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BS - Cardiovascular System > Congenital Heart Defects > Flashcards

Congenital Heart Defects Flashcards

1
Q

What is dextrocardia?

A

A rare condition in which the apex of the heart points towards the right side of the chest

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2
Q

In what 2 ways may dextrocardia arise?

A
  1. as a result of abnormal cardiac looping

2. it may be induced during gastrulation (week 3)

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3
Q

How may dextrocardia result from abnormal cardiac looping?

A

Normal looping involves a bend to the RHS, ventrally and caudally

In dextrocardia, it bends to the left

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4
Q

How may dextrocardia occur during gastrulation?

A

Cilia sweep cells to the correct sides of the body

In Kartagener syndrome, the cilia may sweep cells to the wrong side of the body

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5
Q

What is isolated dextrocardia?

A

This is when only the heart is on the opposite side of the body

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6
Q

Why does isolated dextrocardia not usually cause problems?

A

As long as the major vessels connect to the correct structures, there are no issues

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7
Q

What other structural defects is isolated dextrocardia associated with?

A

Abnormal connections with veins and arteries

Abnormal septation of the heart

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8
Q

What happens in dextrocardia if the vessels transpose?

A

Serious complications

e.g. oxygenated blood will be sent to the lungs

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9
Q

What is the role of the ductus arteriosus in the foetus?

A

It joins the aorta to the pulmonary trunk

It is used for blood to pass from the PT into the aorta and bypass the lungs

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10
Q

Why does the ductus arteriosus close at birth?

A

It closes due to increasing oxygen tension and a decrease in circulating prostaglandins

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11
Q

What does the ductus arteriosus become in the adult?

A

Ligamentum arteriosum

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12
Q

What happens in patent ductus arteriosus?

A

The ductus arteriosus remains open after birth

This causes shunting of blood from the aorta to the pulmonary artery

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13
Q

What is the result of having a patent ductus arteriosus in an adult?

A

Oxygenated blood travels back to the lungs, and then returns to the heart to be pumped out again

This increases the workload of the heart

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14
Q

Why does the blood flow through the ductus arteriosus in the opposite direction to the foetus?

A

In a foetus, blood moves from pulmonary trunk to aorta

In an adult, blood moves from the aorta to the pulmonary artery

Blood moves down a pressure gradient

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15
Q

What are the 3 main conditions that patent ductus arteriosus can lead to?

A
  1. pulmonary hypertension
  2. ventricular hypertrophy
  3. heart failure
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16
Q

Why does patent ductus arteriosus lead to pulmonary hypertension?

A

there is increased pressure going towards the lungs

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17
Q

What is ventricular hypertrophy?

Why is it necessary in patent ductus arteriosus?

A

The muscle of the ventricle increases in thickness

This is needed to allow the ventricle to work against the extra pressure

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18
Q

In what cardiac defect is a patent ductus arteriosus essential for life?

A

Coarctation of the aorta

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19
Q

How is patent ductus arteriosus treated?

Why?

A

Prostaglandin inhibitors

Prostaglandins keep the ductus arteriosus open

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20
Q

As the septum primum reaches full septation, what happens?

A

There is cell apoptosis to develop a small opening

This allows blood to pass from one side of the heart to the other

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21
Q

How does blood flow through the septa in a foetus and why?

A

Blood must pass through the foramen primum before the foramen secundum

This is due to the holes in the 2 septa being misaligned

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22
Q

After birth, why does the septum primum push against the septum secundum and fuse?

A

There is an increased amount of blood entering the left atrium

this pushes the septum primum against the septum secundum

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23
Q

What happens if the septum primum and septum secundum fail to fuse after birth?

A

This leads to probe patent foramen ovale

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24
Q

How common is probe patent foramen ovale?

A

Very common and occurs in 1 in 4 people

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25
Q

Why is probe patent foramen ovale usually asymptomatic?

A

The higher pressure in the left atrium pushes the septum primum against the septum secundum

This mechanically shuts the valve

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26
Q

When will a probe patent foramen ovale become symptomatic?

A

If there is a higher pressure in the right atrium, this pushes the flimsy septum primum open

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27
Q

What happens if the flimsy septum primum is pushed open?

