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Pediatrics > test 4 part 2 > Flashcards

test 4 part 2 Flashcards

1
Q

Three names for the same type of defect dealing with the AV sulcus

A
  • AVSD: Atrio-ventricular septal defect
  • ECD: Endocardial cushion defect
  • AVC: Atrio-ventricular canal defect
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2
Q

Definition: AVC/ECD/AVSD Defects

A
  • 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 the primum atrial septum, the A-V valves, and the inlet ventricular septum
  • AV valves fail to separate leaving common AV valve
  • Common valve may be insufficient
  • Pulmonary vascular obstructive disease secondary to high pulmonary flow usually occurs early
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3
Q

Lower part of atrial septum deficient / missing results in

A

• Left to right shunt

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4
Q

Upper part of ventricular septum deficient / missing results in

A

• Left to right shunt

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5
Q

Epidemiology: A-V Canal

A
  • Prevalenc of all congenital heart disease is approximately 8 per 1000 live births
  • AVSD is the 5th most common occurring CHD
    * 4% to 5% total congenital cases; prevalence of 0.3 to 0.4 per 1000 live births
  • Can be assessed with more complex problems
  • It is also present in 60% of patients with heterotaxy syndrome
    * Disorder where some organs form on opposite side of body
    * Often associated with asplenia (increased chance of infection) (might not have a spleen)
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6
Q

Morbidity and Mortality A-V Canal

A
  • Children with a complete AV canal fail to thrive in the first few months of life
  • Patients may survive the first few years of life if the PVR is high
  • High PVR decreases left to right shunting which increases LVEF
  • If AV canal is repaired between 4-6 months of life, survival is >80%
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7
Q

Day of Outflow tract septation and days of atrial and Ventricular septation and development

A
  • Day 27-37: Atrial and Ventricular septation and development
  • Day 29: Outflow tract septation
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8
Q

Embryology of AVSD

A
  • AV septal defects occur at the embryonic age 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 atrio-ventricular canal
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9
Q

What are the end results of developmental problems of the AV canal

A
  • Deficiency of the:
    * Primum atrial septum
    * Ventricular septum
    * Septal leaflet of the tricuspid valve
    * Anterior leaflet of the mitral valve
  • AV valves becomes offset
  • Anterior leaflet of the AV valve extends across septum
  • If the leaflet opens preferentially toward a ventricle
    * Limits flow to other ventricle (one ventricle bigger than the other)
    * Hypoplasia occurs creating an unbalanced AV Canal
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10
Q

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

A
  • Complete (CAVSD)
    * Balanced (how the common valve is postitioned in the ventricles)
    * Unbalanced (how the common valve is postitioned in the ventricles)
  • Transitional (TAVSD)
  • Partial (PAVSD)
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11
Q

Complete AVSD: Balanced

A
  • most common
  • 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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12
Q

Complete AVSD: Unbalanced

A
  • One of the ventricles may be hypoplastic

* Size will be different

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13
Q

Complete AV Canal

A 
• Complete AVC has defects in all structures formed by the endocardial cushions.
• ASD
• VSD
• Common AV valve
- Blood in ALL 4 chambers can mix
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14
Q

Transitional AV Canal

A

• Normal ASD present
• Bridge of tissue forms anterior to posterior dividing common valve into right and left component
• Mitral valve has cleft (additional commissure)
• Only small VSD remains
- STILL HAVE ASD BUT A SMALL VSD
• A transitional atrioventricular septal defect behaves more like a partial
atrioventricular septal defect, even thought it looks more like a complete atrioventricular septal defect (i.e. has a VSD).

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15
Q

Partial AV Canal

A

• 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
• Primum ASD
• Cleft mitral valve
• Geometry of valve may be affected – usually leads to MR
- Only partial mixing of the blood through the ostium primum ASD (limits amount of mixing because it must go through ASD)

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16
Q

Partial AV Canal Considerations

A
  • Conduction system disruption (because AV node is being shifted)
    * A-V node displaced inferiorly between coronary sinus and ventricular crest
  • Coronary sinus ostium often displaced
  • Associated anomalies
    * PDA, Persistent Left SVC
17
Q

Surgical Interventions for AV Canal

A
  • It’s all about pulmonary blood flow
    • Flow can be too high or too low
    • Depends on size of septal defects – normally left to right
    • Pulmonary damage will lead to right to left (IF NOT FIXED)
    • Large VSD or unbalanced ventricles could produce right to left
    • Keep flow as “normal” as possible
  • Choice of palliation versus complete repair depends on many variables. TIMING OF INTERVENTION IS IMPORTANT.
    • Age; Patient health; Severity disease; Patient tolerance of treatment; Expectations for course of disease
18
Q

