Atrio-Ventricular Canal (AVC) Endocardial Cushion Defects (ECD) Atrio-Ventricular Septal Defects (AVSD)

Question 1

Definition:AVSD/ECD/AVC Defects

Answer 1

A deficiency or absence of septal tissue immediately above and/or below the normal plane of A-V valves. The valves are abnormal in shape and/or function.
Incomplete fusion of the endocardial cushions
which form primum atrial septum, A-V valves, and inlet ventricular septum

Question 2

Incidence of congenital heart disease is approximately

Answer 2

8 per 1000 live births.

Question 3

AVSD is the

Answer 3

5th most common occurring CHD.

Question 4

AVSD is commonly associated with

Answer 4

Down’s syndrome and cardiac malformations such as Tetralogy of Fallot (TOF), Double outlet right ventricle (DORV), and sub- aortic stenosis (SAS)

Question 5

down syndrome is also present

Answer 5

in 60% of patients with heterotaxy* syndrome.

• *Certain organs forming on the opposite side of the body

Question 6

children with a complete AV canal fail to

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thrive in the first few months of life.

Question 7

Patients may survive the first few years of life if the

Answer 7

PVR is high.

• High PVR decreases left to right shunting , increases LVEF

Question 8

If AV canal is repaired between

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4-6 months of life, survival is >80%.

Question 9

An endocardial cushion defect consists of defects in

Answer 9

lower atrial and upper ventricular septa, and deficiencies in the mitral/tricuspid valves.
Also called AVC, or AVSD

Question 10

Atrioventricular septal defects can be classified into one of three categories called

Answer 10

Complete • Partial • Transitional

CAVSD) (PAVSD) (TAVSD

Question 11

AVSD Classification

Balanced

Answer 11

• Ventricles are equal in size
• Size is relatively normal
• Both left and right AV valves may equally share the common AV valve orifice. This arrangement is termed a balanced defect.

Question 12

AVSD Classification unbalanced

Answer 12

• One of the ventricles may be hypoplastic

* Size will be different

Question 13

AV septal defects occur at the embryonic age and occurs because

Answer 13

of 34-36 days when fusion of the endocardial cushions fails.. This occurs when the endocardial cushion fibroblasts fail to migrate normally to form the septum of the AVC.

Question 14

• After fusing with the endocardial cushion, if there is a small residual opening at the ECC it is called

Answer 14

ostium primum ASD (AVSD).

Question 15

Embryology of AVSD

What is the end result?

Answer 15

Deficiency of the primum atrial septum, the ventricular septum, the septal leaflet of the tricuspid valve, and the anterior leaflet of the mitral valve occurs
• AV valves becomes offset • Anterior leaflet of the AV valve extends across septum

Question 16

If the leaflet opens preferentially toward a ventricle, (limiting flow to the other ventricle),

Answer 16

hypoplasia occurs and creates an unbalanced AVSD

Question 17

Complete AVSD

Answer 17

• Defect is one in which there are defects in all structures formed by the endocardial cushions.
• Therefore, there are defects (holes) in the atrial and ventricular septal, and the AV valve remains undivided or “common”. all chambers can mix

Question 18

Partial AVSD

Answer 18

• A partial atrioventricular septal defect is one in which the part of the ventricular septum formed by the endocardial cushions has filled in: (no VSD)

Question 19

Partial AVSD fills in by

Answer 19

issue from the AV valves or directly from the endocardial cushion tissue causing
• tricuspid and mitral valves dividing into two distinct valves. valvular geometry may be affected

Question 20

Partial AVSD

• The defect is, therefore,

Answer 20

primarily in the atrial septum and mitral valve.

Question 21

Partial AVSD. This type of atrial septal defect is referred to as an

Answer 21

ostium primum atrial septal defect, and is usually associated with a cleft in the mitral valve that causes the valve to leak (mitral regurgitation-MR)

Question 22

Partial AVSD Considerations

Answer 22

Conduction system disruption (A-V node displaced inferiorly between coronary sinus and ventricular crest)
• Coronary sinus ostium often displaced
• Associated anomalies: PDA, persistent LSVC

Question 23

Transitional AVSD. looks similar to the complete form of atrioventricular septal defect, but the

Answer 23

leaflets of the common AV valve are stuck to the ventricular septum, thereby effectively dividing the valve into two valves and closing most of the hole between the ventricles.

Question 24

Transitional AVSD

• As a result, a transitional atrioventricular septal defect behaves more like a

Answer 24

partial atrioventricular septal defect, even thought it looks more like a complete atrioventricular septal defect.

Question 25

Surgical Repair of AVSD | • Palliation for excessive pulmonary flow:

Answer 25

* PA Band: • Increases PVR | * Decreases Pulmonary Flow • Decreases Pulmonary Over-circulation

Question 26

Surgical Repair of AVSD | Palliation for insufficient pulmonary flow:

Answer 26

In patients with inadequate pulmonary flow/hypoxemia, aBlalock-Taussig- Thomas shunt or central shunt will be used.

