Lecture 6 - Development of cardiovascular system 2

Question 1

Dextrocardia

Answer 1

result of abnormal cardiac looping

may be induced during gastrulation when laterality is determined

Question 2

What is isolated dextrocardia associated withʔ

Answer 2

other structural defects including abnormal connections with veins, arteries or abnormal septation of heart/

Question 3

Patent ductus arteriosus

Answer 3

allows shunting of blood from aorta to pulmonary artery. oxygenated blood returns to lungs from aorta and pumped out again - increases cardiac workload - pulmonary hypertension,ventricular hypertrophy and heart failure.
may be an isolated defect or occur with other cardiac defects

Question 4

Why does the ductus arteriosus close at birthʔ

Answer 4

due to an increasing oxygen tension and decrease in circulating prostaglandins.

Question 5

how is ductus arteriosus treatedʔ

Answer 5

prostaglandin inhibitors

Question 6

Atrial septal defects

Answer 6

failure of septum primum and secundum to fuse at birth - probe patent foramen ovale. its a possibility that they do not overlap and leave a gap. most commonly defects in septum secundum

Question 7

probe patent foramen ovale

Answer 7

occurs 1 in 4 people

usually asymptomatic, higher pressure in lA pushes septum primum against secundum and mechanically shuts valve.

Question 8

Why would pulmonary hypertension cause problems in Patent foramen ovaleʔ

Answer 8

There is higher pressure in right atrium. pushes flimsy septum primum open and allow blood flow from right to left

Question 9

Ostium secundum defects

Answer 9

excessive apoptosis, in septum primum or inadequate development of septum secundum such as foramen ovale.
Blood shunted from left to right
can enlarge ra and ventricle
small defects asymptomatic, larger defects - surgical repair

Question 10

common atrium

Answer 10

complete absence of atrial septum.

no development of septum primum or secundum

Question 11

Premature closure of foramen ovale

Answer 11

hypertrophy of the right side of the heart and underdevelopment of the left side. baby usually dies after birth shortly.

Question 12

Ventricular septal defect

Answer 12

most common congenital defect
down's syndrome
can effect membranous or muscular part
muscular part - often resolve themselves
left - right shunting
can result in pulmonary hypertension and hypertrophy of right ventricle

Question 13

Sepatational defects of the truncus arteriosus

Answer 13

septum formation depends on migration of neural crest cells
abnormal neural crest cell migration can lead to defects in septation of truncus arteriosis into pulmonary trunk and aorta.

Question 14

What are the different types of septational defects of truncus arteriosusʔ

Answer 14

Persistent truncus arteriosus
transposition of great vessels
tetralogy of fallot

Question 15

persistent truncus arteriosus

Answer 15

conotruncal septum absent
undivided truncus communicates with both ventricles - receives ox and deox bloody.
Symptoms - cyanosis, lethargy, breathlessness, delayed growth
corrected surgically

Question 16

Transposition of great vessels

Answer 16

septum does not spiral, runs straight down
aorta arises from right ventricle and pulmonary artery from lv.
incompatible with life unless accompanying shunt such as VSD or patent foramen ovale or ductus arteriosus exists.
cyanosis - can be corrected surgically

Question 17

how can a ventricular septal defect be beneficialʔ

Answer 17

when great vessels are transposed, an accompanying shunt will reverse the process

Question 18

Tetralogy of Fallot

Answer 18

unequal division of truncus arteriosus caused by anterior displacement of the aorticopulmonary septum.

Question 19

What are the 4 classical cardiac defects in tetralogy of fallot

Answer 19

1. pulmonary stenosis due to enlarged right ventricle
2. ventricular septal defect
3. overriding aorta
4. right ventricular hypertrophy
   leads to cyanosis

Question 20

Coarctation of aorta

Answer 20

narrowing of aorta that occurs near ductus arteriosus.
cause unknown - may be due to abnormal migration of cells from ductus arteriosus.
preductal or post -ductal

Question 21

Preductal coarctation of the aorta

Answer 21

during development ductus arteriosus compensates for narrowing
after birth, usually remains patent
then obliteration occurs, causes rapid decline of infant - hypoperfusion of lower body

Question 22

how is preductal coarctation of aorta treated

Answer 22

using prostaglandins - keeps ductus arteriosus open

Question 23

What is differential cyanosisʔ

Answer 23

upper body and head well perfused, lower body cyanotic

Question 24

Post - ductal coarctation of the aortaʔ

Answer 24

more common than preductal
collateral circulation established
blood passes from subclavian - internal thoracic - intercostal arteries - descending aorta
internal thoracic and intercostal arteries enlarge to carry greater flow