Etiologies of congenital heart disease.
- single gene defects
- environmental factors
- maternal ingestion of toxic substances
- viral exposures
The heart is the first organ to complete its development.
HEART TUBE SEGMENTS:
- Truncus Arteriosus
- Conus Cordus OR Bulbus Cordus
- The Common Ventricle
- The Common Atrium
- Sinus Venosus
The Truncus Arteriosus forms:
The Bulbus Cordis OR Conus Cordus forms:
Outlet of Ventricles
The Common Ventricle forms:
Inlet of Ventricles.
The Common Atrium forms:
Right & Left Atria
The Atrioventricular Canal forms _____ & _____ between the Common Ventricle and Common Atrium.
TV & MV
Formation of the Heart Loop:
- Dextro- OR d-looping (Rightward)
- Levo- OR l-looping (Leftward)
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
- endocardial cushions
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.
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.
- Bulbar ridges
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.
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.
- 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.
- 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.
Tetralogy of Fallot:
- Infundibular stenosis: RVOT or LVOT
- Overriding Ao or dextropositioned Ao.
- Treatment: VSD patch, PS graft to widen.
- Gene defects, like Down's Syndrome may contribute to Tetralogy of Fallot.
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.
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
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.
Total Anomalous Pulmonary Venous Return:
No Pulm V.(s) go into the LA.
Partial Anomalous Pulmonary Venous Return:
- One or more of the Pulm V.(s) do not go into the LA.
Coarctation of the Ao
- Preductal Coarctation
- Postductal Coarctation
- @ Ductus
Interruption of Ao Arch -- Duct dependent lesion. (6-10% of congenital cases are Coarctations).
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.
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".
Hypoplastic Left-Heart Syndrome:
Refer to image.
LV is almost non existent.
- 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.
Distribution of Oxygenated blood from the Ao:
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.
- Flows throught the Pulm A and into the lungs---12% of RV output.
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.