ABSTRACT
Intracardiac malformations leading to a cardiac left-to-right shunt postnatally include atrial septal defects (ASDs), atrioventricular septal defects (AVSDs), and ventricular septal defects (VSDs). These lesions constitute the largest group of cardiac defects detected during fetal life, the most common being VSD and AVSD.1,2
Anatomy An ASD is a common congenital defect seen in children, occurring in 1 in 1500 live births.3 It can present as an isolated defect or in association with complex congenital heart defects. Several mechanisms cause the formation of an atrial communication, leading to several defect types (Figure 21.1):
• Secundum ASD • Primum ASD (also named AVSD-partial or transitional
type) • Sinus venosus ASD (superior and inferior types) • Coronary sinus ASD
Secundum ASD is the most common atrial communication in children. It occurs when the septum primum fails to cover the oval fossa, which is patent and allows right-to-left flow of oxygenated blood to the heart and brain during fetal life. This failure of the septum primum can result in a single defect or fenestrated defect, as well as a wide range of defect sizes.
