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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
Why is probe patent foramen ovale usually asymptomatic?
The higher pressure in the left atrium pushes the septum primum against the septum secundum This mechanically shuts the valve
26
When will a probe patent foramen ovale become symptomatic?
If there is a higher pressure in the right atrium, this pushes the flimsy septum primum open
27
What happens if the flimsy septum primum is pushed open?
Blood can shunt from right to left
28
What is the primum/secundum atrial septal defect caused by?
Malformations in the septum primum or septum secundum They do not overlap fully, and therefore leave a gap
29
What is the result of a primum/secundum atrial septal defect?
An opening in the septum means that blood can pass from one atrium to the other
30
In which septum do defects usually occur ?
Septum secundum
31
What type of defect will excessive apoptosis in the septum primum lead to?
An ostium secundum defect This is because the hole is too large to fill
32
How else may an ostium secundum defect be caused?
Inadequate development of the septum secundum This can lead to the formaen ovale and ostium (foramen) secundum overlapping
33
What is the result of a ostium secundum defect?
Blood is shunted from left to right This can cause enlargement of the right atrium and ventricle
34
How are ostium secundum defects treated?
Small defects < 5mm are usually asymptomatic as there is not much mixing of blood Larger defects require surgical repair
35
What is cor triloculare biventriculare?
It is also called common atrium It is a rare cardiac defect with complete absence of the atrial septum
36
What causes cor triloculare biventriculare?
Failure of development of the septum primum and septum secundum This leads to formation of one common chamber
37
What is the major consequence of cor triloculare biventriculare?
Mixing of oxygenated and deoxygenated blood
38
What is 'premature closure of the foramen ovale'?
This occurs when the foramen ovale closes during prenatal life
39
How does premature closure of the foramen ovale affect the right and left sides of the heart?
It results in hypertrophy of the right side of the heart And underdevelopment of the left side of the heart
40
Why does premature closure of the foramen ovale lead to underdevelopment of the left side of the heart?
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
Why does premature closure of the foramen ovale lead to hypertrophy of the right side of the heart?
The right ventricle becomes thicker and more muscular to deal with the increased volume of blood
42
Why does premature closure of the foramen ovale usually result in death after birth?
The undeveloped left heart cannot pump sufficient amounts of blood around the body after birth
43
What are the most common congenital heart defects?
Ventricular septal defects
44
Which part of the heart may be affected by a ventricular septal defect?
Either the muscular or membranous part of the interventricular septum
45
How do defects of the muscular part of the interventricular septum resolve themselves?
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
What is the result of having a ventricular septal defect on blood flow?
It allows left to right shunting of blood This leads to an increased amount of blood in the right heart
47
What can ventricular septal defects cause?
Pulmonary hypertension Hypertrophy of the right ventricle
48
Why does a ventricular septal defect lead to pulmonary hypertension?
There is an increased amount of blood and increased pressure going to the lungs
49
What does formation of the conotruncal septum rely on?
The conotruncal swellings that form the conotruncal septum rely on the migration of neural crest cells from the neural tube
50
What does abnormal neural crest cell development or migration lead to?
Defects in septation of the truncus arteriosus into the pulmonary trunk and the aorta
51
What type of septation does the common outflow tract rely on?
Spiral septation The spiral must develop in an even format to develop into a pulmonary trunk and aorta
52
What will transposition of the great vessels lead to?
The aorta will lead to the lungs The pulmonary trunk will lead to the rest of the body
53
What is the state of the conotruncal septum in persistent truncus arteriosus?
The conotruncal septum is completely absent It cannot fuse with the interventricular septum
54
What happens in persistent truncus arteriosus?
The undivided truncus arteriosus is in communication with both ventricles It receives both oxygenated and deoxygenated blood
55
What are symptoms of persistent truncus arteriosus?
1. cyanosis at birth 2. lethargy 3. breathlessness 4. delayed growth
56
What happens if persistent truncus arteriosus is not fixed surgically?
It results in heart failure and death within 2 years
57
What is the state of the conotruncal septum that leads to transposition of the great vessels?
The conotruncal septum does not form in a spiral It runs straight down
58
In which situations is transposition of the great vessels compatible with life?
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
What happens in transposition of the great vessels?
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
What is tetralogy of Fallot?
A collection of 4 abnormalities caused by the same primary defect
61
What causes the abnormalities in tetralogy of Fallot?
Anterior displacement of the aorticopulmonary septum causes unequal division of the truncus arteriosus
62
What are the 4 cardiac defects present in tetralogy of Fallot?
1. pulmonary stenosis 2. ventricular septal defect 3. overriding aorta 4. right ventricular hypertrophy
63
What is pulmonary stenosis?
Narrowing of the pulmonary trunk
64
What is the ventricular septal defect present in tetralogy of Fallot?
the last section of the conotruncal septum cannot form properly This is where the membranous part of the ventricular septum attaches to
65
What is overriding aorta?
Rightward displacement of the aorta And the aorta is larger than usual
66
What causes right ventricular hypertrophy?
The higher pressure on the right side of the heart
67
What is the consequence of tetralogy of Fallot?
Poor oxygenation of the body leading to cyanosis
68
How many births are affected by Tetralogy of Fallot?
1 in 1000 births It is not fatal
69
What is coarctation of the aorta?
Narrowing of the aorta that occurs near the ductus arteriosus
70
What is the consequence of coarctation of the aorta?
Not enough blood can pass through the systemic circulation
71
What is the cause of coarctation of the aorta?
The cause is unknown but is may be due to abnormal migration of cells from the ductus arteriosus
72
How is coarctation of the aorta classified?
In relation to the ductus arteriosus It is either preductal or postductal
73
What is the difference between preductal and postductal coarctation of the aorta?
Preductal - the narrowing occurs before the ductus arteriosus Postductal - the narrowing occurs after the ductus arteriosus
74
What happens to the ductus arteriosus after birth if coarctation is preductal?
It usually remains open It acts as a shunt to bypass the coarctation
75
What happens to an infant with preductal coarctation, if the ductus arteriosus is obliterated?
It causes rapid decline of the infant with hypoperfusion of the lower body This leads to differential cyanosis
76
What is meant by differential cyanosis in preductal coarctation?
The upper body and head are well perfused The lower body is cyantotic
77
How is preductal coarctation of the aorta treated? Why is postductal coarctation not treated this way?
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
Which type of coarctation of the aorta is more common?
Postductal coarctation
79
What happens during development in postductal coarctation of the aorta?
A collateral circulation is established to bypass the narrowing
80
What is the first part of the collateral circulation?
Blood passes from the arch of the aorta into the subclavian arteries
81
What do the subclavian arteries join to in the collateral circulation?
The subclavian arteries lead to the internal thoracic arteries
82
How does blood pass from the internal thoracic arteries into the descending aorta in collateral circulation?
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
As a result of coarctation of the aorta, what happens to the internal thoracic and intercostal arteries?
They enlarge in order to carry greater blood flow

BS - Cardiovascular System (20 decks)

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