Description

• Anatomy:
  • Opening in the atrial septum allowing flow of blood between the 2 atria
  • Patent foramen ovale is similar, but is not open the majority of the time, causes no hemodynamic disturbance, and is not considered an atrial septal defect (ASD) (no tissue defect)
• Types (by location in the interatrial septum) (1):
  • 75%: Ostium secundum defect occurs in the fossa ovalis region.
  • 15%: Ostium primum defect occurs in the inferior septum; often associated with cleft mitral valve and failure of endocardial cushion development.
  • 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.
• 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 2 ventricles.
  • Causes excessive blood flow through the right-sided circulation, ultimately leading to reactive pulmonary hypertension and possibly heart failure
• Management (1):
  • Symptomatic patients or patients with a high degree of shunt flow should undergo closure to reduce subsequent morbidity and mortality.
  • Ostium primum and sinus venosus defects are treated surgically.
  • Percutaneous closure is an alternative to surgical repair for many patients with secundum ASD.
• Systems affected: Cardiovascular; Pulmonary

• 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.

Epidemiology

• Predominant age: Newborn, but may be diagnosed at any age
• Predominant sex: Female > Male (2:1)
• No race predilection
• 4 per 10,000 births

Prevalence
Accounts for 10% of congenital heart defects, and 25–30% of congenital heart defects detected in adulthood

Risk Factors

• Other congenital heart defects
• Family history (~7–10% recurrence)
• Thalidomide, alcohol exposure in utero

• Most cases are spontaneous.
• 5% with chromosomal abnormalities; other rare mutations exist
• ~25% prevalence in Down syndrome

Pathophysiology

• Flow across ASD usually left-to-right shunt because of higher left-sided pressures:
  • There can be 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 right heart failure.

Commonly Associated Conditions

• 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, e.g.:
  • Holt-Oram syndrome: Secundum defect with bony abnormalities of forearms + hands (0.95 per 100,000)
  • Ellis-von-Creveld syndrome: Chondroectodermal dysplasia + ASD
  • VACTERL (vertebral, anorectal, cardiac, tracheoesophageal, renal/urinary and limb defects)