• Group of anomalies that share a
defect in atrioventricular septum
and abnormal AV valves.
• Also known as Endocardial cushion
defect, AV canal defect, canalis
persistent atrioventricular ostium
• Broadly divided into partial and
• 4 TO 5 % Of congenital heart defects.
• Estimated occurrence of 0.19 in 1,000 live births
• Male = female or slight female preponderance.
• Downs syndrome: 40 to 45% have heart disease.
• Of which 45% have avsd.
• > 75 % of these are the complete form.
• Conversely approximately 50% of avsd patients have
Rogers, Edwards : Recognised morphological similarity
of ostium primum ASD and complete defect in 1948
Wakai, Edwards : Term of partial and complete AV
canal defect in 1956
Bharati & Lev : Term of Intermediate & Transitional in
Rastelli: Described the of common anterior leaflet in
Lillehei : 1st repair of AVSD in 1954
Kirklin, Watkin, Gross: Open repair using oxygenator
• Defect in endocardial cushion development and fusion.
• Additional pathways have now been illustrated, which
shows that “dorsal mesenchymal protrusion”(vestibular
spine) is responsible for formation of avsd.
• In partial AVSDs, incomplete fusion of the superior and
inferior endocardial cushions results in a cleft in the mid-
portion of the left AV valve anterior leaflet often associated
• In contrast, complete AVSD is associated with lack of
fusion between the superior and inferior cushions and,
consequently, with the formation of separate anterior and
posterior bridging leaflets along the subjacent ventricular
• Since the dextrodorsal conus cushion contributes to the
development of the right AV valve and the outflow tracts lie
adjacent to their respective inflow tracts, AVSDs may be
associated with conotruncal anomalies, such as tetralogy of
Fallot and double-outlet right ventricle (RV).
In addition, shift of the AV valve orifice may result in
connection of the valve primarily to only one ventricle,
creating disproportionate or unbalanced ventricles.
• Prior to 1964, hospital mortality
for patients with AVSD was 60 %.
• Rastelli et al. from the Mayo
Clinic published their work in
1968 and operative mortality
between 1964 and 1967
decreased to 20 % .
Anatomical Classification of AVSD
Based bridging of LSL across
Rastelli type A : (55%) Anterior
bridging leaflet divided and
attached to crest of ventricular
• Interventricular communication
beneath the anterior bridging
leaflet may be minimal or
absent in some cases owing to
extensive interchordal fusion.
Anatomical Classification of AVSD
Rastelli type B : (3%)
anterior bridging leaflet
larger , straddles the
septum and papillary
muscle attachment to
band of RV.
Chordal anchors are absent
Anatomical Classification of AVSD
Rastelli type C : (30%)
anterior bridging leaflet
is larger than in type B.
• its medial papillary
muscle attachments fuse
to the right-sided anterior
• Free interventricular
• Also called free floating
• The subtype of complete
AVSD has some bearing
on the likelihood of
• Type A usually is an
isolated defect and is
frequent in patients with
• Type C is encountered
with other complex
anomalies, such as
tetralogy of Fallot, double-
outlet RV, complete
transposition of the great
arteries, and heterotaxy
• Two separate annuli
• Ostium primum asd and cleft left anterior av valve.
• The cleft in the left AV valve anterior leaflet is directed
toward the midportion of the ventricular septum, along the
anteroinferior rim of the septal defect.
• The left AV valve orifice is triangular rather than elliptical (
as in a normal heart) and resembles a mirror-image
tricuspid valve orifice.
• The cleft left AV valve usually is regurgitant and, with time,
becomes thickened and exhibits histologic alterations that
resemble myxomatous mitral valve prolapse.
• Although patients with partial AVSD may be asymptomatic
until adulthood, symptoms of excess pulmonary blood flow
typically occur in childhood
• Tachypnea and poor weight gain occur most commonly
when the defect is associated with moderate or severe left
AV valve regurgitation or with other hemodynamically
significant cardiac anomalies.
• Patients with primum ASDs usually have earlier and more
severe symptoms, including growth failure, than patients
with secundum ASDs.
• Tachypnea and failure to thrive invariably occur early in
infancy as a result of excessive pulmonary blood flow
• All patients with complete AVSD have symptoms by 1year
• AV valve regurgitation compounds these problems.
The outcome of live-born patients with AVSD depends on
specific morphology of the defect
The size of the ventricular septal defect
Degree of ventricular hypoplasia
Degree of AV valve regurgitation
Presence or absence of LVOT obstruction
Presence or absence of coarctation of aorta
Associated syndromes (cardiac and noncardiac)
Patients with the complete form of AVSD and large VSD not
undergoing repair die in infancy with CHF & PAH
Those who survive without surgery into childhood usually
develop pulmonary vascular obstruction and eventually die with
Berger and his colleagues found that only 54% of patients born
with a complete form of AVSD were alive at 6 months of age, 35%
at 12 months, 15% at 24 months, and 4% at 5 years of age
This data would support surgical intervention in the first 3–6
months of age
Berger TJ,et al Ann Thorac Surg 1979; 27: 104–11.
