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Atrial Septal Defect (ASD)

Basics

  • Congenital defect of the interatrial septum; patent foramen ovale (PFO) is not ASD.
  • Types:
  • Ostium secundum (75%, midseptum)
  • Ostium primum (15-20%, inferior septum, often with cleft mitral valve)
  • Sinus venosus (5-10%, superior-posterior septum near SVC, with partial anomalous pulmonary venous return)
  • Coronary sinus defect (<1%)
  • Left-to-right shunting causes right-sided volume overload and pulmonary hypertension.

Epidemiology

  • Incidence: ~1 in 1500 live births.
  • Female:male ratio 2–4:1.
  • ASDs comprise 13% of congenital heart defects.
  • Most common congenital heart lesion in adults is secundum ASD (>90%).

Etiology and Pathophysiology

  • Left-to-right shunting due to higher left atrial pressure.
  • Shunt size and ventricular pressures determine severity.
  • Reversal to right-to-left shunting with pulmonary hypertension leads to Eisenmenger syndrome, cyanosis, and clubbing.
  • Genetic associations: familial cases rare; 25% prevalence in Down syndrome; 5% with chromosomal abnormalities.

Risk Factors

  • Family history, maternal age >35 years, teratogenic exposures (thalidomide, alcohol, tobacco), gestational diabetes.

Commonly Associated Conditions

  • May be isolated or part of complex cardiac defects (e.g., anomalous pulmonary venous return).
  • Syndromes: Holt-Oram, Ellis-van Creveld, VACTERL, Down, Noonan syndromes.

Diagnosis

History

  • Often asymptomatic; incidental murmur in childhood.
  • Large ASDs present with right heart failure, tachypnea, recurrent infections, failure to thrive.
  • Adults present with palpitations, exercise intolerance, dyspnea, syncope, edema, cyanosis, or fatigue.

Physical Exam

  • Hyperdynamic precordium, palpable pulmonary artery pulse.
  • Auscultation: fixed, widely split S2 (key finding), systolic ejection murmur (pulmonic flow), diastolic rumble (tricuspid flow).
  • Eisenmenger syndrome: cyanosis, clubbing, JVD, edema.

Differential Diagnosis

  • Other congenital heart diseases, right bundle branch block.

Diagnostic Tests & Interpretation

  • Transthoracic echocardiography (TTE) with Doppler: initial test, sensitivity varies by ASD type.
  • Transesophageal echocardiography (TEE): for detailed morphology or pre-procedure planning.
  • Oximetry at rest/activity for cyanosis/Eisenmenger.
  • ECG: may show right/left heart strain patterns.
  • Cardiac catheterization: evaluates pulmonary vascular resistance, reserved for select cases.
  • Cardiac MRI/CT: adjunct for anatomy and shunt quantification.
  • Chest X-ray: assess right heart/pulmonary artery enlargement.

Treatment

General Measures

  • Most small secundum ASDs (<8 mm) close spontaneously by 18 months; close follow-up necessary.
  • Surgical closure generally needed for primum and sinus venosus defects.

Medication

  • Manage secondary conditions: heart failure (diuretics, digoxin), pulmonary hypertension (prostanoids, endothelin receptor antagonists, PDE-5 inhibitors).
  • Treat arrhythmias with anticoagulation and rhythm or rate control.
  • Antibiotic prophylaxis not recommended for unrepaired isolated ASDs.
  • Post-device closure antiplatelet therapy (aspirin +/- clopidogrel for ≥6 months).

Surgery/Procedures

  • Closure indications: defects >8 mm, symptomatic patients, right heart enlargement, or paradoxical embolism.
  • Percutaneous device closure preferred for secundum ASD in adults; surgery standard for other types.
  • Maze procedure for atrial arrhythmias when indicated.

Ongoing Care

  • Cardiology follow-up every 3 months to 5 years based on clinical status.
  • Periodic ECG, echocardiography, exercise testing for advanced disease.
  • Monitor for late complications post repair.
  • Pregnancy tolerated with repaired or small ASDs; contraindicated with Eisenmenger syndrome.

Patient Education

  • Resources: American Heart Association, Mayo Clinic websites.
  • Avoid scuba diving and high-altitude travel without cardiology consultation in unrepaired ASD.

Prognosis

  • Early closure (<25 years) reduces morbidity, including pulmonary hypertension and arrhythmias.
  • Untreated ASDs have high mortality by 60 years and risk of complications.

Complications

  • Unrepaired: heart failure, stroke, atrial arrhythmias, pulmonary infections, pulmonary hypertension, paradoxical embolism.
  • Surgically repaired: arrhythmias, embolic events.
  • Device closure: rare device embolization, perforation, thrombus, endocarditis.

References

  1. Bradley EA, Zaidi AN. Atrial septal defect. Cardiol Clin. 2020;38(3):317-324.
  2. Oster M, Bhatt AB, Zaragoza-Macias E, et al. Interventional therapy vs medical therapy for secundum ASD: systematic review. J Am Coll Cardiol. 2019;73(12):1579-1595.
  3. Stout KK, Daniels CJ, Aboulhosn JA, et al. 2018 AHA/ACC guideline for adults with congenital heart disease. J Am Coll Cardiol. 2019;73(12):1494-1563.
  4. Scacciatella P, Marra S, Pullara A, et al. Percutaneous closure of ASD in adults: long-term outcomes. J Invasive Cardiol. 2015;27(1):65-69.

ICD10 Codes

  • Q21.2 Atrioventricular septal defect
  • Q21.1 Atrial septal defect
  • I23.1 Atrial septal defect as current complication following acute myocardial infarction

Clinical Pearls

  • ASD often missed due to subtle presentation; fixed widely split S2 is hallmark.
  • Early closure in childhood ideal; some benefit to closure in older patients.
  • Percutaneous closure preferred for secundum ASD; surgery standard for others.
  • Routine endocarditis prophylaxis not recommended for unrepaired ASDs.
  • PFOs common, usually no treatment needed if asymptomatic.