Tetralogy of Fallot Flashcards
(17 cards)
What is Tetralogy of Fallot (TOF)?
A congenital condition that consists of 4 coexisting pathologies:
- VSD, overriding aorta, pulmonary valve stenosis, and right ventricular hypertrophy.
What is VSD in TOF?
VSD allows blood to flow between the ventricles.
What is the overriding aorta in TOF?
the overriding aorta refers to the fact that the entrance to the aorta (the aortic valve), is placed further to the right than normal, above the VSD → therefore when the right ventricle contracts and sends blood upwards, the aorta is in the direction of travel of that blood → so a greater proportion of deoxygenated blood enters the aorta from the right side of the heart (instead of going through the pulmonary valve and to the lungs)
What is pulmonary valve stenosis in TOF?
stenosis of the pulmonary valve provides greater resistance against the flow of blood from the right ventricle → this encourages blood to be shunted from the right heart to the left ⇒ cyanosis
What is right ventricular hypertrophy in TOF?
the increased strain on the muscular wall of the right ventricle as it attempts to pump blood against the resistance of the left ventricle and pulmonary stenosis causes RV hypertrophy, with thickening of the heart muscle
What is a R→L cardiac shunt in TOF?
It means blood bypasses the child’s lungs, leading to deoxygenated blood entering systemic circulation and causing cyanosis.
What are some risk factors of TOF?
Rubella infection, increased age of the mother (>40 years), alcohol consumption in pregnancy, and diabetic mother.
What investigations are carried out for TOF?
Echocardiogram (produces Doppler flow studies) and chest x-ray may show a ‘boot shaped’ heart due to RV thickening.
What murmur may be heard in TOF?
Ejection systolic murmur caused by pulmonary stenosis, heard loudest in the pulmonary area.
How is TOF typically presented?
- most cases picked up during antenatal scans
- ejection systolic murmur caused by the pulmonary stenosis can be heard on new born baby check
- severe cases present with heart failure before one year of age
- milder cases can present as older children once they start to develop signs and symptoms of heart failure
What are the signs and symptoms of TOF?
- cyanosis
- clubbing
- poor feeding
- poor weight gain
- ejection systolic murmur heard loudest in the pulmonary area
- tet spells
What are Tet spells?
- intermittent symptomatic periods where the right to left shunt becomes temporarily worsened, precipitating a cyanotic episode → this happens when the pulmonary vascular resistance increases or the systemic resistance decreases
- eg. if the child is physically exerting themselves, they’re generating a lot of co2 → this is a vasodilator that causes systemic vasodilation and therefore reduces the systemic vascular resistance → blood flows at the path of least resistance, so blood will be pumped from the RV to the aorta instead of the pulmonary vessels (less resistance in the aorta than pulmonary vessels), bypassing the lungs
What can precipitate Tet spells?
Physical exertion, crying, or increased pulmonary vascular resistance can worsen the shunt.
What is the immediate management for Tet spells?
- older children may squat when a tet spell occurs
- younger children can be positioned with their knees to their chest
- squatting increases the systemic vascular resistance
- this encourages blood to enter the pulmonary vessels
What is the medical management for TOF?
- supplementary oxygen as hypoxia is fatal
- beta blockers: relax the RV and improve flow to the pulmonary vessels
- IV fluids: increase pre-load, increasing the volume of blood flowing to the pulmonary vessels
- morphine: decrease respiratory drive ⇒ more effective breathing
- sodium bicarbonate: buffer any metabolic acidosis that occurs
- phenylephrine infusion: increase systemic vascular resistance
What is the management in neonates with TOF?
Prostaglandin infusion to maintain the ductus arteriosus, allowing blood to flow from the aorta back to the pulmonary arteries.
What is the definitive treatment for TOF?
Total surgical repair by open heart surgery.
