  • Generally start with transthoracic Doppler imaging of the entire atrial septum (sensitivity is ˜89% for secundum, ˜100% for primum, and ˜44% of sinus venosus ASDs), with progression to transesophageal echocardiography (TEE) if transthoracic echocardiography (TTE) is nondiagnostic
  • Patients with right ventricular overload by TTE but an otherwise negative study should have further testing.
  • Oximetry: Cyanosis may suggest Eisenmenger syndrome (right-to-left shunting).
  • ECG is not typically diagnostic, but findings include the following:
    • Right axis deviation
    • Right atrial enlargement (tall P in inferior leads)
    • Right ventricular conduction delay
    • Q wave in lead V1
    • Right bundle branch block
    • Leftward axis, inverted P wave in lead III (sinus venosus)
    • Leftward axis (ostium primum)
Follow-Up Tests & Special Considerations
  • Bubble contrast enhancement may be helpful.
  • TEE may be required to define ASD morphology and to locate the pulmonary veins; often used prior to percutaneous closure. TEE has excellent sensitivity and specificity.
Diagnostic Procedures/Other
  • Cardiac catheterization (1)[C]
    • Demonstrates right ventricle enlargement, location/fraction of the shunt, size of the ASD, any valvular disease, and overall anatomy
    • Used to assess pulmonary vascular resistance if pulmonary hypertension is suspected, particularly if surgery is planned
    • Generally not used in young patients for initial diagnosis, more often reserved for use when
  • Part of a planned interventional closure
  • Evaluating other disease simultaneously (e.g., coronary artery disease)
  • Visualization by other methods insufficient
  • Cardiac magnetic resonance: a noninvasive follow-up to echo that allows viewing the defect/pulmonary veins and measurement of shunt fraction and right ventricular function—particularly useful for sinus venosus defects (2)
  • Exercise testing: useful to quantify symptoms not consistent with clinical findings or to document change over time (1)[C]
  • Chest x-ray: may demonstrate right ventricular and pulmonary artery enlargement, increased pulmonary vascular markings
  • Cardiac CT scans can also define ASDs but with significant radiation exposure.
  • 75% of small secundum ASDs (<8 mm) will close spontaneously by 18 months of age; however, close follow-up is warranted (2).
  • The likelihood of spontaneous closure is mainly determined by defect diameter: >10 mm at time of diagnosis is unlikely to spontaneously close (4).
  • Primum and sinus venosus defects do not generally close and generally require surgical closure (2).
First Line
  • Treatment of secondary atrial fibrillation/supra-ventricular tachycardia with anticoagulation and cardioversion, followed by anticoagulation with maintenance of sinus rhythm if possible, or rate control if this fails (1)[A]
  • Pulmonary vasodilator therapy may be considered for adults with progressive/severe pulmonary vascular disease (1)[B].
  • Treatment of heart failure (diuretics, oxygen, digoxin, etc.)

Second Line
  • Antibiotic prophylaxis is NOT recommended for unrepaired/isolated ASDs.
  • The American Heart Association (AHA) recommends antibiotic prophylaxis against infective endocarditis during dental procedures for 6 months after the repair in patients whom a device or prosthetic material is used (5)[B].
    • In patients with repaired ASD who have a residual defect at or adjacent to the device, prophylaxis is recommended indefinitely.
    • If prophylaxis is indicated, for dental procedures, amoxicillin 2 g (adults) or 50 mg/kg (children). Other options include cephalosporins (e.g., ceftriaxone 1 g [adults] or 50 mg/kg [children] IM or IV) or clindamycin 600 mg PO (adults) or 20 mg/kg PO (children) or azithromycin 500 mg PO (adults) or 15 mg/kg (children) in patients who are penicillin-sensitive (5,6)[B].
  • To prevent thrombus formation after device deployment, aspirin alone or a combination of aspirin and clopidogrel 75 mg for at least 6 months is recommended (7).
  • The majority of small secundum defects, <6 mm, close spontaneously by 2 years of age, and some as late as 5 years. Closure is generally indicated in children with:
    • Defect >8 mm (unlikely to close) in children older than 2 years of age (to allow time for spontaneous closure, even though uncommon)
    • Defects of any size in a child older than 5 years with related symptoms
  • Closure for secundum defects is not recommended in asymptomatic patients before 2 years of age given the possibility of spontaneous closure.
  • In adults, secundum closure via percutaneous trans-catheter device or surgery to reduce subsequent morbidity and mortality, if:
    • Right side heart enlargement regardless of symptoms (1)[B]
    • Pulmonary systemic flow ratio is 2:1 (or >1.5:1 and <21 years old according to the AHA)
    • Symptoms such as documented orthodeoxia/platypnea or paradoxical embolism (1)[C]
  • Surgical repair is standard for a sinus venosus, coronary sinus, or primum ASD (1,2)[B]. These defects rarely close spontaneously and are not considered amenable to percutaneous closure.
