Congenital defects Flashcards
How does the heart start embryologically
Clusters of angiogenic cells on mesodermal cardiogenic plate
Briefly describe steps of heart development
- R/L endocardial tubes fuse into a single cardiac tube
- Folding into bulboventricular loop
- Atrial, ventricular and outflow tract septation
Name the 3 anatomical connections found in foetal circulation
Foramen ovale
Ductus Arteriosus
Ductus venosus
Describe resistance in foetal circulation
High resistance pulmonary circulation
Low resistance systemic circulation
How is foetal able to stay healthy despite congenital defect
Foetal circulation may bypass abnormalities via anatomical connections
Blood bypasses obstruction via one of these
How does blood go from the placenta to the foetus
Oxygenated blood flows from umbilical vein into the ductus venosus and into right side of the heart
What circulatory changes occur post birth
Closure of ductus arteriosus, ductus venosus and foramen ovale
Drop in pulmonary vascular resistance–> drop in pulmonary pressure
How does blood flow in foetal circulation
Oxygenated blood goes through foramen ovale, into left atrium and into head and neck
How long do foramen ovale and ductus arteriosus stay open
12-72 hours post birth
What is PPHN
Persistent pulmonary hypertension
Baby still has high pulmonary artery pressure so blood shunts from right to left
Presents as blue baby
What is a common cause of PPHN
Group B streptococcal pneumonia
What are the 2 main categories of congenital heart disease
Cyanotic- patient is blue
Acyanotic- patient is pink
What produces the blue colour in cyanotic congenital heart disease
Amount of deoxygenated Hb (g/l)
What are the parameters for defining cyanosis
- Deoxygenated Hb is >50g/l in capillaries
- Deoxygenated Hb is >34g/l in arterial blood
What are the hallmarks for cyanosis due to congenital heart disease
- Normal alveolar gas exchange (normal CO2)
- No dyspnoea
- Normal pulmonary venous saturations
What are the hallmarks for cyanosis due to lung disease (eg pneumonia)
- Impaired alveolar gas exchange (CO2 may be high)
- Tachypnoea and recession
- Reduced pulmonary venous saturations
What do the following result from
a) cyanosis due to CHD
b) cyanosis due to lung disease
a) shunting of deoxygenated blood from R to L
b) Oxygen diffusion problems or ventilation/ perfusion mismatch
Where does blood mixing occur in transposition of the great vessels?
Mixing from ductus arteriosus and foramen ovale
What defects are seen in tetralogy of fallot
Misalignment of outflow tract
Ventricular septal defect
Right ventricle hypertrophy due to trying to pump against resistance
R–L shunt
What is the difference between atresia and stenosis
Atresia= valve completely blocked Stenosis= valve is narrowed
What is total anomalous pulmonoary venous drainage
Pulmonary veins go back into RA instead of left–> blood mixing
What is truncus arteriosus
Aorta and PA haven’t separated`
What are the 2 main groups of acyanotic congenital heart defects
- Left right shunts
- Left heart outflow tract obstruction
Effect of left- right shunt
Increased pulmonary blood flow leading to pulmonary oedema/ hypertension
