3 Embryology - congenital heart defects

Question 1

Ventricular septal defect (VSD)

Answer 1

opening in interventricular septum

lood L –> R (due to rpessure)

Question 2

Name the 4 main congenital defects of the heart

Answer 2

1. ASD
2. VSD
3. Tetralogy of Fallot
4. Transposition of great vessels

Question 3

Transposition of the great vessels (arteries)

Answer 3

conotruncal septum doesn’t spiral (between pulmonary trunk & aorta)
doesn’t produce dual circulatory system - instead 2 parallel systems - don’t mix
RV attached to aorta, LV attached to pulmonary trunk

Question 4

natural treatment of transposition of great arteries

Answer 4

ASD (connection between left + right atrium)
ductus arteriosus (join pulmonary trunk to aorta)
to allow oxygenated blood to mix with deoxygenated blood
because this is a cyanotic heart defect
otherwise, it will just be deoxygenated blood going around body via aorta from RV

Question 5

tetralogy of Fallot - the main defects

Answer 5

1. overriding aorta
2. right ventricular hypertrophy
3. pulmonary stenosis
4. VSD

Question 6

Patent ductus arteriosus (PDA)

Answer 6

acyanotic (oxy –> deoxy)
ductus arteriosus (shunt blood pulmonary artery –> aorta) before lungs functioning
shut after birth when pressure in P. artery falls
failure to close –> PDA
blood flow from aorta –> P. artery (high –> low)

Question 7

effects of chronic left –> right shunting

Answer 7

e.g. ASD, VSD, PFO, PDA
vascular remodelling of pulmonary circulation
increase body pulmonary resistance
if pulmonary resistance > systemic circulation, shunt will reverse, pressure on right side > left - Eisenmenger syndrome

Question 8

patent foramen ovale

Answer 8

a type of ASD
clinically silent - higher Left pressure - closure of flap valve (foramen ovale) but doesn’t seal (ASD)
can be how venous embolism reaches systemic circulation if right pressure of heart increases slightly (paradoxical embolism)

Question 9

Coarctation of aorta

Answer 9

narrowing of aortic lumen at ligamentum arteriosum (ductus arteriosus)
increases afterload of left ventricle –> left ventricular hypertrophy (harder to pump blood from LV to rest of body)
vessels to head + upper limbs appear proximal to coarctation - not affected
blood to body reduced –> weak femoral pulse, upper body hypertension (heart pumping quicker and harder for lower body, but upper body supply normal, so hypertension)

Question 10

Tricuspid atresia

Answer 10

tricuspid (RA –> RV) not developed –> no entry to right ventricle
must have ASD + VSD / PDA (ductus arteriosus doesn’t shut) for blood –> lungs

Question 11

Atrial septal defect

Answer 11

foramen ovale doesn’t close (opening between 2 atrium)

left atrial pressure > RA, so oxygenated –> deoxy (acyanotic)

Question 12

What is overriding aorta?

Answer 12

normally in tetralogy of Fallot

the aorta is placed over the VSD

Question 13

Explain tetralogy of Fallot

Answer 13

there is narrowing of outflow of the RV, so higher pressure is required to pump blood out of the RV to lungs (deoxy). However, due to the VSD present, the RV pressure increases and can pump blood into the LV (mixing deoxy with oxy to body (cyanotic). The increased pressure in the RV can lead to RV hypertrophy
there is also an overriding aorta where the aorta originates where the VSD is

Question 14

What can cyanotic heart defects lead to?

Answer 14

cyanosis (pt going blue)

Question 15

hypoplastic left heart

Answer 15

left ventricle & ascending aorta fail to develop properly and PFO (patent foramen ovale - foramen ovale not sealed) or ASD are also present
blood supply enter systemic circulation via PDA (patent ductus arteriosus) - pulmonary trunk to aorta

Question 16

What keeps the PDA open after birth?

Answer 16

PDA (pulmonary artery –> aorta)
prostaglandin
until baby’s heart large enough to operate on