Cardiology - Coarctation of the Aorta, TGA & Tetralogy of Fallot Flashcards
(107 cards)
1
Q
What is coarctation of the aorta?
A
A congenital condition where there is narrowing of the aortic arch (or descending aorta).
Narrowing of the aorta reduces the pressure of blood flowing to the arteries that are distal to the narrowing. It increases the pressure in areas proximal to the narrowing, such as the heart and the first three branches of the aorta.
2
Q
Where does coarctation of the aorta usually occur around?
A
The ductus arteriosus.
3
Q
What condition is coarctation of the aorta often associated with?
A
Turners syndrome
4
Q
What are 4 conditions that coarctation of the aorta is associated with?
A
1) Turner’s syndrome
2) Bicuspid aortic valve
3) Berry aneurysms
4) Neurofibromatosis
5
Q
Is coarctation of the aorta more common in males or females?
A
Males (despite an association with Turner’s syndrome).
6
Q
Often, what is the only indication of coarctation of the aorta in neonates?
A
Weak femoral pulses.
7
Q
How will coarctation of the aorta affect BP?
A
Perform a four limb BP:
1) High BP in limbs supplied from arteries that come before the narrowing
2) Lower BP in limbs that come after the narrowing
8
Q
What type of BP should be performed in coarctation of the aorta?
A
Four limb BP
9
Q
Exam findings in coarctation of aorta in infancy?
A
1) Weak femoral pulses
2) Four limb BP findings
3) Systolic murmur: heard below the left clavicle (left infraclavicular area) and below the left scapula
4) Tachypnoea and increased work of breathing
5) Poor feeding
6) Grey and floppy baby
7) Radio-femoral delay
10
Q
What additional 3 signs of coarctation of aorta may develop over time?
A
1) Left ventricular heave due to left ventricular hypertrophy
2) Underdeveloped left arm where there is reduced flow to the left subclavian artery
3) Underdevelopment of the legs
11
Q
What key sign is seen in adults in coarctation of the aorta?
A
HTN
12
Q
Management of coarctation of aorta?
A
Mild - patients can live symptom free until adulthood
Severe - emergency surgery shortly after birth.
13
Q
What is there a risk of in cases of critical coarctation?
A
Risk of heart failure and death shortly after birth.
14
Q
What is given in cases of critical coarctation that require emergency surgery?
A
Prostaglandin E –> used to keep the ductus arteriosus open while waiting for surgery
15
Q
Purpose of Prostaglandin E in severe coarctation of aorta cases?
A
Used keep the ductus arteriosus open while waiting for surgery.
This allows some blood flow flow through the ductus arteriosus into the systemic circulation distal to the coarctation.
16
Q
Surgical management of coarctation of aorta?
A
Surgery is performed to correct the coarctation and to ligate the ductus arteriosus.
17
Q
What does transposition mean?
A
In each others place
18
Q
What are the great arteries?
A
1) The pulmonary artery
2) The aorta
19
Q
What is transposition of the great arteries (TGA)?
A
A type of congenital heart defect where the attachments of the aorta and the pulmonary trunk to the heart are swapped (“transposed”).
This means the right ventricle pumps blood into the aorta and the left ventricle pumps blood into the pulmonary vessels.
20
Q
Is TGA cyanotic or acyanotic?
A
Usually acyanotic.
This is due to there being two separate circulations that don’t mix: one travelling through the systemic system and right side of the heart and the other traveling through the pulmonary system and left side of the heart.
21
Q
What is the hallmark of TGA?
A
Ventriculoarterial discordance
This is when the aorta arises from the morphologic right ventricle and the pulmonary artery arises from the morphologic left ventricle
21
Q
In the majority of patients (60%) with TGA, where is the aorta in relation to the pulmonary artery?
What is this called?
A
The aorta is anterior and to the right of the pulmonary artery (dextro-transposition of the great arteries [d-TGA]).
21
Q
What are the 2 possible classifications of TGA?
A
1) Dextro-transposition of the great arteries [d-TGA]) –> the aorta is anterior and to the right of the pulmonary artery
2) Levo-transposition of the great arteries [l-TGA]) –> the aorta may be anterior and to the left of the pulmonary artery
22
Q
What is the most common cause of cyanosis in the new born?
A
TGA
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Is TGA more common in males or females?
Males (60-70%)
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Describe what happens in dextro-TGA
The pulmonary and systemic circulation run in parallel, causing oxygenated blood to recirculate only in the pulmonary circulation and deoxygenated systemic blood to bypass the lungs.
