FRCA Notes

Atrial Septal Defect Closure

ASD appears in the curriculum under 'Knowledge of common congenital heart defects including... ASD'.

One is also required to 'Recall the abnormalities found in the adult patient with congenital heart disease... and the implications for anaesthesia in these patients'.

ASD appeared as a Paediatric CRQ in 2020 (51% pass rate), although based on examiner feedback a good chunk of the question seemed to be about clinical features.

Resources

  • Atrial septal defects account for 6-10% of congenital cardiac disease, and up to 17% of grown-up congenital heart disease (GUCH)

By location

  • Ostium secundum ASD (60 - 70%)
    • Occurs due to excessive resorption of the ostium primum or deficiency growth of the ostium secundum septum
    • Manifests after birth as a defect in the fossa ovalis

  • Ostium primum ASD (15 - 20%)
    • Occurs due to a defect in the endocardial cushion
    • Is often associated with MR due to an anterior leaflet cleft

  • Sinus venosus ASD (5 - 15%)

  • Unroofed coronary sinus

By size

  • The physiological sequelae of ASDs are largely unrelated to their site, depending more on the size of the defect and the degree of shunt
  • Small defects are associated with small shunts, and there is typically little haemodynamic compromise
  • Larger defects and can lead to:
    • Significant left-to-right shunt
    • Increased pulmonary blood flow
    • RV, RA, LA and pulmonary artery dilatation
    • Pulmonary hypertension
    • RV failure

Symptoms

  • Most small ASDs are asymptomatic e.g. up to 30% have small PFOs which are inconsequential in the majority of patients

  • Exertional dyspnoea (30% by their 20's, 75% by 40's)
  • Palpitations from dysrhythmias
  • Stroke in otherwise young or healthy individuals e.g. due to PFO

Signs

  • Hypoxia
  • Fixed, split second heart sound
  • Pulmonary flow murmur
  • Features of right heart overload

Investigations

  • ECG
    • RBBB + either LAD (ostium primum ASD) or RAD (ostium secundum ASD)
    • Atrial arrhythmias; typically AF or Aflutter due to atrial dilatation

  • TTE
    • Raised right sided heart pressures
    • Tricuspid or pulmonary valve disease
    • Atrial dilatation
    • RV dilatation

  • Bubble test
    • Air bubbles seen in both LA and RA on echocardiogram during a Valsalva manoeuvre
    • Often the only finding for small PFOs

  • ASD closure is indicated for:
    1. Significant left-to-right shunting of blood e.g. enough shunt to cause right heart fluid overload
    2. Cryptogenic stroke
    3. Decompression illness e.g. divers, fighter pilots

Outcomes

  • Overall shunt closure improves life expectancy, especially if shunt fraction ≥1.7 or raised PA pressure
    • Early (<25yrs old) shunt closure is associated with normal functional outcome and life expectancy
    • Late closure may be associated with premature death
  • Closure associated with a much lower risk of cerebrovascular events (7%) vs. medical therapy alone (33%)

Surgical vs. percutaneous closure

  • Compared to surgical shunt closure, percutaneous closure is associated with:
    • Similar success rate without major complication
    • Lower rate of minor complications
    • Lower average length of stay
  • Long-term outcomes from percutaneous closure are still being established

Perioperative management of the patient requiring ASD closure


  • Patients with ASD are at higher risk of perioperative complications such as:
    • Arrhythmias
    • RV dysfunction or failure
    • Acute pulmonary hypertension
    • Shunt reversal with consequent systemic hypoxia
    • Paradoxical embolic phenomena

  • Most closures are performed percutaneously, but large (>3cm) or complicated ASDs should be referred for surgical closure

History and examination

  • Assessment for cardiac symptoms/features as above
  • Presence of other congenital abnormalities, cardiac or otherwise
  • Drug history; may be on anticoagulants or anti-arrhythmics if in AF/Flutter

Investigations

  • FBC
  • U&E if indicated
  • Clotting profile if on anticoagulants

  • Pre-operative TOE is mandatory to:
    • Confirm presence of defect and its size
    • Assess for complexity i.e. associations with other abnormalities

  • Percutaneous closure if typically performed as a day-case, unless:
    • Significant pulmonary hypertension
    • Requirement for other interventions requiring post-operative care e.g. right heart catheterisation

Monitoring and access

  • AAGBI
  • Arterial line

  • TOE is used to:
    • Ensure appropriate closure device placement
    • Confirm device stability after placement
    • Prevent complications e.g. interference with other cardiac structures (typically pulmonary vein or mitral valve)
    • Allow early detection of thrombus formation

  • Some centres may use intra-cardiac echocardiography inserted into the RA via the femoral vein

Surgical technique

  • Right femoral vein access
  • 6F catheter on guidewire advanced into RA
  • Wire passed across ASD, guided by fluoroscopy and TOE
  • Closure device passed into LA and then pulled back against intra-atrial septum
  • Placement and stability confirmed with TOE

Anaesthetic technique

  • As the patient is supine and in the catheter lab with TOE in situ, they are generally done under GA with I&V
  • Avoid nitrous oxide; can increase intravascular bubble size
  • TIVA or volatile maintenance acceptable
  • Short-acting drugs are preferable, especially if performed as a day-case procedure

  • Antibiotic prophylaxis according to local guidelines
  • Heparin (e.g. 100 IU per kg) may be required

Haemodynamic goals

  • The key is to avoid factors which cause large:
    • Increases in PVR, as this can precipitate pulmonary hypertension and RV failure
    • Decreases in SVR, as the low pressure can precipitate right-to-left shunt and systemic hypoxia
    • Increases in SVR, as this can exacerbate left-to-right shunting, causing RV failure

  • One should take care to avoid air in lines as this risks paradoxical embolism

Haemodynamic goals


  • Remain supine for 2hrs post-removal of venous sheath
  • Typically 6 months aspirin and clopidogrel, or warfarin if already indicated for another reason
  • Follow up TTE in 6 months


Complication Notes
Air embolism Leads to transient myocardial ischaemia, ST-segment changes and RWMA on TOE
Often spontaneously resolves
Arrhythmias Atrial manipulation during closure device placement can cause AF or Aflutter
May need DCCV
Thrombus formation On either the closure device itself or its applicator
Necessitates full anticoagulation
Admit for monitoring for neurological deficit
Pericardial tamponade Due to wire damage of cardiac structures
May need drain or open intervention
Closure device embolisation Very rare
MI
Stroke
Haemorrhage