Atrial Septal Defect (ASD)
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- 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.
- Predominant age: Newborn, but may be diagnosed at any age
- Predominant sex: Female > Male (2:1)
- No race predilection
- 4 per 10,000 births
Accounts for 10% of congenital heart defects, and 25–30% of congenital heart defects detected in adulthood
- 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
- 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)