A

Blood can shunt from right to left

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28
Q

What is the primum/secundum atrial septal defect caused by?

A

Malformations in the septum primum or septum secundum

They do not overlap fully, and therefore leave a gap

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29
Q

What is the result of a primum/secundum atrial septal defect?

A

An opening in the septum means that blood can pass from one atrium to the other

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30
Q

In which septum do defects usually occur ?

A

Septum secundum

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31
Q

What type of defect will excessive apoptosis in the septum primum lead to?

A

An ostium secundum defect

This is because the hole is too large to fill

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32
Q

How else may an ostium secundum defect be caused?

A

Inadequate development of the septum secundum

This can lead to the formaen ovale and ostium (foramen) secundum overlapping

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33
Q

What is the result of a ostium secundum defect?

A

Blood is shunted from left to right

This can cause enlargement of the right atrium and ventricle

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34
Q

How are ostium secundum defects treated?

A

Small defects < 5mm are usually asymptomatic as there is not much mixing of blood

Larger defects require surgical repair

35
Q

What is cor triloculare biventriculare?

A

It is also called common atrium

It is a rare cardiac defect with complete absence of the atrial septum

36
Q

What causes cor triloculare biventriculare?

A

Failure of development of the septum primum and septum secundum

This leads to formation of one common chamber

37
Q

What is the major consequence of cor triloculare biventriculare?

A

Mixing of oxygenated and deoxygenated blood

38
Q

What is ‘premature closure of the foramen ovale’?

A

This occurs when the foramen ovale closes during prenatal life

39
Q

How does premature closure of the foramen ovale affect the right and left sides of the heart?

A

It results in hypertrophy of the right side of the heart

And underdevelopment of the left side of the heart

40
Q

Why does premature closure of the foramen ovale lead to underdevelopment of the left side of the heart?

A

Blood cannot go from the right to the left side of the heart

The left side does not receive as much blood, so cannot develop properly

41
Q

Why does premature closure of the foramen ovale lead to hypertrophy of the right side of the heart?

A

The right ventricle becomes thicker and more muscular to deal with the increased volume of blood

42
Q

Why does premature closure of the foramen ovale usually result in death after birth?

A

The undeveloped left heart cannot pump sufficient amounts of blood around the body after birth

43
Q

What are the most common congenital heart defects?

A

Ventricular septal defects

44
Q

Which part of the heart may be affected by a ventricular septal defect?

A

Either the muscular or membranous part of the interventricular septum

45
Q

How do defects of the muscular part of the interventricular septum resolve themselves?

A

They resolve themselves as the child grows

As they grow, the muscles get bigger and the gap decreases in size until it eventually fuses

46
Q

What is the result of having a ventricular septal defect on blood flow?

A

It allows left to right shunting of blood

This leads to an increased amount of blood in the right heart

47
Q

What can ventricular septal defects cause?

A

Pulmonary hypertension

Hypertrophy of the right ventricle

48
Q

Why does a ventricular septal defect lead to pulmonary hypertension?

A

There is an increased amount of blood and increased pressure going to the lungs

49
Q

What does formation of the conotruncal septum rely on?

A

The conotruncal swellings that form the conotruncal septum rely on the migration of neural crest cells from the neural tube

50
Q

What does abnormal neural crest cell development or migration lead to?

A

Defects in septation of the truncus arteriosus into the pulmonary trunk and the aorta

51
Q

What type of septation does the common outflow tract rely on?

A

Spiral septation

The spiral must develop in an even format to develop into a pulmonary trunk and aorta

52
Q

What will transposition of the great vessels lead to?

A

The aorta will lead to the lungs

The pulmonary trunk will lead to the rest of the body

53
Q

What is the state of the conotruncal septum in persistent truncus arteriosus?

A

The conotruncal septum is completely absent

It cannot fuse with the interventricular septum

54
Q

What happens in persistent truncus arteriosus?

A

The undivided truncus arteriosus is in communication with both ventricles

It receives both oxygenated and deoxygenated blood

55
Q

What are symptoms of persistent truncus arteriosus?

A
  1. cyanosis at birth
  2. lethargy
  3. breathlessness
  4. delayed growth
56
Q

What happens if persistent truncus arteriosus is not fixed surgically?

