Atrioventricular septal defects represent a group of anatomic lesions with varying pathophysiologies, but they share a common developmental origin in the arrest or abnormal development of the endocardial cushions in the embryonic atrioventricular canal. We will consider the terms atrioventricular septal defect, atrioventricular canal defect, and endocardial cushion defect as synonyms; and for this chapter, we will use the term atrioventricular septal defect (AVSD) as this is the preferred term utilized in The International Pediatric and Congenital Cardiac Code (www.IPCCC.net). [1], [2], [3], [4], [5], [6], [7]

AVSD includes a wide range of pathophysiologies ranging from simple ASD physiology to complex single ventricle physiology. This chapter will be limited to balanced AVSDs with biventricular physiology; unbalanced AVSD with single ventricle physiology will be discussed in another chapter. In addition to the anatomic spectrum of AVSD, there are important cardiac and non-cardiac associated anomalies that will be described.

The key to surgical management is an in depth understanding of the anatomy, not only of the atrioventricular valves but also the ventricular septal defect, the conduction system and the left ventricular outflow tract.

Key learning Points

• Understand the anatomical differences between partial, transitional and complete AVSDs.
• Learn the Rastelli classification of complete AVSD.
• Know the frequently associated abnormalities – specifically LVOTO, AVSD with Tetralogy of Fallot.
• Anatomy of the conduction system
• Physiology and natural history for each type of AVSD
• Timing and types of Surgery
  • Single patch,
  • Modified single patch,
  • Two patch,
  • PA band.
• Surgical outcomes
• Late reoperations
  • Cleft repair, LVOTO relief.

Synonyms

• Bridging leaflet = common leaflet
• Superior bridging leaflet= anterior bridging / common leaflet
• Inferior bridging leaflet = posterior bridging / common leaflet
• Lateral leaflet = mural leaflet