Atrioventricular Septal Defects

• AV Canal Defect.
• Endocardial Cushion Defect.
• A flaw in the development of the endocardial cushions.
• Endocardial cushions contribute to the formation of the atrial and ventricular septum, septal leaflets of TV and anterior leaflet of MV.
• Account for 5% of all CHD.
• 15-20% of children with Down’s Syndrome(Trisomy 21) will have an AVSD.

Common Characteristics of AVSDs

• Both the right and left AV valve components insert at the same level (common AV junction).
• Absence of atriventricular septum.
• Normal heart: AoV is wedged between TV and MV.
• AVSD heart: AoV is unwedge and displaced anteriorly.
• Elongated LVOT.
• Counter-clockwise rotation of LV papillary muscle.
• Cleft left AV valve component, directed towards the ventricular septum. 

Types of AVSDs

• Complete AVSD.

• Partial/Incomplete AVSD.

• Transitional AVSD.

Complete AVSD

• Ostium primum ASD.
• Inlet VSD.
• Common AV valve-AV valves do not divide in utero.

Rastelli Classification for Stradling A-VVs

• Type A: chordal attachments from superior bridging leaflet to the crest of IVS.
• Type B: chordal attachments from superior bridging leaflet to an anomalous papillary muscle LV.
• Type C: free floating leaflet with attachment to papillary muscles on both sides of IVS.

Unbalanced AVSD

• Complete AVSD with a dominant ventricle and underdeveloped ventricle.
• RV dominant is associated with aortic arch obstruction.
• LV dominant is associated with pulmonary stenosis or atresia.

Partial/Incomplete AVSD

• Ostium Primum ASD with a cleft MV and/or TV.
• Inlet VSD with a cleft MV and/or TV.
• Ventricular septum tissue fills in from either endocardial cushion tissue or AV valve tissue leaving only ASD.
• MV and TV are divided into two distinct halves

Transitional AVSD

• Rare.
• Common AV valves leaflets are stuck to most of the VSD creating two valve orifices.
• LV to RA shunt.
• Three leaflets with cleft in left AV valve.

    

Conditions Associated w/AVSDs

• PDA 10%.
• TOF 10%
• DiGeorge Syndrome.
• Down’s Syndrome.
• Ellis Van Crevald Syndrome.
• Asplenia-right isomerism.
• Polysplenia-left isomerism.
• Secundum ASD.
• Double orifice MV.
•  PS.
• Discrete AS.

Hemodynamics of AVSDs

• L-R shunts.
• Might see LV-RA shunt.
• RAE due to TR/ASD.
• LAE due to MR/VSD.
• R-L if Eisenmingers or if there is presence of episodic pulmonary vasoconstriction (PHTN).
• In newborns shunts may not be seen due to high pulmonary resistance. 

Complications of AVSDs

• Acyanotic unless accompanied by PHTN.
• Blood is recirculated to lungs leading to pulmonary edema if untreated.
• Pulmonary Edema: lungs are engorged with blood and causes fluid to leak from bloodstream into airspaces of the lungs.
• Leads to difficult breathing.
• All leads to congestive heart failure. 

AVSDs by Echo

• Distinguish between complete or incomplete.
• Assess valvular attachments.
• Assess location and extent of atrial and ventricular septal defects.
• Document atrioventricular valvular attachments to ventricular septum.
• Assess MR/TR.
• Determine if there is a dominant ventricle.
• R/O associated lesions. 

ASVD Surgical Repair

• Aim of repair is to close all intracardiac shunts and establish two competent AV valves.
• Except in very young patients, the cleft MV is closed.
• Repair for complete AVSD is recommended between 3-6 months.
• Most common problem later in life is worsening MR.
• Patients will be followed to assess progression of MR/TR or MS/TS. 

AVSD Post-Op Echo

• Assess MV and TV velocities for stenosis or regurgitation.
•  R/O residual VSD/ASD.
• R/O effusion/tamponade.