1. Developmental Defects of Cardiovascular System
Biology of Disease CH0576
Developmental Defects of Cardiovascular System
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2. Congenital Defects
Given that the embryological and foetal development of the heart and the CVS is so complex, it may be assumed that there would be a vast range of congenital abnormalities.
In actual fact around 90% of the congenital defects can be grouped together under 4 main headings:-
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3. Congenital Defects The four major headings being:-
Septal defects
Patent Ductus Arteriosus
Pulmonary or Aortic Stenosis
Misplacement of Major Vessels, or Transposition.
Most cardiac malformations are evident at or shortly after birth.
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4. Congenital Defects
They may well become evident due to some symptom of cardiac failure or impairment of function:-
Cyanosis
Breathlessness
Feeding difficulties
Failure to thrive in neonatal period.
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5. Congenital Defects
In some instances (the vast minority) the malformations are attributed to maternal factors:-
maternal rubella infection
chronic alcohol abuse
In the majority of cases there are no clear links with any known teratogenic factors.
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6. Congenital Defects
The main cardiac abnormalities can be functionally divided into two major groups:-
Those which cause an abnormal ‘shunting’ of blood between the two sides of the heart.
Those which are associated with an obstruction to blood flow from the heart.
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7. Congenital Defects
The abnormal ‘shunting’ is usually a movement from left to right hand side of the heart.
Due to Left > Right, in terms of pressure.
These defects are not (at least initially) associated with cyanosis.
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8. Congenital Defects
If there is some obstruction to blood flow from the right hand side of the heart, there will tend to be a right to left shunt.
As a consequence the lungs will largely be bypassed.
As de-oxygenated blood passes into the systemic circulation, cyanosis will develop.
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9. Septal Defects
Defects within the septa or walls of the heart can occur in either the atria or the ventricles.
Atrial Defects:
These are the most common of the septal defects.
Lesion is usually at the level of the foramen ovale, from foetal circulation.
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10. Atrial Septal Defect After birth the pressure in Lt > Rt.
Blood passes via the lesion from left to right.
The right side of the heart receives more blood than usual.
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11. Atrial Septal Defect
Rt ventricle, in response to increased functional demand, undergoes hypertrophy.
The pulmonary artery also responds to the over-distension by enlarging.
Pulmonary arterial hypertrophy
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12. Atrial Septal Defect
The presence of an audible murmur on routine physical examination occurring at systole, over the second intercostal space, indicates a likely defect.
Catheterisation of the heart indicates that the oxygen content of the right atrial blood is > that of the superior or inferior vena cavae.
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13. Atrial Septal Defect
Should the infant’s condition warrant treatment, the defect can readily be closed surgically.
The surgical procedure nowadays carrying a very low mortality rate.
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14. Ventricular Septal Defect
These defects are more serious than the atrial septal defects.
Largely due to the much higher pressures involved.
The major problem being that the child with such a defect can develop a rapidly progressing pulmonary hypertension.
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15. Ventricular Septal Defect
Initially the symptoms are of a left to right shunt with a systolic murmur.
With the continuation of the situation there will be an pulmonary resistance to flow, due to  pulmonary arterial pressure
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16. Ventricular Septal Defect
Eventually RVP>LVP and hence the shunt will be reversed.
Blood will pass through the lesion from Rt to Lt.
As a consequence the lungs are largely by-passed.
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17. Ventricular Septal Defect
As a result of bypassing the high resistance pulmonary circuit:-
Cyanosis in the tissues.
2º Polcythaemia.
Finger clubbing, may develop as a result of  pO2 in the peripheral blood.
It is essential that ventricular septal defects are diagnosed and treated as early as possible.
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18. Patent Ductus Arteriosus
DA is the channel by which blood passes from the right heart into the aorta in foetal life.
Deflated lungs are bypassed and blood is passed to the placenta for oxygenation
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19. Patent Ductus Arteriosus
This duct often remains open as the result of a range of congenital defects.
Patency of the duct is more common in females (2x).
A recognised link with maternal rubella infection.
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20. Patent Ductus Arteriosus
Blood continually passes into the pulmonary circuit from the aorta (as, unlike in foetus) aortic pressure > pulmonary artery pressure.
This causes a characteristic ‘machinery murmur’, reaching a crescendo in systole, when the aortic pressure reaches around 125mm Hg.
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21. Patent Ductus Arteriosus
Eventually a pulmonary hypertension would result, due to the increase in pulmonary blood flow  continuous over - distension of the pulmonary artery.