PA Banding – Excess Pulmonary Flow

A
  • Palliation for excessive pulmonary blood flow
    • Increases PVR (without affecting pulmonary vasculature)
    • Decreases Pulmonary Flow
    • Decreases Pulmonary Over-circulation
  • Reduce the potential for development of pulmonary vascular damage
  • used more with balance
19
Q

PA Banding - Complications

A

• Band migration and distortion of PA branches (could effect flow to one side or the other)
• Erosion of band into the lumen of the PA (could go through PA tissue and go into the artery)
• Distortion of pulmonary valve
• Subannular ventricular hypertrophy and thickening of the outflow tract
- when the band is removed and the hypertrophy and outflow track are changed permanently which increases life long pulmonary pressure
- damage to the pulmonary vasculature happens before damage to the ventricle

20
Q

Insufficient Pulmonary Flow

A
  • Insufficient flow can be caused by combination of congenital problems
    • Combination of Tetralogy of Fallot (TOF) and AV canal
    • Left unbalanced AV canal (small right ventricle)
  • Purpose of palliation
    • Ensure adequate pulmonary blood flow using arterial to pulmonary artery shunt
    • Does not require CPB but it is a SHUNT that steals arterial blood flow
21
Q

Palliation for Insufficient pulmonary Flow

A
  • Blalock-Tausig Shunt
    * Subclavian artery to pulmonary artery (direct connection, no artificial graft)
    * Modified using any systemic artery to the pulmonary artery (direct connection or via artificial graft)
  • Central Shunt
    * Connect aortic root / ascending aorta to pulmonary artery usually with graft
22
Q

The treatment of choice for an AV Canal is

A
  • complete surgical repair.
23
Q

Two Types of Complete Repair of the AV canal

A
  • Bi-ventricular Repair
    * RV and LV normal and functional
  • Univentricular Repair
    * Single ventricle (i.e. VSD so large there is no separation)
    * AV canal combined with TOF
    * Left unbalanced AV canal with small RV
24
Q

Bi-ventricular Repair

A
  • True repair of defect – Returns flow patterns to normal – Requires CPB
    • The VSD is often closed with a synthetic patch (Dacron, Gore Tex), or bovine pericardium
    • The ASD is often closed with a pericardial patch
    • Valve repair technique:
    • Attempt to repair the abnormal valve. This is accomplished by suturing/cutting the cleft to recreate a two-leaflet mitral valve.
    • The tricuspid valve may also be repaired.
25
Q

Surgical Goals of Univentricular Repair

A
  • The eventual goal of surgical repair is to separate pulmonary and venous outflow – ensure venous blood goes through pulmonary system
  • Usually done with staged procedures, culminating in the Fontan Procedure.
26
Q

Stage One: Blalock-Taussig (BT) shunt

A

• Usually performed within the first few days after birth
• Establishes a systemic-to-pulmonary artery shunt between the brachiocephalic artery (or the right subclavian artery) and the right pulmonary artery via (usually) a tubed homograft or synthetic graft.
- Does not require CPB

27
Q

Stage Two: Bi-Directional Glenn Procedure or Hemi-Fontan

A

• Usually performed at 4-6 months after birth as a bridge to Fontan completion
• 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.
- Starts process of diverting venous flow through pulmonary system –
Removes the A-V shunt – Can be completed without CPB

28
Q

Stage 3: Fontan Completion

A

• 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)
Completes replumbing so all venous return goes through the pulmonary system – Requires CPB

29
Q

Fontan

A 
- Connect IVC to PA
        • Intracardiac
                • Atrial baffle
                • Lateral tunnel
        • Extracardiac
- sometimes add a fenestration as a pop off valves to maintain acceptable pulmonary pressures
30
Q

Why is atrioventricular canal a concern?

A
  • 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.
    • 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
    • CHF will eventually ensue
31
Q

Palliation Stage

A
  • Shunts: Usually done early with small size to prevent damage caused by flow and pressure
  • PA Band: off CPB
  • BT shunt: off CPB
  • Central Shunt: both on and off CPB
32
Q

Surgical Repair: Bi-ventricular

A

• Cannulation
• Arterial: Aortic cannulation
• Venous: Bicaval cannulation
• LV Vent: Flexible vent when the heart is open
• Aortic Cross-Clamp w/ multiple antegrade CP dosing depending
on solution
• CPB time is moderate in length

33
Q

Surgical Repair: Univentricular

A
  • Bi-Directional Glenn
    * Can be done off-bypass
    * Single atrial cannula
    * Aortic arterial cannula
  • Fontan
    * Single atrial cannula
    * Aortic arterial cannula

Pediatrics (37 decks)

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