Infants with 10 ASD presenting in infancy have a poor outcome,
mainly because of the associated risk factors that bring these
infants to early attention
Those with the partial form of AVSD and minimal left AV valve
regurgitation seem to fare the best without surgery, although
there is still likely considerable morbidity and mortality
According to Somerville, 50% die before 20 years of age and only
25% survive beyond 40 years of age
Atrial fibrillation in these patients was an important cause of late
morbidity and mortality
Superior” QRS axis with the QRS axis between -40 and -1500
Most of the patients have a prolonged PR interval
More than 50% have atrial enlargement
RVH or RBBB is present in all cases (2/3rd have rsR, RSR or Rr in lead
V1, and the rest have a qR or R pattern) & many have LVH
In 10 ASD findings are same as 20 ASD except for enlargement of the
LA & LV when MR is significant
In complete AVSD cardiomegaly is always present and involves all
four cardiac chambers. Pulmonary vascular markings are increased,
and the main PA segment is prominent
Primary imaging technique for diagnosing AVSD
The internal cardiac crux is the most consistent imaging
Apical four-chamber imaging plane clearly visualizes the
Several echocardiac features are shared by all forms of
Deficiency of a portion of the inlet ventricular septum
Inferior displacement of the AV valves
The most common left AV valve abnormality, a cleft, is best
visualized from the parasternal and subcostal short-axis
In the transitional form of partial AVSD, there is aneurysmal
replacement of a portion of the inlet ventricular septum
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
Cardiac Catheterization & Angiography
Left to-right shunting increases the oxygen saturation in RA
Sample from high in the SVC usually represents the best
mixed venous oxygen saturation (normal or 40 to 50%)
Usually a further increase in oxygen saturation in the RV
Pulmonary venous oxygen saturation is frequently reduced
to 93–95% in older individuals with very large L to R shunts
LA & LV O2 saturation is often decreased to as low as 86–88%
• Complete AVSD
a. Uncontrolled heart failure:
Complete surgical repair as soon as possible (Class I)
b. Controlled heart failure: Complete surgical repair by 3 months
of age (Class I)
c. Pulmonary artery banding: May be considered in select
patients under 3 months of age (Class IIb).
ii. Partial or intermediate AVSD, stable, and with normal
pulmonary artery pressures: Surgical repair at 2–3 years of age
iii. Associated moderate or severe AV valve regurgitation may
necessitate early surgery in partial or intermediate forms.
iv. Pulmonary artery banding is reserved for complex cases and
in patients with contraindications for cardiopulmonary bypass
Surgery for moderate-to-severe left AV valve regurgitation
is recommended as per the guidelines for mitral
vi. Surgery for left ventricular outflow tract obstruction is
reasonable with a peak systolic gradient of ≥50 mmHg, or
at a lesser gradient if heart failure symptoms are present,
or if concomitant moderate-to-severe atrioventricular or
aortic regurgitation is present (Class IIa).
vii. Those presenting beyond 6 months of life with
significant pulmonary hypertension and suspected elevated
PVR should be referred to a higher center for further
evaluation to assess operability.
Recommendations for follow-up
i. Lifelong follow-up is required.
ii. In patients with no significant residual abnormality,annual
follow-up is required till 10 years of age followed by 2–
The patient should undergo physical examination, ECG,
and echocardiography at each visit, and a Holter monitor
test may be required in select cases.
iii. IE prophylaxis is recommended for 6 months after
surgical closure. However, all patients are advised to
maintain good oro-dental hygiene after this period also.
Notas do Editor
The development of the heart starts with the generation of the precardiac mesoderm forming
two bilateral primary heart fields. These heart fields eventually fuse thereby creating the linear
primary heart tube [27,28]. This heart tube consists of a myocardial outer mantle, an acellular matrix,
often referred to as the cardiac jelly, and an inner endocardial tube . The heart tube is initially
suspended from the rest of the embryo over its entire length by the dorsal mesocardium. During
cardiac looping this dorsal mesocardium largely disintegrates with the exception of the persisting
dorsal mesocardium at the venous pole of the heart . As the heart tube remodels, the atrial and
ventricular chambers expand by a process sometimes referred to as ballooning . During this process
the chambers gradually lose most of the cardiac jelly between the myocardium and endocardium with
the exception of the cardiac jelly at the atrioventricular junction (AVJ) and the outflow tract (OFT).
In these parts of the heart, the cardiac jelly is accumulating in the subendocardial space resulting in the
formation of prominent cushions. While in the early stage of their development these extracellular
matrix-rich cushions do not contain any cells, a subsequent endocardial epithelial-to-mesenchymal
transformation (endoEMT) generates a cohort of endocardially-derived mesenchymal cells that
gradually migrates into and populates the cushions a process that is initiated around ED 9.5 in
the mouse . Within the AV junction, the two major (or midline) AV cushions form first. Around
ED12.5, the major cushions fuse, thereby dividing the common AV canal into the left and right AV
junction. In the left AV junction, forming the communication between the left atrium and left ventricle,
the left AV valve (or mitral valve in the human) will develop, and in the right AV junction, connecting
right atrium and right ventricle, the right AV valve (or tricuspid valve in the human) will form.
The fused major AV cushions play a significant role in AV valve development as the aortic (or anterior)
leaflet of the left AV valve, as well as the septal leaflet of the right AV valve derive from the fused major
cushions [33,34]. Importantly, the fused major cushions also form the mesenchymal base on which
the atrial septal complex develops . After the formation of the major AV cushions a second set of
cushions forms at the lateral AV junctions (Figure 2). These lateral AV cushions, which also become
populated with mesenchymal cells as a result of endoEMT, are significantly smaller than the major
cushions. The right lateral cushion eventually forms the parietal leaflet of the right AV valve, while the
left lateral cushion forms the parietal (or mural/posterior) leaflet of the mitral valve.
Transitional AVSD is a subtype of partial AVSD. This term is
used when a partial AVSD also has a small inlet VSD that is
partially occluded by dense chordal attachments to the ventricular
septum. Intermediate AVSD is a subtype of complete
AVSD that has distinct right and left AV valve orifices despite
having only one common annulus. These separate orifices are
referred to as right and left AV valve orifices rather than tricuspid
and mitral. This also is true when describing the valves
after repair of complete AVSD. The VSD in intermediate AVSD
is large similar to other forms of complete AVSD