This results in cyanosis unless there is mixing of oxygenated blood and deoxygenated blood.
25
What are 3 common anatomic sites for mixing of oxygenated and deoxygenated blood in TGA that allows life to be sustained?
1) Patent foramen ovale or atrial septal defect
2) Ventricular septal defect
3) Patent ductus arteriosus
26
What happens in levo-TGA [also called as CC-TGA]?
The ventricles have switched places as opposed to the arteries.
This is acyanotic as deoxygenated blood can return from the systemic circulation and enter the pulmonary circulation to be oxygenated before entering the systemic circulation again.
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Which type of TGA can be acyanotic?
Levo-TGA [also called as CC-TGA].
However, the right ventricle and tricuspid valve is not accustomed to the higher pressures of the left side of the heart. There is hypertrophy over time, which can result in tricuspid regurgitation and heart failure.
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What are the maternal risk factors for TGA?
1) Age >40 y/o
2) Maternal diabetes
3) Rubella
4) Poor nutrition
5) Alcohol consumption
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When is TGA often diagnosed?
During pregnancy with antenatal ultrasound scans.
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Presentation of TGA?
1) Cyanosis: at birth or within 24 hours (if no mixing at the atrial level)
2) Mild cyanosis (particularly when crying) might be evident)
3) Signs of congestive heart failure may appear over first 3-6 weeks:
- tachypnoea
- sweating
- poor feeding
- failure to gain weight
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How can some patients with TGA initially compensate at birth?
A patent ductus arteriosus or ventricular septal defect can initially compensate by allowing blood to mix between the systemic circulation and the lungs.
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Examination findings in TGA?
1) Prominent right ventricular heave
2) Single second heart sound, loud A2
3) Systolic murmur potentially if VSD present
4) No signs of respiratory distress
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Management of TGA?
1) Emergency prostaglandin E1 infusion --> to keep the ductus arteriosus patent as a temporary solution that allows mixing of blood
2) Correct metabolic acidosis
3) Emergency atrial balloon septostomy to allow for mixing
4) Definitive --> surgical correction
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Definitive investigation in TGA?
Echo
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What is a typical CXR finding in TGA?
“Egg on a string” due to potentially narrowed upper mediastinum; cardiomegaly and increased pulmonary vascular markings
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Purpose of Prostaglandin E1 in TGA?
Keeps the ductus arteriosus patent as a temporary solution that allows mixing of blood.
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What is the surgical management of TGA?
A cardiopulmonary bypass machine is used to perform an “arterial switch” procedure within a few days of birth. If present, a VSD or ASD can be corrected at the same time.
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What is a balloon septostomy?
Why may it be indicated in TGA?
Balloon septostomy involves inserting a catheter into the foramen ovale via the umbilicus, and inflating a balloon to create a large atrial septal defect.
This allows blood returning from the lungs (on the left side) to flow to the right side of the heart and out through the aorta to the body.
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What is the most ommon cyanotic congenital heart disease (CHD) presenting after the neonatal period?
Tetralogy of Fallot (TOF)
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What does 'tetralogy' mean?
Refers to something made up of four parts.
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What are the 4 defects seen in TOF?
1) Ventricular septal defect (VSD)
2) Pulmonary stenosis
3) Overriding aorta
4) Right ventricular hypertrophy (this is a physiological adaptation)
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What is TOF sometimes referred to as?
'Blue baby syndrome'
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What genetic conditions can TOF be associated with?
1) Down's syndrome
2) DiGeorge syndrome
3) CHARGE syndrome
4) VACTERL association
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What % of those with Down's syndrome are born with a form of congenital heart disease?
40% (e.g. TOF, ASD, VSD)
45
What is DiGeorge syndrome?
Caused by a microdeletion on the long arm of chromosome 22. It is also known as 22q11.2 deletion syndrome.
It is autosomal dominant.
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What are the salient features of DiGeorge syndrome?
Mneumonic: CATCH-22
C - Cardiac abnormalities (commonly Tetralogy of Fallot)
A - Abnormal facies (cleft palate, hypertelorism and short philtrum)
T - Thymic aplasia/hypoplasia
C - Cleft palate
H - Hypocalcaemia/hypoparathyroidism
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What is CHARGE syndrome?
CHARGE is a complex syndrome with a wide range of mental and physical disabilities.
