Learning objectives

• Describe the causes and consequences of ASD
• Recognize risk factors for ASD
• Diagnose ASD
• Anesthetic management of patients with ASD

Definition & mechanisms

• Atrial septal defect (ASD) is one of the most common types of congenital heart defects, occurring in about 25% of children
• Failure to close the septum between the right and left atria
• Small defects usually close spontaneously during childhood
• Large defects that do not close spontaneously may require percutaneous or surgical intervention 
• Blood flows from the left atrium to the right atrium causing a left-to-right shunt
• Increase in pulmonary vascular resistance due to chronic volume overload, resulting in pulmonary hypertension
• Once pulmonary pressures equal systemic pressures, the shunt across the ASD reverses, and deoxygenated blood flows into the left atrium and systemically (Eisenmenger syndrome)
• Other complications:
  • Atrial dysrhythmias
  • Right-sided congestive heart failure
  • Transient ischemic attack/stroke

Risk factors

ASD types

• Ostium secundum defect: Increased reabsorption of the septum primum in the atrium’s roof, or the septum secundum does not occlude the ostium secundum
• Ostium primum defect: Failure of the septum primum to fuse with the endocardial cushions
• Sinus venosus defect: Superior and inferior defects occur, and neither involves the true membranous septum:
  • Superior defect: The orifice of the superior vena cava overrides the atrial septum above the oval fossa and drains both the left and right atria
  • Inferior defect: The orifice of the inferior vena cava overrides both atria
• Coronary sinus defect: A defect or hole in the common wall between the left atrium and the coronary sinus creates a communication between the right and left atria

Diagnosis

• Transthoracic echocardiogram (gold standard diagnostic imaging modality)
• Cardiac CT and MRI
• Exercise testing can help determine the reversibility of shunt flow and the response of patients with pulmonary artery hypertension to activity
• Cardiac catheterization is contraindicated in young patients who present with small, uncomplicated ASDs.
• Differential diagnosis:
  • Atrioventricular septal defect
  • Ventricular septal defect
  • Cyanotic congenital heart disease (sinus venosus defects and coronary sinus defects)
    • Total anomalous pulmonary venous return
    • Pulmonary stenosis
    • Truncus arteriosus
    • Tricuspid atresia

Management

SVR, systemic vascular resistance; PVR, pulmonary vascular resistance

Suggested reading

• Menillo AM, Lee LS, Pearson-Shaver AL. Atrial Septal Defect. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535440/
• Yen P. ASD and VSD Flow Dynamics and Anesthetic Management. Anesth Prog. 2015;62(3):125-130.
• Calvert PA, Klein AA. Anaesthesia for percutaneous closure of atrial septal defects. Continuing Education in Anaesthesia Critical Care & Pain. 2008;8(1):16-20.

Clinical updates

Shimizu et al. (A&A Practice, 2024) describe the first reported use of remimazolam for general anesthesia in pediatric cardiac surgery, detailing a 6-year-old undergoing minimally invasive ASD repair with cardiopulmonary bypass who was maintained on remimazolam and remifentanil under EEG guidance, with stable hemodynamics and no need for vasoactive support. EEG showed predominant slow and beta activity with dynamic changes during bypass and rewarming, and despite concerns about dilution during CPB, anesthetic depth remained adequate; the patient awoke promptly without flumazenil, had no intraoperative awareness, and experienced an uneventful recovery, suggesting remimazolam may be a feasible option for pediatric cardiac anesthesia pending further dosing and monitoring data. 

Takahashi et al. (JA Clinical Reports, 2023) report the first pediatric open-heart surgery in a patient with Freeman–Sheldon syndrome (FSS), detailing successful closure of an ASD under total intravenous anesthesia to avoid malignant hyperthermia triggers and dopamine antagonists, with uncomplicated intubation despite microstomia. They emphasize anticipatory airway planning, avoidance of volatile agents and succinylcholine, and the use of dexmedetomidine as an adjunct for postoperative analgesia to facilitate early extubation without respiratory depression, highlighting its role in minimizing opioid use while requiring careful hemodynamic monitoring.