Embryology-CV Developmental Abnormalities

Question 1

In the embryonic heart, the crista terminals separates what two structures?

Answer 1

Sinus venosus and embryonic atrium.

Question 2

What structure is located in the crista terminalis?

Answer 2

SA node.

Question 3

How does fetal blood flow circulate?

Answer 3

Umbilical vein -> ductus venosus bypasses liver -> IVC/SVC -> foramen ovale and foramen secundum bypass right ventricle -> left atrium -> left ventricle -> aorta. Blood that does go through the right ventricle goes through the pulmonary artery and into the aorta, bypassing the lungs.

Question 4

When do most congenital heart defects form?

Answer 4

Weeks 3-8. This is because the heart is forming at this period and often, mothers don’t even know they’re pregnant at this point.

Question 5

What is the most common cause of congenital heart defects?

Answer 5

Trisomy 21. AV septal and valve defects.

Question 6

What environmental factors can cause congenital heart defects?

Answer 6

Congenital rubella infection, gestational diabetes and teratogens.

Question 7

What are the main categories of congenital heart defects?

Answer 7

Left to right shunt, right to left shunt and obstruction

Question 8

Atresia

Answer 8

blockage or absence of a normal opening

Question 9

Overriding aorta

Answer 9

Instead of arching to the left the aorta is displaced to the right so that it appears to arise from both ventricles.

Question 10

Why wouldn’t a left to right ASD cause blue baby?

Answer 10

Because oxygenated blood is being shunted away and tissues continue to get oxygenated blood.

Question 11

In an adult there is a hole in the atrial septum. What structure is absent?

Answer 11

Septum secundum. It is the second wall that divides the atria into two sides.

Question 12

What abnormalities can cause formation of an atrial septal defect?

Answer 12

1) Excessive resorption of the septum primum 2) Large formation of oval foramen caused by a short septum primum 3)Septum secundum does not form 4) Common atrium

Question 13

Why would someone really want their ASD corrected?

Answer 13

Blood clots are likely to form in the right atrium. Smaller blood clots are not as big of a problem in the lungs. If the clot can get into the left atrium, a smaller clot can easily cause a stroke.

Question 14

Developmental defects in the endocardial cushions can result in what congenital heart defects?

Answer 14

ASD (foramen primum does not close), VSD (IV septum does not close) and AVSD (atrioventricular septum is open)

Question 15

What portions of the AV valves would be absent in an AVSD?

Answer 15

The septal leaflet of the tricuspid and anterior leaflet of the mitral valve.

Question 16

What is the most common congenital heart defect? What causes these?

Answer 16

VSD. 1) Deficient swelling from conotruncal septum 2) Failure of endocardial cushion fusion. 3) Insufficient development of muscular septum. This causes high pressure blood in the left to flow to the right.

Question 17

How does the tetralogy of Fallot cause blue baby syndrome?

Answer 17

The defects ultimately result in a right to left shunt, putting deoxygenated blood into systemic circulation. 1) Pulmonary stenosis 2) Patent ductus arteriosus 3) Overriding aorta 4) interventricular septal defect 5) Enlarged right ventricle.

Question 18

Where do the outflow tracts form from?

Answer 18

Bulbus cordis

Question 19

What can you give a premature baby to keep its ductus arteriosus open? When would you do this? What other structure would you hope is still there?

Answer 19

Prostaglandins. You would do this in the event of aortic coarctation, aortic valvular atresia, and transposition of the great vessels. You would hope the patent foramen ovale is still there so oxygenated blood can flow left to right, go out the pulmonary artery, through the ductus arteriosus, into the aorta and into the periphery.

Question 20

How does a patent ductus arteriosus cause strain on the heart?

Answer 20

Higher pressure in the aorta pushes blood from the aorta into the pulmonary artery. This will increase pressure in the heart.

Question 21

Why do babies fail to thrive when there is a persistent truncus arteriosus?

Answer 21

The truncus arteriosus normally separates into the aortic an pulmonary arteries down at the ventricular level by the conotruncal septum. Failure of this septum to form results in VSD and a single outflow tract with no specification of blood for the lungs or blood for the periphery.

Question 22

What are the different types of truncus arteriosus are there?

Answer 22

Pulmonary arteries come off trunk close together, they come off independently or they come off the thoracic aorta.

Question 23

How can malformations in the conotruncal septum (aorticopulmonary trunk) result in pulmonary stenosis? Aortic stenosis? Valve malformations?

Answer 23

*

Question 24

Why would you try to maintain the ductus arteriosus and hope there was a patent foramen ovale in a baby with pulmonary valvular atresia?

Answer 24

So that blood from the vena cava can flow from right to left atria, into the left ventricle, out the aorta, through the patent ductus arteriosus and into the lungs to be oxygenated.

Question 25

Which aortic arch disintegrates? What clinical symptoms may present when this arch does not disintegrate?

Answer 25

The right portion of the dorsal aorta (aortic arch 6). When this doesn't disintegrate a vascular ring forms around the trachea and the esophagus. The patient may experience dysphagia from squeezing of the esophagus by the vessels.

Question 26

What type of aortic coarctation is most serious?

Answer 26

A post-ductal aortic coarctation. This happens past the ductus arteriosus and the baby must then develop a collateral circulation (via sublclavian and internal thoracic arties) because the ductus arteriosus can't help out at all.

Question 27

Where does blood go without impedance in aortic coarctation?

Answer 27

The head.

Question 28

When would a ligamentum arteriosum cause dysphagia in a patient?

Answer 28

When a right aortic arch forms and the ligamentum arteriosum forms a ring around the trachea and esophagus.

Question 29

How does the body maintain blood supply when the 4th aortic arch is obliterated or interrupted?

Answer 29

The patent ducts arteriosus takes blood to the thoracic aorta and the right aorta persists in order to maintain blood flow to the extremities (although it will be decreased significantly)

Question 30

How do you get blood flow to your right arm if the right 4th aortic arch was obliterated?

Answer 30

Usually the 4th aortic arch forms the right sublacian artery and the left aortic arch. If it doesn't form on the right then it will come from the 7th intersegmental artery from the dorsal aorta.

Question 31

Why would you want a patent foramen ovale in a patient with tricuspid atresia?

Answer 31

So blood from the vena cava can get into the left ventricle, through the ductus arteriosus and into the pulmonary artery and through the lungs for oxygenation.

Question 32

What defects cause a left to right shunt? Which side of the heart is prone to failure in these conditions?

Answer 32

ASD, VSD, patent ductus arteriosus and AVSDs. The right side, you get left to right shunting of blood in these conditions that can cause RV hypertrophy.

Question 33

What defects cause a right to left shunt? What are significant clinical problems with these patients?

Answer 33

Tetralogy of Fallot and the great arteries. Patients will suffer from cyanosis and can get strokes from right atria clots moving through to the left side of the heart and into the brain.