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Cardiovascular > Congenital heart disease > Flashcards

Congenital heart disease Flashcards

1
Q

What are the functions of the placenta?

A

Most of the work of the lungs and kidneys:
Foetal haemostasis, gas exchange, Acid base balance, Transfer of maternal IgG to foetus, nutrient transport, waste transport, Hormone production, Production of prostaglandin E2 which maintains patency of the ductus arteriosus.

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2
Q

Why do the lungs of the foetus not expand?

A

Filled with lung fluid which is continuous with amniotic fluid

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3
Q

How are the gut and liver used in the foetus?

A

Liver has little role in nutrition and waste management (done by placenta)
Gut is only used when foetus swallows amniotic fluid.

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4
Q

Explain foetal circulation?

A

Single loop circulation where blood circulates from the placenta to the heart. A little bit goes to the lungs (not 100% like in adults) then to the brain and body and back to the placenta

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5
Q

What is contained within the umbilical cord?

A

1 umbilical vein: placenta to baby carryinf oxygen and nutrient rich blood
2 umbilical arteries: Baby to placenta carrying deoxygenated blood.

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6
Q

Which 3 shunts help to sustain foetal life?

A

Ductus Venosus
Foraman ovale
Ductus arteriosus

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7
Q

What is the ductus venosus and what is its function?

A

Found in the liver connecting the umbilical vein to the IVC to bypass portal circulation which is not in use.
This is because nutrients from the placenta do not need further processing in the liver

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8
Q

What is the foramen ovale and what is its function?

A

Opening of the atrial septum connecting RA to LA allowing blood to shunt from R to L.
Most oxygenated and nutrient blood from the IVC crosses the RA and passes through the foramen ovale into the left heart

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9
Q

In the fetus, on which side of the heart is the pressure greater?

A

Right side due to resistance in the lungs

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10
Q

What happens to the blood carried by the IVC which does not pass into the foraman ovale?

A

It mixes with deoxygenated venous return, passes into the RV and pulmonary artery

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11
Q

How does the foraman ovale close after birth?

A

Membrane flap on the left side of the foramen ovale (Septum primum)

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12
Q

What is the ductus arteriosus and what is its function?

A

Connects the pulmonary bifurcation to the descending aorta. This means only a little blood goes t the lungs of the fetus

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13
Q

What percentage of the right ventricular output goes to the lungs in the fetus and why?

A

7% because resistance in the lungs is very high as they are fluid filled.

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14
Q

Why is the pressure in the systemic circulation so low?

A

The placenta is a large vascular organ with many large blood vessels therefore most of the blood in the RV goes into the descending aorta via the ductus arteriosus

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15
Q

What maintains the patency of the ductus arteriosus?

A

Circulating prostaglandin E2 produced by the placenta.

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16
Q

What happens to oxygen saturations at birth?

A

Initially baby very blue with saturations at 60-65%
Baby inflates lungs and crys. Within 10 minutes saturations rise to 85%.
The cord will constrict, be clamped and cut

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17
Q

What happens to pulmonary vascular resistance at birth?

A

Decreases as the baby breaths in and the lungs physically expand reducing intrathoracic pressure.
This increases circulating oxygen which acts as a vasodilator in the lungs

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18
Q

What happens to the systemic vascular resistance at birth?

A

Increases as the cord is clamped and cut, the placenta is removed from the systemic circulation => increase in SVR.

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19
Q

Overall what is the result of the circulatory changes at birth?

A

More cardiac output to the lungs and less blood through ductus arteriosus and foramen ovale closes as pressure in LA is now greater then pressure in RA.

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20
Q

What leads to the constriction of the ductus arteriosus?

A

1) Increased partial pressure of oxygen leads to vasoconstriction (unique smooth muscle)
2) Decreased flow to to decreased resistance in pulmonary circulation.
3) Decreased prostaglandin circulated as detached from placenta

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21
Q

When does the functional and anatomical closure of the ductus arteriosus occur?

A

Functional closure within hours to days- can be re-opened in the first few days of life if needed
Anatomical closure within 7-10 days => formation of the ligamentum arteriosum.

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22
Q

What is the ligamentum arteriosum?