It is caused by a mutation of CHD7 on chromosome 8 in 80 to 90% of cases.
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Clinical features of CHARGE syndrome?
C - Colomba
H - Heart defects
A - Atresia choanae (bone blocking the nasal passage which causes difficulty breathing)
R - Restriction of growth and development
E - Ear abnormalities and deafness
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Tetralogy of Fallot can be associated with the presence of other congenital cardiac abnormalities.
What are some examples?
1) Right aortic arch (25%)
2) Abnormal coronary artery anatomy (5 to 10%)
3) Pulmonary atresia
4) Aorticopulmonary collateral vessels
5) Patent ductus arteriosus
6) Atrioventricular septal defect
7) Atrial defect
8) Absent pulmonary valve
50
What causes the development of TOF?
The development begins in utero and is caused by a single developmental error.
1) Normally, the primitive truncus arteriosus is split in two by the evolving spiral septum.
2) However, in Tetralogy of Fallot, the truncus arteriosus FAILS to divide --> the spiral septum cannot fuse with the growing muscular ventricular septum causing a VSD.
3) There is narrowing of the pathway from the right ventricle to the pulmonary artery --> causes pulmonary artery stenosis.
4) The aortic root is enlarged and extends over the right ventricle outflow tract --> causing the overriding aorta.
5) Right ventricular hypertrophy occurs as a physiological adaptation to increased afterload in the heart.
51
What happens after birth in TOF?
Normally --> the ductus arteriosus and foramen ovale close as they are not required.
In TOF:
1) The VSD allows the mixing of oxygenated and deoxygenated blood.
2) This means deoxygenated blood enters the aorta and is pumped to the rest of the body --> cyanosis.
3) Overriding aorta means that the aortic valve is placed further to the right than normal, above the VSD. The aorta is also enlarged.
4) When the right ventricle contracts and pumps blood upwards, the aorta is in the direction of travel of that blood --> more deoxygenated blood enters the aorta from the right side of the heart.
5) Pulmonary stenosis means there is greater resistance to the flow of blood from the right ventricle into the pulmonary artery.
6) Instead of deoxygenated blood flowing through the pulmonary artery to the lungs, blood is pushed through the VSD into the aorta.
7) The pulmonary stenosis along with the overriding aorta causes deoxygenated blood to be shunted from the right to the left side of the heart causing cyanosis.
8) The right ventricle is pumping blood into the pulmonary artery under great resistance due to pulmonary stenosis, and due to pressures from the left ventricle being directly transmitted to the right ventricle because of the open VSD --> right ventricular hypertrophy.
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What is the impact of the VSD in TOF?
This allows the mixing of oxygenated and deoxygenated blood so deoxygenated blood enters the aorta and is pumped to the rest of the body --> cyanosis.
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What is the impact of the overriding aorta in TOF?
This means that the aortic valve is placed further to the right than normal, above the VSD.
The aorta is also enlarged.
When the right ventricle contracts and pumps blood upwards, the aorta is in the direction of travel of that blood. Therefore, more deoxygenated blood enters the aorta from the right side of the heart.
54
What is the impact of the pulmonary stenosis in TOF?
This means there is greater resistance to the flow of blood from the right ventricle into the pulmonary artery.
The pulmonary stenosis along with the overriding aorta causes deoxygenated blood to be shunted from the right to the left side of the heart causing cyanosis.
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What is the degree of cyanosis in TOF related to?
The severity of the pulmonary stenosis.
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Risk factors for ToF?
1) 1st-degree family history of congenital heart disease
2) A parent with Tetralogy of Fallot
3) A parent with DiGeorge syndrome
4) Foetal exposure to teratogens in utero --> alcohol, warfarin and trimethadione
5) Poorly controlled maternal diabetes
6) Maternal intake of retinoic acid
7) Congenital Rubella infection
8) Increased maternal age (over 40 years old)
57
What is the most common type of VSD associated with ToF?
Perimembranous VSD.
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Pulmonary stenosis can be classified according to its location.
What is the most common site in ToF?
The infundibular septum (50%)
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How may right ventricular hypertrophy be seen on a CXR?
As the 'boot' sign.
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Describe the aorta in ToF vs normal
Compared to the normal heart, the aorta in TOF is dilated and displaced over the intraventricular septum.
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What causes aortic dilatation in ToF?
Aortic dilatation is caused by an increase in blood flow through the aorta as it receives blood from both ventricles via the VSD.
