An atrioventricular canal defect, also known as an endocardial cushion defect, is characterized by a complete absence of the atrioventricular septum. It results from abnormal differentiation and remodeling of endocardial cushion mesenchyme that fails to form the septal tissue. It presents with a common atrioventricular ring, a five leaflet valve guarding the common AV orifice, and an unwedged left ventricular outflow tract. Surgical repair is usually done between 2 to 4 months of age to close the septal defects and reconstruct the valves. Techniques include single patch, double patch, and modified single patch closure.

1. ATRIOVENTRICULAR CANAL
DEFECT
By
Dr VASANTHI
DNB- CARDIAC SURGERY
MADRAS MEDICAL MISSION

2. Formation of interatrial and interventricular
septum

4. AV canal formation

11. AV CANAL DEFECT
• Characterized by complete absence of AV
septum
• Mechanism of development : Abnormal
differentiation and remodeling of endocardial
cushion mesenchyme into valvoseptal tissue

12. • Also called as
– Endocardial cushion defect,
– Canalis atrioventricularis communis,
– persistent atrioventricular ostium

13. Features:
• A common
atrioventricular ring
• A five leaflet valve that
guards the common AV
orifice
• An unwedged left
ventricular outflow tract

14. • Mitral & tricuspid valves achieve the same
septal insertion level because the mitral
annulus is displaced toward the apex
• The distance from mitral annulus to the left
ventricular apex is less than the distance from
the aortic annulus to the apex

15. • In the normal heart, the aortic valve is wedged
between the mitral and tricuspid annuli. In AVSD the
aortic valve is displaced anteriorly and creates an
elongated, so-called gooseneck deformity of the
LVOT

16. Incidence
• AVSDs account for 4% to 5% of congenital
heart disease
• Gender distribution is approximately equal or
may show a slight female preponderance

17. History
• Rogers, Edwards : Recognized morphology of primum
ASD in 1948
• Wakai, Edwards : Term of partial and complete AV
canal defect in 1956
• Bharati& Lev : Term of Intermediate & Transitional in
1980
• Rastelli: Described the of common anterior leaflet in
1966
• Lillehei: 1strepair of AVSD in 1954
• Kirklin, Watkin, Gross: Open repair using oxygenator

18. Morphology –classification 1

19. • In partial AVSDs, incomplete fusion of the
superior and inferior endocardial cushions
results in a cleft in the midportion of the AML
,often associated with MR
• Complete AVSD associated with lack of fusion
between the superior and inferior cushions

21. Anatomical classificationII (Rastelli)
• Based on the relationships of
the anterior bridging leaflets
to the crest of the
ventricular septum or RV
papillary muscles
• Rastelli type A : the anterior
bridging leaflet is tightly
tethered to the crest of the
IVS, occurring in 50% to 70%

22. • Rastelli type B : (3%), the
anterior bridging leaflet is
not attached to the IVS;
rather, it is attached to an
anomalous RV papillary
muscle and is almost always
associated with unbalanced
AV canal with right
dominance
• Rastelli type C : (30%) a free-
floating anterior leaflet is
attached to the anterior
papillary muscle.

23. Classificiation III
• Based on level of shunting
– Interatrial and interventricular sunt
– Interatrial shunt only (primum ASD )
– Interventricluar shunt only(av canal VSD)
– AVCD with intact IAS and IVS

24. Classification IV
• Depending upon the size of ventricular
chambers(univentricular or biventricular)
– Balanced type
– Unbalanced type

25. • Unbalanced AVCD: 1.ventircular
hypoplasia,2.malalignment of the AV valve
junction. later may affect size of ventricle
development
• Unbalanced Right dominant type : associated
with arch hypoplasia,coarctation of aorta
• Unbalanced with left dominant : associated
with pulmonary stenosis/atresia

26. Lev description of conduction
• Inferior displacement of AV node and
coronary sinus. Bundle of His is also displaced
inferiorly and coursing at the inferior rim of
scooped out basal portion of IVS

27. Associated anomalies
Partial AVSD:
• Most common ostium secondum ASD & LSVC to
CS
Complete AVSD
• Type A usually is an isolated defect and is
frequent in patients with Down syndrome.
• Type C –TOF, DORV, TGA and heterotaxy
syndromes

28. Fetal physiology
• Oxygenated blood may cross the IAS to the RA
• Increase the PO2 of blood in RA, RV, PA
• Slightly higher PO2of blood perfusing the lungs
would decrease pulmonary vasoconstriction and
increase pulmonary blood flow
• It may retard the development of a thick medial
muscle layer, so that a more rapid decrease in
PVR may occur after birth

29. • An interesting association may develop in some
infants of an obligatory left-to-right shunt
through the AV canal defect simultaneous right-
to-left shunting through the ductus arteriosus
• The increased pulmonary blood flow and PA
pressure interfere with the normal postnatal
maturation of the pulmonary arterioles leads to
early development of Pulmonary vascular
obstructive disease

30. Clinical manifestation
Partial AVSD
• Patients with primum ASD - usually asymptomatic
during childhood.
• Dyspnea, easy fatigability, recurrent RTI and
growth retardation may be present early in life if
associated with major MR or common atrium
Complete AVSD
• Tachypnea and failure to thrive invariably occur
early in infancy & virtually all patients have
symptoms by 1 year of age because of pulmonary
vascular obstructive disease

31. Echocardiography
• Primary imaging technique for diagnosing AVSD
• The internal cardiac crux is the most consistent imaging landmark
• Apical four-chamber imaging plane clearly visualizes the internal crux
• The primum ASD is seen as an absence of the lower IAS

33. Cardiac cath
• Rarely required for diagnosis
• In older patient it may have a role in assessing the
degree of pulmonary vascular obstructive disease or
CAD
• A large Lt to Rt shunt at the atrial level demonstrated
by a significantly higher oxygen saturation sampled
from the RA compared with the blood in the IVC & SVC
• In complete AVSD the PASP is invariably at or near
systemic level, while in partial AVSDs, the PASP is
usually <60% of systemic pressure
• LV angiography -gooseneck deformation of the LVOT

34. Goose neck deformity
• The left ventricular outflow tract is elongated
and narrowed. The arrows point to the mitral
cleft.

35. Management
• Elective surgical repair -2 to 4 months of age.
• Early in case of down syndrome because of
their known tendency to develop early
pulmonary vascular obstructive disease
• Palliative:
– Unbalanced AV canal (PA banding )

36. Corrective surgeries
• Single patch technique
• Double patch technique
• Modified single patch technique

37. Double patch technique
• Separate patch for both ASD and VSD closure
• VSD –dacron and ASD – pericardial patch to avoid
hemolysis in case of AVVR
• Mitral valve cleft is closed by coaptation of SBL
and IBL using horizontal mattress
• Kirklin tech : attaching ASD patch to the right of
AV node invloves suturing the right inferior leaflet
.leaving CS ->LA
– Advantage : far from conductive tissue
– Diaadvantgae : some desaturation becoz of CS->LA

38. • Mcgoon tech:ASD patch is attached to the left
inferior leaflet draining CS-> Ra.

39. Single patch tehcnique

40. Modified Single patch tehcnique
• c/a australian technique

41. • Disadvantage : development of lvoto because
of VSD is closed primarily witout patch
material

42. Corrective