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

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

Flashcards in Atrio-Ventricular Canal (AVC) Endocardial Cushion Defects (ECD) Atrio-Ventricular Septal Defects (AVSD) Deck (50):
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Definition:AVSD/ECD/AVC Defects

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

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Incidence of congenital heart disease is approximately

8 per 1000 live births.

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AVSD is the

5th most common occurring CHD.

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AVSD is commonly associated with

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

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down syndrome is also present

in 60% of patients with heterotaxy* syndrome.
• *Certain organs forming on the opposite side of the body

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children with a complete AV canal fail to

thrive in the first few months of life.

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Patients may survive the first few years of life if the

PVR is high.
• High PVR decreases left to right shunting , increases LVEF

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If AV canal is repaired between

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

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An endocardial cushion defect consists of defects in

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

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

Complete • Partial • Transitional
(CAVSD) (PAVSD) (TAVSD)

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AVSD Classification
Balanced

• 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.

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AVSD Classification unbalanced

• One of the ventricles may be hypoplastic
• Size will be different

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AV septal defects occur at the embryonic age and occurs because

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.

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

ostium primum ASD (AVSD).

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Embryology of AVSD
What is the end result?

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

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

hypoplasia occurs and creates an unbalanced AVSD

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Complete AVSD

• 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

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Partial AVSD

• 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)

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Partial AVSD fills in by

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

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Partial AVSD
• The defect is, therefore,

primarily in the atrial septum and mitral valve.

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

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)

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Partial AVSD Considerations

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

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

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.

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

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

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Surgical Repair of AVSD
• Palliation for excessive pulmonary flow:

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

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Surgical Repair of AVSD
Palliation for insufficient pulmonary flow:

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

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Surgical Repair of AVSD
• Palliation (overview)

PA Band B-T Shunt Central Shunt

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• Two Types of Complete Repair

• Bi-ventricular Repair • Univentricular Repair

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The treatment of choice for an AVSD is

complete surgical repair.

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Bi-ventricular Repair
• The VSD is often closed with

a synthetic patch (Dacron).

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Bi-ventricular Repair. the ASD is often closed with

a pericardial patch

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Bi-ventricular Repair Valve repait technique

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.

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Surgical Goals of Univentricular Repair

• 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.

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Univentricular Repairs AVSD
• Stage One

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.

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Univentricular Repairs AVSD
• Stage two

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.

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Hemi-Fontan Procedure
(Bi-directional CavopulmonaryAnastomosis)

• Anastamosis PA/Right atrial appendage • SVC is patched

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Univentricular Repairs AVSD
• Stage 3

• 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).

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Fontan
Intracardiac

Atrial Baffle Lateral Tunnel

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FONTAN fenestration acts as

POP OFF VALVE

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Why is atrioventricular canal a concern?

• 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.

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Pathophysiology of atrioventricular canal on lungs

• 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

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CPB Circuit Considerations of AVSD
• Palliation stage

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

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May/may not utilize CPB (standby)

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

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

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

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

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

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Surgical Repair: Univentricular • Bi-Directional Glenn Shunt:

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

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

• Single Atrial Cannula (DHCA) • Aortic arterial

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Defect of the endocardial cushions • 3 Types:

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

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Surgical Summary of Repairs
• Complete:

• ASD patch • VSD patch • Valve repair

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Surgical Summary of Repairs staged procedures

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