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Clinical features will vary depending on the subtype of TOF.
What are the 3 major subtypes of ToF?
1) TOF with a milder form of pulmonary stenosis
2) TOF with pulmonary atresia
3) TOF with absent pulmonary valve
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When do children with ToF with mild pulmonary stenosis typically present?
- Usually asymptomatic at birth.
- Around the age of 1 to 3 years, the child develops cyanosis (as the child and the heart grows).
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When do children with ToF with mod-severe pulmonary stenosis (i.e. pulmonary atresia) typically present?
Will present within the first few weeks of life with cyanosis and respiratory distress.
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When do children with ToF with an absent pulmonary valve typically present?
The child will develop cyanosis and respiratory distress within the first few hours of life --> as the deoxygenated blood can only flow into the lungs via a patent ductus arteriosus.
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What happens in TOF with absent pulmonary valve?
1) The pulmonary valve is markedly dysplastic and is effectively regurgitant to a moderate or severe degree.
2) This causes enlargement of the branch pulmonary arteries as well as the right ventricle.
3) The branch pulmonary arteries enlarge so much sometimes that they may obstruct the tracheal tree and there may be associated tracheo or bronchomalacia as a result.
4) The deoxygenated blood can only flow into the lungs via a patent ductus arteriosus.
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Clinical general exam findings in ToF?
1) Central cyanosis
2) Clubbing
3) Respiratory distress
4) Poor feeding & poor weight gain
5) 'Tet spells'
The level of stenosis will determine when and how they present.
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What may typical findings on cardiovascular examination in ToF include?
- Thrill
- Heave (due to right ventricular hypertrophy)
- An ejection systolic murmur loudest in the 2nd intercostal space, upper left sternal edge (pulmonary area)
- Ejection click due to the closure of the dilated aortic valve in diastole
- Single S2 due to closure of the aortic valve in diastole with reduced pulmonary valve closure due to PA stenosis
- Continuous murmur at the left upper sternal edge if there is a patent ductus arteriosus
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Differentials to consider in ToF?
Consider other types of cyanotic congenital heart disease:
1) Transposition of the Great Arteries (TGA)
2) Total anomalous pulmonary venous drainage (TAPVD)
3) Hypoplastic left heart syndrome (HLHS)
4) VSD with Eisenmenger syndrome
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How are many cases of ToF identified?
Antenatal screening.
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What is the investigation of choice for establishing diagnosis of ToF?
Echo.
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What murmur is heard in ToF?
Ejection systolic murmur heard loudest in the pulmonary area (second intercostal space, left sternal border)
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What is the ejection systolic murmur caused by in ToF?
Pulmonary stenosis.
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Investigations in ToF?
Bedside:
- O2 sats
- ECG: to detect heart chamber enlargement and arrhythmia
Labs:
- Genetic testing e.g. Down's syndrome
Imaging:
- CXR:
- Cardiac MRI
- Cardiac catheterisation
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How many ToF present on an ECG?
TOF may present with right axis deviation and right ventricular hypertrophy
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What may a CXR show in ToF?
1) A boot-shaped heart (due to RVH)
2) Reduced pulmonary vascular markings (due to reduced pulmonary blood flow)
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What causes the ejection click in TOF?
Clicks in TOF occur due to closure of the dilated aorta.
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What is a 'Tet spell'?
These are intermittent symptomatic periods where the right to left shunt becomes temporarily worsened, precipitating a cyanotic episode.
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What causes a 'tet spell'?
This happens when the pulmonary vascular resistance increases or the systemic resistance decreases.
For example:
1) If the child is physically exerting themselves they are generating a lot of carbon dioxide
2) Carbon dioxide is a vasodilator that causes systemic vasodilation and therefore reduces the systemic vascular resistance.
3) Blood flow will choose the path of least resistance, so blood will be pumped from the right ventricle to the aorta rather than the pulmonary vessels, bypassing the lungs.
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What may 'tet spells' be precipitated by?
- Walking
- Physical exertion
- Crying
- Dehydration
- Anaemia
The child will become irritable, cyanotic and short of breath.
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Features of a 'tet spell'?
These are characterised by:
1) Paroxysm of hyperpnoea - rapid, deep respirations secondary to stimulation of the respiratory centre
2) Irritability
3) Increasing cyanosis
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What age do tet spells typically occur?
2 months to 2 years but peak age of incidence is usually between 2-4 months of life.