A

Ligament reminisce of the ductus arteriosus

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23
Q

What are the consequences of failure of duct closure?

A

Blood now moves from the aorta into the pulmonary circulation down a pressure gradient.
=> Heart failure (too much blood in the pulmonary circulation and pulmonary hypertension)
=> Steal (other end organs are not well perfused as blood is diverted to lungs
NB: may also contribute to other pre-term complications

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24
Q

When is there a high incidence of patent ductus arteriosus?

A

Pre-term infants

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25
What is the treatment for patent ductus arteriosus?
Watchful waiting, NSAIDs or surgery
26
Why are NSAIDs used in patent ductus arteriosus?
They inhibit prostaglandin production which will reduce circulating levels and support duct closure.
27
Give an example of a duct dependent congenital disease?
Interruption of the aortic arch. | There is no way for the blood to get into the descending aorta exept through ductus arteriosus
28
What can be given to maintain duct patency until surgery can be carried out?
IV infusions of prostaglandin E2
29
Why may a large artrial or ventricular septal defect only become symptomatic at 6-8 weeks old?
Pulmonary resistance continues to fall to normal adult levels over the first 2-3 months. In the newborn the pressure differences between right and left circulations are only small so blood doesn't really move
30
Persistent pulmonary hypertension of the newborn is considered a failure of adaption at birth. Who is more likely to suffer and why does it happen?
More likely in sick babies = sepsis (group B strep), hypoxic insult, Meconium aspiration syndrome or cold stress. Can be related to an underlying anatomical abnormality eg congenital diaphragmatic hernia
31
What are the consequences of PPHN?
Pressure in the Ra is still greater then the LA so blood continues to move across the foremen ovale and deoxygenated blood enters the left side of the heart. The ductus arteriosus also remains open as there is still high flow as the blood moves down a pressure gradient. More deoxygenated blood flows into the descending aorta.
32
What are the signs of PPHN?
Cyanosis- difficult to see | Large difference between pre and post ductal oxygen saturations. Right hand sats = 80%. Left foot sats =60%.
33
What is the treatment for PPHN?
Supportive = ventilation to improve oxygenation and inhaled NO as a vasodilator as the systemic BP is very high. ECMO (Extracorporeal membrane oxygenation) Very serious cases for essentially cardio pulmonary bypass untl the pressure drops.
34
What is a congenital heart disease?
Abnormality of the structure of the heart which is present at birth. A gross structural abnormality in the heart or ntrathoracic great vessels that is actually or potential of functional significance. NB: doesn't include genetic arrythmias or cardiomyopathies
35
What is the incidence of congenital heart disease in Scotland?
8 per 1000 births with 3 per 1000 births being major defects
36
What is the spectrum of severity for congenital heart defects?
``` Mild = assymptomatic, may resolve spontaneously (may progress to a more severe condition in adulthood) Moderate = requires specialist intervention and monitoring in a cardiac centre Severe = Present severely il/ die in new born period or early infancy ```
37
Define major congenital heart disease?
Requires surgery within the first year of life. Either corrective or palliative (palliative meaning normal cardiac function cannot be achieved)
38
When does congenital heart disease present?
Antenatal screening Immediately after birth as cyanosis 24 hour baby check- murmurs, abnormal pulses, cyanosis 3-7 days- duct dependent diseases (circulatory collapse, shock, cyanosis, sudden death 4-6 weeks- large VSDs (cardiac failure, reduced feeding, failure to thrive, breathlessness) 6-8 weeks- GP check with murmurs an incidental finding.
39
What percentage of congenital heart defects be diagnosed on a 20 week scan?
Should include a 4 chamber view of the heart and an outflow tract view. Needs skilled people to pick up abnormalities (~35% are detected) Challenges: obese mother, baby moving or in wrong position
40
If a congenital heart disease is picked up on the 20 week scan what is the management plan?
Disease dependent Termination as some hearts are so abnormal there are no surgical options Deliver in a cardiac surgical centre eg Glasgow Plan for a prostaglandin infusion if its a duct dependent defect
41
What is involved in a newborn screening at 24 hours old?
Femoral pulses, heart sounds and presence of murmurs | Pre and post ductal saturations (standard in some regions)
