1.2.2 Development of Heart and Cardiovascular System

Question 1

When does the heart first beat in embryological development?

Answer 1

Day 22

Question 2

List the most common congential anamolies.

Answer 2

VSD - 42%

ASD - 10%

Pulmonary stenosis - 7%

PDA - 7%

Tertralogy of Fallot - 5%

Aortic valve stenosis - 4%

Atrioventricular septal (canal) defect - 4%

TGA - 4%

Persistent truncus arteriosus - 1%

Question 3

At day 20, when the embryo begins to fold both cranially on itself and medially, what structures are being formed?

Answer 3

1. Cranial fold starts the formation of the aortic arch
2. right and left endocardial tubes start to come towards each other
3. endocardial tubes are developing adjacent to fluid filled sack, the pericardial cavity

Question 4

At day 21, the fusion of the right and left endocardial tube in the cardiogenic region leads to the formation of what?

Answer 4

a single heart tube

Question 5

Draw the pericardial sac at day 21-22.

Include aortic sac, bulbis cordis, ventricle, atrium, sinus venosus

Answer 5

Question 6

Describe how the pericardial sac twists and folds into the heart structure.

Answer 6

Question 7

At day 22 the heart starts to beat, what are the four layers of the heart at this point?

Answer 7

1. Endocardium (primitive endocardium)
2. Cardiac jelly (ECM)
3. Myocardium (heart muscle)
4. Epicardium (visceral pericardium)

Question 8

The breakdown of what structure leads to the formation of the transverse pericardial sinus?

Answer 8

Dorsal mescardium

Question 9

Another image of how the heart tube twists into form.

Answer 9

Typically twist to the left.

Question 10

In what two conditions is the base of the heart directed to the right side of the body as opposed to the left? What differentiates the two conditions?

Answer 10

Dextrocardia (1/12,000 births) - increased risk of additional heart defects

Situs Inversus - all organs are completely reversed (1/7000 births) - only slight increased risk of additional heart defects

Question 11

What helps form the septum intermedium (which helps separate atrium from ventricles)?

Answer 11

Endocardial cushions (posterior and anterior), Day 28

Question 12

Abnormalities in endocardial cushions can lead to what type of defects?

Answer 12

ASD, VSD, AV canal defects, and TGA

Question 13

What type of cells contribute to the cells that form the endocardial cushion?

Answer 13

Neural crest cells

Question 14

People who have a variety of craniofacial defects are at greater risk of having endocardial cushion defects. What condition could lead to increased risk of atrioventricular septal (canal) defects?

Answer 14

Trisomy 21, Downs

Question 15

What is believed to impair/inhibit neural crest cell migration?

Answer 15

Binge drinking alcohol

Question 16

What causes atrioventricular septal (canal) defects? What is true about the four chambers of the heart?

Answer 16

Endocardial cushion defect; no separation of the four chambers

Question 17

What are the main clinical symptoms of the atrioventricular septal (canal) defects?

Answer 17

Tachypnea, poor feeding, growth retardation around 6 weeks of age as pulmonary vascular resistance continues to fall

Question 18

What two structures help to separate the R and L atria? Describe the characteristics of each.

Answer 18

Septum primum and septum secundum. The secundum is stiffer than the primum. The primum is more pliable.

Question 19

The interface b/t the septum primum and septum secundum forms what structure? As an embryo this allows blood to travel in what direction?

Answer 19

Oval Foramen

It allows blood to flow from the R atrium to the L atrium. After birth, the L atrium becomes a higher pressure system stopping this flow.

Question 20

What type of shunt is ASD? What murmur is commonly associated with ASD?

Answer 20

L to R shunt

“split” S2

Question 21

What is the most common type of ASD? What is the male to female ratio?

Answer 21

Secundum; 2 females for every male

Question 22

Why is a patent foramen ovale not considered an ASD?

Answer 22

B/c no septal tissue is missing, it is just that the two atrial septa fail to fuse with each other. Interatrial shunting cannot occur as long as L atrial pressure exceeds R atrial pressure.

Question 23

What structure grows into the right atrium? The left atrium?

Answer 23

R atrium: sinus venarum

L atrium: pulmonary veins

Question 24

What begins to grow up from the inferior wall of the ventricles towards the septum intermedium during the 4th week?

Answer 24

Muscular interventricular septum

Question 25

Most common heart defect? Type of shunt?

Answer 25

VSD, L to R shunt

Question 26

What is different about the presentation of small VSDs and large VSDs?

Answer 26

Small VSD: systolic murmurs by 48 hrs after birth Large VSD: present at 3 to 12 wks with tachypnea, grunting respiration, and slow weight gain

Question 27

What ultimately divides into the aorta and pulmonary trunk?

Answer 27

Truncus Arteriosus

Question 28

What is the most common type of interventricular septal defect?

Answer 28

Membranous (thin) portion of interventricular septum

Question 29

What are some possible of congential heart defects that come as a result of failure of the sepetation of the truncus ateriosus outflow tract?

Answer 29

TGA Pulmonary stenosis PTA TOF

Question 30

What happens in TGA? What is their saving grace?

Answer 30

Aorta sits of the right ventricle and pulmonary artery sits over the left ventricle. The PDA will help the patient get some oxygenated blood until surgery can be done to swap the position of the arteries

Question 31

For newborns w/ TGA to survive, there must be communication between the two sides of the heart. What two structures can help with this communication?

Answer 31

Peristent or patent foramen ovale or PDA

Question 32

What is PTA? How do newborns present and what will happen without surgical intervention?

Answer 32

Persistent truncus arteriosus is a congenital cardiac malformation in which the outflow of the heart is through a single vessel rather than a pulmonary trunk and aorta. Present w/ cyanosis. Most die of CHF unless surgically corrected

Question 33

What is the clinical presentation of TOF?

Answer 33

Newborns can be cyanotic and fail to thrive Most often: detected during well baby checks, months after they leave the hospital. Sudden incidences of cyanosis w/ hyperpnea are common from 2 mo to the 2 y. Surgery is necessary for survival into adulthood.

Question 34

What determines the severity of TOF?

Answer 34

degree of pulmonary stenosis

Question 35

How will more severe pulmonic stenosis affect heart sounds?

Answer 35

More pulmonic stenosis, greater splitting of S2

Question 36

What is aortic stenosis?

Answer 36

Condition in which the leaves (cusps) of the aortic valve become stiff or fuse together, leaving only a smaller opening for blood to leave the L ventricle

Question 37

In adults, aortic valvular stenosis can lead to what?

Answer 37

Enlargement of the aortic arch due to jetting of blood

Question 38

What is coarction of the aorta?

Answer 38

Constriction in the aorta 95% of the time just above or just below the attachment of the ductus arteriosus

Question 39

What is the hallmark that leads to diagnosis of coarction of the aorta in an adult?

Answer 39

**HTN in upper extremities and hypotension in the lower limbs**, murmur heard posteriorly in the interscapular regions, notching of the under surface of ribs

Question 40

What are III, IV, VI arch of the of the aorta

Answer 40

III - common and part of internal carotid artery IV - right subclavian artery (R) and arch of the aorta (L) VI (pulmonary arteries)