A

It results in heart failure and death within 2 years

57
Q

What is the state of the conotruncal septum that leads to transposition of the great vessels?

A

The conotruncal septum does not form in a spiral

It runs straight down

58
Q

In which situations is transposition of the great vessels compatible with life?

A

It is incompatible with life unless a shunt exists

This may be:

  1. ventricular septal defect
  2. patent foramen ovale
  3. patent ductus arteriosus
59
Q

What happens in transposition of the great vessels?

A

The aorta arises from the RV

The pulmonary artery arises from the LV

Oxygenated blood is going to the lungs, and deoxygenated blood is travelling around the body

60
Q

What is tetralogy of Fallot?

A

A collection of 4 abnormalities caused by the same primary defect

61
Q

What causes the abnormalities in tetralogy of Fallot?

A

Anterior displacement of the aorticopulmonary septum causes unequal division of the truncus arteriosus

62
Q

What are the 4 cardiac defects present in tetralogy of Fallot?

A
  1. pulmonary stenosis
  2. ventricular septal defect
  3. overriding aorta
  4. right ventricular hypertrophy
63
Q

What is pulmonary stenosis?

A

Narrowing of the pulmonary trunk

64
Q

What is the ventricular septal defect present in tetralogy of Fallot?

A

the last section of the conotruncal septum cannot form properly

This is where the membranous part of the ventricular septum attaches to

65
Q

What is overriding aorta?

A

Rightward displacement of the aorta

And the aorta is larger than usual

66
Q

What causes right ventricular hypertrophy?

A

The higher pressure on the right side of the heart

67
Q

What is the consequence of tetralogy of Fallot?

A

Poor oxygenation of the body leading to cyanosis

68
Q

How many births are affected by Tetralogy of Fallot?

A

1 in 1000 births

It is not fatal

69
Q

What is coarctation of the aorta?

A

Narrowing of the aorta that occurs near the ductus arteriosus

70
Q

What is the consequence of coarctation of the aorta?

A

Not enough blood can pass through the systemic circulation

71
Q

What is the cause of coarctation of the aorta?

A

The cause is unknown but is may be due to abnormal migration of cells from the ductus arteriosus

72
Q

How is coarctation of the aorta classified?

A

In relation to the ductus arteriosus

It is either preductal or postductal

73
Q

What is the difference between preductal and postductal coarctation of the aorta?

A

Preductal - the narrowing occurs before the ductus arteriosus

Postductal - the narrowing occurs after the ductus arteriosus

74
Q

What happens to the ductus arteriosus after birth if coarctation is preductal?

A

It usually remains open

It acts as a shunt to bypass the coarctation

75
Q

What happens to an infant with preductal coarctation, if the ductus arteriosus is obliterated?

A

It causes rapid decline of the infant with hypoperfusion of the lower body

This leads to differential cyanosis

76
Q

What is meant by differential cyanosis in preductal coarctation?

A

The upper body and head are well perfused

The lower body is cyantotic

77
Q

How is preductal coarctation of the aorta treated?

Why is postductal coarctation not treated this way?

A

Administering prostaglandins to keep the ductus arteriosus open

If the coarctation occurs after the ductus arteriosus, there is no point in keeping it open

78
Q

Which type of coarctation of the aorta is more common?

A

Postductal coarctation

79
Q

What happens during development in postductal coarctation of the aorta?

A

A collateral circulation is established to bypass the narrowing

80
Q

What is the first part of the collateral circulation?

A

Blood passes from the arch of the aorta into the subclavian arteries

81
Q

What do the subclavian arteries join to in the collateral circulation?

A

The subclavian arteries lead to the internal thoracic arteries

82
Q

How does blood pass from the internal thoracic arteries into the descending aorta in collateral circulation?

A

The internal thoracic arteries lead to anterior intercostal arteries

The anterior intercostal arteries anastomose with the posterior intercostal arteries

Blood leads from the posterior intercostal arteries into the descending aorta

83
Q

As a result of coarctation of the aorta, what happens to the internal thoracic and intercostal arteries?

A

They enlarge in order to carry greater blood flow

BS - Cardiovascular System (20 decks)

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