Question 27

Surgical Repair of AVSD | • Palliation (overview)

Answer 27

PA Band B-T Shunt Central Shunt

Question 28

• Two Types of Complete Repair

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• Bi-ventricular Repair • Univentricular Repair

Question 29

The treatment of choice for an AVSD is

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complete surgical repair.

Question 30

Bi-ventricular Repair | • The VSD is often closed with

Answer 30

a synthetic patch (Dacron).

Question 31

Bi-ventricular Repair. the ASD is often closed with

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a pericardial patch

Question 32

Bi-ventricular Repair Valve repait technique

Answer 32

Attempt to repair the abnormal valve. This is accomplished by suturing/cutting the cleft (the cut in the valve leaflets) to recreate a two-leaflet mitral valve. • The tricuspid valve may also be repaired.

Question 33

Surgical Goals of Univentricular Repair

Answer 33

• The eventual goal of surgical repair is to separate pulmonary and venous outflow, and is usually done with staged procedures, culminating in the Fontan Procedure.

Question 34

Univentricular Repairs AVSD | • Stage One

Answer 34

Blalock-Taussig (BT) shunt: usually performed within the first few days after birth, and establishes a systemic-to-pulmonary artery shunt between the brachiocephalic artery or the right subclavian artery, to the right pulmonary artery via (usually) a tubed homograft or synthetic graft.

Question 35

Univentricular Repairs AVSD | • Stage two

Answer 35

Bi-Directional Glenn Procedure or Hemi-Fontan: usually performed at 4-6 months after birth as a bridge to Fontan completion. The BT shunt and pulmonary artery band is usually removed. The superior vena cava is then attached to right pulmonary artery, creating a systemic venous-to- pulmonary connection.

Question 36

Hemi-Fontan Procedure | Bi-directional CavopulmonaryAnastomosis

Answer 36

• Anastamosis PA/Right atrial appendage • SVC is patched

Question 37

Univentricular Repairs AVSD | • Stage 3

Answer 37

• Fontan Completion: Usually performed at 2-3 years of age; the inferior vena cava is connected to the right pulmonary artery via a tunnel like patch within the right atrium (Lateral Tunnel Fontan), or by creating a conduit for IVC flow outside the right atrium (Extracardiac Fontan).

Question 38

Fontan | Intracardiac

Answer 38

Atrial Baffle Lateral Tunnel

Question 39

FONTAN fenestration acts as

Answer 39

POP OFF VALVE

Question 40

Why is atrioventricular canal a concern?

Answer 40

* If not treated, this heart defect can cause lung disease. * larger volume of blood than normal must be handled by the right side of the heart. * causes higher volume than normal and higher pressure than normal in the blood vessels in the lungs.

Question 41

Pathophysiology of atrioventricular canal on lungs

Answer 41

* The lungs are able to cope with this extra volume of blood at high pressure for a while. * lungs become damaged by this extra volume of blood at high pressure. * The blood vessels in the lungs get thicker. * With time, these changes in the lungs become irreversible

Question 42

CPB Circuit Considerations of AVSD | • Palliation stage

Answer 42

Shunts: Usually done early with small size to | prevent damage caused by flow and pressure

Question 43

May/may not utilize CPB (standby)

Answer 43

PA Band:off CPB BT shunt: OFF CPB Central Shunt : both on and off CPB

Question 44

CPB Circuit Considerations of AVSD • Surgical Repair: Bi-ventricular • Cannulation:

Answer 44

Arterial: Aortic cannulation • Venous: Bicaval cannulation • LV Vent:Flexible vent when the heart is open

Question 45

CPB Circuit Considerations of AVSD | • Surgical Repair: Bi-ventricular CROSS CLAMP and cpb time

Answer 45

Aotic Cross-Clamp w/ multiple antegrade CP dosing | • CPB time is moderate in length

Question 46

Surgical Repair: Univentricular • Bi-Directional Glenn Shunt:

Answer 46

* Single Atrial Cannula • (Circulatory arrest – short or off-pump) * Aortic Arterial

Question 47

Surgical Repair: Univentricular • Bi-Directional Glenn Shunt. fontan

Answer 47

• Single Atrial Cannula (DHCA) • Aortic arterial

Question 48

Defect of the endocardial cushions • 3 Types:

Answer 48

• Complete Partial Transitional. Will be: • Unbalanced Balanced. corrected by Complete Repair Staged Procedures

Question 49

Surgical Summary of Repairs | • Complete:

Answer 49

• ASD patch • VSD patch • Valve repair

Question 50

Surgical Summary of Repairs staged procedures

Answer 50

1. Palliative Shunt - BTS - Central 2. Bi-Directional Glenn 3. Fontan Procedure