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Pathophysiology of a tet spell
1) There is an increase in right to left shunting and a fall in arterial oxygen saturations
2) After the initial drop in arterial oxygen saturation, there is an increase in right ventricular outflow tract obstruction, an increase in pulmonary vascular resistance and/or a decrease in systemic resistance.
3) This creates a vicious cycle which stimulates the respiratory centre. This causes hyperpnea and an increase in adrenergic tone with circulating catecholamines.
4) The increase in circulating catecholamines causes increased contractility which leads to increased outflow tract obstruction.
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What will auscultation of the heart during a tet spell reveal?
There will be a reduced/absent murmur due to decreased pulmonary blood flow and a tightly ‘shut’ infundibulum.
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How will children with ToF typically manage a tet spell themselves?
By squatting or bringing their knees to their chest.
Squatting increases the systemic vascular resistance which pushes blood into the pulmonary vessels.
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What can management of a tet spell include?
1) Position the child with their knees at their chest
2) Oxygen
3) Morphine: decreases respiratory drive
4) IV fluids: increase pre-load which increases the volume of blood which flows into the pulmonary vessels
5) Beta-blockers (propranolol): relaxes the right ventricle infundibulum and improves the flow of blood to the pulmonary vessels
6) Phenylephrine infusion: increases systemic vascular resistance
7) Emergency ventricular outflow tract stent or BT shunt
8) Sodium bicarbonate if there is metabolic acidosis
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Role of morphine in a tet spell?
Decreases respiratory drive, resulting in more effective breathing.
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Role of propanolol in a tet spell?
Relaxes the right ventricle infundibulum and improves the flow of blood to the pulmonary vessels
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Role of a Phenylephrine infusion in a tet spell?
increases systemic vascular resistance
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What is the gold standard for confirmation of diagnosis of ToF?
Echo
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Role of IV fluids in a tet spell?
Can increase pre-load, increasing the volume of blood flowing to the pulmonary vessels.
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When does surgical intervention of ToF typically occur?
Surgical intervention typically occurs within the first year of life.
Some patients receive a bridging procedure before complete repair of the Tetralogy of Fallot.
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What can be given in some patients with ToF that can maintain a patent ductus arteriosus?
A prostaglandin infusion.
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What is the purpose of maintaining a patent ductus arteriosus in ToF with prostaglandins?
When might this be necessary?
This allows blood to flow from the aorta back to the pulmonary arteries thereby maintaining the blood flow to the pulmonary circulation.
This is necessary when there is not enough forward flow from the heart through the pulmonary valve into the lungs.
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When are surgical bridging procedures used in ToF?
Bridging is used in infants who have poor pulmonary artery anatomy or co-morbidities who are not suitable to undergo surgical repair immediately.
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Purpose of bridging procedures in the management of ToF?
Bridging procedures help relieve cyanosis and defers the need for complete surgical repair.
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Medical management options in ToF?
1) Squatting
2) Prostaglandin (PG) infusion
3) Beta blockers
4) Morphine
5) Saline 0.9% bolus
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Role of squatting in ToF?
Parents may observe the infants squatting or keeping their knees to their chest – this manoeuvre helps increase venous return, therefore increases systemic resistance.
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What is a Blalock-Taussig (BT) shunt?
This can be placed as a form of intermediate management in ToF until a complete repair can be conducted.
It allows babies to grow so they are better suited for their complete repair.
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How does a BT shunt work in ToF?
The BT shunt mimics a patent ductus arteriosus and increases pulmonary blood flow before a complete repair can be performed.
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What are the 2 ways of performing a BT shunt?
1) Anastomosis of the subclavian artery to the pulmonary artery
2) Modified BT shunt: this is an artificial shunt made from synthetic material
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How is surgical repair of a ToF done?
The complete repair is performed under cardiopulmonary bypass. A midline sternotomy incision is performed. The right ventricle outflow tract/pulmonary artery stenosis is resected. The pulmonary artery is enlarged and the VSD is closed with a patch.
103
Left untreated, what are some complications of ToF?
1) Arrhythmias: AF & atrial flutter
2) Heart failure
3) Infective endocarditis
4) Stroke
5) Polycythaemia
6) Cardiac transplant
7) Death
Even post corrective surgery, patients are at higher risk of developing long term complications such as pulmonary regurgitation (PR), arrhythmias, exercise intolerance and sudden death.
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What age does surgical repair of ToF typically occur?
Between 3 months - 4 years.
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