  • Percutaneous closure is considered the treatment of choice of secundum ASD in adults (8)[A]. It is a safe and effective with satisfactory long-term clinical follow up. In addition, the use of closure device does not significantly affect aortic or mitral valve function (8)[B].
  • Secundum ASDs that are suitable for percutaneous closure should be ˜35 mm in stretched balloon diameter and should have a sufficient rim of surrounding atrial tissue.
  • Closure is not indicated for patients who have developed irreversible severe pulmonary hypertension without continued shunting or those who never develop symptoms and have an ASD <5 mm (1)[B].
  • Overall, closing small asymptomatic secundum ASDs is controversial and not often done.
  • Maze procedure may be considered before or after closure for patients with intermittent or chronic atrial tachyarrhythmias (1)[C].
Echocardiography can be used to monitor both repaired and unrepaired ASDs.
Patient Monitoring
  • In otherwise asymptomatic healthy children, follow up until defect has closed or become negligible in size.
  • Appropriate evaluation and management for atrial tachyarrhythmias in patients with long-term follow-up (1)[C]
  • If ASD repaired as an adult, periodic long-term follow-up is indicated (1)[C].
  • ASDs repaired in childhood generally do not have late complications.
  • In female patients with unrepaired ASD and Eisenmenger syndrome, pregnancy is not recommended due to increased risk of maternal and fetal mortality (1)[C].
  • Pregnancy is well tolerated in patients with repaired ASD and small unrepaired ASDs (1)[A].
  • Scuba diving and high-altitude travel must be approached with caution in patients with unrepaired ASDs; consultation is recommended.
For patient education materials on this topic, consult the following:
  • American Heart Association: http://www.heart.org
  • Mayo Clinic information: http://www.mayoclinic.com/health/atrial-septal-defect/DS00628
  • ASD closure in asymptomatic or minimally symptomatic adults reduces morbidity but not mortality (9).
  • ASD closure before age 25 years in symptomatic adults reduces morbidity and likely also mortality.
  • ASD repair deferred until after adolescence may not decrease long-term risk of future atrial arrhythmias.
  • Up to 50% mortality by age 50 years in untreated symptomatic patients with large defects.
1. Warnes CA, Williams RG, Bashore TM, et al. ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to develop Guidelines on the Management of Adults with Congenital Heart Disease). Developed in collaboration with the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;52(23):e143-e263.
2. Geva T, Martins JD, Wald RM. Atrial septal defects. Lancet. 2014;383(9932):1921-1932.
3. van der Linde D, Konings EE, Slager MA, et al. Birth prevalence of congenital heart disease worldwide: a systematic review and meta-analysis. J Am Coll Cardiol. 2011;58(21):2241-2247.
4. Hanslik A, Pospisil U, Salzer-Muhar U, et al. Predictors of spontaneous closure of isolated secundum atrial septal defect in children: a longitudinal study. Pediatrics. 2006;118(4):1560-1565.
5. Nishimura RA, Carabello BA, Faxon DP, et al. ACC/AHA 2008 guideline update on valvular heart disease: focused update on infective endocarditis: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines: endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation. 2008;118(8):887-896.
6. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007;116(15):1736-1754.
7. Inglessis I, Landzberg MJ. Interventional catheterization in adult congenital heart disease. Circulation. 2007;115(12):1622-1633.
8. Scacciatella P, Marra S, Pullara A, et al. Percutaneous closure of atrial septal defect in adults: very long-term clinical outcome and effects on aortic and mitral valve function. J Invasive Cardiol. 2015;27(1):65-69.
9. Attie F, Rosas M, Granados N, et al. Surgical treatment for secundum atrial septal defects in patients >40 years old. A randomized clinical trial. J Am Coll Cardiol. 2001;38(7):2035-2042.
Additional Reading
Geva T, Martins JD, Wald RM. Atrial septal defects. Lancet. 2014;383(9932):1921-1932.
See Also
Aortic Valvular Stenosis; Coarctation of the Aorta; Patent Ductus Arteriosus; Pulmonary Valve Stenosis; Tetralogy of Fallot; Ventricular Septal Defect
  • Q21.1 Atrial septal defect
  • Q21.2 Atrioventricular septal defect
Clinical Pearls
  • ASD is often missed due to subtle clinical presentation.
  • Ideally, hemodynamically significant ASDs should be closed in early childhood, although some benefit from closure is present in older patients.
  • Many ASDs can be treated by catheter-directed percutaneous closure rather than open-heart surgery.
  • Routine endocarditis prophylaxis is not recommended for unrepaired ASDs.
  • Generally, symptomatic and hemodynamically significant ASDs are repaired; management of asymptomatic small ASDs is debated.
  • Patent foramen ovales, unlike large ASDs, are very common and generally require no treatment in asymptomatic individuals.