This would result in hypertrophy of the vessel walls.
This condition should be diagnosed before this situation arises, surgical ligation of the PDA is 100% effective
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22. Aortic Coarctation
This is simply defined as a narrowing, or stenosis, of the aorta.
This condition is essentially divided into two main types:-
Infantile
Adult type.
These conditions differ in the position of the stenosis, and in their outcome!
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23. Aortic Coarctation
Infantile type is associated with the coarctation being proximal to the DA.
The DA remains patent.
In this form of condition a number of other cardiac abnormalities are common.
The infantile type is not consistent with life, and is generally seen in still-born infants.
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24. Aortic Coarctation
In the Adult type the stenosis is at or just distal to the DA, which is closed.
Coarctation of the aorta is associated with the presence of a loud systolic murmur, caused by turbulence at the stenotic site.
Murmur is generally loudest towards the base of the heart.
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25. Aortic Coarctation
Aortic constriction increases the workload on the left ventricle, triggering left ventricular hypertrophy ( a poor prognostic indicator, as previously seen).
Cardiac output is maintained at normal levels and the blood flow to the upper part of the body is normal or increased, as the pressure proximal to the stenotic site is higher.
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26. Aortic Coarctation
The blood makes its way to the lower part of the body by means of greatly dilated collateral vessels.
This collateral circulation fails to develop in the infantile type, as blood enters the aorta through the patent DA, beyond the constriction.
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27. Aortic Coarctation
The clinical picture of aortic coarctation is clear and characteristic:-
There is arterial hypertension of the upper part of the body.
Relative weakness and delay (or lag) in the pulse in the lower limbs, compared to that of the upper body and arms.
Evidence of an anastomotic collateral circulation.
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28. Aortic Coarctation Again, early surgical intervention is ideal.
In most cases the condition is discovered after some secondary complication has arisen.
Mild coarctations are consistent with a relatively long life.
Average life span is greatly diminished.
Generally few symptoms may be evident in childhood.
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29. Aortic Coarctation Potential hazards which may occur, include:-
Severe hypertension in upper body resulting in cardiac failure and/or CVAs
Bacterial endocarditis at the stenotic site.
Aneurysm formation immediately above or below the constriction.
Aortic rupture.
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30. Aortic Coarctation Treatment:
Aided by the well developed collateral circulation the surgeon clamps off the aorta above and beyond the stenosis.
The aorta is surgically divided, and the stenotic site removed.
The divided ends can either be sutured together or the stenotic area replaced by a catheter
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31. Aortic Coarctation
Occasionally the treatment can cause a further problem:-
When the full force of the arterial pressure hits the wall of the aorta, distal to the coarctation, the result can be a widespread necrosis of the branches of the abdominal aorta.
Resulting in a widespread gangrene of the small intestine.
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32. Tetralogy of Fallot
As the name suggests this a syndrome with four major features.
Probably the most important congenital lesion of the heart.
It is the most common lesion causing cyanosis.
About 70% of ‘blue babies’ are examples of this syndrome.
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33. Tetralogy of Fallot
It is essentially a VSD associated with other cardiac abnormalities.
The 4 features being:-
A high VSD
Pulmonary stenosis
Dextraposed over-riding aorta
Right ventricular hypertrophy
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34. Tetralogy of Fallot
Basic change in this tetralogy is the dextraposed aorta.
This causes the pulmonary artery stenosis.
The aorta is thick walled and wide compared with the stenotic pulmonary artery
The aorta over-rides the VSD and so receives blood from both ventricles.
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35. Tetralogy of Fallot
If the pulmonary stenosis is extensive or complete the DA must remain patent, to allow blood flow to the lungs.
Early closing of the DA in these circumstances would result in death.
Most cases are surgically treated
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36. Tetralogy of Fallot
The surgical operation known as the Blalock-Taussig procedure may be employed.
This bypasses the obstruction by creating an artificial DA, through which an adequate supply of blood can reach the lungs.
The subclavian artery is anastomosed with the pulmonary artery.
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37. Tetralogy of Fallot
The increase in blood flow to the lungs causes an increase in blood flow to the left heart.
This raises LVP, and minimises any right to left shunt.
Hence the cyanosis is relieved.
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38. Tetralogy of Fallot
Other surgical procedures which have been employed include the removal of and replacement of the pulmonary valve.
Resection of the stenotic region of the pulmonary artery has also been employed.
Complications may include bacterial endocarditis.
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