Congenital Heart Defects

Question 1

What is a congenital defect?

Answer 1

People born with abnormality

Question 2

What is dextrocardia?

Answer 2

Rare condition where heart points to right side of chest instead of left

Question 3

What could dextrocardia be a result of?

Answer 3

1. Abnormal cardiac looping 2. Induced during gastrulation (week 3) when laterality (right and left side) is determined

Question 4

What other structural defects could isolated dextrocardia be associated with?

Answer 4

Abnormal connections with veins and arteries or abnormal septation of the heart

Question 5

In a foetus, what is purpose of ductus arteriosus?

Answer 5

Connection between aorta and pulmonary artery (2 vessels leaving heart), allowing blood to bypass lungs as baby receives O2 from mother’s circulation

Question 6

What causes ductus arteriosus to close after birth? What is purpose of it closing?

Answer 6

Increasing O2 tension and decrease in circulating prostaglandins Blood can then bypass heart and go straight to lungs

Question 7

What happens if ductus arteriosus fails to close?

Answer 7

Causes too much blood to circulate to baby’s lungs and heart. Oxygenated blood travels back to the lungs, then returns to the heart to be pumped out again. Increase workload of heart.

Question 8

What can patent ductus arteriosus lead to?

Answer 8

1. Pulmonary hypertension 2. Heart failure 3. Ventricular hypertrophy

Question 9

How can patent ductus arteriosus lead to pulmonary hypertension?

Answer 9

Too much blood circulating through the heart’s main arteries through a patent ductus arteriosus can lead to pulmonary hypertension, which can cause permanent lung damage

Question 10

How can patent ductus arteriosus lead to heart failure?

Answer 10

A patent ductus arteriosus can eventually cause the heart to enlarge and weaken

Question 11

What is a patent ductus arteriosus treated with?

Answer 11

Prostaglandin inhibitors (e.g. ibuprofen)

Question 12

What can atrial septal defects be caused by?

Answer 12

Failure of septum primum and secundum to fuse after birth

Question 13

What can cause failure of septum primum and secundum to fuse?

Answer 13

Malformations in the septum primum or secundum (most common) such that they don’t overlap. Leaves gap so blood can flow between atria.

Question 14

What is a patent foramen ovale?

Answer 14

Foramen ovale (small, flap-like opening present in wall between right and left atria) fails to close during infancy

Question 15

How common is a patent foramen ovale?

Answer 15

1 in 4 people

Question 16

Why is a patent foramen ovale usually asymptomatic?

Answer 16

Higher pressure in LA pushes septum primum against septum secundum and mechanically shuts valve

Question 17

When can a patent foramen ovale cause problems?

Answer 17

If there is higher pressure in RA this can push the flimsy septum primum open and allow blood to shunt from right to left

Question 18

What is the ostium/foramen secundum?

Answer 18

A foramen in the septum primum (not the same as the foramen ovale which is an opening in the septum secundum)

Question 19

What is an ostium secundum defect? What is it caused by?

Answer 19

Caused by excessive apoptosis in septum primum causing abnormally large opening. Or by inadequate development of the septum secundum – such as when the foramen ovale and foramen secundum overlap.

Question 20

What is result of ostium secundum defect?

Answer 20

Blood is shunted left to right - Can cause enlargement of right atrium and ventricle - Small defects are asymptomatic (<5mm)

Question 21

What is a ‘common atrium’?

Answer 21

Complete absence of atrial septum

Question 22

What is ‘common atrium’ caused by?

Answer 22

Failure of development of septum primum and secundum

Question 23

What is result of premature closing of foramen ovale?

Answer 23

Results in hypertrophy of the right side of the heart and underdevelopment of the left side - No blood passing into left side so it doesn’t develop - Death usually occurs shortly after birth

Question 24

When does premature closing of foramen ovale occur?

Answer 24

During prenatal life

Question 25

What is the most common congenital defect?

Answer 25

Ventricular septal defect

Question 26

What do ventricular septal defects often affect?

Answer 26

Can affect the muscular or membranous part of the interventricular septum (Muscular defects often resolve themselves as child grows)

Question 27

What do ventricular septal defects result in?

Answer 27

Shunting of blood from left to right –> resulting in pulmonary hypertension and hypertrophy of right ventricle

Question 28

What do the conotruncal swellings that form the conotruncal septum rely on?

Answer 28

The migration of neural crest cells from the neural tube

Question 29

What can lead to defects in septation of truncus arteriosus into pulmonary trunk and aorta?

Answer 29

Abnormal crest cell development/migration

Question 30

What is result of truncus arteriosus?

Answer 30

• Oxygen-poor blood and oxygen-rich blood are mixed together as blood flows to the lungs and the rest of the body - Too much blood goes to the lungs and the heart works harder to pump blood to the rest of the body

Question 31

In truncus arteriosus, what valve is present?

Answer 31

Instead of having both an aortic valve and a pulmonary valve, babies with truncus arteriosus have a single common valve (truncal valve)

Question 32

What is persistent truncus arteriosus?

Answer 32

Conotruncal septum completely absent so cannot fuse with inter ventricular septum (ventricular septal defects)

Question 33

What is result of persistent truncus arteriosus?

Answer 33

Undivided truncus is in communication with both ventricles and receives oxygenated and deoxygenated blood Must be surgically corrected or causes heart failure

Question 34

What is the transposition of great vessels?

Answer 34

Conotruncal septum runs straight down instead of forming in a spiral. Aorta arises from right ventricle and pulmonary artery arises from left ventricle.

Question 35

What needs to exist to survive with the transposition of great vessels?

Answer 35

An accompanying shunt such as a VSD, patent foramen ovale or patent ductus arteriosus

Question 36

What is ‘Tetralogy of Fallot’?

Answer 36

Collection of 4 abnormalities caused by the same primary defect. 1. Pulmonary stenosis 2. Ventricular septal defect 3. Overriding aorta 4. Right ventricular hypertrophy (caused by higher pressure on right side) All cause poor oxygenation of body (cyanosis)

Question 37

What is Tetralogy of Fallot’ caused by?

Answer 37

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

Question 38

What is coarction of the aorta?

Answer 38

Narrowing of the aorta that occurs near the ductus arteriosus

Question 39

What are the 2 classifications of coarction?

Answer 39

1. Preductal 2. Post ductal

Question 40

What is preductal coarction of aorta?

Answer 40

During development, the ductus arteriosus compensates for narrowing –> ductus arteriosus usually remains patent after birth

Question 41

What can obliteration of the ductus arteriosus in infants result in? What is it treated by?

Answer 41

Rapid decline of infant with hypo perfusion of lower body. Treated by administering prostaglandins to keep ductus arteriosus open

Question 42

What is differential cyanosis?

Answer 42

Upper body and head well perfused, lower body cyanotic

Question 43

What is post ductal coarction of aorta?

Answer 43

More common During development a collateral circulation is established to bypass the narrowing

Question 44

What is this collateral circulation in post ductal coarction?

Answer 44

Blood passes through the subclavian arteries to the internal thoracic arteries to intercostal arteries to the descending aorta

Question 45

What is result of post ductal coarction and this collateral circulation?

Answer 45

Internal thoracic and intercostal arteries enlarge to carry greater blood flow