What is Tetralogy of Fallot?
congenital cardiac malformation. It is the most common form of congenital cyanotic heart disease.
Epidemiology of TOF
- TOF accounts for up to 10% of congenital cardiac abnormalities, making it the most common cyanotic heart defect.
- Typically manifests at 1-2 months of life
RFs of TOF
- Family history of congenital heart disease
- Rubellainfection
- Alcohol consumption in pregnancy
- Diabetic mother
- Down syndrome: trisomy 21
- DiGeorge syndrome: chromosome 22q11 deletion
- Edwards’ syndrome
What does TOF cause?
- Pulmonary stenosis: RV outflow obsruction - harder for deoxygenated blood to get into pulmonary circulation
- RV hypertrophy: To push blood past stenosis
- VSD: Blood shunts between ventricles - RV hypertrophy means pressure on right higher than left so blood shunted from right to left > deoxygenated blood enters LV and systemic circulation
- Overriding aorta: More deoxygenated blood in aorta
What happens as a result of this pulmonary stenosis
- cyanosis
- clubbing
- difficulty feeding
- failure to gain weight
In early neonatal period, how is pulmonary stenosis compensated for?
Patent ductus arteriosus - allow deoxygenated blood to enter pulmonary circultion - ductus arteriosus closes around day 2 and they start to be come symptomatic
What are Tet spells/ hypercyanotic spells
cyanosis is exacerbated as the infants demand for oxygen increase (e.g. when crying or feeding). Their heart will try to pump more (deoxygenated) blood, leading to a sudden decrease in oxygen saturation
How do infants respond to tet spells
Bring knees to chest like theyre squatting
Signs of TOF
- Ejection systolic murmur: due to pulmonary stenosis
- Reduced SpO2, particularly when distressed
- Respiratory distress
- Cyanosis
- Clubbing
Symptoms of TOF
- Poor weight gain or ‘failure to thrive’
- Difficulty feeding
- Hypercyanotic or ‘tet’ spells: cyanosis, breathlessness and syncope, particularly when crying or feeding
- Squatting posture
Investigations and diagnosis
- ECG
- Echo + doppler flow studies
- Chest X ray
Hypercyanotic tet spells management
- Conservative
- Oxygen
- BBs
- IV fluids
- Morphine
Neonatal cyanosis management
Prostaglandin e.g.alprostadil: used in symptomatic babies at birth to maintain a ductus arteriosus, thus allowing shunting of deoxygenated blood into the pulmonary circulation
Definitive management of TOF
- Blalock-Taussig (BT) shunt: atemporarypalliative measure performed for patients that remain persistently cyanotic whilst awaiting definitive surgery. It increases pulmonary arterial blood flow.
- Definitive surgery
Complications of TOF
- Tet spells
- Congestive Cardiac failure
- Arrhythmias
- Pulmonary regurgitation
What is coarctation of the aorta?
- Coarctation of the aorta is defined as a narrowing in the aorta. There is an infant (70%) and an adult form (30%).
- Males more than females
- More likely in people with Turners syndrome
Where does the coarction happen in infant form
comes after the aortic arch, which branches off to the upper extremities and to the head, and before the ductus arteriosus. In infantile coarctation, the ductus arteriosus is usually still open
What happens in infant form coarction
- Deoxygenated blood leaves RV > Blood travels from HP to LP - in this case low pressure in aorta below constriction so blood moves through ductus arteriosus into aorta
- Causes cyanosis - as dexoygenated blood travels into systemic circulation
Where does adult form coarction of the aorta happen?
- usually happens in adults just distal to the ligamentum arteriosus.
- There is therefore no mixing of deoxygenated and oxygenated blood.
- Pressure high upstream of coarctation and low downstream of coarctation
Upstream effects of coarction of aorta
- Blood flow increases into the aortic branches, and thus blood pressure increases in the upper extremities and the head.
- Increased cerebral blood flow means an increased risk of berry aneurysms.
- The increased pressure also tends to cause dilation of the aorta as well as increasing the risk of dissection.
Downstream effects of coarction of aorta
- Blood flow downstream from the constriction is decreased, causing decreased blood pressure in the lower extremities = patients will have a weak pulse in lower extremities.
- Since blood pressure’s lower, patients sometimes experience claudication in their legs due to reduced perfusion.
- Decreased perfusion of the kidneys causes the activation of the renin-angiotensin aldosterone system, which results in water retention and ultimately increases blood pressure, causing hypertension.
Rib notching
Coarction of aorta causes this
SEEN on X ray from only ribs 3-9
Signs of coarction of aorta
- Weak femoral pulse
- Tachypnoea
- LV heave
- Cyanosis of lower extremities
Symptoms of coarction of aora
- Poor feeding
- Grey and floppy baby
- Claudication in lower extremities
- Headaches and nose bleeds: due to hypertension
