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Etiologies of congenital heart disease.
(5)
- single gene defects
- environmental factors
- maternal ingestion of toxic substances
- viral exposures
- unknown
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The heart is the first organ to complete its development.
Single tube:
Complete heart:
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HEART TUBE SEGMENTS:
(5)
- Truncus Arteriosus
- Conus Cordus OR Bulbus Cordus
- The Common Ventricle
- The Common Atrium
- Sinus Venosus
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The Truncus Arteriosus forms:
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The Bulbus Cordis OR Conus Cordus forms:
Outlet of Ventricles
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The Common Ventricle forms:
Inlet of Ventricles.
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The Common Atrium forms:
Right & Left Atria
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The Atrioventricular Canal forms _____ & _____ between the Common Ventricle and Common Atrium.
TV & MV
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Formation of the Heart Loop:
- NL
- Dextro- OR d-looping (Rightward)
- ABNL
- Levo- OR l-looping (Leftward)
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Septation:
Begins to take place around _____ day OR _____ day.
The _____ are first.
At no time during fetal development are the ____ completely separated.
The ____ ____ are also developing.
- 30th OR 31st
- atria
- atria
- endocardial cushions
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3 types of ASD's:
- Ostium Primum: located near the AV valves, usually has valvular involvement.
- Ostium secundum: located in the middle of the septum. (Most common).
- Sinus Venosus: located high in the atrium.
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Formation of the IVS and Role of the Bulbus Cordis.
End of ____ week, the primitive ventricle grows and dilates.
There is a communication between ______.
____ ____ are created.
The ______ develops from the bulbous cordis.
This remains open until the ____ week.
- 4th
- ventricles
- Bulbar ridges
- infundibulum
- 7th
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4 types of VSD's:
(REFER TO DRAWING)
- Perimembranous: located above the crista supraventricularis. (80% of VSD's) The communication between the LV and RA.
- Muscular: located below the crita supraventricularis. (5-20% of VDS's) The most common defect in infants.
- Infracristal
- Supracristal
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Endocardial Cushion Defect:
Highly associated with Down's Syndrome.
Failure of the cushions to form and migrate during embryonic development. There can be a partial AV canal or a complete AV canal defect. Without repair there will be heart failure.
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Tricuspid Atresia:
- If there is a disruption between the balance of proliferation and reabsorbtion, the tricuspid valve will not form normally.
- If the valve doesn't form at all, there would be no communication between the RA and RV.
- Blood clots are more prevalent.
- Treatment: Surgery.
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Ebstein's Anomaly:
- Atria acts as ventricles and visa versa.
- Rt to Lt shunting may be present.
- TR will probably be present.
- Disruption of TV annulus, which could cause electrical conduction problems.
- WPW Syndrome (Wolf Parkinson White)
- Heart Failure will result, if not treated.
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Tetralogy of Fallot:
- Infundibular stenosis: RVOT or LVOT
- VSD
- RVH
- Overriding Ao or dextropositioned Ao.
- Treatment: VSD patch, PS graft to widen.
- Gene defects, like Down's Syndrome may contribute to Tetralogy of Fallot.
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Tet spells:
Occurs when drinking/eating. Fingers, lips, and toes turn blue. Baby then begins to gasp for air... then squats to help increase the volume of blood flow to the heart and lungs.
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Transposition of the Great Arteries:
The Ao will come off of the Rt ventricle and the Pulm A will come off of the Lt ventricle.
Could be PDA and VSD's present.
Treatment: Norwood procedure
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Corrected Transposition of the Great Arteries:
- ABNL l-looping (leftward)
- LV will be anteriorly placed versus the RV will be posteriorly placed.
The swapping of ventricles.
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Total Anomalous Pulmonary Venous Return:
No Pulm V.(s) go into the LA.
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Partial Anomalous Pulmonary Venous Return:
- (PAPVR)
- One or more of the Pulm V.(s) do not go into the LA.
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Coarctation of the Ao
- Preductal Coarctation
- Postductal Coarctation
- @ Ductus
Interruption of Ao Arch -- Duct dependent lesion. (6-10% of congenital cases are Coarctations).
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Semilunar Valve Development:
- 3 outgrowths of subendocardial tissue forms around both the Ao & Pulm orifices.
- Between 6th and 9th weeks of gestation.
- Ao Arch is also forming.
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Atrioventricular Valve Development:
- After the endocardial cushions fuse, the tissue that surrounds each canal begins to proliferate.
- Occurs during 5th and 6th week of gestation.
- Similar outgrowths appear.
- Programmed cell death of the myocardial tissue takes place.
- This leaves behind a few fine strands known as the "chordae tendineae".
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Hypoplastic Left-Heart Syndrome:
Refer to image.
LV is almost non existent.
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Fetal Circulation:
- O2 rich blood from placenta travels through the umbilical vein.
- Half of the umbilical blood is shunted through the fetal ductus venosus and proceeds directly into the IVC.
- The other half passes through the portal vein to the liver and into the IVC through the hepatic veins.
- Majority of IVC blood entering the RA is directed to the LA through the foramen ovale.
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Distribution of Oxygenated blood from the Ao:
Coronary A(s):
Upper Extremeties:
Lower Extremeties:
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Distribution of SVC blood:
- It passes to RV.
- Flows into the Pulm A and through either the ductus arteriosus into the Desc. Ao --- 88% of RV output.
- OR
- Flows throught the Pulm A and into the lungs---12% of RV output.
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Transitional Circulation:
As the umbilical cord is clamped, or constricts naturally, the low-resistance placental flow is removed from the system, resulting in an increase in systemic vascular resistance.
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