42
How accurate is the 24 hour baby check?
Some defects will have no symptoms at 24 hours old False negatives: >50% of babies with congenital heart disease were missed by newborn screening and 1/3 of infants with life threatening abnormalities were undiagnosed False positives: > 50% of babies with heart murmurs have no underlying disease.
43
Why does a small VSD give you a false positive at the 24 hour screening?
A small VSD will produce a loud murmur due to lots of turbulence. But no intervention is required as it will close spontaneously
44
What are the causes of cyanosis in babies?
Cardiac disease: Blue with little or no respiratory distress. May have pre/post ductal differential Respiratory disease: Associated with increased work of breathing and CXR changes PPHN: Normally present unwell with a large pre/post ductal differential.
45
How can you differentiate between cycanosis caused by cardiac disease and PPHN?
differentiate between PPHN and cardiac disease with an echo
46
What happens in transposition of the great arteries?
2 independent circulations working independently- systemic circulation is always deoxygenated and pulmonary circulation always oxygenated. Usually mixing of blood through ASD where oxygenated blood from LA passes into RA. The larger the ASD the better the saturations.
47
What is the treatment for transposition of the great vessels?
Surgery but in the meantime insert a catheter into umbilical/femoral vein and the into RA and then LA. Inflate a balloon and pull back to increase the size of the ASD allowing greater mixing of blood
48
How do duct dependent congenital heart diseases present?
Severe cyanosis, tachypnoea, distress, rapid deterioration, Prolonged cap refil, crepitaions, absent pulses, hepatomegaly Very acidotic
49
What are the differentials for the presentation of duct dependant conditions?
Sepsis | Metabolic conditions
50
What is the immediate treatment of a duct dependent condition?
ABCDE: support airway and breathing as necessary Give IV infusion of prostaglandin E2 to open duct Multisystem supportive treatment Transfer to cardiac surgical centre
51
Give examples of duct dependent systemic circulation?
Hypoplastic left heart Interrupted aortic arch Critical aortic stenosis Critical coarctation of aorta
52
Give examples of duct dependent pulmonary circulations?
Tricuspid atresia Pulmonary atresia Critical pulmonary stenosis
53
What is atresia?
Absence of a normal opening
54
What is coarctation?
Congenital narrowing of a short section of the aorta
55
What is hypoplastic left heart?
Where there is a very small left ventricle, ascending aorta and aortic valve => little blood flowing through the left side of the heart Normally an ASD allowing blood from LA to flow into RA so the systemic circulateion is supplied by the ductus arteriosus
56
What is the treatment for hypoplastic left heart?
3 stage complex surgery which is palliative (normal heart function cannot be restored. High mortality. Total Cavo Pulmonary connection => RV supplies systemic circulation Heart transplant with be required in late teens/twenties
57
Explain pulmonary atresia?
The is no right ventricular output and is associated with a VSD. Circulation to the lungs is supplied by the ductus arteriosus
58
When does cardiac failure present in babies and why?
4-6 weeks (presents now as the pressure difference has become large enough between left and right) Usually seen with moderate to large Left to right shunts => increased pulmonary flow and increased RV load> Pulmonary oedema and right heart failure.
59
What are the signs of a large VSD?
Cardiac failure signs: Breathless, sweatiness, crepitations , hepatomegaly + failure to thrive and slow/reduced feeding
60
where to large VSDs tend to be found?
In the membranous part of the septum and often no mumur at baby check
61
What is the treatment for VSD?
High calorie formula, NG tube and diuretic to help growth as much as possible. Surgery: put a patch over the defect.
62
What follow up is required post surgery for VSD and why?
Follow up during childhood/teenage years as the position of patch can move during growth and you can get arrythmias due to scarring from surgery. Otherwise normal life
63
When is a repiar for a patent ductus arteriosus carried out?
1 year old. Catheter procedure to block the duct. Couple of follow up appointments to check flow and device in correct position => discharge
64
What are some of the non cardiac consequences congenital heart disease?
Hypoxia, surgery and bypass time can lead to developmental problems. Emotional/social/family issues - puts a huge strain on families

Cardiovascular (24 decks)

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